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2. First utilization of magnetically-assisted photocatalytic iron ▫$oxide-TiO_2$▫ nanocomposites for the degradation of the problematic antibiotic ciprofloxacin in an aqueous environmentJosip Radić, Gregor Žerjav, Lucija Jurko, Perica Bošković, Lidija Fras Zemljič, Alenka Vesel, Andraž Mavrič, Martina Gudelj, Olivija Plohl, 2024, izvirni znanstveni članek Opis: The emergence of antimicrobial resistance due to antibiotics in the environment presents significant public health, economic, and societal risks. This study addresses the need for effective strategies to reduce antibiotic residues, focusing on ciprofloxacin degradation. Magnetic iron oxide nanoparticles (IO NPs), approximately 13 nm in size, were synthesized and functionalized with branched polyethyleneimine (bPEI) to obtain a positive charge. These IO-bPEI NPs were combined with negatively charged titanium dioxide NPs (TiO2@CA) to form magnetically photocatalytic IO-TiO2 nanocomposites. Characterization techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), electrokinetic measurements, and a vibrating sample magnetometer (VSM), confirmed the successful formation and properties of the nanocomposites. The nanocomposites exhibited a high specific surface area, reduced mobility of photogenerated charge carriers, and enhanced photocatalytic properties. Testing the photocatalytic potential of IO-TiO2 with ciprofloxacin in water under UV-B light achieved up to 70% degradation in 150 min, with a degradation rate of 0.0063 min−1. The nanocomposite was magnetically removed after photocatalysis and successfully regenerated for reuse. These findings highlight the potential of IO-TiO2 nanocomposites for reducing ciprofloxacin levels in wastewater, helping curb antibiotic resistance. Ključne besede: photocatalytic degradation, magnetic iron oxide-TiO2 nanocomposites, hetero-agglomeration, multifunctionality, antibiotic ciprofloxacin, antimicrobial resistance Objavljeno v RUNG: 09.09.2024; Ogledov: 451; Prenosov: 6 Celotno besedilo (14,48 MB) Gradivo ima več datotek! Več... |
3. Plastic Waste Precursor-Derived Fluorescent Carbon and Construction of Ternary FCs@CuO@TiO2 Hybrid Photocatalyst for Hydrogen Production and Sensing ApplicationAkansha Metha, Rayees Ahmad Rather, Blaž Belec, Sandra Gardonio, Ming Fang, Matjaž Valant, 2022, izvirni znanstveni članek Opis: A sustainable nexus between renewable energy production and plastic abatement is imperative for overall sustainable development. In this regard, this study aims to develop a cheaper and environmentally friendly nexus between plastic waste management, wastewater treatment, and renewable hydrogen production. Fluorescent carbon (FCs) were synthesized from commonly used LDPE (low-density polyethylene) by a facile hydrothermal approach. Optical absorption study revealed an absorption edge around 300 nm and two emission bands at 430 and 470 nm. The morphological analysis showed two different patterns of FCs, a thin sheet with 2D morphology and elongated particles. The sheet-shaped particles are 0.5 μm in size, while as for elongated structures, the size varies from 0.5 to 1 μm. The as-synthesized FCs were used for the detection of metal ions (reference as Cu2+ ions) in water. The fluorescence intensity of FCs versus Cu2+ ions depicts its upright analytical ability with a limit of detection (LOD) reaching 86.5 nM, which is considerably lesser than earlier reported fluorescence probes derived from waste. After the sensing of Cu2+, the as-obtained FCs@Cu2+ was mixed with TiO2 to form a ternary FCs@CuO@TiO2 composite. This ternary composite was utilized for photocatalytic hydrogen production from water under 1.5 AM solar light irradiation. The H2 evolution rate was found to be ~1800 μmolg−1, which is many folds compared to the bare FCs. Moreover, the optimized FCs@CuO@TiO2 ternary composite showed a photocurrent density of ~2.40 mA/cm2 at 1 V vs. Ag/AgCl, in 1 M Na2SO4 solution under the illumination of simulated solar light. The achieved photocurrent density corresponds to the solar-to-hydrogen (STH) efficiency of ~0.95%. The efficiency is due to the fluorescence nature of FCs and the synergistic effect of CuO embedded in TiO2, which enhances the optical absorption of the composite by reaching the bandgap of 2.44 eV, apparently reducing the recombination rate, which was confirmed by optoelectronic, structural, and spectroscopic characterizations. Ključne besede: plastic waste, fluorescent carbo, sensing of metal ions, photocatalytic hydrogen production Objavljeno v RUNG: 25.02.2022; Ogledov: 2469; Prenosov: 49 Celotno besedilo (5,98 MB) |
4. Chemical (in)stability of interfaces between different metals and Bi[sub]2Se[sub]3 topological insulatorKatja Ferfolja, Mattia Fanetti, Sandra Gardonio, Matjaž Valant, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Opis: In recent years a classification of materials based on their topological order gained popularity due to the discovery of materials with special topological character – topological insulators (TI). TI have different band structure than regular insulators or conductors. They are characterized by a band gap in the bulk of the material, but at the surface they possess conductive topological surface states (TSS) that cross the Fermi level. TSS are a consequence of the non-trivial bulk band structure and have properties that differ from ordinary surface states. They are robust toward contamination and deformation of the surface. Additionally, they are also spin polarized, which means that an electron spin is locked to a crystal momentum and, therefore, backscattering during transport is suppressed [1]. Due to their specific properties the TI could be used in fields of spintronics, quantum computing and catalysis [2].
The investigation of the interfaces between metals and the TI has not been given much attention even though its characterization is interesting from fundamental physics and applicative point of view. (In)stability of the contacts with metal electrodes, in a form of a chemical reaction or diffusion, has to be taken into account since it can affect the transport properties of the material or increase the contact resistance. Our research is dedicated to the study of the metal/TI interfaces, in particular to Bi2Se3 with deposited metals that are relevant for electrical contacts (Au, Ag, Pt, Cr, Ti). The thermal and chemical stability of the interfaces are of fundamental importance for understanding the contact behavior, therefore, we focused our work to the characterization of these properties. The metal/TI interfaces are investigated mainly with an electron microscopy (SEM, TEM, STM), EDX microanalysis and XRD. Our previous studies showed that the interface between Bi2Se3, and Ag deposited either chemically or from a vapor phase, results in the formation of new phases already at room temperature [3]. On the contrary, Au deposited on the Bi2Se3 surface shows very limited reactivity and is stable at RT, but diffusion and coalescence of the metal are observed starting from 100 °C [4]. In this contribution, we will present further characterization on the evolution of the Ag/Bi2Se3 and Au/Bi2Se3 interfaces, show preliminary results about recently investigated systems (Pt/Bi2Se3, Ti/Bi2Se3) and compare the thermal and chemical stability of the systems under investigation. Ključne besede: thermal lens spectrometry, photothermal beam deflection spectroscopy, dye remediation, photothermal technique, photocatalytic degradation, reactive blue 19, TiO2 modification Objavljeno v RUNG: 20.08.2021; Ogledov: 2996; Prenosov: 0 Gradivo ima več datotek! Več... |
5. Improved photocatalytic activity of SnO[sub]2-TiO[sub]2 nanocomposite thin films prepared by low-temperature sol-gel methodKsenija Maver, Iztok Arčon, Mattia Fanetti, Samar Al Jitan, Giovanni Palmisano, Matjaž Valant, Urška Lavrenčič Štangar, 2021, izvirni znanstveni članek Opis: The objective of this research was to investigate how the photocatalytic activity of pure TiO2 can be improved by
SnO2 modification. Different molar ratios of tin to titanium were prepared. The correlation between tin concentration
and structural properties was investigated to explain the mechanism of photocatalytic efficiency and
to optimize the synthesis conditions to obtain enhanced activity of the SnO2-modified TiO2 photocatalysts under
UV-irradiation. The SnO2-modified TiO2 photocatalysts were prepared by a low-temperature sol-gel method
based on organic tin and titanium precursors. The precursors underwent sol-gel reactions separately to form
SnO2-TiO2 sol. The sol-gels were deposited on a glass substrate by a dip-coating technique and dried at 150 ◦C to
obtain the photocatalysts in the form of a thin film. To test the thermal stability of the material, an additional set
of photocatalysts was prepared by calcining the dried samples in air at 500 ◦C. The photocatalytic activity of the
samples was determined by measuring the degradation rate of an azo dye. An increase of up to 30% in the
photocatalytic activity of the air-dried samples was obtained when the TiO2 was modified with the SnO2 in a
concentration range of 0.1–1 mol.%. At higher SnO2 loadings, the photocatalytic activity of the photocatalyst
was reduced compared to the unmodified TiO2. The calcined samples showed an overall reduced photocatalytic
activity compared to the air-dried samples. Various characterization techniques (UV-Vis, XRD, N2-physisorption,
TEM, EDX, SEM, XAS and photoelectrochemical characterization) were used to explain the mechanism for the
enhanced and hindered photocatalytic performances of the SnO2-modified TiO2 photocatalysts. The results
showed that the nanocrystalline cassiterite SnO2 is attached to the TiO2 nanocrystallites through the Sn-O-Ti
bonds. In this way, the coupling of two semiconductors, SnO2 and TiO2, was demonstrated. Compared to
single-phase photocatalysts, the coupling of semiconductors has a beneficial effect on the separation of charge
carriers, which prolongs their lifetime for accessibility to participate in the redox reactions. The maximum increase
in activity of the thin films was achieved in the low concentration range (0.1–1 mol.%), which means that
an optimal ratio and contact of the two phases is achieved for the given physical parameters such as particle size,
shape and specific surface area of the catalyst. Ključne besede: photocatalytic activity, Sn-modified TiO2, low-temperature, thin films, XAS analysis Objavljeno v RUNG: 05.07.2021; Ogledov: 3528; Prenosov: 0 Gradivo ima več datotek! Več... |
6. Sn-modified TiO[sub]2 thin film photocatalysts prepared by low-temperature sol-gel processing : dissertationKsenija Maver, 2021, doktorska disertacija Opis: Due to many advantageous physiochemical properties, titanium dioxide (TiO2) is the most widely used photocatalyst in numerous applications, such as wastewater treatment and air purification, self-cleaning surfaces and energy conversion (H2 generation). However, one of its disadvantages is the high electron-hole recombination rate, and coupling with other semiconductors is one of the strategies to improve it. The objective of this dissertation was to investigate how the photocatalytic activity of pure TiO2 can be improved by tin modification and to explain the mechanism of increased or hindered photoactivity in correlation with the structural properties of the modified TiO2 photocatalysts.
A new low-temperature sol-gel synthesis route was developed to prepare Sn- or SnO2-modified TiO2 photocatalysts. In both cases, organic tin and titanium precursors were used. Tin in the form of Sn cations was used to prepare Sn-modified TiO2. In this case, the precursors went through the sol-gel reaction together to form a Sn-TiO2 sol. In the case of SnO2 modification, the SnO2 sol was prepared separately and additionally mixed with the TiO2 sol to form a TiO2/SnO2 bicomponent semiconductor system. Different molar ratios of tin to titanium were prepared to investigate the correlation between the tin concentration and the photocatalytic properties of the photocatalysts in the form of thin films. The results were used to optimize the synthesis conditions to obtain an improved activity of the modified TiO2 photocatalysts under UV-irradiation.
The photocatalytic activity of the thin films was determined by measuring the degradation rate of an azo dye. An increase of up to 40 % in the photocatalytic activity of the dried samples (at 150 °C) was achieved when the TiO2 was modified with the Sn or SnO2 in a concentration range of 0.1 to 1 mol.%. At higher Sn or SnO2 loadings and after calcination of the samples at 500 °C, the photocatalytic activity of the photocatalyst was reduced compared to the unmodified TiO2.
Different characterization techniques (UV-Vis, XRD, nitrogen physisorption, TEM, SEM and XAS) were employed to clarify the mechanism responsible for the enhanced and hindered photocatalytic performance of the Sn- and SnO2-modified TiO2 photocatalysts. The results showed that a nanocrystalline structure is already achieved in the samples by the low-temperature film treatment (drying at 150 °C) and that the photocatalytic efficiency is mainly influenced by the crystalline phase composition: anatase/rutile in the case of Sn-modified and TiO2/SnO2 in the case of SnO2-modified TiO2. The crystal size and specific surface area differ insignificantly between the equally thermally treated samples and partly explain the differences in photoefficiency of the calcined samples compared to the dried samples. The structural study at the atomic level, using the Sn K-edge EXAFS, revealed that Sn cations act as nucleation sites for the anatase to rutile transformation in the Sn-modified TiO2 photocatalysts, while in the SnO2-modified TiO2 samples the nanocrystalline cassiterite SnO2 is bound to the TiO2 nanocrystallites via the Sn-O-Ti bond. In both cases, the advantage of coupling the two semiconductors was achieved by separating the charge carriers and thus prolonging their lifetime for accessibility to participate in the redox reactions. The maximum activity enhancement was achieved in the low concentration range (0.1–1 mol.%), which means that an optimal ratio and contact of the two phases are obtained for the given physical parameters, such as particle size, shape and specific surface area of the catalyst. Ključne besede: Sn-modified TiO2, SnO2-modified TiO2, low-temperature sol-gel, thin films, photocatalytic activity, anatase/rutile system, Sn K-edge EXAFS, dissertations Objavljeno v RUNG: 09.06.2021; Ogledov: 5940; Prenosov: 170 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
7. Photodegradation mechanisms of reactive blue 19 dye under UV and simulated solar light irradiationZeinab Ebrahimpour, Olena Pliekhova, Humberto Cabrera, Mahmoud Abdelhamid, Dorota Korte, Komlan Segbéya Gadedjisso-Tossou, Joseph J. Niemela, Urška Lavrenčič Štangar, Mladen Franko, 2021, izvirni znanstveni članek Ključne besede: reactive blue 19, photocatalytic, photosensitization, thermal lens, UV-Vis Objavljeno v RUNG: 02.02.2021; Ogledov: 3330; Prenosov: 0 Gradivo ima več datotek! Več... |
8. Improved photocatalytic activity of anatase-rutile nanocomposites induced by low-temperature sol-gel Sn-modification of TiO2Ksenija Maver, Iztok Arčon, Urška Lavrenčič Štangar, Mattia Fanetti, Saim Emin, Matjaž Valant, 2020, izvirni znanstveni članek Opis: The Sn-modified TiO2 photocatalysts are prepared by low-temperature sol-gel processing based on organic titanium
and tin precursors with varied Sn concentrations (from 0.1–20 mol .%). The role of Sn dopant as the
promotor of the formation of TiO2 rutile crystalline phase is explained and the optimal Sn concentration for
preparation of efficient Sn-modified titania photocatalyst is determined. Up to 40 % increase in photocatalytic
activity is achieved in Sn-modified TiO2 photocatalytic thin films dried at 150 °C with low Sn concentrations in
the range from 0.1 to 1 mol .%. At low Sn concentrations optimal ratio between anatase and rutile (nano)crystals
is obtained, which facilitates charge separation at the TiO2 photocatalyst’s surface. When the concentration of Sn
increases above 5 mol.% or when the films are calcined at 500 °C, the relative amount of rutile phase with
inferior photocatalytic activity, increases and the nanocrystals of titania grow, leading to fewer active sites per
unit mass and the reduction of activity in comparison to unmodified TiO2. Ključne besede: Anatase-rutile
Sn-modified TiO2
XAS analysis
Photocatalytic activity Objavljeno v RUNG: 10.02.2020; Ogledov: 3710; Prenosov: 0 Gradivo ima več datotek! Več... |
9. Correlations between photocatalytic activity and chemical structure of Cu-modified TiO2-SiO2 nanoparticle compositesT. Čižmar, doktorska disertacija Opis: The objective of this dissertation was to examine how copper modification can improve the photocatalytic activity of TiO2-SiO2 and to explain the correlation between Cu concentration and chemical state of Cu cations in the TiO2-SiO2 matrix, as well as the photocatalytic activity under the UV/solar irradiation.
The Cu-modified TiO2-SiO2 photocatalysts were prepared by a low temperature sol-gel method based on organic copper, silicon and titanium precursors with varied Cu concentrations (from 0.05 to 3 mol%). The sol-gels were dried at 150 °C to obtain the photocatalysts in the powder form. To test thermal stability, additional set of photocatalysts was obtained by calcinating dried samples in air at 500 °C for 1 h.
The photocatalytic activity was determined by a fluorescence-based method of terephthalic acid decomposition. Up to three times increase in photocatalytic activity of air-dried samples is obtained when TiO2-SiO2 matrix is modified with Cu in a narrow concentration range from 0.05 to 0.1 mol%. At higher Cu loadings the photocatalytic activity of Cu-modified photocatalyst is smaller than in the unmodified reference TiO2-SiO2 photocatalyst. Calcined samples showed significantly reduced photocatalytic activity compared to air-dried samples.
XRD analysis showed that all Cu-modified TiO2-SiO2 nanocomposites with different Cu concentrations have the same crystalline structure as unmodified TiO2-SiO2 nanocomposites (air-dried or calcined). The addition of Cu does not change the relative ratio between the anatase and brookite phase or unit cell parameters of the two TiO2 crystalline structures. TEM analysis showed that the addition of Cu does not change the morphology of TiO2-SiO2 catalyst dried at 150 °C.
The Cu K-edge XANES and EXAFS analysis were used to determine valence state and local structure of Cu cations in Cu-modified TiO2-SiO2 photocatalyst. The results elucidate the mechanism responsible for the improved or hindered photocatalytic activity. In the air-dried samples with low Cu content, which exhibit largest activity, Cu-O-Ti connections are formed, suggesting that the activity enhancement is due to Cu(II) cations attachment on the surface of the photocatalytically active TiO2 nanoparticles, so Cu(II) cations may act as free electron traps, reducing the intensity of recombination between electrons and holes at the TiO2 photocatalyst’s surface. At higher Cu loadings no additional Cu-O-Ti connections are formed, instead only Cu-O-Cu connections are established, indicating the formation of amorphous or nanocrystalline Cu(II) oxide, which hinders the photocatalytic activity of TiO2. Calcination of Cu-modified TiO2-SiO2 photocatalysts at 500 °C induces significant structural changes: Cu-O-Ti connections are lost, Cu partially incorporates into the SiO2 matrix and amorphous copper oxides, which again reduce the photocatalytic activity of the material, are formed. Ključne besede: titanium dioxide, Cu-modified TiO2-SiO2 photocatalyst, photocatalytic activity, Cu K-edge XANES, EXAFS. Objavljeno v RUNG: 17.12.2018; Ogledov: 5591; Prenosov: 158 Celotno besedilo (3,05 MB) |
10. Photocatalytic properties of metal modified TiO2 by photothermal techniquesZeinab Ebrahimpour, Olena Pliekhova, Humberto Cabrera, Dorota Korte, Urška Lavrenčič Štangar, Mladen Franko, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: Thermal lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive Blue 19, TiO2 modification Objavljeno v RUNG: 09.11.2018; Ogledov: 4509; Prenosov: 0 Gradivo ima več datotek! Več... |