Dosežki študijskega programa Nanoznanosti in nanotehnologije
Achievements of the Nanosciences and Nanotechnology study program
Andreja Abina
Uporaba teraherčnih karakterizacijskih metod pri analizi gradbenih in konstrukcijskih materialov
Application of terahertz characterization methods for building and construction materials
Mentor in somentor / Supervisor and Co-Supervisor: Aleksander Zidanšek
THz metode smo uporabili za strukturno analizo različnih gradbenih materialov. Pri polimernih penah, aerogelnem kompozitu in mikrokapsuliranem fazno spremenljivem materialu smo iz THz spektroskopskih konstant določili gostoto pene in IR absorpcijo. Struktura zrn polimernih pen je bila analizirana s THz slikanjem z upoštevanjem velikosti zrn, praznin in napak. V kombinaciji z metodami obdelave slik in analize delcev so bile THz metode uporabljene za analizo granulacije in kemijske obdelave kalcijevih mikropolnil. Rezultati kažejo, da je THz metode mogoče uporabiti za analizo gradbenih materialov, njihove sestave, gostote, usmerjenosti vlaken, prisotnosti dodatkov, granulacije in koncentracije v mešanicah, vizualizacijo skritih notranjih in površinskih napak, proizvodnih pomanjkljivosti in nehomogenih struktur v submilimetrskem merilu ločljivosti. To bi lahko omogočilo optimizacijo proizvodnih postopkov za izboljšanje mehanskih in fizikalno-kemijskih lastnosti materiala.
THz methods were used for the structural analysis of building materials. For polymer foam, aerogel composite and microencapsulated phase change material, the THz spectroscopic constants were used to determine foam density and IR absorption. The foam’s bead structure was analysed by THz imaging considering bead size, air voids and defects. In combination with image processing and particle analysis methods, THz methods were applied to the analysis of calcium-based microfillers’ granulation and chemical treatment. Results indicate that the THz method can be applied to analyse building materials, their composition, density, fibre orientation, additive presence, granulation, and concentration in mixtures, visualise hidden internal and surface defects, manufacturing imperfections and inhomogeneous structures, in a submillimetre resolution scale. This could enable the optimisation of production processes to improve the mechanical and physicochemical material properties.
Določanje porazdelitve praznin v polimerni peni s THz slikanjem, signalnim procesiranjem in analizo delcev.
Determination of void distribution in polymer foam by THz imaging, signal processing and particle analysis.
Andraž Bradeško
Sklopitev elektrokaloričnega in elektromehanskega odziva v relaksorskih feroelektrikih za dielektrično hlajenje
Coupling of electrocaloric and electromechanical responses in relaxor ferroelectrics for dielectric cooling
Mentor in somentor / Supervisor and Co-Supervisor: Tadej Rojac, Zdravko Kutnjak
Doktorsko delo Andraža Bradeška je bilo osredotočeno na načrtovanje, modeliranje in testiranje naprave za elektrokalorično hlajenje, ki uporablja debeloplastne strukture iz keramike Pb(Mg1/3Nb2/3)O3 (PMN) v obliki ročic. Ročice zagotavljajo tako elektrokalorično (EK) hlajenje kot elektromehansko upogibanje, s čimer ustvarimo termične stike med ročicami. V sklopu raziskav je kandidat tudi testiral stabilnost EK odziva PMN med ciklanjem z električnim poljem. Odkril je, da je degradacija EK odziva povezana z nastankom prevodnih mej med zrni, ki nastanejo zaradi s poljem induciranega prehoda iz pseudokubične (ergodične) v romboedrično (ne-ergodično) feroelektrično fazo. Iz eksperimentalnih podatkov je kandidat izrisal t.i. diagram električnega polja–temperature (E–T), s čimer je razložil EK degradacijo med ciklanjem. S tem je določil pogoje ciklanja za stabilno EK delovanje keramike PMN.
The PhD thesis of Andraž Bradeško was focused on the design, modelling and testing of a novel electrocaloric (EC) device that uses Pb(Mg1/3Nb2/3)O3 (PMN) thick-film cantilever structures to provide both electrocaloric cooling and electromechanical bending, the latter used as a thermal switch concept. Among the various theoretical and experimental studies, the candidate also tested the PMN material in terms of EC fatigue, i.e., stability of the EC response as a function of electric-field cycling. He discovered that the EC fatigue is intimately related to the occurrence of conductive grain boundaries during cycling, triggered by the field induced transition from the pseudocubic (ergodic) to rhombohedral-like (non-ergodic) ferroelectric phase. The construction of the electric-field–temperature (E–T) diagram using EC measurement data explained this fatigue behavior and made possible to design the cycling conditions for a stable EC response over almost million field cycles.
Elektrokalorična (EK) odzivnost keramike Pb(Mg1/3Nb2/3)O3 (PMN) prikazana v t.i. E–T diagramu (E – električno polje, T – temperatura), kjer sta prikazana tudi področja stabilnosti romboedrične in psevdokubične faze. Eksperimentalni podatki prikazujejo razliko v EK ciklanju pri različnih temperaturah (~290 K and ~325 K). Z naraščajočo temperaturo je prehod v feroelektirčno (romboedrično) fazo onemogočen, kar razloži stabilnost EC odziva PMN med ciklanjem pri 325 K (~50°C).
Electrocaloric (EC) responsivity of Pb(Mg1/3Nb2/3)O3 (PMN) ceramics mapped in an electric-field–temperature (E–T) diagram (rhombohedral and pseudocubic phase regions are marked). The data revealed the differences in the EC cycling trajectories at different temperatures (~290 K and ~325 K). With increasing temperature the transition to the ferroelectric (rhombohedral) becomes more difficult, explaining the stability of the EC response of PMN when field-cycled at 325 K (~ 50°C).
Dejvid Črešnar
Topološko inducirani fenomeni in kalorični efekti v kondenzirani materiji
Topology-induced phenomena and caloric effects in condensed matter
Mentor in somentor / Supervisor and Co-Supervisor: Zdravko Kutnjak, Brigita Rožič
Tema doktorske disertacije se osredotoča na raziskovanje vpliva topoloških struktur na fazno stabilnost, fazno urejanje in kalorične pojave v sistemih kondenzirane snovi. Model tipa Lebwohl-Lasher je učinkovito opisal eksperimentalne rezultate povezane z odvisnostjo parametra nematičnega reda od koncentracije nanodelcev in temperature. Različni mehanizmi stabilizacije topoloških defektnih struktur s pomočjo zlatih nanodelcev v sistemih s t.i. TGBA fazo so bili določeni ekasperimentalno. Prikaz kontrole elastokaloričnega pojava v tekočekristalnih elastomerih z različnimi dejavniki kot so koncentracija zamreževalca, temperatura zamreženja in uporabljena napetost med zamreževanjem. Razvoj fenomenološkega modela na osnovi replične metode, s katerim je mogoče kvalitativno dobro opisati vpliv kritičnosti na elastokalorični pojav. Dejvid Črešnar: 7 znanstvenih člankov, od tega eden v reviji z IF >7.5.
The doctoral dissertation topic focuses on investigating topological structures’ influence on phase stability, phase ordering, and caloric phenomena in condensed matter systems. Lebwohl-Lasher type model effectively described the experimental results related to the nematic order parameter dependence on the concentration of nanoparticles and temperature. Various stabilization mechanisms of topological defect structures with gold nanoparticles in systems with the TGBA phase were studied experimentally. The control of the elastocaloric effect in liquid crystalline elastomers with various factors such as crosslinker concentration and temperature, and applied stress during crosslinking was investigated. A phenomenological model was developed based on the replica trick that qualitatively well-described criticality’s impact on the elastocaloric effect. Dejvid Črešnar: 7 scientific articles, one in a journal with an IF >7.5.
Primer elastokalorične spremembe temperature ∆TeC kot funkcije časa v tekočekristalnih elastomerih po uporabi ali odstranitvi napetostnega polja. Prikazan je tudi vpliv polja na red v materialu.
Example of the elastocaloric temperature change ∆TeC as a function of time in liquid crystal elastomers after applying or removing the stress field. The impact of the field on material order is also shown.
Aljaž Drnovšek
Vpliv topografije in atmosfere na tribološke lastnosti trdih prevlek
The influence of topography and atmosphere on tribological properties of hard coatings
Mentor in somentor / Supervisor and Co-Supervisor: Miha Čekada
V svoji disertaciji dr. Aljaž Drnovšek preučuje tribološko učinkovitost trdih prevlek, s posebnim poudarkom na nodularnih defektih pri magnetronsko napršenih prevlekah. Pri raziskavi je uporabljal tribološki sistem pin-on-disc tribološki tester, s katerim je raziskal, kako nodularni defekti vplivajo na obnašanje obrabe in trenja pri uporabi različnih protiteles, kot sta aluminijev oksid in orodno jeklo. Nov pristop študije posameznega cikla je pokazal, kako te površinske nepravilnosti na površini prevleke določajo lastnosti obrabe in trenja ob prvem nastanku tribološkega stika. Delo prav tako poudarja, kako okoljski pogoji, kot so različne nastavitve atmosfere, spreminjajo potek trenja in obrabe. Podrobne analize sledi tribološke obrabe dajejo vpogled v različne mehanizme obrabe. Študija je pokazala pomembnost kontroliranih laboratorijskih raziskav za napovedovanje realnega delovanja novih in naprednih prevlek.
In his thesis, Dr. Aljaž Drnovšek examined the tribological performance of hard coatings, with a particular focus on nodular defects in magnetron-sputtered coatings. The study uses pin-on-disc testing to explore how these defects impact the wear behavior against different counterbodies, such as alumina and tool steel. The novel cycle-to-cycle approach revealed how asperities on the coating surface dictate the wear and friction properties at the initial formation of the tribological contact. The work also highlights how environmental conditions, such as various atmospheric settings, alter the friction and wear outcomes. Detailed analyses of wear tracks provide insights into the distinct wear mechanisms, emphasizing the importance of controlled laboratory evaluations to predict the real-world performance of new and advanced coatings.
SEM-posnetki nodularnih defektov na obrabni sledi. Defekti so bili izpostavljeni 1 do 128 drsnim ciklom (a-f).
SEM images of the nodular defects in the wear track. The defects were subjected to 1 to 128 sliding cycles (a-f).
Lovro Fulanović
Keramični večplastni elementi na osnovi relaksorskih feroelektrikov za izvedljivo elektrokalorično hlajenje
Relaxor-ferroelectric-based ceramic multilayer elements for viable electrocaloric cooling
Mentor in somentor / Supervisor and Co-Supervisor: Barbara Malič, Vid Bobnar
Elektrokalorični (EK) pojav vzbuja izjemno zanimanje zaradi možnosti uporabe v hladilni tehniki. Volumenska keramika na osnovi Pb(Mg1/3Nb2/3)O3 (PMN) in trdne raztopine PMN-PbTiO3 (PT) izkazuje EK spremembe temperature, ki so med največjimi objavljenimi vrednostmi za relaksorske feroelektrike. Lovro Fulanović je ugotovil, da temperatura maksimuma dielektričnosti v odvisnosti od električnega polja predstavlja okvirno zgornjo mejo območja z največjim EK odzivom v diagramu temperatura – električno polje, kar doslej še ni bilo raziskano. Izdelal je večplastne elemente izbranih EK materialov s tehnologijo nalivanja. V prvi objavljeni študiji je ugotovil, da večplastni elementi tudi po milijon ciklih z amplitudo polja ~100 kV/cm skoraj ne izkazujejo zmanjševanja EK odziva, in so primerni kandidati za uporabo v hladilni tehniki.
The electrocaloric (EC) effect attracts a huge interest due to its possible use in cooling applications. Bulk ceramics based on Pb(Mg1/3Nb2/3)O3 (PMN) and PMN-rich PMN-PbTiO3 (PT) solid solutions exhibit EC temperature changes, which are among the highest reported for relaxor ferroelectric oxides. Lovro Fulanović found that the temperature of the peak dielectric permittivity as a function of the electric field roughly represents the upper boundary of the interval with the maximum EC response within the temperature–electric field diagram, which has not been studied earlier. Using tape-casting technology, he fabricated multilayer EC cooling elements. The EC elements showed an almost fatigue-less EC response even after a million cycles at the field amplitude of ~100 kV/cm and are thus suitable candidates for EC cooling applications.
Stabilnost elektrokaloričnega pojava v večplastnih elementih iz svinčevega magnezijevega niobata. a) Normirane vrednosti elektrokalorične temperaturne spremembe (ΔTEK) v odvisnosti od števila ciklov električnega polja. Izseka na sliki prikazujeta temperaturno spremembo (ΔT) prvega in milijontega cikla pod električnim poljem z magnitudo 110 kV/cm. b) 3D model večplastnega elementa. c) Mikrostruktura preseka večplastnega elementa, posneta z vrstičnim elektronskim mikroskopom.
Stability of electrocaloric effect in multilayer elements of lead magnesium niobate. a) Normalized values of electrocaloric temperature changes (ΔTEC) versus number of applied electric filed cycles. First and millionth temperature changes (ΔT) upon electric field of 110 kV/cm are presents in insest. b) 3D model of multilayer elements c) Microstructure of multilayer element cross-section obtained on scanning electron microscope.
Apparao Gudimalla
Stabilizacija topoloških defektov v tekočih kristalih s pomočjo kiralnosti in nanodelcev
Chirality and nanoparticles enforced stabilization of topological defects in liquid crystals
Mentor in somentor / Supervisor and Co-Supervisor: Samo Kralj, Brigita Rožič, Sabu Thomas
Apparao Gudimalla je v disertaciji Stabilizacija topoloških defektov v tekočih kristalih s pomočjo kiralnosti in nanodelcev predstavil svoje teoretične in eksperimentalne raziskave mehanizmov, ki stabilizirajo tekoče kristalne konfiguracije s periodičnimi mrežami linijskih defektov. Osredotočil se je na modre faze in sučno zrnate smektične strukture, ki vsebujejo mreže disklinacij in dislokacij. Preučeval je pogoje, ki omogočajo stabilnost takšnih struktur s poudarkom na vplivom kiralnosti in geometrije nanodelcev, ki se ujamejo v linijske defekte. Periodičnost takšnih struktur potencialno omogoča številne aplikacije, predvsem na področju fotonike in občutljivih merilnih napravah. Poleg tega so takšne strukture zanimive s stališča bazične znanosti. Osnovni gradniki preučevanih struktrur so namreč topološko sorodni skyrmionom in vrtinčnim defektom v superprevodnikih.
Apparao Gudimalla presented in the dissertation Chirality and nanoparticles enforced stabilization of topological defects in liquid crystals his theoretical and experimental studies of stabilization mechanisms of liquid crystal structures exhibiting lattices of line defects. He focused on Blue Phases (BPs) and Twist Grain Boundary (TGB) structures which are characterised by disclinations and dislocations, respectively. He studied conditions stabilizing these structures, focusing on the impact of molecular chirality and geometry of nanoparticles trapped within line defects. Periodicity of such configurations could enable several applications, in particular in photonics and sensing devices. Furthermore, such structures are of interest for fundamental physics. Namely, basic constituents of BPs and TGBs are topologically related to skyrmions and vortices in type II superconductors, respectively.
Shematska predstavitev TGB strukture.
Schematic presentation of the TGB structure.
Nataša Hojnik
Dekontaminacija mikotoksinov z uporabo plazme pri atmosferskem tlaku
Decontamination of mycotoxins with atmospheric pressure plasma
Mentor in somentor / Supervisor and Co-Supervisor: Uroš Cvelbar, Martina Modic
Dr. Nataša Hojnik je v svojih raziskavah uporabljala hladno plazmo pri atmosferskem tlaku (CAP) proizvedeno s površinsko razelektritvijo (»surface barrier discharge« – SBD) molekul zraka, s čim je dosegla razgradnjo različnih vrst mikotoksinov. Preučevala je vpliv CAP na aflatoksin B1 (AFB1) in določila razkrojne poti s štirimi najpomembnejšimi transformacijskimi produkti. Nadaljnji testi toksičnosti so pokazali, da se je strupenost plazemsko obdelanega AFB1 znižala na vrednosti, primerljive z negativno kontrolo. Primerljiva učinkovitost dekontaminacije je bila dosežena tudi pri zrnih koruze, kontaminiranih z AFB1, z zanemarljivim vplivom na površino koruznih zrn. Dr. Hojnik je sodelovala tudi pri raziskovanju novih načinov detekcije mikotoksinov z uporabo visoko zmogljivih plazmonskih substratih, ki temeljijo na plazemsko proizvedenih vertikalnih votlih ogljikovih nanocevkah in omogočajo hitro detekcijo AFB1, ZEN, alternariola, in FB1 pri ppb koncentracijskih vrednostih.
Dr. Nataša Hojnik conducted a comprehensive study on cold atmospheric plasma (CAP) decontamination of mycotoxins, demonstrating that a surface barrier discharge (SBD) plasma system using ambient air can degrade mycotoxins such as aflatoxins (AFs), fumonisins (FBs), trichothecenes, and zearalenone (ZEN). She focused on aflatoxin B1 (AFB1), identifying the reaction pathways in CAP-induced degradation with four major transformation products. Further toxicity tests revealed the reduction of the toxicity of CAP treated AFB1 to levels comparable to the negative control. CAP treatment of AFB1-contaminated corn achieved similar decontamination efficiency, with surface analysis revealing minimal impact on corn kernels. Additionally, Dr. Hojnik contributed to the research on new mycotoxin detection methods using high-performance plasmonic substrates based on plasma-grown vertical hollow carbon nanotubes, enabling rapid detection of AFB1, ZEN, alternariol, and FB1 at ppb concentrations.
Demonstracija degradacije mikotoksina AFB1 s hladno atmosfersko plazmo (CAP).
Demostration of CAP induced complete reduction of mycotoxin AFB1.
Jitka Hreščak
Sinteza in karakterizacija nedopirane in s stroncijem dopirane keramike na osnovi kalijevega natrijevega niobata
Synthesis and characterization of undoped and strontium-doped potassium sodium niobate ceramics
Mentor in somentor / Supervisor and Co-Supervisor: Andreja Benčan Golob, Barbara Malič
Jitka Hreščak je v okviru svojega doktorskega dela raziskala sintezo, strukturo in mikrostrukturo piezoelektrične, okolju prijazne keramike na osnovi nedopiranega in s stroncijem dopiranega alkalijskega niobata. Ugotovila je, da kristalna struktura Nb2O5, kot reagenta za sintezo, pomembno vpliva na potek in s tem na ponovljivost sinteze alkalijskega niobata v trdnem stanju. Prav tako, je s strukturnimi raziskavami razložila mehanizem zmanjšanja zrn v visoko dopirani keramiki, kjer se tvori sekundarna faza, v kateri se segregirajo kationske vrzeli, ki nastanejo kot posledica dopiranja s stroncijem. Hkrati narašča delež nizkokotnih mej med zrni, sledenje pa vpliva na rast zrn in povzroča izrazito zmanjšanje zrn v alkalijskem niobatu.
Jitka Hreščak, as part of her doctoral research, investigated the synthesis, structure, and microstructure of environmentally friendly piezoelectric ceramics based on undoped and strontium-doped alkaline niobate. She found that the crystal structure of Nb2O5, used as a reagent for synthesis, significantly affects the course and thus the reproducibility of the solid-state synthesis of alkaline niobate. Additionally, through structural research, she explained the mechanism of grain size reduction in highly doped ceramics, where a secondary phase forms, in which cationic vacancies segregate as a result of strontium doping. Simultaneously, the proportion of low-angle grain boundaries increases, which affects grain growth and causes a significant reduction in grain size in alkaline niobate.
Slika zmletih delcev Nb2O5, posneto s presevno elektronsko mikroskopijo, z vložki, ki prikazujejo FFT izbranih območij.
Transmission electron microscopy image of the milled Nb2O5 particles with insets showing fast Fourier transforms (FFTs) of the selected areas.
Patricija Hribar Boštjančič
Mehanizmi koloidne stabilizacije magnetnih nanoploščic
Mechanisms for colloidal stabilization of magnetic nanoplatelets
Mentor in somentor / Supervisor and Co-Supervisor: Alenka Mertelj, Darja Lisjak
Edini danes znani sistem feromagnetnih ferofluidov sestavljajo magnetne nanoploščice na osnovi barijevega heksaferita. Dr. Patricija Hribar Boštjančič je raziskovala koloidne sisteme dotičnih nanoploščic. Natančno je ovrednotila in razložila interakcijske mehanizme v alkoholnih disperzijah magnetnih nanoploščic. Določila je pogojne koloidne lastnosti za feromagnetno ureditev nanoploščic in fazno obnašanje sistema magnetne nanoploščice–alkohol–surfaktant. Znanje je uporabila na različnih, do tedaj še neraziskanih, koloidnih sistemih, vključno s tekočimi kristali. S svojimi raziskavami je pomembno prispevala k razvoju prvih tekočih magnetov in feromagnetnih tekočin na sploh.
The only currently known system of ferromagnetic ferrofluids consists of magnetic nanoplates based on barium hexaferrite. Dr. Patricija Hribar Boštjančič researched the colloidal systems of the respective nanoplates. She accurately evaluated and explained the interaction mechanisms in alcoholic dispersions of magnetic nanoplates. She determined the conditional colloidal properties for the ferromagnetic arrangement of the nanoplates and the phase behaviour of the magnetic nanoplate–alcohol–surfactant system. She applied her knowledge to various, previously unexplored colloidal systems, including liquid crystals. With her research, she made a significant contribution to the development of the first liquid magnets and ferromagnetic fluids in general.
Fotografija suspenzije nanopločic barijevega heksaferita s polarizacijskim optičnim mikroskopskom (sredina) s shematskim prikazom orientacije magnetnih nanoploščic v izotropnem črnem področju (levo) in v sivem nematskem področju (desno). Magnetne domene lahko opazimo v nematskem sivem področju.
Polarized optical microscopy photo of the barium hexaferrite nanoplatelets suspension (centre) with a schematic representation of the orientation of magnetic nanoplatelets in the isotropic black region (left) and in the greyish nematic region (right). Magnetic domains can be observed in the nematic grey region.
Uroš Jagodič
Nastanek topoloških defektov v tekoče kristalnih sistemih z netrivialno geometrijo
Formation of topological defects in liquid crystal systems of non-trivial geometry
Mentor in somentor / Supervisor and Co-Supervisor: Igor Muševič
Tekoči kristali so znani po zelo bogatem naboru topoloških pojavov, ki jih v njih lahko raziskujemo. Doktorsko delo dr. Uroša Jagodiča obravnava nastanek topoloških defektov ob polimernem mikrodelcu v obliki Kochove zvezde, ki je potopljen v tekoči kristal, kakor tudi nastanek topoloških defektov preko Kibble-Zurekovega mehanizma pri izredno hitrem ohlajanju tekočega kristala čez fazni prehod v izotropno fazo. V okviru doktorskega dela je dr. Jagodič razvil vrsto novih in izvirnih merskih metod, ki so omogočale opazovanje in karakterizacijo topoloških defektov.
Liquid crystals are well known for very rich topological phenomena that could be explored using optical techniques. The PhD Thesis by Dr. Uroš Jagodič explores the onset of topological defects around a polymer microparticle in the form of a Koch star that is immersed in a nematic liquid crystal, as well as the emergence of topological defects via Kibble-Zurek mechanism during the extremely fast cooling across the phase transition. Dr. Uroš Jagodič developed a number of novel and original techniques that alowed for exploring and analyzing various topological defects in nematic liquid crystals.
Slike prikazujejo fraktalni polimerni mikrodelec v obliki Kochove zvezde, ki je potopljen v nematski tekoči kristal. Posnetek na levi strani je bil narejen pri povišani temperaturi, ko je tekoči kristal izotropna tekočina. Sliki na desni pa kažeta polarizacijski sliki istega delca ko je tekoči kristal v nematski fazi. Nehomogenosti nastanejo zaradi topoloških defektov v tekočem kristalu, ki so lokaliziranih v vogalih in nam omogočajo njihovo štetje in razpoznavanje.
The figure shows a fractal polymer particle in the form of a Koch star that is immersed in a nematic liquid crystal. The panel on the left shows the structure at elevated temperature, where the liquid crystal is isotropic liquid. The panels on the righ show the same particle imaged under polarized light at temperature, where the liquid crystal is in the nematic phase. The inhomogenieties are due to topological defects in the liquid crystal that are trapped at corners and allow for numbering and identification of topologila defects.
Eva Jarc Jovičić
Vloga lipidnih kapljic pri odpornosti rakavih celic na stres
The role of lipid droplets in cancer cell stress resistance
Mentor in somentor / Supervisor and Co-Supervisor: Toni Petan
Dr. Eva Jarc Jovičić je v doktorski disertaciji preučevala vlogo lipidnih kapljic (LK) pri odpornosti rakavih celic na stres. Rezultati te študije so razkrili nove mehanizme, preko katerih LK uravnavajo prenos maščobnih kislin po celici ter prispevajo k zaščiti rakavih celic pred pomanjkanjem hranil in neravnovesjem v homeostazi lipidov. Poleg tega so njene raziskave privedle do pomembnega odkritja o nastanku pro-tumorigenih lipidnih mediatorjev v človeških rakavih celicah. Ugotovila je, da LK delujejo kot osrednji regulatorji maščobnih kislik, ki jih celica uporabi za sintezo teh signalnih molekul. Te ugotovitve so tudi razkrile, da je kanonična pot nastanka lipidnih mediatorjev, ki jo uravnavajo encimi fosfolipaze A2, prav tako odvisna od metabolizma LK, in zato spreminjajo dolgo veljavno paradigmo o nastanku lipidnih mediatorjev.
In her doctoral dissertation, dr. Eva Jarc Jovičić studied the role of lipid droplets (LDs) in the resistance of cancer cells to stress. The results of this study uncovered novel mechanisms mediated by LDs that regulate intracellular fatty acid fluxes, contributing to the protection of cancer cells against nutrient and lipid imbalances. Furthermore, her research provided key insights into the biosynthesis of pro-tumourigenic lipid mediators in human cancer cells by demonstrating that LDs act as central managers of their substrate fatty acids. These findings also shifted the membrane-centric paradigm of lipid mediator synthesis by revealing that the canonical, phospholipase A2-driven pathway of lipid mediator production also depends on LD metabolism.
Lipidi so pomembni za proizvodnjo energije in so prekurzorji eikozanoidov, mitogenih signalnih molekul, ki spodbujajo rast tumorjev. Lipidne kapljice delujejo kot glavni regulatorji prenosa lipidov v celici, s čimer podpirajo tako signalne poti lipidnih mediatorjev kot tudi proizvodnjo energije. Sproščanje lipidov iz lipidnih kapljic vpliva na odpornost rakavih celic na presnovni stres, tako da postaja inhibicija sproščanja zanimiva kot potencialna strategija za zmanjšanje proliferacije rakavih celic in rasti tumorjev.
Lipids are used for energy production during stress or may be converted into eicosanoids, mitogenic signalling molecules which promote tumour growth. Lipid droplets function as major regulators of cellular lipid trafficking, thereby supporting both lipid mediator signalling and energy production. Lipid release from lipid droplets thus controls cancer cell resistance to stress and its inhibition may be a valid strategy to reduce cancer cell proliferation and tumour growth.
Patricia Jovičević-Klug
Mehanizmi in vpliv globokega podhlajevanja na lastnosti jekel
Mechanisms and effect of deep cryogenic treatment on steel properties
Mentor in somentor / Supervisor and Co-Supervisor: Bojan Podgornik
Raziskovalka je raziskala učinek in mehanizme globokega podhljevanja (DCT) pri uporabi na jeklih. Doktorska študija je pokazala, da DCT povzroča mikrostrukturne spremembe, kot so nastajanje bolj finozrnate mikrostrukture, tvorba novih zrn, premikanje dislokacij, sprememba topnosti legirnih atomov, transformacija zaostalega avstenita in bolj intenzivna precipitacija. Spremembe mikrostrukture imajo predvsem pozitivne, lahko pa sprožijo tudi negativne učinke, kar je prikazano v doktorskem delu. V primeru jekel se je izkazalo, da obdelava z DCT zmanjša gostoto defektov v kristalni strukturi in povzroči bolj homogeno izločanje manjših in bolj sferično oblikovanih karbidov, s čimer izboljša predvsem žilavost, odpornost na utrujanje, natezna trdnost in odpornost proti koroziji. Po drugi strani pa poslabša abrazijska obrabna odpornost. Učinek DCT pa je močno odvisen od vrste jekla, njegove obdelave in kemične sestave (zlasti vsebnosti kroma, kobalta in volframa). DCT ima večji učinek na izločanje in porazdelitev karbidov pri jeklih, obogatenih z ogljikom, pri visokih vrednostih kobalta pa se učinek izgine. Rezultati dela so pokazali, da na učinkovitost DCT vplivajo tudi parametri toplotne obdelave (temperatura avstenitizacije in popuščanja). Na splošno so za nizko ogljična jekla in orodna jekla bolj primerne visoke temperature avstenitizacije, medtem ko se pri visokoogljikovih jeklih in hitroreznih jeklih boljša učinkovitost DCT pokaže z znižanjem temperature avstenitizacije in povišanjem temperature popuščanja.
Researcher has investigated the effect and mechanisms of deep cryogenic treatment (DCT) when applied on steels. PhD study showed that DCT induces microstructural changes such as grain size refinement, formation of new grains, movement of dislocations, change of solubility of alloying atoms, alteration of crystal structure and new phase formation. Those changes in the material have positive, but can also trigger negative effects, as proven within this work. In the case of steels DCT treatment has shown to reduce density of defects in crystal structure and results in more homogeneous precipitation of smaller and more spherically shaped carbides, thus improving toughness, fatigue resistance, tensile strength and corrosion resistance, but reducing abrasive wear resistance. However, the effect of DCT strongly depends on the steel type, its processing and chemical composition (especially chromium, cobalt and tungsten). DCT has a higher effect on carbon-enriched steels in relation to carbides precipitation and distribution, and no effect for cobalt rich. Additionally, heat treatment parameters (austenitizing and tempering temperature) also influence DCT effectiveness. In general, for lower carbon steels and tool steels the preferable heat treatment conditions for more intense carbides precipitation and properties improvement are high austenitizing temperatures, whereas for high carbon steels and high speeds steels better DCT effectiveness switches toward lower austenitizing/higher tempering temperatures.
Vpliv globokega podhlajevanja na razvoj karbidov in površinsko kemijo jekel.
Carbides evolution and surface chemistry during deep cryogenic treatment of steel.
Mojca Juteršek
Biotehnološka proizvodnja spolnih feromonov žuželk in infektivni klon virusa krompirja Y kot orodji pri zaščiti rastlin
Biotechnological production of insect sex pheromones and potato virus Y infectious clone as tools in plant protection
Mentor in somentor / Supervisor and Co-Supervisor: Špela Baebler
Uporaba spolnih feromonov žuželk v integriranem varstvu rastlin pred škodljivci omogoča vrstno-specifičen nadzor žuželčjih škodljivcev, kar zmanjšuje uporabo običajnih insekticidov. V tem delu smo prispevali k razvoju rastlinskih tovarn kot trajnostne platforme za proizvodnjo spolnih feromonov žuželk. Iskali smo molekulske mehanizme, ki vodijo do zaustavitve rasti v transgenih rastlinah, ki proizvajajo velike količine spolnih feromonov moljev. Analiza transkripcijskega reprogramiranja je razkrila močan, stresu podoben odziv z znižanjem regulacije anaboličnih procesov in zvišanjem izražanja genov, povezanih s sekundarnim in hormonskim metabolizmom ter stresom. Kot glavni vzrok zastoj v rasti smo določili neravnovesje med signalizacijo giberelinske in jasmonske kisline ter predlagali možne genetske tarče, katerih inaktivacija bi lahko vodila do izboljšane rasti v visoko produktivnih rastlinah.
The application of insect sex pheromones in integrated pest management provides species-specific control of insect pests, reducing the use of conventional insecticides. In this work, we contributed to the development of plant biofactories as a sustainable platform for the production of insect sex pheromones. We characterized molecular perturbation leading to growth arrest in transgenic plants producing high amounts of moth sex pheromones. Analysis of the transcriptional reprogramming revealed a strong, stress-like response with downregulation of anabolic processes and upregulation of genes related to secondary, hormone metabolism, and stress. We identified the crosstalk between gibberellic acid and jasmonic acid signalling as the main culprit for stress-induced growth penalty and proposed possible genetic targets whose inactivation could result in high-producing plant lines with improved growth.
Shematski prikaz biosinteze feromonov moljev v SxP. Encimi, izraženi s transgeni, so prikazani zeleno (AtrD11, HarFAR in EaDAcT), proizvedeni feromoni pa modro (Z11-16:OH-(Z)-11-heksadecen-1-ol, Z11-16: OAc-(Z)-11-heksadecil acetat, Z11-16:Ald-(Z)-11-heksadecilal, ki nastanejo pri pretvorbi z neznano endogeno oksidazo, kot je označeno z „?“).
Schematic representation of lipid-derived moth pheromone biosynthesis in SxP. Transgene-expressed enzymes are shown in green (AtrD11, HarFAR, and EaDAcT) and the produced pheromones in blue (Z11-16:OH—(Z)-11-hexadecen-1-ol, Z11-16: OAc—(Z)-11-hexadecenyl acetate, Z11-16:Ald—(Z)-11-hexadecenal, resulting from conversion with an unknown endogenous oxidase, as denoted by “?”).
Luka Kelhar
Večkomponentna kovinska stekla z vsebnostjo redkih zemelj
Rare earth containing multi-component metallic glasses
Mentor in somentor / Supervisor and Co-Supervisor: Jean-Marie Dubois, Spomenka Kobe
Dr. Luka Kelhar je v doktoratu temeljito preučeval steklasta kovinska stekla, ki vsebujejo cerij in gadolinij. Delo je potekalo s preučevanjem strukture, mikrostrukture, toplotnih in magnetnih lastnosti steklastih zlitin. Proučeval je vlogo dodatkov na strukturne, toplotne in magnetne lastnosti amorfnih zlitin Al-Ce-Fe-Cu. Glavna ugotovitev njegovega dela je bila, da sprememba x pri Al in Ce povzroči nastanek močnih stekel za sestave v bližini x=0,75. Uspešno oviranje kristalizacije izhaja iz dejstva, da slednja sestava leži blizu evtektika v faznem diagramu Al-Ce in ima Tl že pri 900 K. Sestave z več ali manj Ce kažejo kristalne odboje v vzorcih XRD, kar kaže na prisotnost kristalitov v steklasti matrici. Kar zadeva toplotne lastnosti, stekla, bogata s Ce, izkazujejo izredno nizko Tg, ki znaša 350 K za x=1, ki se nato z manjšimi količinami Ce povečuje. Značilna temperatura Tx sledi temperaturi Tg, podoben trend upadanja z več Ce pa je mogoče opaziti tudi pri Tm. Po drugi strani pa se Tl povečuje z večjimi dodatki Ce.
The PhD subject of Dr. Luka Kelhar was a fundamental study of cerium- and gadolinium-containing glassy metallic glasses. The work was conducted by investigating the structure, microstructure, thermal and magnetic properties of the glassy alloys. He studied the role of additions on the structural, thermal and magnetic properties of amorphous Al-Ce-Fe-Cu alloys. The main conclusion of his work was that the variation of x in the case of Al and Ce results in the formation of strong glasses for compositions in the vicinity of x=0.75. Successful hindering of the crystallization stems from the fact that the latter composition lies near the eutectic in the Al-Ce phase diagram and features Tl as low as 900 K. Compositions with more or less Ce exhibit crystalline reflections in the XRD patterns, suggesting the presence of crystallites in the glassy matrix. Regarding the thermal properties, Ce-rich glasses exhibit extremely low Tg, equaling 350 K for x=1, which subsequently increases with lesser amounts of Ce. Characteristic temperature Tx follows that of Tg and a similar, decreasing trend with more Ce can be observed for Tm. Tl, on the other hand, increases with higher additions of Ce.
TEM-preiskava vzorca y=0. a) TEM-posnetek z označenimi kvadratki, ki predstavljajo območja * in **. b) Kombinirani SAED-vzorec eksperimentalnega dela (leva polovica), rotacijskega povprečja [30] (zgornji desni del) in simulirani SAED-vzorec (spodnji desni del) kubične strukture CeO2 (PDF#: 00-004-0593). c) Območje s kristalitom CeO2, označeno z * v delu a. Kvadratni oklepaji označujejo vidno ravnino, vstavek v zgornjem desnem delu pa prikazuje FFT kristalita z označenimi mrežnimi ravninami. d) Amorfna matrika, ki ustreza kvadratnemu območju ** v delu a. Vstavek v zgornjem desnem delu ustreza FFT amorfne matrike.
TEM investigation of the sample y=0. a) TEM micrograph with marked squares representing the areas * and **. b) Combined SAED pattern of the experimental part (left half), the rotational average [30] (upper-right section) and simulated SAED pattern (bottom-right) of cubic CeO2 (PDF#: 00-004-0593) structure. c) Area with a crystallite of CeO2, marked with * in part a. Square brackets outline the view-plane and the inset in the upper right part shows FFT of the crystallite, with labelled lattice planes. d) Amorphous matrix, which corresponds to the square area ** in part a. Inset in the upper right corresponds to the FFT of the amorphous matrix.
Evgeniya Khomyakova
Integration of screen-printed bismuth ferrite thick films onto ceramic and metal substrates
Integracija debelih plasti bizmutovega ferita na keramične in kovinske podlage z metodo sitotiska
Mentor in somentor / Supervisor and Co-Supervisor: Andreja Benčan Golob, Tadej Rojac
Evgeniya Khomyakova je študirala interakcije med debelimi, piezoelektričnimi, plastmi bizmutovega ferita, pripravljenih z metodo sitotiska in različnimi, keramičnimi ali kovinskimi, podlagami. Z razumevanjem in obvladovanjem kemijskih interakcij med plastmi ter poznavanjem termičnih razteznostnih koeficientov je uspešno pripravila več 10 mikrometrov debele plasti bizmutovega ferita s primerno fazno sestavo in mikrostrukturo.
Bizmutov ferit je težje polarizirati, saj zahteva uporabo zadosti visokega zunanjega električnega polja. Kot alternativni način polarizacije debelih plasti bizmutovega ferita, je Evgeniya Khomyakova predlagala sintranje plasti nad feroelektričnim-paraelektričnim faznim prehodom. Dokazala je namreč, da se v plasteh pri ohlajanju preko faznega prehoda pojavi gradient tlačnih napetosti, ki vodi do samopolariziranja debelih plasti. Slednje izkazujejo značilno mikrostrukturo s kolumnarnimi zrni.
Evgeniya Khomyakova studied the interactions between thick, piezoelectric layers of bismuth ferrite, prepared using the screen printing method, and various ceramic or metallic substrates. By understanding and controlling the chemical interactions between the layers and knowing the thermal expansion coefficients, she successfully prepared bismuth ferrite layers, tens of micrometers thick, with the appropriate phase composition and microstructure. Bismuth ferrite is more difficult to polarize as it requires the application of a sufficiently high external electric field. As an alternative method of polarizing thick bismuth ferrite layers, Evgeniya Khomyakova proposed sintering the layers above the ferroelectric-paraelectric phase transition. She demonstrated that during cooling through the phase transition, a gradient of compressive stresses appears in the layers, leading to self-polarization of the thick layers. These layers exhibit a characteristic microstructure with columnar grains.
EBSD slika debele plasti BiFeO3 na Pt elektrodi. Plast vsebuje kolumnarna, naključno usmerjena zrna z jasno vidnimi domenami.
EBSD orientation map of BiFeO3 thick film on Pt electrode. The film possesses columnar, randomly orientated grains with clearly visible domains.
Martin Košiček
Kristalna struktura in fazne transformacije v 1D nanostrukturah
Crystal structure and phase transformations in 1D nanostructures
Mentor in somentor / Supervisor and Co-Supervisor: Uroš Cvelbar, Janez Zavašnik
V svoji doktorski nalogi se je dr. Martin Košiček osredotočil na temeljne procese, ki potekajo med termično in plazemsko podprto rastjo ter faznimi transformacijami nanostruktur kovinskih oksidov, s posebnim poudarkom na nanožicah bakrovega oksida kot modelnega materiala. V začetni fazi raziskav je raziskal in opisal mehanizem termične rasti CuO nanostruktur. Sledilo je optimiziranje pogojev rasti in razvoj strategij za doseganje najmanjšega premera nanostruktur in največjega razmerja med debelino in dolžino nanožic. Sintetizirane nanostrukture so bile nato uporabljene kot modelni material za raziskovanje in razjasnitev mehanizmov ter pojavov, ki se dogajajo na nanoskali med faznimi transformacijami izmenjav kisikovih anionov z žveplovimi. V tem kontekstu je dr. Košiček ugotovil, kako omejevanje količine kovinskih kationov vpliva na mehanizem fazne transformacije. Poleg tega je ovrednotil in opisal razlike v mehanizmih med termičnimi in plazemsko podprtimi faznimi transformacijami.
In his PhD research, Dr. Martin Košiček focused on the fundamental processes occurring during the thermal and plasma-assisted growth and phase transformations of metal oxide nanowires (NWs), with a particular emphasis on copper oxide NWs as a model material. In the initial phase of his PhD, he investigated and described the elusive mechanism of thermal CuO NW growth. This was followed by the optimization of growth conditions and the development of strategies to achieve the smallest NW diameter and the highest NW aspect ratio. The synthesized nanowires were subsequently used as templates to explore and elucidate the mechanisms and phenomena occurring at the nanoscale during oxide-sulfide anion exchange phase transformations. In this context, Dr. Košiček determined how limiting the quantity of metallic cations influences the phase transformation mechanism. Furthermore, he evaluated and described the differences in mechanisms between thermal and plasma-assisted phase transformations.
TEM slika CuO nanožic (levo) z elektronsko difrakcijo (desno), ki kaže na prisotnost centralne dvojčične meje. Ta defekt je glavni razlog za rast nanožic v eni smeri.
TEM micrograph of CuO NWs (left) with selected area electron diffraction pattern (right) showing presence of a central twin boundary. Formation of this defect is the main reason why CuO NWs grow unidirectionally.
Mateja Košir
Termoelektrični materiali na osnovi ZnO
Thermoelectric materials based on ZnO
Mentor in somentor / Supervisor and Co-Supervisor: Slavko Bernik
Termoelektrični (TE) materiali omogočajo direktno pretvorbo toploto v električno energijo, kar daje edinstveno možnost za izkoriščanje odpadne toplote. Za uporabo pri visokih temperaturah bi bili zlasti primerni oksidni TE materiali, ki pa bi morali imeti bistveno boljše TE lastnosti od sedanjih. Homologne faze ZnkIn2Ok+3 dajejo velike možnosti za izboljšanje TE lastnosti keramike tipa n na osnovi ZnO. V doktorski disertaciji z naslovom Termoelektrični materiali na osnovi ZnO je Mateja Košir pojasnila mehanizem nastajanja homolognih faz ZnkIn2Ok+3 in njegov vpliv na sintranje, rast zrn in TE lastnosti keramike ZnO-In2O3. V primeru dopiranja z Al je ugotovila, da se vgrajuje na obe primarni mesti In v homologni fazi Zn5In2O8, kar vpliva na strukturo faze, koncentracijo in mobilnost nosilcev naboja in posledično njene TE lastnosti. Pokazala je tudi, da mikrovalovno sintranje omogoča hitrejšo in energijsko učinkovito pripravo keramike ZnO-In2O3 ob vsaj 70% manjši porabi energije kot klasično sintranje.
Thermoelectric (TE) materials enable direct conversion of heat into electrical energy, which provides a unique opportunity for utilization of waste heat. For use at high temperatures, oxide TE materials would be particularly suitable, but they should have significantly better TE properties than the current ones. Homologous phases ZnkIn2Ok+3 provide great opportunities for improving the TE properties of n-type ZnO ceramics. In her doctoral dissertation entitled Thermoelectric materials based on ZnO, Mateja Košir explained the formation mechanism of homologous phases ZnkIn2Ok+3 and its influence on sintering, grain growth and TE properties of ZnO-In2O3 ceramics. In the case of doping with Al, she found that it incorporates into both primary In sites in the homologous phase Zn5In2O8, which affects their structure, concentration and mobility of charge carriers and, consequently, its TE properties. She also showed that microwave sintering enables faster and energy efficient preparation of ZnO-In2O3 ceramics with at least 70% less energy consumption than conventional sintering.
HR HAADF STEM in EDXS analize homologne faze Zn5In2O8 dopirane z Al so dokončno potrdile, da Al zamenjuje In na obeh primarnih mestih v homologni fazi in sicer oktaederska mesta v bazalnih ravninah inverznih mej (IBs) in trigonalna bi-piramidalna mesta v cik-cak inverznih mejah (IBs).
HR HAADF STEM and EDXS analysis of the Al-doped Zn5In2O8 homologous phase finally confirmed that Al substitutes for In on both the primary sites in the homologous phase, the octahedral sites in the basal-plane inversion boundaries (IBs) and the trigonal bi-pyramidal sites in the zig-zag inversion boundaries (IBs).
Karla Kosmač
Vpliv aditivov na kompleksno viskoznost kompozitnega sistema Nd-Fe-B s polifenilen sulfidom (PPS)
Influence of additives on complex viscosity of Nd-Fe-B magnet material bonded with polyphenylene sulfide (PPS)
Mentor in somentor / Supervisor and Co-Supervisor: Spomenka Kobe, Boris Saje
V študiji so bili na podlagi treh različnih funkcionalnih dodatkov razviti trije različni magnetni materiali Nd-Fe-B z vezanim PPS. Glavni cilj je bil določiti merilno metodo, ki bi omogočila odkrivanje strukturnih razlik med materiali med razvojem različnih konstitucij materialov. Merilno metodo je določila na rotacijskem reometru za izotropni magnetni prah Nd-Fe-B, vezan s termoplastičnim polimerom PPS (polifenilensulfid).
S kompleksnimi reološkimi meritvami je opisala obnašanje materiala med postopkom ekstrudiranja pri želenih strižnih hitrostih. Opazovala je učinke dodatkov na magnetne, mehanske in reološke lastnosti materialov. V industrijskem merilu je dosegla odlične rezultate: gostota 5,12 g/cm3, remanenca (Br) 528 mT, koercitivnost (Hcj) 820 kA/m, največji energijski produkt (BH)max 49 kJ/m3 in srednja upogibna trdnost pri pretrgu 131,8 N. Njeno odlično delo predstavlja tako pomemben prispevek k temeljnemu znanju kot tudi izjemno pomemben aplikativni dosežek, kar dokazuje tudi nagrada Gospodarske zbornice Slovenije za magistrsko delo.
In the study three different Nd-Fe-B with PPS-bonded magnet materials were developed based on three different functional additives. The main objective was to determine a measurement method that would allow to detect material structural differences during the development of different material constitutions. She determined the measurement method on a rotational rheometer for isotropic Nd-Fe-B magnetic powder bonded with PPS (polyphenylene sulphide) thermoplastic polymer. She used complex rheological measurements to describe the behaviour of the material during the extrusion process at desired shear rates. She observed the effects of the additives on the magnetic, mechanical, and rheological properties of the materials. On an industrial scale, she achieved excellent results: density 5.12 g/cm3, remanence (Br) 528 mT, coercivity (Hcj) 820 kA/m, maximum energy product (BH)max 49 kJ/m3, and mean flexural strength at break 131.8 N. Her excellent work represents both a significant contribution to basic knowledge and an extremely important applied achievement, as evidenced by the award for the thesis from the Slovenian Chamber of Commerce and Industry.
Ekstruzija mešanice Nd-Fe-B prahove z dodatki – industrijski postopek.
Extrusion processing of mixture of Nd-Fe-B powders and additives on an industrial scale: a) schematic, b) production equipment.
Nina Kostevšek
Sinteza hibridnih nanodelcev s kombiniranim magneto-fototermičnim efektom za medicinske aplikacije
Synthesis of hybrid nanoparticles with combined magneto-photothermal effect for medical applications
Mentor in somentor / Supervisor and Co-Supervisor: Kristina Žužek
Splošni koncept disertacije in znanstveni cilj sta bila razviti teranostični sistem večmodalnih nanodelcev na osnovi sistema FePt/SiO2/Au za diagnosticiranje in zdravljenje in raka. Sistem hkrati omogoča tako diagnosticiranje preko magnetne resonance (MR), ter tudi terapijo preko magnetne manipulacije in toplotne stimulacije. Dr. Kostevšek je predlagala kemijske sintezne poti za dosego končnih lastnosti sistema, tj. visoko magnetizacijo, dolgo skrajševanje časa T2 za MR, SiO2 prevleko za dosego biokompatibilnosti in funkcionalizacijo z Au za dosego fototermičnega učinka. Slednji je bil izražen v zahtevanem drugem biološkem oknu pri približno 800 nm. Poleg tega je doktorantka uspešno prikazala tudi princip delovanja sistema in vitro. Delo je bilo objavljeno v Nanoscale IF= 7,23.
The overall concept and scientific goal of the dissertation were to develop a theranostic system of multimodal nanoparticles based on the FePt/SiO2/Au system for cancer diagnosis and treatment. The developed system simultaneously enables diagnosis through magnetic resonance (MR) and therapy via magnetic manipulation and thermal stimulation. Dr. Kostevšek proposed chemical synthesis routes to achieve the final properties of the system, namely high magnetization, long T2 shortening time for MRI, SiO2 coating for biocompatibility, and Au functionalization to achieve the photothermal effect. The latter was expressed in the required second biological window at approximately 800 nm. Additionally, the doctoral candidate successfully demonstrated the proof-of-concept of the system in vitro. The work was published in Nanoscale with an IF of 7.23.
Shematski prikaz teranostičenga sistema na osnovi nanodelcev FePt/SiO2/Au za zdravljenje raka ter princip delovanja.
Schematics of the FePt/SiO2/Au nanoparticles theranostic system for cancer treatment proof of principle.
Ana Kračun
Dodajanje in vpliv nanodelcev pri izdelavi jekla s postopkom litja
Addition and influence of nano-particles in the manufacture of cast steel
Mentor in somentor / Supervisor and Co-Supervisor: Bojan Podgornik
V svojem doktorskem delu se je raziskovalka osredotočila na raziskavo možnosti uporabe različnih nano-delcev kot armaturnih elementov v jekleni matrici dodanih pri postopku konvencionalnega litja kovin, ter kako ti nano-delci, vključujoč tip, velikost in koncentracijo, vplivajo na homogenost in razvoj mikrostrukture ter mehanske in protiobrabne lastnosti jekla, predvsem trdoto, žilavost, natezno trdnost, odpornost na utrujanje ter visoko temperaturno odpornost na lezenje. S poglobljenim eksperimentalnim delom, podprtim s termodinamskimi simulacijami je dokazala, da je mogoče tudi s konvencionalnim postopkom litja izdelati nano-kompozit z armirano jekleno matrico in homogeno porazdelitvijo nanodelcev, ki vodi do občutno boljših lastnosti nerjavnega jekla. Ob tem je ugotovila, da stopnja izboljšanje lastnosti zavisi od tipa, velikosti in porazdelitve nano-delcev, pri čemer najboljše rezultate dosegamo z dodajanjem do 50 nm velikih nano-delcev TiB2 in Y2O3 v koncentraciji do 0,5%, ter uporabo disperzijskega sredstva za čim bolj homogeno porazdelitev nano-delcev v jekleni matrici.
In her doctoral work, the researcher focused on the investigation of the possibility of using different nanoparticles as reinforcing elements in the steel matrix added during the conventional metal casting process, and how these nanoparticles, including type, size and concentration, affect the homogeneity and development of the microstructure and mechanical and anti-wear properties of steel, especially hardness, toughness, tensile strength, fatigue resistance and high temperature creep resistance. Through in-depth experimental work, supported by thermodynamic simulations, she proved that it is possible to produce a nano-composite with a reinforced steel matrix and a homogeneous distribution of nanoparticles, which leads to significantly better properties of stainless steel, even with a conventional casting process. At the same time, she found that the degree of improvement in properties depends on the type, size and distribution of nanoparticles, whereby the best results are achieved by adding up to 50 nm nano-particles TiB2 and Y2O3 in a concentration of up to 0.5%, and using a dispersion agent for as homogeneous a distribution of nano-particles in the steel matrix as possible.
Uspešna inkorporacija nano-delcev v jekleno matrico s klasičnim postopkom litja in doseganje občutno izboljšanih mehanskih in triboloških lastnosti jekla.
Successful incorporation of nano-particles into the steel matrix using the classic casting process and achieving significantly improved mechanical and tribological properties of steel.
Lovro Kramer
Tarčenje cisteinskih katepsinov v vnetnih obolenjih
Targeting cysteine cathepsins in inflammatory diseases
Mentor in somentor / Supervisor and Co-Supervisor: Boris Turk
Cisteinski katepsini pogosto prispevajo k napredovanju raka zaradi njihovega prekomernega izražanja v tumorskem mikrookolju, zaradi česar so privlačne tarče za neinvazivno diagnostično slikanje. V svoji doktorski disertaciji “Tarčenje cisteinskih katepsinov v vnetnih obolenjih” je Lovro Kramer tarčil tumorski katepsin B z načrtovanimi proteini iz ankirinskih ponovitev (DARPini). Selektivni DARPin 8h6 je inhibiral katepsin B s pikomolarno afiniteto (Ki = 35 pM), pri čemer se je vezal na mesto z nizko strukturno ohranjenostjo v katepsinih, kar smo potrdili s kristalno strukturo kompleksa. DARPin 8h6 je zaviral aktivnost katepsina B v tumorjih ex vivo, poleg tega pa smo DARPin uspešno uporabili za in vivo optično slikanje v mišjih modelih raka dojke, kjer je bil katepsin B vezan na celično membrano tumorskih ali stromalnih celic, ali pa v zunajceličnem okolju. Ta pristop potrjuje, da je katepsin B obetavna tarča za diagnostiko in teranostiko pri raku in ostalih vnetnih boleznih.
Cysteine cathepsins often contribute to cancer progression due to their overexpression in the tumour microenvironment and therefore present attractive targets for non-invasive diagnostic imaging. In his doctoral work “Targeting cysteine cathepsins in inflammatory diseases” Lovro Kramer targeted tumour-associated cathepsin B using designed ankyrin repeat proteins (DARPins). The selective DARPin 8h6 inhibited cathepsin B with picomolar affinity (Ki = 35 pM) by binding to a site with low structural conservation in cathepsins, as revealed by the X-ray structure of the complex. DARPin 8h6 blocked cathepsin B activity in tumours ex vivo and was successfully applied in in vivo optical imaging in two mouse breast cancer models, in which cathepsin B was bound to the cell membrane or secreted to the extracellular milieu by tumour and stromal cells. The approach validated cathepsin B as a promising diagnostic and theranostic target in cancer and other inflammation-associated diseases.
Inovativni pristop na osnovi DARPin-a, ki se selektivno veže na katepsin B, je omogočil učinkovito in vivo slikanje tumorjev in validiral katepsin B kot obetavno tarča za diagnostiko in teranostiko pri raku.
Innovative approach based on a selective cathepsin B-binding DARPin enables efficient in vivo imaging of tumors and validates cathepsin B as a promising diagnostic and theranostic target in cancer.
Maja Križnik
Vloga kratkih nekodirajočih RNA pri imunskem odgovoru rastlin krompirja na okužbo z virusom krompirja Y
The regulatory role of small RNAs in immune responses of Solanum tuberosum to Potato virus Y infection
Mentor in somentor / Supervisor and Co-Supervisor: Kristina Gruden, Špela Baebler
Pokazali smo, da so male RNA (sRNA) pomembna komponenta v rastlinskem imunskem signalnem omrežju, ki nadzoruje vzpostavitev tolerantnega odziva krompirja (cv. Désirée) na virus (krompirjev virus Y). V okviru študije je bilo pripravljeno regulatiorno omrežje sRNA, ki povezuje sRNA in njihove tarče ter s tem fiziološke procese. To je v kombinaciji z eksperimentalnimi podatki omogočilo razjasnitev regulatornega vezja, ki je bilo funkcionalno dokazano, in tako prispevalo k razumevanju odzivov rastlin v agroekosistemih.
We showed that small RNAs (sRNAs) are an important component within the plant immune signalling network that controlls the establishment of a tolerant response of potato (cv. Désirée) to the virus (potato virus Y). During the work, a sRNA regulatory network was prepared, that connected sRNAs and their targets, and by that to physiological processes. This, in combination with experimental data, allowed the elucidation of a regulatory circuit, which was functionally proven, thus contributing to our understanding of plant responses in agroecosystems.
Novo regulatorno omrežje, v katerem male RNA zavirajo biosintezo in signalizacijo giberelina v tolerantnih rastlinah, kar pojasnjuje ravnovesje med boleznijo in rastjo, ki ga opazimo pri tolerantnem odzivu.
A novel regulatory circuit where small RNAs repress gibberellin biosynthesis and signalling in the tolerant plants, explaining the balance between disease and development observed in the tolerant response.
Pavlo Kurioz
Topološki defekti v frustriranih nematikih
Topological defects in frustrated nematics
Mentor in somentor / Supervisor and Co-Supervisor: Samo Kralj, Milan Ambrožič
Kandidatove raziskave so bile usmerjene k razumevanju splošnih mehanizmov nastanka, stabilizacije in kontroliranja singularnih in nesingularnih topoloških ekscitacij. Kot tesni sistem je izbral nematične tekoče kristale. Obravnaval je konfiguracije, ki jim je vsilil močne topološke naboje, prikazal je številne elektrostatske analogije, analiziral je vpliv zunanje ukrivljenosti na število in položaj topoloških defektov (TD), preučeval je interakcije med ustreznimi nanodelci in TD in dinamično generirane topološke ekscitacije v plan-paralelnih celicah.
His investigations were directed towards an understanding of general mechanisms to generate, stabilize and manipulate singular and nonsingular topological excitations in axial fields. As laboratory test ground he used nematic liquid crystals. In particular, he considered configurations to which he enforced relatively large topological charges, he demonstrated new electrostatic analogies, he analyzed the impact of extrinsic curvature on number and position of topological defects (TDs), he study interactions between appropriate nanoparticles and TDs, and he analyzed diverse dynamically generated topological excitations in plane-parallel cells.
Dvoosna struktura površinskega točkovnega defekta.
Biaxial structure of surface boojum.
Denis Kutnjak
Odkrivanje in študij raznolikosti virusov s sekvenciranjem naslednje generacije
Discovery and diversity studies of viruses with next generation sequencing
Mentor in somentor / Supervisor and Co-Supervisor: Maja Ravnikar
V raziskavi, ki je bila objavljena v reviji Journal of Virology, se je Denis Kutnjak posvetil študiju eksperimentalne evolucije virusa Y krompirja na genotipih krompirja, ki so različno občutljivi na virus. S pomočjo visoko zmogljivega sekvenciranja (HTS) malih RNA inpopulacijsko genetskih analiz je uspel zaznati različne selekcijske pritiske, ki delujejo navirusne populacije v različno občutljivih genotipih krompirja. Rezultati njegovega raziskovalnega dela so pomembni za razumevanje raznolikosti in evolucije virusov, še zlasti pa predstavljajo pomemben prispevek na področju odkrivanja novih virusov in študija raznolikosti virusnih populacij znotraj gostiteljev. Raziskovalno delo je prispevalo tudi k odkritju novega rabdovirusa pri otrocih, ki je bil do tedaj odkrit le pri netopirjih in za karakterizacijo vakcin in virusnih terapevtikov. Pridobljena znanja je uporabil v okviru diagnostičnega laboratorija in Evropskega referenčnega laboratorija, ki deluje na NIB z izdelavo delotoka za analizo podatkov visoko zmogljivega sekvenciranja za odkrivanje in karakterizacijo virusov v vzorcih rastlin in hrane.
In a study published in the Journal of Virology, Denis Kutnjak devoted himself to studying the experimental evolution of potato Y virus on potato genotypes that are differently susceptible to the virus. Through high-performance sequencing (HTS) of small RNA and population genetic analysis has been able to detect various selection pressures acting on viral populations in potato genotypes of varying susceptibility. The results of his research work are important for understanding diversity and virus evolution, and in particular make an important contribution in the field of detection of new viruses and study of the diversity of viral populations within hosts and for the characterisation of vaccines and viral therapeutics. He applied the acquired knowledge within the framework of the diagnostic laboratory and the European Reference Laboratory, which operates at the NIB by producing a workflow for the analysis of high-performance sequencing data for the detection and characterization of viruses in plant and food samples.
Krožna predstavitev genoma PVY z grafiranimi frekvencami SNP v skupinah sRNA in VP, ki ustrezajo rezultatom aminokislinske substitucije BLOSUM62, in rekombinacijskimi točkami, ki jih je zaznal ViReMa (samo za skupino VP).
Circular representation of PVY genome with plotted frequencies of SNPs in the sRNA and VP pools, corresponding BLOSUM62 amino acid substitution scores, and recombination points detected by ViReMa (only for the VP pool).
Tjaša Lukan
Časovnoprostorska študija preobčutljivostnega odgovora krompirja na okužbo s krompirjevim virusom Y
Spatiotemporal study of potato hypersensitive response-conferred resistance to Potato virus Y
Mentor in somentor / Supervisor and Co-Supervisor: Kristina Gruden, Špela Baebler
Preučevali smo odziv imunskega omrežja pri odpornosti, ki jo povzroča preobčutljivost (HR) v interakciji krompirja in virusa. Analizirali smo procese v območju celične smrti in okoliškem tkivu na ultrastrukturni, biokemični in genski ravni izražanja, da bi razkrili prostorsko-časovno regulacijo imunskega odziva. Z natančnim vzorčenjem smo pokazali, da je transkripcijski odziv v območju celične smrti in okoliškem tkivu odvisen od salicilne kisline (SA). Vzgojili smo transgene krompirjeve rastline z utišanim genom RBOHD, da bi preučili njegovo vlogo pri odpornosti. Pri teh rastlinah je funkcionalnost odziva na odpornost motena, analiza transkriptoma pa je pokazala prostorsko deregulacijo UDP-glukoziltransferaze, kar vodi v moteno prostorsko kopičenje SA. Tako smo dokazali, da je RBOHD potreben za prostorsko kopičenje SA in nasprotno, da je RBOHD pod transkripcijsko regulacijo SA.
We studied the immunity network response in hypersensitive response (HR)-conferred resistance in potato-virus interaction. We analyzed the processes in the cell death zone and surrounding tissue on the ultrastructural, biochemical and gene expression levels to reveal the spatiotemporal regulation of the immune response. Using a precise sampling we showed that the transcriptional response in the cell death zone and surrounding tissue is dependent on salicylic acid (SA). We produced transgenic potato plants with silenced RBOHD to study its role in resistance. In those plants, the functionality of the resistance response is perturbed, while transcriptome analysis showed spatial deregulation of UDP‐glucosyltransferase, leading to perturbed spatial accumulation of SA. We thus show that RBOHD is required for the spatial accumulation of SA, and conversely, RBOHD is under the transcriptional regulation of SA.
Prostorsko-časovna analiza akumulacije virusa (PVY) in maskerskega gena za obrambni odziv PR1B v območju celične smrti (A) in okoliškem tkivu (B-D, zgoraj). Shema medsebojne povezanosti sinteze salicilne kisline (SA) in RBOHD prek regulatorne povratne zanke v imunskem odzivu (spodaj).
Spatiotemporal analysis of virus accumulation (PVY) and defence response marker gene PR1B in the cell death zone (A) and surrounding tissue (B-D, top). The scheme of salicylic acid (SA) synthesis and RBOHD interconnectedness through a regulatory feedback loop in immunity response (bottom).
Ivan Madan
Fotoinducirani neravnovesni fazni prehodi v kupratnih superprevodnikih
Photoinduced non-equilibrium phase transitions in cuprate superconductors
Mentor in somentor / Supervisor and Co-Supervisor: Dragan Mihailović
Raziskave nadzora in manipulacije kvantnih stanj, kot je superprevodnost, na različnih časovnih skalah, ki jih je v svojem delu opisal Ivan Madan, so privedle do številnih pomembnih odkritij, povezanih z dinamiko superprevodnih stanj v različnih visokotemperaturnih superprevodnikih. Zlasti meritve obnovitve vrzeli v različnih superprevodnikih z ultrakratkimi laserskimi sunki pod različnimi pogoji in laserski nadzor kvantnih centrov faznega zdrsa v superprevodnih nanovodnikih so privedle do vrste objav v Nature Communications, Science Advances, Physical Review in Scientific reports. Raziskave dinamike superprevodniškega stanja pomembno vplivajo na poskuse razkritja fotoinduciranega superprevodniškega stanja, medtem ko nadzor faznega zdrsa razkriva novo pot za nadzor kvantnih impulzov superprevodniškega toka v napravah za kvantno računalništvo.
Investigations of control and manipulation of quantum states such as superconductivity on different timescales described in the thesis by Ivan Madan have led to a number of important discoveries related to the dynamics of superconducting states in various high-temperature superconductors. In particular, measurements of the gap recovery in different photoexcited superconductors under different conditions and the laser control of quantum phase slip centers in superconducting nanowires led to a series of publications in Nature Communications, Science Advances, Physical Review and Scientific reports. The investigations of superconducting state dynamics have important bearing on attempts to reveal a photoinduced superconducting state, while phase slip control reveals a novel route to control superconducting flux quantum pulses in quantum computing devices.
Preklapljanje kvantnih faznih zdrsnih centrov v tankih nanožicah MoN z uporabo ultrakratkih svetlobnih pulzov.
Switching quantum phase slip centers in thin MoN nanowires using ultrashort light pulses.
Neelakandan Marath Santhosh
Plazemsko omogočeno oblikovanje hibridnih ogljikovih nanostruktur za shranjevanje energije
Plasma-enabled design of hybrid carbon nanostructures for energy storage applications
Mentor in somentor / Supervisor and Co-Supervisor: Uroš Cvelbar, Gregor Filipič
V sistematični raziskavi je Dr. N. M. Santosh (Mentor: Prof. Dr. Uroš Cvelbar in somentor: Dr. Gregor Filipič) razvil hitro in učinkovito plazemsko podprto metodo za razvoj hibridnih nanostrukturiranih elektrodnih materialov za izboljšanje zmožnosti shranjevanja litijevih ionov v baterijah. Zasnovana elektroda je bila sestavljena iz ogljikovih nanocevk (VCNT) in nikljevega sulfida (Ni3S2) z morfologijo, ki spominja na brokoli. S ciljanjem na razvoj novih energetskih materialov naslednje generacije, razvit elektrodni material presega zmogljivosti večine podobnih elektrodnih materialov z doseganjem ultra-visoke specifične kapacitete in izvrstne dolgoročne stabilnosti pri shranjevanju litijevih ionov. Rezultati nakazujejo, da prevodna narava in nastanek defektov med elektrokemijskim testiranjem dodatno izboljšajo celotno zmogljivost materiala. Ker so ultra-zmogljivi energijski materiali kritični pri razvoju alternativnih energijskih virov, bi lahko izsledki te raziskave zagotovile pot k razvoju nizkocenovnih baterijskih materialov naslednje generacije.
In a systematic study, Dr N. M. Santhosh (Supervisor: Prof. Uroš Cvelbar and Co-supervisor: Gregor Filipič) developed a plasma-assisted fast and feasible method to develop hybrid nanostructured electrode materials to advance the Li-ion storage capabilities of batteries. The electrode architecture comprised carbon nanotube (VCNT) and nickel sulfide (Ni3S2) with a broccoli-like morphology. Targeting the next-generation energy materials, the designed electrode material outperforms most similar electrode materials by achieving ultra-high specific capacity and excellent long-term stability for Li-ion storage. The obtained results indicated that the conductive nature and formation of defects during the electrochemical testing enhance the total performance of the material. Considering ultra-high-performing energy materials are critical for designing alternative energy sources, the findings of this research could provide a path towards designing next-generation battery materials at a low cost.
Shema strukture hibridne elektrode Ni3S2@VCNT in poti difuzije Li-ionov med elektrokemijsko reakcijo. TEM slika (vložek) hibridne elektrode razkriva brokoliju podobno morfologijo s polikristaliničnimi značilnostmi materiala.
The schematic of Ni3S2@VCNT hybrid electrode structure and the Li-ion diffusion pathways during the electrochemical reaction. The TEM micrograph (inset) of the hybrid electrode reveals the broccoli-like morphology with polycrystalline features of the material.
Živa Marinko
Sinteza in lastnosti anodno oksidiranih filmov na kovinskem titanu za fotokatalitske aplikacij
Synthesis and properties of anodically oxidised films on metal titanium substrate for photocatalytic applications
Mentor in somentor / Supervisor and Co-Supervisor: Miran Čeh
Dr. Živa Marinko je preučevala procese anodne oksidacije različnih kovinskih sistemov z namenom pridobiti tanke polprevodne oksidne filme na kovinskih substratih za fotokatalitsko, fotoelektrokatalitsko in elektrokatalitsko razgradnjo organskih snovi (POP) v odpadnih vodah in v zraku. Med svojim delom se je tako predvsem osredotočila na anodno oksidacijo kovinskega titana v različnih morfoloških oblikah (folija, žica) in sicer v nevodnih medijih na osnovi etilen glikola. Pri svojem delu se je dr. Živa Marinko predvsem osredotočila na optimizacijo eksperimentalnih pogojev anodne oksidacije (V, t, sestava elektrolita) z namenom pridobiti TiO2 nanocevke na površini substrata z visoko fotokatalitično aktivnostjo, kar je sproti preverjala z razgradnjo modelne organske spojine kafeina.
Dr. Živa Marinko studied anodic oxidation processes of various metal systems with the aim of obtaining thin semiconducting oxide films on metal substrates for photocatalytic, photoelectrocatalytic and electrocatalytic decomposition of organic substances (POP) in waste water and in air. During her work, she mainly focused on the anodic oxidation process of metallic titanium in various morphological forms (foil, wire) in non-aqueous media based on ethylene glycol. In her work, dr. Živa Marinko mainly focused on the optimization of the experimental conditions of anodic oxidation (V, t, composition of the electrolyte) with the aim of obtaining highly-efficient TiO2 nanotubes on the surface of the substrate with high photocatalytic activity. This was readily confirmed by degradations studies of model organic compound caffeine.
Fotokatalitska aktivnost štirih vzorcev TiO2 NT. (A) razgradnja kofeina in (B) meritve fotoluminiscence.
Photocatalytic activity of four TiO2 NTs samples. Main aspects of this section’s research are presented. (A) Caffeine degradation and (B) photoluminescence measurements.
Aleksander Matavž
Brizgalno tiskanje in strukturno pogojene lastnosti feroelektričnih tankoplastnih struktur
Inkjet printing and structure property relations of ferroelectric thin-film structures
Mentor in somentor / Supervisor and Co-Supervisor: Vid Bobnar, Barbara Malič
Brizgalno tiskanje je edinstvena alternativa konvencionalnim metodam oblikovanja funkcionalnih struktur. V doktorski disertaciji Brizgalno tiskanje in strukturno pogojene lastnosti feroelektričnih tankoplastnih struktur dr. Aleksander Matavž naslavlja osnovne izzive, povezane s tiskanjem črnil na osnovi raztopin na neporozne podlage. Med najopaznejšimi dosežki je razvoj metode za konformno nanašanje funkcionalnih oksidnih plasti z izbranimi dimenzijami, obliko, debelino plasti in njihovim zaporedjem. Za potrditev koncepta je izdelal večplastne feroelektrične kondenzatorje s konfiguracijo, nedosegljivo s konvencionalnimi metodami nanosa. Večplastni kondenzatorji so izkazali funkcionalni odziv, ki je bistveno presegal naprave z eno plastjo.
The additive manufacturing of functional structures by inkjet printing offers a unique and powerful alternative to conventional top-down patterning methods. The doctoral dissertation Inkjet printing and structure property relations of ferroelectric thin-film structures of Dr. Aleksander Matavž addresses fundamental challenges related to the printing of solution-based inks on non-porous substrates. Among most notable achievements is the development of a method for conformal stacking of functional oxide layers according to the user-defined geometry, sequence arrangement, and layer thickness. Multilayer proof-of-the-concept devices had the configuration unattainable by conventional processing techniques and exhibited functional response significantly exceeding single-layer devices.
Fotografije zaporedno natisnjenih LNO in PZT ter sheme pripadajočih prerezov. Izmenično brizgalno tiskanje je bilo uporabljeno za izdelavo enoplastnih (SLC) in večplastnih (MLC) kondenzatorjev z odličnimi funkcionalnimi lastnostmi.
Optical images of sequentially printed LNO and PZT and a schematic of corresponding cross section. Alternating stacking was used to fabricate a single layer (SLC) and multilayer (MLC) capacitors with excellent functional properties.
Léonard Jean Moriau
Nanokompoziti kot elektrokatalizatorji za uporabo v reakcijah v gorivni celici in elektrolizatorju
Nanocomposites as electrocatalysts for the use in fuel cell and electrolyzer reactions
Mentor in somentor / Supervisor and Co-Supervisor: Nejc Hodnik
V svoji doktorski disertaciji Nanokompoziti kot elektrokatalizatorji za uporabo v reakcijah gorivnih celic in elektrolizatorjev je dr. Leonard Moriau obravnaval aktivnost in stabilnost elektrokatalizatorjev za vodikovo ekonomijo. Njegove raziskave so bile osredotočene na i) stabilnost Pt-zlitin za reakcijo redukcije kisika, ii) odkritje primernega materiala za podporo iridija za reakcijo tvorbe kisika in iii) sintezo cenejšega, učinkovitejšega bifunkcionalnega katalizatorja. Rezultat disertacije je bila predstavitev novega pristopa k preučevanju elektrokatalizatorjev, ki združuje napredno karakterizacijo, kot sta TEM na identični lokaciji in pretočna elektrokemijska celica sklopljena z ICP-MS. Predstavljen je bil tudi nov nosilec (TiON) za iridijev katalizator in sintetiziran je bil nov, učinkovitejši bifunkcionalni katalizator. Njegovo delo je vodilo do 15 objav v prestižnih revijah (IF od 4,2 do 29,7) in je bilo citirano več kot 400-krat.
In his doctoral dissertation Nanocomposites as Electrocatalysts for the use in Fuel Cell and Electrolyser Reactions, Dr. Leonard Moriau worked on the activity and stability of electrocatalysts for the hydrogen economy. His research was focus on i) the stability of Pt-alloys for oxygen reduction reaction ii) the discovery of a suitable material to support iridium for oxygen evolution reaction and iii) the synthesis of a cheaper, more efficient, bifunctional catalyst for both reactions. The thesis resulted in the presentation of a new approach to study electrocatalysts combining advanced characteristics techniques like identical location TEM and online inductively coupled plasma – mass spectrometry. A new support (TiON) was also presented for iridium catalyst and, a new, more efficient bifunctional catalysts was synthesized that works for both fuel cell and electrolyser. His work led to 15 publications in prestigious journal (IF from 4.2 to 29.7) and was cited more than 400 times.
Shema dvofunkcijskega katalizatorja za reakciji redukcije in tvorbe kisika. Kovinski nanodelci (PtCu v rumeni barvi, Ir v modri in Ru v rdeči) so podprti s podlago, ki jo sestavlja list grafena, prekrit s TiON.
Scheme of a bifunctional catalyst for the oxygen reduction and the oxygen evolution reactions. Metal nanoparticles (PtCu in yellow, Ir in blue and Ru in red) are supported by a support composed of a graphene sheet covered by TiON.
Maruša Mrak
Vpliv temperature na hidratacijo belitno-kalcijevo sulfoaluminatnih cementov
Influence of temperature on the hydration of belite-calcium sulfoaluminate cements
Mentor in somentor / Supervisor and Co-Supervisor: Sabina Dolenec, Nina Daneu
Razumevanje hidratacije cementa je ključnega pomena, saj cement predstavlja enega najpomembnejših gradbenih materialov. Pri proizvodnji cementa se sprostijo velike količine CO2, ki predstavljajo kar 8 % svetovnih antropogenih emisij CO2. Eden izmed pristopov k zniževanju emisij CO2 je uporaba alternativnih veziv kot so belitno-kalcijevo sulfoaluminatni cementi. Poleg tega ti cementi porabijo tudi manj energije pri sintezi, omogočajo pa tudi recikliranje odpadnih surovin. Dr. Maruša Mrak je v okviru doktorskega dela z naslovom Vpliv temperature na hidratacijo belitno-kalcijevo sulfoaluminatnega cementa (mentorica doc. dr. Sabina Dolenec, somentorica izr. prof. dr. Nina Daneu) proučevala vpliv temperature na hidratacijo belitno-sulfoaluminatnih cementov različnih sestav, rezultati pa so pokazali spremembe v vrsti in sestavi hidratacijskih produktov, kinetiki procesov hidratacije ter vpliv na njihove reološke lastnosti, mikrostrukturo in tlačne trdnosti.
Understanding the hydration of cement is crucial, as cement represents one of the most important building materials. During the production of cement, large amounts of CO2 are released, representing as much as 8% of global anthropogenic CO2 emissions. One of the approaches to reducing CO2 emissions is the use of alternative binders such as belite-calcium sulfoaluminate cements. In addition, these cements also consume less energy during the production and enable the recycling of waste materials. Dr. Maruša Mrak in her doctoral dissertation The influence of temperature on the hydration of belite-calcium sulfoaluminate cements (supervisor Asst. Prof. Dr. Sabina Dolenec, co-supervisor Assoc. Prof. Dr. Nina Daneu) studied the hydration of different belite-calcium sulfoaluminate cements, and the results showed significant changes in type and composition of hydration products, the kinetics of hydration processes at various curing temperatures and the influence of temperature on their rheological properties, microstructure and compressive strengths.
a) Primerjava sestav faz pri različnih temperaturah glede na XRD. b) Izračunane sestave faz v cm3 na 100 g nehidratiziranega cementa v odvisnosti od temperature z uporabo GEMS. c) Slika FE-SEM ettringita pri 20 °C po 150 dneh hidratacije, ki kaže podolgovato morfologijo. d) Analize EDS cementnih past pri 150 dneh hidratacije pri različnih temperaturah nege.
a) Comparison of the phase assemblages at different temperatures according to XRD. b) Calculated phase assemblages in cm3 per 100 g unhydrated cement as a function of temperature using GEMS. c) FE-SEM image of ettringite showing elongated morphology at 20 °C after 150 days of hydration. d) EDS analyses of cement pastes at 150 days of hydration at different curing temperatures.
Anja Pecman
Karakterizacija rastlinskega viroma z uporabo različnih strategij obogatitve virusnih nukleinskih kislin in platform visoko zmogljivega sekvenciranja
Characterization of plant viromes using different viral nucleic acids enrichment strategies and high-throughput sequencing platforms
Mentor in somentor / Supervisor and Co-Supervisor: Maja Ravnikar, Ion Gutierrez Aguirre
V dosežku z naslovom „Sistematična primerjava sekvenciranja z nanoporami in sekvenciranja z illumino za odkrivanje rastlinskih virusov in viroidov z uporabo pristopa sekvenciranja celotne RNK“ je Anja primerjala delovanje platforme Oxford nanopore sekvenciranja z uveljavljeno platformo Illumina za odkrivanje rastlinskih virusov in viroidov. Rezultati so pokazali, da z ustreznimi protokoli priprave knjižnic in sekvenciranja, naprava nanopore MinION omogoča enakovredno zaznavanje vrste virusov in viroidov kot Illumina. Uspešnost neposrednega RNA sekvenciranja totRNA je bila z napravo MinION nižja v primerjavi sekvenciranja z Illumino, vendar pa se je znatno izboljšala pri uporabi deplecije rRNA, ali ko je bilo vključeno pomnoževanje cDNA ali oboje. Študija je bila objavljena v reviji Frontiers in microbiology (IF: 5.2) in je služila kot podlaga za nedavno pridobljeno akreditacijo po standardu ISO 17025 za nanopore sekvenciranje za diagnostiko rastlinskih virusov in viroidov, prvo tako akreditacijo na svetovni ravni.
In the achievement entitled «Systematic comparison of nanopore and illumina sequencing for the detection of plant viruses and viroids using total RNA sequencing approach”, Anja compared the performance of Oxford nanopore sequencing platform, with the well sgtablished Illumina platform for detection of plant virus and viroids. The results showed that with appropriate library preparation and sequencing protocols nanopore MinION device gave equivalent detection of a range of viruses and viroids than Illumina. The performance of MinION direct RNA sequencing of totRNA was lower than Illumina sequencing, but improved significantly when rRNA depletion was incorporated or when cDNA amplification or both were incorporated. The study was published in Frontiers in microbiology (IF: 5.2) and served as basis for the recently obtained accreditation under ISO 17025 of nanopore sequencing for diagnostics of plangt viruses and viroids, first such accreditation at global level.
Pregled študije, opravljene v izbranem dosežku (del slike je bil ustvarjen s programom BioRender.com).
An overview of the study conducted in the selected achievement (part of the figure was created with BioRender.com).
Tanja Pečnik
Mikrostruktura in dielektrične lastnosti tankih plasti (Ba,Sr)TiO3, pripravljenih s sintezo v raztopini
Microstructure and dielectric properties of solution-derived (Ba,Sr)TiO3 thin films
Mentor in somentor / Supervisor and Co-Supervisor: Barbara Malič
Tanja Pečnik je v svoji disertaciji raziskovala feroelektrične tanke plasti na osnovi Ba0.5Sr0.5TiO3 (BST), z napetostno nastavljivo dielektričnostjo za uporabo v mikrovalovnem območju. Tanke plasti z debelinami od 90 do 400 nm na polikristaliničnih korundnih podlagah, pripravljene s sintezo v raztopini, je pripravila s hitrim segrevanjem pri temperaturi 900 °C. Dielektričnost plasti z debelinami do približno 240 nm v kHZ in GHz območju je naraščala kot posledica naraščajoče velikosti zrn. Z nadaljnjim povečanjem debeline se je dielektričnost plasti nekoliko zmanjšala, kar je razložila s prisotnostjo interkristalnih razpok, ki nastanejo med sproščanjem nateznih napetosti v plasteh kot posledica razlik v termičnih raztezkih plasti in podlage.
In the frame of the study of solution-derived tunable ferroelectric Ba0.5Sr0.5TiO3 (BST) thin films for microwave applications, Tanja Pečnik explained a nonlinear dependence of dielectric properties on film thickness. The films deposited on polycrystalline alumina substrates with thicknesses in the range from 90 to 400 nm were rapid thermally annealed at 900 °C. In the lower film-thickness range, up to about 240 nm, the dielectric permittivity in kHz and in GHz range increased as a consequence of grain size increase (dielectric grain size effect). As the film thickness increased a gradual decrease of permittivity was related to the existence of intergranular cracks that form as a consequence of the relaxation of the tensile residual stress due to the thermal expansion mismatch between the film and the substrate.
Dielektričnost tankih plasti BST izkazuje odvisnost od debeline plasti, velikosti zrn in nateznih napetosti.
Dielectric permittivity of BST thin films revealing combined influences of film thickness, grain size and residual tensile stress.
Anna Pogrebna
Časovno-ločljive optične raziskave kvazidelčne in kolektivne dinamike v železovih pniktidih
Time-resolved optical study of quasiparticle and collective dynamics in iron pnictides
Mentor in somentor / Supervisor and Co-Supervisor: Tomaž Mertelj
Feromagnetizem in superprevodnost sta antagonistična pojava. Njuna koeksistenca implicira feromagnetni parameter reda moduliran na skali krajši od superprevodne koherenčne dolžine ali šibko izmenjalno sklopitev med potujočimi superprevodnimi elektroni in lokaliziranimi urejenimi spini. V nekaterih superprevodnikih iz skupine železovih pniktidov je bila nedvoumno pokazana koeksistenca feromagnetizma in superprevodnosti. Narava koeksistence je še nedorečena, saj spinska struktura ni popolnoma jasna, poročila o jakosti sklopitve pa kontroverzna. V Eu(As,P)2Fe2 smo z neposrednim optičnim eksperimentom “pump-probe” pokazali, da je sklopitev šibka, saj je prenos dodatne energije iz potujočih elektronov na lokalizirane spine veliko počasnejši kot elektronsko fononska relaksacija, kar kaže na koeksistenco brez modulacije feromagnetnega reda na kratki skali. Poleg tega je polarizacijska analiza koherentno vzbujenih spinskih ekscitacij nepričakovano pokazala na preprosto feromagnetno ureditev z dvema različnima orientacijama domen.
Ferromagnetism and superconductivity are antagonistic phenomena. Their coexistence implies either a modulated ferromagnetic order parameter on a lengthscale shorter than the superconducting coherence length or a weak exchange coupling between the itinerant superconducting electrons and the localized ordered spins. In some iron based pnictide superconductors the coexistence has been clearly demonstrated. The nature of the coexistence, however, remains elusive since no clear understanding of the spin structure in the superconducting state has been reached and the reports on the coupling strength are controversial. We showed in Eu(As,P)2Fe2, by a direct optical pump-probe experiment that the coupling is weak, since the transfer of the excess energy from the itinerant electrons to ordered localized spins is much slower than the electron-phonon relaxation, implying the coexistence without the short-lengthscale ferromagnetic order parameter modulation. Remarkably, the polarization analysis of the coherently excited spin wave response points towards a simple ferromagnetic ordering of spins with two distinct types of ferromagnetic domains.
(a) Oscilirajoči del izotropne tranzientne odbojnosti v superprevodnem EuFe2(As0.81P0.19)2 v šibkem magnetnem polju. Črte predstavljajo prilagoditve z modelom dušenega oscilatorja. Frekvenca (b), razpadni čas (c) in amplituda v odvisonsti od magnetnega polja. Črte v (b) so prilagoditve z modelom enoosnega feromagneta. Vstavek v (a) je shematska predstavitev precesije v šibkem magnetnem polju z ustrezno projekcijo vzdolž osi z.
(a) The oscillatory part of the isotropic transient reflectivity component in superconducting EuFe2(As0.81P0.19)2 at low magnetic fields. The lines represent the damped oscillator fits. The frequency (b), decay time (c) and amplitude (e) of the oscillations as functions of the magnetic field. The lines in (b) are uniaxial ferromagnet fits. The inset to (a) schematically shows magnetization precession in small magnetic fields with corresponding projections onto the z-axis.
Mojca Presečnik
Mikrostrukturne in termoelektrične lastnosti keramike tipa p v sistemu Ca-Co-O
Microstructural and thermoelectric characteristics of p-type ceramics in the Ca-Co-O system
Mentor in somentor / Supervisor and Co-Supervisor: Slavko Bernik
Termoelektrični moduli na osnovi termoelektričnih materialov tipa n in p edini omogočajo direktno pretvorbo odpadne toploto v električno energijo na osnovi Seebeckovega efekta. Oksidni termoelektrični materiali so primerni za uporabo pri visokih temperaturah. V doktorski disertaciji z naslovom Mikrostrukturne in termoelektrične lastnosti keramike tipa p v sistemu Ca-Co-O je Mojca Presečnik določila optimalne pogoje za klasično keramično sinteze spojine Ca3Co4O9. Uporaba enofaznih prahov z optimalno morfologijo in velikostjo zrn, ji je omogočila preučevanje vpliva različnih metod procesiranja, tako že poročanih kot tudi novih, na mikrostrukturo in termoelektrične lastnosti keramike Ca3Co4O9. Tako je uspešno izdelala nedopirano keramiko Ca3Co4O9 z najboljšimi poročanimi termoelektričnimi lastnostmi. Rezultati njenih raziskav so pokazali smernice in možnosti za izboljšanje termoelektričnih lastnosti z mikrostrukturo.
Thermoelectric modules based on n- and p-type thermoelectric materials are the only ones that enable the direct conversion of waste heat into electrical energy based on the Seebeck effect. Oxide thermoelectric materials are suitable for high temperature applications. In her doctoral dissertation entitled Microstructural and thermoelectric properties of p-type ceramics in the Ca-Co-O system, Mojca Presečnik determined the optimal conditions for the classical ceramic synthesis of the compound Ca3Co4O9. The use of single-phase powders with optimal morphology and grain size allowed her to study the influence of different processing methods, both previously reported and new, on the microstructure and thermoelectric properties of Ca3Co4O9 ceramics. Thus, she successfully produced undoped Ca3Co4O9 ceramics with the best reported thermoelectric properties up to that time. The results of her research showed guidelines and possibilities for improving thermoelectric properties with microstructure.
Microstrukturna optimizacija, ki je omogočila pripravo termoelektrične keramike Ca3Co4O9 tipa p z najvišjo vrednostjo ZT 0,31 pri 600°C poročano v literaturi.
Microstructural optimisation enabled preparation of the p-type thermoelectric Ca3Co4O9 ceramics with the highest ZT value of 0.31 at 600°C reported in the literature.
Andraž Rešetič
Polimerno dispergirani tekočekristalni elastomeri
Polymer-dispersed liquid crystal elastomers
Mentor in somentor / Supervisor and Co-Supervisor: Boštjan Zalar
V sklopu doktorskega dela z naslovom “Polimerno dispergirani tekočekristalni elastomeri” je dr. Andraž Rešetič (mentor prof. dr. Boštjan Zalar) razvil nov pametni kompozitni material s temperaturno odvisnim oblikovnim odzivom. Novi polimerno dispergirani tekočekristalni elastomeri (PDTKE) so zasnovani tako, da se s temperaturo deformirajo podobno kot tekočekristalni elastomeri (TKE), vendar s prednostjo enostavne obdelave in možnosti oblikovanja v poljubne oblike. PDTKE kompoziti so sestavljeni iz mikroskopsko velikih TKE delcev, dispergiranih v silikonski matriki, ki so pripravljeni z zmrzovanjem in mletjem TKE materiala ter magnetnim urejanjem. Na ta način se funkcionalizira običajni silikon s termomehanskimi lastnostmi TKE dopanta, kar omogoča temperaturno odvisno in reverzibilno deformacijo kompozita med vnaprej pripravljenimi oblikami. Delo je bilo objavljeno v reviji Nature Communications. Raziskave na podlagi PDTKE nadaljuje na ARRS aplikativnem projektu kot nosilec projekta.
As part of his doctoral dissertation titled “Polymer-Dispersed Liquid Crystal Elastomers”, dr. Andraž Rešetič (mentor prof. dr. Boštjan Zalar) developed a new smart composite material with temperature-dependent shape response. The new polymer-dispersed liquid crystal elastomers (PDLCE) are designed to deform with temperature changes similarly to liquid crystal elastomers (LCE) but with the advantage of easy processing and the ability to be shaped into various forms. PDLCE composites consist of microscopically sized LCE particles dispersed in a silicone matrix, prepared by freezing and grinding the LCE material and then magnetically aligning the LCE particles. In this way, ordinary silicone is functionalized with the thermomechanical properties of the LCE dopant, allowing for temperature-dependent and reversible deformation of the composite into pre-prepared shapes. The work was published in the journal Nature Communications. He continues his research on PDLCE’s under an ARRS applied project as the project leader.
Dvoplastne kombinacije termomehansko aktivnega in inertnega PDLCE materiala vodijo do različnih oblikovnih odzivov.
Combinations of bilayered thermomechanically active and inert PDLCE material leads to different morphing configurations.
Rok Rudež
Razvoj debeloplastne oksidne elektronske keramike
Development of thick-film oxide-based electronic ceramics
Mentor in somentor / Supervisor and Co-Supervisor: Slavko Bernik
Sitotisk je tradicionalna tehnologija izdelave debelih filmov elektronskih komponent, integriranih v elektronske naprave. Prednosti te tehnologije so miniaturizacija, hitra in enostavna metoda izdelave kompleksnih struktur in nizki stroški izdelave. Slabosti pri oksidni elektronski keramiki sta lahko nizka zelena gostota filmov in izhlapevanje hlapnih komponent zaradi velikega razmerja med površino in volumnom debelih filmov. V doktorski disertaciji z naslovom Razvoj debeloplastne oksidne elektronske keramike je Rok Rudež z uporabo tehnologije sitotiska preučeval izdelavo debeloplastnih varistorjev na osnovi ZnO in termoelektričnih mikrogeneratorjev. Na osnovi razvoja past z zelo visokim deležem varistorskega prahu je izdelal debeloplastne varistorje z odličnimi tokovno-napetostnimi karakteristikami. Kot prvi je uspešna izdelal oksidne termoelektrične mikrogeneratorje na osnovi keramike (ZnO)5In2O3 tipa n in Ca3Co4O9 tipa p in pojasnil glavne probleme pri njihovi izdelavi s sitotiskom.
Screen printing is a traditional technology for producing thick films of electronic components integrated into electronic devices. The advantages of this technology are miniaturization, a fast and simple method of manufacturing complex structures, and low manufacturing costs. Disadvantages of oxide electronic ceramics can be low green density of the films and evaporation of volatile components due to large surface-to-volume ratio of thick films. In his doctoral dissertation entitled Development of thick-film oxide-based electronic ceramics, Rok Rudež studied the production of thick-film varistors based on ZnO and thermoelectric microgenerators using screen printing technology. Based on the development of inks with a very high contents of varistor powder, he produced thick-film varistors with excellent current-voltage characteristics. He was the first to successfully produce oxide thermoelectric microgenerators based on n-type ceramics (ZnO)5In2O3 and p-type Ca3Co4O9 and explained the main problems in their production by screen printing.
Mikrostruktura prečnega prereza debeloplastnih varistorjev, pripravljenih s sitotiskom past z deležem suhe snovi a) 50 ut. %, b) 60 ut. %, c) 65 ut. % in d) 70 ut. %, žgani pri 900°C 15 minut, in njihove tokovno-napetost (I-U) karakteristike e) prebojna napetost (UT), koeficient nelinearnosti (), tok puščanja (IL) in f) nazivna prebojna napetost (UN) vs. gostota toka (J).
Cross-section microstructure of thick-film varistors prepared by screen printing of inks with solids load of a) 50 wt.%, b) 60 wt.%, c) 65 wt.%, and d) 70 wt.%, sintered at 900°C for 15 minutes, and their current-voltage (I-U) characteristics e) threshold voltage (UT), coefficient of nonlinearity (), leakage current (IL) and f) nominal breakdown voltage (UN) vs. current density (J).
Gavrilo Šekularac
Korozija in protikorozijska zaščita aluminijevih zlitin s konverzijskimi prevlekami na osnovi cirkonija
Corrosion and corrosion protection of aluminium alloys by zirconium conversion coatings
Mentor in somentor / Supervisor and Co-Supervisor: Ingrid Milošev
Predmet doktorske disertacije je mehanizem korozije in protikorozijska zaščita aluminijevih zlitin s konverziijskimi prevlekami. Gavrilo Šekularac je s koavtorji J. Kovačem in I. Milošev objavil tri znanstvene članke v uglednih revijah z visokim faktorjem vpliva, ki obravnavajo tvorbo in karakterizacijo konverzijskih prevlek na osnovi cirkonija. Namen je bil razviti, optimizirati in preučiti mehanizem tvorbe prevlek cirkonijevega oksida s pretvorbo iz raztopine heksafluorcirkonske kisline na vrsto različnih aluminijevih zlitin. Raziskan je bil vpliv različnih parametrov konverzije na stopnjo korozijske zaščite prevlek in postavljen mehanizem tvorbe in zaščite prevlek na vsaki posamezni zlitini. Obsežno raziskovalno delo je bilo v letu 2020 strnjeno v treh prispevkih v revijah Journal of The Electrochemical Society in Corrosion Science, ki so bili prenesen več kot 8,300 krat in citirani več kot 130-krat. V okviru disertacije je G. Šekularac prvi avtor pri štirih in koavtor pri enem znanstvenem članku. Skupno imajo članki več kot 150 citatov.
The subject of the doctoral dissertation is the mechanism of corrosion and anti-corrosion protection of aluminium alloys with conversion coatings. Gavrilo Šekularac, with co-authors J. Kovač and I. Milošev, published three scientific articles in reputable journals with a high impact factor, dealing with the formation and characterization of zirconium-based conversion coatings. The aim was to develop, optimize and study the mechanism of the formation of zirconium oxide coatings by conversion from a solution of hexafluorozirconic acid to a range of different aluminium alloys. The influence of different conversion parameters on the degree of corrosion protection of coatings was investigated, and the mechanism of formation and protection of coatings on each alloy was established. The extensive research work was summarized in three papers in the Journal of The Electrochemical Society and Corrosion Science in 2020, which were downloaded more than 8,300 times and cited more than 130 times. Within the dissertation framework, G. Šekularac is the first author of four and co-author of one scientific article. In total, the articles have more than 150 citations.
The figure schematically shows the structure of the zirconium conversion coating on the aluminum alloy AlSi7Mg0.3 after preparation and after five days of immersion in a sodium chloride solution, when oxyfluorides are gradually transformed into oxides. Below are the polarization curves (left) and the impedance and open circuit potential versus immersion time (right).
Slika shematično prikazuje strukturo cirkonijeve konverzijske prevleke na aluminijevi zlitini AlSi7Mg0,3 po pripravi in po petih dneh potopitve v raztopino natrijevega klorida, ko se oksifluoridi postopoma transformirajo v okside. Spodaj sta prikazani polarizacijski krivulji (levo) in impedanca in potencial odprtega kroga v odvisnosti od časa potopitve (desno).
Melita Sluban
Sinteza in uporaba enodimenzionalnih nanostruktur na osnovi titana in kisika
One-dimensional Ti,O-based nanostructures: synthesis and application
Mentor in somentor / Supervisor and Co-Supervisor: Polona Umek
Dr. Melita Sluban je v okviru svojega doktorskega dela z naslovom Sinteza in uporaba enodimenzionalnih nanostruktur na osnovi titana in kisika (mentorica dr. Polona Umek) ukvarjala z raziskavami funkcionalnih lastnosti 1D titanatnih in TiO2 materialov in pretvorbami med njimi. Nanocevke protoniranega titanata so učinkovito katalizirale aldolno kondenzacijo med benzaldehidom in cikoheksanonom, za kar je zadoščala že katalitska količina materiala. V drugem delu raziskav se je osredotočila na pretvorbo protoniranih titanatnih nanopasov v nanopasove titanovega dioksida; raziskovala je vpliv različnih reakcijskih pogojev na fizikalne lastnosti in fotokatalitsko učinkovitost razgradnje izopropanola. Zadnji del raziskav je bil usmerjen v sintezo nanopasov titanovega oksinitrida. Ugotovila je, da hitrost nitridacije vpliva na superprevodnost nastalih titanoksinitridnih nanopasov. V okviru tematike doktorskega dela je objavila 7 člankov, pri 4 je prva avtorica.
In her PhD thesis One-dimensional Ti,O-based nanostructures: Synthesis and application dr. Melita Sluban studied three one-dimensional (1D) Ti,O-based nanomaterials, including the transformations among them. Protonated titanate nanotubes efficiently catalysed the aldol condensation between benzaldehyde and cyclohexanone, for which the catalytic amount of the material was sufficient. The second part of her research focused on the transformation of protonated titanate nanoribbons and titanium dioxide nanoribbons; she investigated the influence of different reaction conditions on the physical properties and photocatalytic efficiency of isopropanol decomposition. The last part of the research focused on synthesising titanium oxynitride nanoribbons. She found that the rate of nitridation affects the superconductivity of the resulting titanium oxynitride nanoribbons. She has published 7 papers within the scope of her PhD thesis, 4 of which she is the first author.
Razvoj poroznosti Ti(O,N) nanopasov z reakcijskim časom. SEM posnetki izhodnih protoniranih titanatnih nanopasov (levo), in po nitridaciji na 800 °C v toku amonijaka po 4 in 8 urah (desno).
Morphology evolution of the Ti(O,N) nanoribbons with the reaction time. Scanning electron microscopy images of the precursor hydrogen titanate nanoribbons (left)) and titanium oxynitride nanoribbons derived after calcination at 800 °C in a flow of ammonia for 4 h (middle) and 30 h (right).
Urša Tiringer
Hibridne barierne sol-gel prevleke z lastnostjo samoceljenja za protikorozijsko zaščito aluminijevih zlitin
Hybrid sol-gel coatings with barrier and self-healing properties for corrosion protection of aluminium alloys
Mentor in somentor / Supervisor and Co-Supervisor: Ingrid Milošev
Tema doktorske disertacije sodi na področje protikorozijske zaščite aluminijevih zlitin, ki se uporabljajo v avtomobilski in letalski industriji. Tema je aktualna, saj je razvoj novih prevlek, ki so alternativa dosedanjim kromatnim prevlekam, nujno potreben. Kromatne spojine so namreč rakotvorne in strupene in zato močno omejene v Evropski uniji v zadnjih letih. Kandidatka je razvila hibridno sol-gel prevleko na osnovi GPTMS, TEOS in SiO2. Tej prevleki, ki deluje kot bariera korozijskemu mediju, je dodala cerijev(III) nitrat, ki pomaga pri t. i. samo-celjenju prevleke po poškodbi. Dobljeni rezultati, ki so osnovani na inovativnem pristopu k sintezi prevlek, njihovi večplastni karakterizaciji in testiranju v relevantnem okolju, so pomemben prispevek k znanstveni zakladnici, obenem pa so osnova za nadaljnji razvoj v industrijske namene.
The topic of the doctoral dissertation belongs to the field of anti-corrosion protection of aluminium alloys used in the automotive and aviation industries. The topic is contemporary, as developing new coatings that are an alternative to the existing chromate coatings is necessary. Namely, chromate compounds are carcinogenic and toxic and have therefore been heavily restricted in the European Union in recent years. The candidate developed a hybrid sol-gel coating based on GPTMS, TEOS and SiO2. To this coating, which acts as a barrier to the corrosive medium, she added cerium(III) nitrate, which helps with the so-called i. self-healing of the coating after damage. The results are based on an innovative approach to the synthesis of coatings, their multilayer characterization, and their testing in a relevant environment, which are important contributions to the scientific treasury. At the same time, they are the basis for further development for industrial purposes.
Leva stran prikazuje slike vzorcev aluminijeve zlitine 7075-T6 po 50-dnevnem testiranju s solnim razpršilom: neprevlečeni vzorci, vzorci, prevlečeni z GTS sol-gel prevleko in GTS-Ce prevleko, kot je opisano v legendi). Desna stran slike predstavlja potenciodinamske polarizacijske krivulje, posnete za te vzorce v 0,1 M raztopini NaCl, kar potrjuje odlično zaščito razvitih sol-gel prevlek.
The left panel shows images of aluminium alloy 7075-T6 samples after salt-spray testing for 50 days: non-coated samples, samples coated with GTS sol-gel coating and GTS-Ce coating, as described in the legend). The right panel presents potentiodynamic polarisation curves recorded for these samples in 0.1 M NaCl solution, confirming excellent protection of developed sol-gel coatings.
Špela Tomaž
Razkrivanje molekularnih mehanizmov interakcij med rastlinami in patogeni pri vinski trti in krompirju s funkcionalno analizo
Unravelling the molecular mechanisms of plant-pathogen interactions in grapevine and potato through functional analysis
Mentor in somentor / Supervisor and Co-Supervisor: Anna Coll Rius
Transkripcijski faktorji TGA so ključni regulatorji izražanja genov v imunskem odzivu rastlin. V tej študiji smo raziskali vlogo skrajšanega StTGA2.1 (mini-TGA), ki nima bZIP domene, v odpornosti krompirja. Transgene linije krompirja s povečanim izražanjem mini-TGA so pokazale večjo odpornost proti okužbi s virusom Y krompirja. Z analizo transkriptoma smo identificirali potencialne genetske tarče mini-TGA. Med njimi so bile peroksidaze razreda III, za katere smo potrdili vlogo mini-TGA pri aktivaciji njihovih promotorjev. Nazadnje smo s pomočjo strukturnega modeliranja in simulacij molekularne dinamike predvideli, da kompaktna molekularna arhitektura mini-TGA po vezavi heterodimera spremeni konformacijo DNA, kar omogoča aktivacijo transkripcije.
TGA transcription factors are vital regulators of gene expression in plant immunity. Here, we investigated the role of truncated StTGA2.1 (mini-TGA), lacking the full bZIP domain, in potato immunity. Transgenic potato lines overexpressing mini-TGA showed improved resistance to potato virus Y infection. Using transcriptome analysis we identified potential genetic targets of mini-TGA. Among them were class III peroxidases, for which we confirmed the role of mini-TGA for the activation of their promoters. Finally, via structural modeling and molecular dynamics simulations, we hypothesized that the compact molecular architecture of mini-TGA distorts DNA conformation upon heterodimer binding to enable transcriptional activation.
Molekularna arhitektura StTGA2.1 (mini-TGA, oranžna) in StTGA2.3 (zelena). Medtem ko sta C-terminalni regije obeh proteinov visoko ohranjeni, ima StTGA2.3 na N-koncu domeno bZIP, medtem ko ima StTGA2.1 le delno leucinsko zadrgo.
Molecular architectures of StTGA2.1 (mini-TGA, orange) and StTGA2.3 (green). While the C-terminal regions of both proteins are highly conserved, the N-terminus of StTGA2.3 harbors bZIP domain, while StTGA2.1 only has a partial leucine zipper.
Špela Trafela
Razvoj nanostrukturiranih receptorskih elementov za detekcijo formaldehida v alkalnih medijih na osnovi redoks sistema Ni(OH)2/NiOOH-Ni
Development of nanostructured redox couple Ni(OH)2/NiOOH-Ni based receptor elements for detection of formaldehyde in alkaline media
Mentor in somentor / Supervisor and Co-Supervisor: Kristina Žužek
Delo Dr. Špele Trafela, je bilo tekom doktorskega usposabljanja usmerjeno v elektrokemijsko sintezo na niklju osnovanih receptorskih elementov, ki kažejo velik potencial za hitro in cenovno ugodno določanje toksičnega formaldehida (HCHO) v alkalnih raztopinah. Pripravljeni so bili receptorski elementi različnih dimenzij, 2-D tanki filmi in 1-D nanožice, katerih sestava je temeljila na niklju in katalitično aktivnih površinskih mestih redoks para: Ni(OH)2/NiOOH. Odlične katalitične lastnosti KOH-modificiranih Ni nanopalčk je strukturno ovrednotila in podprla s študijo senzoričnih lastnosti. Preko teh študij je bilo dokazano, da KOH-modificirane Ni nanopalčke dosežejo najnižjo mejo detekcije (8 ppm). Preko študije je sistem v sodelovanju z drugimi inštitucijami in partnerji povzdignila na nivo senzorske platforme. Dr. Špela Trafela je rezultate svojega doktorskega dela med drugim objavila v reviji Electrochimica Acta z faktorjem vpliva 6.9.
During her doctoral training, Dr. Špela Trafela focused on the electrochemical synthesis of Ni-based catalysts, known as receptor elements, which show great potential for the rapid and cost-effective detection of toxic formaldehyde (HCHO) in alkaline aqueous solutions. Various receptor elements, including 2-D films and 1-D nanowires, were prepared, composed of Ni and catalytically active Ni(OH)2/NiOOH surface sites. The excellent catalytic properties of KOH-modified Ni nanorods were structurally evaluated and supported by a study of their sensor properties. These studies demonstrated that KOH-modified Ni nanorods achieve the lowest detection limit (8 ppm). This study elevated the system to the level of a sensor platform developed in collaboration with different partners. Dr. Špela Trafela published part of the results in Electrochimica Acta journal, with an impact factor of 6.9.
Shema procesa izdelave elektrokemičnega senzorja IoT: a) FEG-SEM slike receptorskega elementa na osnovi Ni(OH)2-Ni nanožic (pogled z leve zgoraj in z desne strani), b) zaslon na osnovi sintetičnega papirja tiskane elektrode (pSPE) s posameznimi plastmi (črnila) in c) izdelan sistem za zaznavanje HCHOaq z dimenzijami. Zasnova in dimenzije d) laboratorijske opreme (Gamry) in e) IoT izdelanega elektrokemičnega senzorja za zaznavo HCHO.
The schematic of the IoT electrochemical sensor fabrication process: a) FEG-SEM images of the Ni(OH)2-Ni NWs-based receptor element (left–top view and right–side view), b) the synthetic paper-based screen printed electrodes (pSPE) with its individual (ink) layers, and c) the fabricated HCHOaq detection system with its dimensions. Design and dimensions of d) laboratory equipment (Gamry) and e) IoT fabricated electrochemical sensor for HCHO testing.
Marko Vrabelj
Raziskave elektrokaloričnega pojava v polikristaliničnem relaksorskem feroelektriku 0,9Pb(Mg1/3Nb2/3)O3-0,1PbTiO3
Investigations of the electrocaloric effect in the polycrystalline 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 relaxor ferroelectric
Mentor in somentor / Supervisor and Co-Supervisor: Barbara Malič, Zdravko Kutnjak
Elektrokalorični (EK) pojav, to je sprememba temperature v dielektričnem materialu pod vplivom električnega polja, vzbuja izjemno zanimanje zaradi možnosti uporabe v hladilni tehniki, pri čemer je merilo EK pojava EK sprememba temperature. Volumenska keramika na osnovi trdne raztopine 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-10PT) izkazuje EK spremembe temperature, ki so med največjimi objavljenimi vrednostmi za relaksorske feroelektrike. Marko Vrabelj je prvi pokazal, da obstaja povezava med mikrostrukturo in elektrokaloričnim odzivom volumenske keramike, kar pomeni, da k optimalnemu EC odzivu materiala lahko prispeva tudi načrtovanje mikrostrukture. Pojasnil je nelinearno odvisnost elektrokalorične spremembe temperature od velikosti zrn volumenske keramike PMN-10PT.
The electrocaloric (EC) effect, a temperature change in a dielectric material obtained upon applying an electric field, attracts a huge interest due to its possible use in cooling applications, with the EC temperature change being a measure of the EC effect. Bulk ceramics based on 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-10PT) solid solutions exhibit EC temperature changes, which are among the highest reported for relaxor ferroelectric oxides. Marko Vrabelj was the first to show the relationship between the microstructure and the EC temperature change, meaning that an optimum grain size range contributes to the material’s high EC response. Furthermore, he explained the nonlinear dependence of the EC temperature change on the grain size of bulk PMN-10PT ceramics.
Elektrokalorična sprememba temperature volumenske keramike 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-10PT) z različnimi velikostmi zrn v odvisnosti od zunanjega električnega polja.
Electrocaloric temperature change of 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-10PT) bulk ceramics with different grain sizes as function of the applied electric field.
Xuan Xu
Recikliranje in ponovna predelava trajnih magnetov na osnovi sistema Nd-Fe-B z elektrokemijskimi metodami
Recycling and reprocessing of Nd-Fe-B permanent magnets via electrochemical methods
Mentor in somentor / Supervisor and Co-Supervisor: Kristina Žužek
Tema doktorske disertacije Xuan Xu-ja je bilo inovativno recikliranje in predelava magnetov Nd-Fe-B z elektrokemičnimi pristopi. Predlagal je nove pristope pri sintezi Nd-Fe zlitine, s čimer je premikal meje obstoječih raziskav, saj je uspel v nanosu kovinskega Nd z sočasnim nanosom prehodne kovine Fe. Poleg tega je predlagal povsem nov pristop k selektivnemu elektrokemijskem jedkanju magnetov Nd-Fe-B, ki omogoča izločanje trdih magnetnih zrn Nd2Fe14B, s čimer je skrajšal recikliranje in zmanjšal stroške ter okoljski vpliv. Nadalje je s predstavitvijo povsem novega koncepta popolnega elektrokemijskega jedkanja korenito spremenil vidike recikliranja trajnih magnetov Nd-Fe-B, s čimer je premostil izzive metode hidrometalurgije v stroških, uporabi kemikalij in proizvodnji odpadkov. Delo je bilo patentirano leta 2020 in objavljeno v reviji Green Chemistry Communication, z faktorjem vpliva 9,46. Članek je bil označen kot eden najbolj vročih člankov revije v tekočem letu.
The topic of Xuan Xu’s doctoral dissertation was the innovative recycling and processing of Nd-Fe-B magnets using electrochemical approaches. He proposed new approaches in the synthesis of Nd-Fe alloy, pushing the boundaries of existing research by successfully depositing metallic Nd simultaneously with a transition metal (Fe). Additionally, he suggested a completely new approach to the selective electrochemical etching of Nd-Fe-B magnets, enabling the extraction of hard magnetic grains Nd2Fe14B, thus reducing recycling time and decreasing costs and environmental impact. Furthermore, by introducing a completely new concept of total electrochemical etching, he fundamentally changed the aspects of recycling permanent Nd-Fe-B magnets, surpassing current hydrometallurgy methods in costs, chemical usage, and waste production. The work was patented in 2020 and published in the journal Green Chemistry Communication, with an impact factor of 9.46. The paper was recognized as one of the hottest articles in the journal for that year.
