1. Razvoj nanoplazmonskih materialov za uporabo v procesih heterogene fotokatalize : doktorska disertacijaŠpela Slapničar, 2025, doctoral dissertation Abstract: Titanov dioksid (TiO2) je dobro uveljavljen fotokatalitski material, zlasti na področju čiščenja vode in zraka. V doktorski disertaciji smo se zato osredotočili na razvoj in optimizacijo plazmonskih fotokatalizatorjev na TiO2 nosilnem fotokatalizatorju, za učinkovito fotokatalitsko razgradnjo onesnažil. Posebno pozornost smo namenili vplivu sinteznih parametrov, morfologiji nosilnega katalizatorja TiO2 ter velikosti, obliki in vrsti plazmonskih kovin na fotokatalitsko aktivnost materialov. Cilj obsežne in sistematične raziskave je bil prispevati k boljšemu razumevanju ključnih dejavnikov, ki vplivajo na lastnosti katalizatorjev ter tako pospešiti razvoj naprednih fotokatalizatorjev za okoljske aplikacije.
V prvem delu raziskav smo se osredotočili na znane Au+TiO2 katalizatorje s tehniko mokre impregnacije, pri čemer smo spreminjali medij (voda ali etanol), čas mešanja in končno temperaturo sinteze. Rezultati so pokazali, da ti parametri močno vplivajo na velikost Au nanodelcev ter posledično na fotokatalitsko aktivnost materialov. Zlati nanodelci so imeli najmanjši premer, ko je mešanje v etanolu potekalo dalj časa, s končnim korakom kalcinacije. Ta vzorec je imel tudi najvišjo generacijo nosilcev naboja in najučinkovitejšo razgradnjo bisfenola A (BPA), kar potrjuje pomemben vpliv sinteznih parametrov na končne lastnosti katalizatorja.
Nadalje smo raziskali vpliv morfologije nosilnega materiala na fotokatalitske lastnosti. Pripravili smo TiO2 v obliki nanopalic (TNR) in nanodelcev (TNP) ter nanje nanesli Au nanodelce. Rezultati so pokazali, da različne morfologije vplivajo na optoelektronske lastnosti materiala. Katalizator TNP+Au je izkazoval večjo sposobnost generacije O2•- radikalov kot TNR+Au, kar je posledica različnih višin Schottkyjeve bariere. Ugotovili smo, da pri razgradnji BPA s TNR+Au ne sodelujejo O2•- radikali, temveč se proces odvija preko interakcije elektronov z molekulami BPA, kar poudarja pomembnost optimizacije Schottkyjeve bariere pri načrtovanju katalizatorjev ter poznavanje mehanizma degradacije onesnažil.
Za raziskavo vpliva morfologije kovine smo preučevali sintezo in karakterizacijo katalizatorjev z morfološko bogatimi delci Au na površini TiO2. Z uravnavanjem količine Na-citrata smo uspeli optimizirati tvorbo pravilno oblikovanih Au nanocvetov. Vzorce smo uporabili za testiranje fotokatalitske aktivnosti pri zmanjšanju NO2 pod vidno svetlobo. Vzorec TNR+NF(0.7) z najbolj definiranimi nanocvetovi se je izkazal z visoko fotokatalitsko aktivnostjo, kar je posledica izrazitega plazmonskega efekta na robovih nanocvetov. Katalizator TNR+NF(1.4) ni pokazal te aktivnosti, kar je pripisano deformiranim nanocvetom in ogljikovim specijam iz Na-citrata. Pri segrevanju na 300 °C so se nanocvetovi spremenili v sferične delce Au, ki niso pokazali fotokatalitske aktivnosti, kar poudarja pomen oblike plazmonske kovine.
V zaključnem delu smo se osredotočili na raziskavo vpliva različnih plazmonskih kovin (Au, Ag, Pt) na lastnosti katalizatorja. Raziskava je pokazala, da izbira plazmonske kovine močno vpliva na učinkovitost prenosa naboja in posledično na aktivnost katalizatorja. Največjo fotokatalitsko aktivnost je izkazoval katalizator TNR-Pt, ki je imel najmanjše nanodelce in najbolj ugodno porazdelitev energijskih pasov. Poskusi razgradnje BPA so potrdili, da so O2•- radikali ključni pri oksidacijskih reakcijah, kjer je bil vzorec TNR-Pt najučinkovitejši.
Celovita karakterizacija sintetiziranih materialov je zagotovila dragocen vpogled na vpliv sinteznih parametrov, morfologije nosilcev, velikosti nanodelcev in izbire plazmonske kovine na fotokatalitsko aktivnost.
Keywords: onesnaženost okolja, heterogena fotokataliza, TiO2, plazmonske kovine, reaktivne kisikove specije
Published in DKUM: 20.11.2025; Views: 0; Downloads: 15
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2. Evaluation of ▫$Au/ZrO_2$▫ catalysts prepared via postsynthesis methods in ▫$CO_2$▫ hydrogenation to methanolT. Vikram Sagar, Janez Zavašnik, Matjaž Finšgar, Nataša Novak Tušar, Albin Pintar, 2022, original scientific article Abstract: Au nanoparticles supported on ZrO2 enhance its surface acidic/basic properties to produce
a high yield of methanol via the hydrogenation of CO2. Amorphous ZrO2-supported 0.5–1 wt.% Au
catalysts were synthesized by two methods, namely deposition precipitation (DP) and impregnation
(IMP), characterized by a variety of techniques, and evaluated in the process of CO2 hydrogenation
to methanol. The DP-method catalysts were highly advantageous over the IMP-method catalyst. The
DP method delivered samples with a large surface area, along with the control of the Au particle
size. The strength and number of acidic and basic sites was enhanced on the catalyst surface. These
surface changes attributed to the DP method greatly improved the catalytic activity when compared
to the IMP method. The variations in the surface sites due to different preparation methods exhibited
a huge impact on the formation of important intermediates (formate, dioxymethylene and methoxy)
and their rapid hydrogenation to methanol via the formate route, as revealed by means of in situ
DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) analysis. Finally, the rate of
formation of methanol was enhanced by the increased synergy between the metal and the support.
Published in DKUM: 10.04.2025; Views: 0; Downloads: 8
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3. Hierarchically porous polyacetylene networks : adsorptive photocatalysts for efficient bisphenol a removal from waterDavid Šorm, Jiří Brus, Albin Pintar, Jan Sedláček, Sebastijan Kovačič, 2024, original scientific article Abstract: In this article, we report a series of functionalizedpolyacetylene-type networks formed by chain-growth insertioncoordination polymerization in high internal phase emulsions(HIPEs). All polymerized HIPEs (polyHIPEs) contain a hierarchi-cally structured, 3D-interconnected porous framework consistingof a micro-, meso- and macropore system, resulting in exception-ally high specific surface areas (up to 1055 m2·g−1) and totalporosities of over 95%. The combination of π-conjugated andhierarchically porous structure in one material enabled the use ofthese polyacetylene polyHIPEs as adsorptive photocatalysts for theremoval of chemical contaminants from water. All polyacetylenepolyHIPEs demonstrated high efficiency in the adsorption ofbisphenol A from water (up to 48%) and the subsequentphotocatalytic degradation. Surprisingly, high adsorption capacitydid not affect the photocatalytic efficiency (up to 58%). On the contrary, this dual function seems to be very promising, as somepolyacetylene polyHIPEs almost completely removed bisphenol A from water (97%) through the adsorption-photooxidationmechanism. It also appears that the presence of polar functional side groups in the polyacetylene backbone improves the contact ofthe polyacetylene network with the aqueous bisphenol A solution, which can thus be more easily adsorbed and subsequentlyoxidized, compensating for the lower specific surface area of some networks, namely, 471 and 308 m2·g−1 in the case of 3-ethynylphenol- and 3-ethynylaniline-based polyacetylene polyHIPEs, respectively.
Keywords: polyacetylenes, emulsion-templating, π-conjugated networks, macroporous polymers, heterogeneous photocatalysis
Published in DKUM: 29.08.2024; Views: 73; Downloads: 63
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4. Highly porous polymer beads coated with nanometer-thick metal oxide films for photocatalytic oxidation of bisphenol AGergő Ballai, Tomaž Kotnik, Matjaž Finšgar, Albin Pintar, Zoltán Kónya, András Sápi, Sebastijan Kovačič, 2023, original scientific article Abstract: Highly porous metal oxide−polymer nanocomposites are attracting considerable interest due to their unique structural and functional features. A porous polymer matrix brings properties such as high porosity and permeability, while the metal oxide phase adds functionality. For the metal oxide phase to perform its function, it must be fully accessible, and this is possible only at the pore surface, but functioning surfaces require controlled engineering, which remains a challenge. Here, highly porous nanocomposite beads based on thin metal oxide nanocoatings and polymerized high internal phase emulsions (polyHIPEs) are demonstrated. By leveraging the unique properties of polyHIPEs, i.e., a three-dimensional (3D) interconnected network of macropores, and high-precision of the atomic-layer-deposition technique (ALD), we were able to homogeneously coat the entire surface of the pores in polyHIPE beads with TiO$_2$-, ZnO-, and Al$_2$O$_3$-based nanocoatings. Parameters such as nanocoating thickness, growth per cycle (GPC), and metal oxide (MO) composition were systematically controlled by varying the number of deposition cycles and dosing time under specific process conditions. The combination of polyHIPE structure and ALD technique proved advantageous, as MO-nanocoatings with thicknesses between 11 ± 3 and 40 ± 9 nm for TiO$_2$ or 31 ± 6 and 74 ± 28 nm for ZnO and Al$_2$O$_3$, respectively, were successfully fabricated. It has been shown that the number of ALD cycles affects both the thickness and crystallinity of the MO nanocoatings. Finally, the potential of ALD-derived TiO$_2$-polyHIPE beads in photocatalytic oxidation of an aqueous bisphenol A (BPA) solution was demonstrated. The beads exhibited about five times higher activity than nanocomposite beads prepared by the conventional (Pickering) method. Such ALD-derived polyHIPE nanocomposites could find wide application in nanotechnology, sensor development, or catalysis.
Keywords: nanovlakna, aerosoli, filtracija, emulsion-templating, macroporous polymers, atomic-layer-deposition
Published in DKUM: 15.04.2024; Views: 249; Downloads: 21
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5. Sustainable in-water synthesis of aliphatic porous polyazines : a versatile platform for conjugated aerogels, polyHIPEs, or carbon foamsTomaž Kotnik, Gregor Žerjav, Zoran Novak, Albin Pintar, Sebastijan Kovačič, 2023, original scientific article Abstract: Access to conjugated porous polymers via synthetically sustainable and straightforward routes is highly desirable, as many polymer systems exhibit high performance but require arduous synthetic protocols that rarely pave the way to commercial reality. In this article, we describe an easily fabricated series of novel highly porous poly(Schiff bases) that feature an aliphatic conjugated backbone obtained with low synthetic complexity from simple reagents such as glyoxal and hydrazine monohydrate in water. The effective synthesis enables the preparation of three different functional scaffolds, i.e., aerogels, polyHIPEs (polymerized HIPEs), and even carbon foams from aliphatic poly(azine) (PAZ) networks. The reported synthetic approach is compared to the literature using ″green chemistry metrics″, such as the E-factor and synthetic complexity (SC) index, and shows dramatic improvements. An E-factor of up to 0.27 for aerogels or 80 for polyHIPEs and an SC index of 2.7 are much lower than those for poly(arylene)-based conjugated analogues, indicating good scalability, sustainability, and low cost. PAZ materials feature impressive red/near IR-shifted optical absorption band edges, with an electrochemical band gap of 1.45 eV. Aliphatic PAZ scaffolds are characterized by high flexibility compared to aromatic analogues and do not fail at compressive loads of up to 70%. Finally, carbonization at 500 °C leads to highly porous carbonaceous scaffolds with a high N content of up to 29 wt % (21 mmol of nitrogen per gram carbon material).
Published in DKUM: 13.03.2024; Views: 696; Downloads: 24
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6. Razgradnja lignoceluloznega materiala trdnih organskih odpadkov z glivo Pleurotus ostreatus pred procesom anaerobne fermentacije v trdnem stanjuNataša Belšak Šel, 2015, doctoral dissertation Abstract: Omejeni viri, visoke cene in okoljski vpliv fosilnih goriv narekujejo razvoj alternativnih virov energije, med katere spada tudi proizvodnja energije iz lignocelulozne biomase. Lignocelulozna biomasa (LB) kmetijskih, vrtnih in gozdarskih ostankov se v veliki količini kopiči na regionalnem zbirnem centru za ravnanje z odpadki, kjer jo uporabijo v procesu kompostiranja. Z našo nalogo smo raziskali možnosti proizvodnje bioplina iz lokalno zbrane LB. S tem namenom smo optimirali in nadgradili proces anaerobne fermentacije LB za pridobitev biometana, obnovljivega vira energije. Izdelali smo pilotni sistem šaržnih reaktorjev s strnjenim slojem in križnim pretakanjem izcedne vode, z namenom simulacije procesa na ustrezni velikosti glede na vstopno biomaso.
Pri izvedbi eksperimentov v reaktorjih na pilotnem merilu, smo glavni poudarek namenili študiji vpliva pretakanja izcedne vode med reaktorji na proizvodnjo bioplina. Rezultati tovrstnih poskusov so pokazali, da je pretakanje izcedne vode med reaktorji ključnega pomena za stabilnost procesa in povečano proizvodnjo bioplina.
Raziskave kažejo, da je proizvodnjo bioplina iz LB možno povečati z učinkovito predobdelavo. Nadgradnjo procesa anaerobne fermentacije smo izvedli z biološko predobdelavo LB. In sicer smo glivo P.ostreatus gojili direktno na LB, v nadaljevanju smo za razgradnjo LB uporabili le encime glive. V laboratorijskem sistemu AMPTS smo določili biometanski potencial LB in LB preraščeni z glivo. Postopek predobdelave LB, pri katerem smo glivo gojili direktno na vzorcih LB, se je izkazal za neučinkovitega, saj je bil biometanski potencial vzorcev preraščenih z glivo mnogo nižji od biometanskega potenciala LB, ki ni bil izpostavljen nobeni predobdelavi.
Naše raziskave smo nato nadaljevali v smeri gojenja glive na trdnem gojišču, sestavljenem iz pšeničnih otrobov in lignocelulozne biomase, in nato pridobivanja hidrolitičnih in oksidativnih encimov. Iz rezultatov encimskih aktivnosti smo ugotovili, da je gliva P. ostreatus, proizvedla celulitične encime v manjših količinah, medtem ko so bile lakaze, ki razgrajujejo ligninske komponente, proizvedene v velikih količinah. Glede na to, da veljajo lakaze tudi za širše industrijsko zanimive encime, smo z optimizacijo po Taguchi metodi raziskovali vpliv sestave gojišča na produktivnost lakaz. Optimizacija gojišča s Taguchi ortogonalno matriko L18 (21 × 37) se je izkazala za uspešno metodo, s katero smo pridobili podatke za sestavo gojišča na katerem izloči gliva P. ostreatus največ lakaz.
Za primerjavo učinkovitosti razgradnje LB z encimskim ekstraktom, pridobljenim iz gojišč P. ostreatus, smo uporabili dva komercialna encima. Rezultati so pokazali, da je bil encimski ekstrakt učinkovit pri razgradnji LB, kakor tudi pri razgradnji trdnega ostanka po fermentaciji.
Keywords: lignocelulozna biomasa, anaerobna fermentacija, lignocelulozni encimi, Pleurotus ostreatus, encimska hidroliza
Published in DKUM: 07.01.2016; Views: 3359; Downloads: 342
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