870 results on '"Patrik Schmuki"'
Search Results
2. Comparison of the sputtered TiO2 anatase and rutile thin films as electron transporting layers in perovskite solar cells
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Fahimeh Shahvaranfard, Ning Li, Saman Hosseinpour, Seyedsina Hejazi, Kaicheng Zhang, Marco Altomare, Patrik Schmuki, and Christoph J. Brabec
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magnetron sputtering ,perovskite solar cell ,TiO2 anatase ,TiO2 rutile ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Abstract We examine comparatively the performance of sputtered TiO2 rutile and anatase thin films as an electron transport layer (ETL) in MAPbI3‐based perovskite solar cells. Both anatase and rutile TiO2 ETLs are deposited (on fluorine‐doped tin oxide [FTO] substrates) by magnetron sputtering in the form of nanocrystalline thin films. We systematically investigate the role of crystallographic phase composition of TiO2 ETLs on the photovoltaic performance of perovskite solar cells. The champion power conversion efficiencies (PCEs) of 18.4% and 17.7% under reverse scan mode are obtained for perovskite solar cells based on TiO2 anatase and TiO2 rutile ETL, respectively. The results show that the magnetron sputtering deposited ETLs differ from each other only in their phase composition while the overall performance of the devices is not greatly affected by the crystallographic phase of the TiO2 ETLs. Our results point to an important fact that for a proper and reliable comparison between the performance of TiO2 anatase and rutile ETLs, it is crucial to investigate films of similar morphology and structure that are synthesize under similar conditions.
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- 2022
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3. Metal Oxide Nanoparticles: Review of Synthesis, Characterization and Biological Effects
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Andreea Mariana Negrescu, Manuela S. Killian, Swathi N. V. Raghu, Patrik Schmuki, Anca Mazare, and Anisoara Cimpean
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metal oxide nanoparticles ,nanotechnology ,pro-regenerative potential ,cancer therapy ,antimicrobial activity ,nanotoxicity ,Biotechnology ,TP248.13-248.65 ,Medicine (General) ,R5-920 - Abstract
In the last few years, the progress made in the field of nanotechnology has allowed researchers to develop and synthesize nanosized materials with unique physicochemical characteristics, suitable for various biomedical applications. Amongst these nanomaterials, metal oxide nanoparticles (MONPs) have gained increasing interest due to their excellent properties, which to a great extent differ from their bulk counterpart. However, despite such positive advantages, a substantial body of literature reports on their cytotoxic effects, which are directly correlated to the nanoparticles’ physicochemical properties, therefore, better control over the synthetic parameters will not only lead to favorable surface characteristics but may also increase biocompatibility and consequently lower cytotoxicity. Taking into consideration the enormous biomedical potential of MONPs, the present review will discuss the most recent developments in this field referring mainly to synthesis methods, physical and chemical characterization and biological effects, including the pro-regenerative and antitumor potentials as well as antibacterial activity. Moreover, the last section of the review will tackle the pressing issue of the toxic effects of MONPs on various tissues/organs and cell lines.
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- 2022
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4. Self-assembled monolayers enhance the efficiency of Pt single atom co-catalysts in photocatalytic H2 generation
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Yue Wang, Imgon Hwang, Zhenni Wu, and Patrik Schmuki
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Anodic TiO2 layer ,Self-assembled monolayers (SAMs) ,Pt single-atoms ,Photocatalyst ,H2 generation ,Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
Single atom (SA) catalysis, over the last 10 years, has become a forefront in heterogeneous catalysis, electrocatalysis, and most recently also in photocatalysis. Pt SAs on titania have been reported to be a highly effective co-catalyst in photocatalytic H2 generation. Most recently, for the synthesis of SA loading on titania surfaces, some simple immersion techniques have been described. Here we introduce a so far unexplored but evidently very effective approach to enhance the effectivity of Pt SA co-catalysts on anodic TiO2 layers. For this, we first decorate TiO2 surfaces with a partial coverage of headgroups of silane self-assembled monolayers (SAMs) and then deposit Pt SAs on this SAM modified surface. We observe a significantly enhanced photocatalytic activity for H2 generation using this sensitization of the surface with a modified SAM.
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- 2021
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5. Post treatments effect on TiZr nanostructures fabricated via anodizing
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Maria Vardaki, Shiva Mohajernia, Aida Pantazi, Ionela Cristina Nica, Marius Enachescu, Anca Mazare, Ioana Demetrescu, and Patrik Schmuki
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Mining engineering. Metallurgy ,TN1-997 - Abstract
The primary focus of the paper is the fabrication of nanotubes via a two steps anodizing procedure on a TiZr substrate followed subsequent annealing treatments and their effect on surface and biocompatibility. The two step anodizing process is optimized for obtaining uniform and ordered nanotubular structures, that are then annealed in air or reduced in an Ar/H2 environment. The high aspect ratio nanotubular structures (diameter 160 nm, length 9.4 μm) maintained their morphology after annealing or reduction. While the thermal treatments burned-off the fluoride, they converted the tubes to ZrTiO4 (annealing in air) or (Zr0.333 Ti0.666)O2 (reducing). Surface roughness and adhesion forces evaluation of the nanostructures was included in the AFM investigations, and show that these properties can be tuned. In vitro cell response to TiZr substrate and nanotubular coatings were analyzed using HGF-1 gingival fibroblasts cell line and LDH, nitric oxide (NO) and reactive oxygen species (ROS) tests. Regarding the hydrophilic balance of the studied samples, as expected it decreased after annealing and but increased after reduction, with only small change in the cell response. The results suggest that these coatings are biocompatible with human gingival fibroblast and can be used in biomedical applications without generating any considerable inflammatory process. Keywords: Anodizing, Thermal treatments, Roughness, Adhesion, Biocompatibility
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- 2019
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6. Single-Atom Co-Catalysts Employed in Titanium Dioxide Photocatalysis
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Ujjaval Kerketta, Alexander B. Tesler, and Patrik Schmuki
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single-atom co-catalyst ,photocatalysis ,titanium dioxide ,H2 evolution ,water splitting ,N2 fixation ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
With a distinct electronic structure and unsaturated coordination centers, supported single-atoms (SAs) have shown great potential in heterogeneous catalysis due to their superior activity, stability, and selectivity. Over the last few years, the fascination of SA-use spread also over photocatalysis, i.e., a particular case of heterogeneous catalysis in which chemical reactions are activated by charge transfer from an illuminated semiconductor. Titanium dioxide (TiO2) is one of the most studied photocatalytic materials. It is widely used as a light absorbing semiconductor decorated with metallic (nanoparticles and single-atom) co-catalysts. In the current review, we emphasize the role of SAs as a co-catalyst in photocatalysis, and clearly set it apart from the use of single atoms in classic heterogeneous catalysis. The review first briefly describes the principal features of SAs, and gives an overview of most important examples of single-atom co-catalysts. Then, we discuss photocatalysis and key examples of single-atom co-catalysts used on TiO2 photocatalysts and their applications. At last, we provide an outlook for further exploring TiO2-based single-atom photocatalytic systems.
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- 2022
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7. As a single atom Pd outperforms Pt as the most active co-catalyst for photocatalytic H2 evolution
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Gihoon Cha, Imgon Hwang, Seyedsina Hejazi, Ana S. Dobrota, Igor A. Pašti, Benedict Osuagwu, Hyesung Kim, Johannes Will, Tadahiro Yokosawa, Zdeněk Badura, Štěpán Kment, Shiva Mohajernia, Anca Mazare, Natalia V. Skorodumova, Erdmann Spiecker, and Patrik Schmuki
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Catalysis ,Nanomaterials ,Materials characterization ,Science - Abstract
Summary: Here, we evaluate three different noble metal co-catalysts (Pd, Pt, and Au) that are present as single atoms (SAs) on the classic benchmark photocatalyst, TiO2. To trap the single atoms on the surface, we introduced controlled surface vacancies (Ti3+-Ov) on anatase TiO2 nanosheets by a thermal reduction treatment. After anchoring identical loadings of single atoms of Pd, Pt, and Au, we measure the photocatalytic H2 generation rate and compare it to the classic nanoparticle co-catalysts on the nanosheets. While nanoparticles yield the well-established the hydrogen evolution reaction activity sequence (Pt > Pd > Au), for the single atom form, Pd radically outperforms Pt and Au. Based on density functional theory (DFT), we ascribe this unusual photocatalytic co-catalyst sequence to the nature of the charge localization on the noble metal SAs embedded in the TiO2 surface.
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- 2021
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8. Photoelectrochemical performance of TiO2 photoanodes: Nanotube versus nanoflake electrodes
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Xin Zhou, Nikita Denisov, Gihoon Cha, Imgon Hwang, and Patrik Schmuki
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TiO2 nanotubes ,VE-anatase layers ,IPCE ,IMPS ,Photocurrent transients ,Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
In the present work, we compare the photoresponse of vertically erected (VE) single crystal anatase layers with that of widely used TiO2 nanotube layers. These VE-anatase layers were grown hydrothermally, directly on fluorine-doped tin oxide (FTO) glass, and consist of an array of anatase single crystal flakes with preferred (001) facets. As formed, these single crystal layers are fluorine terminated – this termination can be removed by a thermal treatment in air. We compare the photocurrent magnitude and photocurrent transients using intensity-modulated photocurrent spectroscopy (IMPS). We find that the “de-fluorinated” VE-anatase layers show significantly higher photocurrents than the comparable nanotube layers. This high efficiency of the VE-anatase layers is due to the electron transport being 100 times faster in these single crystal electrodes, provided that the blocking fluorine termination is removed.
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- 2021
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9. Intrinsic Cu nanoparticle decoration of TiO2 nanotubes: A platform for efficient noble metal free photocatalytic H2 production
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Seyedsina Hejazi, Shiva Mohajernia, Yuhan Wu, Pavlina Andryskova, Giorgio Zoppellaro, Imgon Hwang, Ondrej Tomanec, Radek Zboril, and Patrik Schmuki
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Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
In this work, we grow intrinsically Cu-doped TiO2 nanotubes (TiNTs) by self-organizing anodization of Ti–Cu binary alloys. We demonstrate that up to a copper concentration of 1.5 at.% in the alloy, self-ordered Cu2+-doped nanotubes can be grown. Under UV illumination the Cu2+ ion-doped oxide structures can be converted to nanotubes that carry metallic nanoparticles (NPs) uniformly decorated on top of the TiNTs. We investigate the formation of these metallic nanoparticles under UV illumination by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The resulting intrinsic copper-doped and decorated TiNTs have a strongly enhanced photocatalytic activity for H2 evolution in comparison to pristine TiNTs. Key is the light-induced conversion of the intrinsic Cu dopant to metallic copper nanoparticles that act as a stable co-catalyst for H2 generation. Keywords: TiO2, Cu doped TiO2, Photocatalytic activity, Intrinsic copper decoration
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- 2019
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10. Macrophage-like Cells Are Responsive to Titania Nanotube Intertube Spacing—An In Vitro Study
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Madalina Georgiana Necula, Anca Mazare, Andreea Mariana Negrescu, Valentina Mitran, Selda Ozkan, Roxana Trusca, Jung Park, Patrik Schmuki, and Anisoara Cimpean
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macrophage ,inflammation ,TiO2 nanotubes ,intertube spacing ,cytokines ,osteoclastogenesis ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
With the introduction of a new interdisciplinary field, osteoimmunology, today, it is well acknowledged that biomaterial-induced inflammation is modulated by immune cells, primarily macrophages, and can be controlled by nanotopographical cues. Recent studies have investigated the effect of surface properties in modulating the immune reaction, and literature data indicate that various surface cues can dictate both the immune response and bone tissue repair. In this context, the purpose of the present study was to investigate the effects of titanium dioxide nanotube (TNT) interspacing on the response of the macrophage-like cell line RAW 264.7. The cells were maintained in contact with the surfaces of flat titanium (Ti) and anodic TNTs with an intertube spacing of 20 nm (TNT20) and 80 nm (TNT80), under standard or pro-inflammatory conditions. The results revealed that nanotube interspacing can influence macrophage response in terms of cell survival and proliferation, cellular morphology and polarization, cytokine/chemokine expression, and foreign body reaction. While the nanostructured topography did not tune the macrophages’ differentiation into osteoclasts, this behavior was significantly reduced as compared to flat Ti surface. Overall, this study provides a new insight into how nanotubes’ morphological features, particularly intertube spacing, could affect macrophage behavior.
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- 2022
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11. Self-assembly of a Ni(I)-photocatalyst for plain water splitting without sacrificial agents
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Shanshan Qin, Zdenek Badura, Nikita Denisov, Ondrej Tomanec, Shiva Mohajernia, Ning Liu, Stepan Kment, Giorgio Zoppellaro, and Patrik Schmuki
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Hydrogen evolution ,Plain water splitting ,Ni(I)-photocatalyst ,Hydrogenated anatase titania ,Self-assembly ,Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
The present work describes a self-assembling photocatalytic system that is observed when illuminating grey titania nanoparticles in suspension with a plain aqueous Ni2+ solution. Such a suspension (in contrast to white titania), under UV illumination, increasingly produces H2 from neutral water. We show that the origin of this self-activation is not the light-induced deposition of Ni0 or another Ni-catalyst compound on the titania surface. Rather, in-situ electron paramagnetic resonance (EPR) clearly indicates that the activation is due to a light-induced formation of a suitable defect structure (Ti3+-OV) on grey titania, combined with the formation of an intermediate monovalent nickel (Ni(I)) electron transfer relay. Remarkably, the resulting Ni+/TiO2/Ti3+ photocatalyst operates in absence of any noble metal or sacrificial agent.
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- 2021
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12. Incorporation of bioactive glass nanoparticles in electrospun PCL/chitosan fibers by using benign solvents
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Liliana Liverani, Jonas Lacina, Judith A. Roether, Elena Boccardi, Manuela S. Killian, Patrik Schmuki, Dirk W. Schubert, and Aldo R. Boccaccini
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Green electrospinning ,Benign solvents ,Bioactive glass ,Composite ,PCL ,Chitosan ,Nanofibers ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Biology (General) ,QH301-705.5 - Abstract
The use of bioactive glass (BG) particles as a filler for the development of composite electrospun fibers has already been widely reported and investigated. The novelty of the present research work is represented by the use of benign solvents (like acetic acid and formic acid) for electrospinning of composite fibers containing BG particles, by using a blend of PCL and chitosan. In this work, different BG particle sizes were investigated, namely nanosized and micron-sized. A preliminary investigation about the possible alteration of BG particles in the electrospinning solvents was performed using SEM analysis. The obtained composite fibers were investigated in terms of morphological, chemical and mechanical properties. An in vitro mineralization assay in simulated body fluid (SBF) was performed to investigate the capability of the composite electrospun fibers to induce the formation of hydroxycarbonate apatite (HCA).
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- 2018
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13. Nanoscale Assembly of BiVO4/CdS/CoOx Core–Shell Heterojunction for Enhanced Photoelectrochemical Water Splitting
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Hana Kmentova, Olivier Henrotte, Rambabu Yalavarthi, Mareike Haensch, Christian Heinemann, Radek Zbořil, Patrik Schmuki, Štěpán Kment, and Alberto Naldoni
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photoelectrocatalysis ,water splitting ,BiVO4 ,clean energy ,visible light ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Porous BiVO4 electrodes were conformally decorated with CdS via a chemical bath deposition process. The highest photocurrent at 1.1 V vs. RHE was achieved for a BiVO4/CdS composite (4.54 mA cm−2), compared with CdS (1.19 mA cm−2) and bare BiVO4 (2.1 mA cm−2), under AM 1.5G illumination. This improvement in the photoefficiency can be ascribed to both the enhanced optical absorption properties and the charge separation due to the heterojunction formation between BiVO4 and CdS. Furthermore, the BiVO4/CdS photoanode was protected with a CoOx layer to substantially increase the photostability of the material. The new BiVO4/CdS/CoOx nanostructure exhibited a highly stable photocurrent density of ~5 mA cm−2. The capability to produce O2 was locally investigated by scanning photoelectrochemical microscope, which showed a good agreement between photocurrent and O2 reduction current maps. This work develops an efficient route to improve the photo-electrochemical performance of BiVO4 and its long-term stability.
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- 2021
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14. Multi-Leg TiO2 Nanotube Photoelectrodes Modified by Platinized Cyanographene with Enhanced Photoelectrochemical Performance
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Mahdi Shahrezaei, Seyyed Mohammad Hossein Hejazi, Yalavarthi Rambabu, Miroslav Vavrecka, Aristides Bakandritsos, Selda Oezkan, Radek Zboril, Patrik Schmuki, Alberto Naldoni, and Stepan Kment
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multi-leg TiO2 nanotube ,platinized cyanographene ,photoanode ,photoelectrochemical properties ,charge transfer ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance.
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- 2020
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15. Lateral Spacing of TiO2 Nanotubes Modulates Osteoblast Behavior
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Madalina Georgiana Necula, Anca Mazare, Raluca Nicoleta Ion, Selda Ozkan, Jung Park, Patrik Schmuki, and Anisoara Cimpean
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spaced TiO2 nanotubes ,osteoblast ,cell adhesion and morphology ,cell proliferation ,osteogenic differentiation ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Titanium dioxide (TiO2) nanotube coated substrates have revolutionized the concept of implant in a number of ways, being endowed with superior osseointegration properties and local drug delivery capacity. While accumulating reports describe the influence of nanotube diameter on cell behavior, little is known about the effects of nanotube lateral spacing on cells involved in bone regeneration. In this context, in the present study the MC3T3-E1 murine pre-osteoblast cells behavior has been investigated by using TiO2 nanotubes of ~78 nm diameter and lateral spacing of 18 nm and 80 nm, respectively. Both nanostructured surfaces supported cell viability and proliferation in approximately equal extent. However, obvious differences in the cell spreading areas, morphologies, the organization of the actin cytoskeleton and the pattern of the focal adhesions were noticed. Furthermore, investigation of the pre-osteoblast differentiation potential indicated a higher capacity of larger spacing nanostructure to enhance the expression of the alkaline phosphatase, osteopontin and osteocalcin osteoblast specific markers inducing osteogenic differentiation. These findings provide the proof that lateral spacing of the TiO2 nanotube coated titanium (Ti) surfaces has to be considered in designing bone implants with improved biological performance.
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- 2019
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16. Radiative and Non-Radiative Recombination Pathways in Mixed-Phase TiO2 Nanotubes for PEC Water-Splitting
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Rambabu Yalavarthi, Alberto Naldoni, Štěpán Kment, Luca Mascaretti, Hana Kmentová, Ondřej Tomanec, Patrik Schmuki, and Radek Zbořil
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charge transfer ,intensity-modulated photocurrent spectroscopy ,phase transitions ,photoelectrochemical impedance spectroscopy ,water-splitting ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Anatase and rutile mixed-phase TiO2 with an ideal ratio has been proven to significantly enhance photoelectrochemical (PEC) activity in water-splitting applications due to suppressing the electron⁻hole recombination. However, the mechanism of this improvement has not been satisfactory described yet. The PEC water oxidation (oxygen evolution) at the interface of TiO2 photoanode and electrolyte solution is determined by the fraction of the photogenerated holes that reach the solution and it is defined as the hole transfer efficiency. The surface and bulk recombination processes in semiconductor photoanodes majorly influence the hole transfer efficiency. In this work, we study the hole transfer process involved in mixed-phase TiO2 nanotube arrays/solution junction using intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS); then, we correlate the obtained hole transfer rate constants to (photo)electrochemical impedance spectroscopy (PEIS) measurements. The results suggest that the enhanced performance of the TiO2 mixed-phase is due to the improved hole transfer rate across the TiO2/liquid interface as well as to the decrease in the surface trap recombination of the holes.
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- 2019
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17. TiO2 Nanotubes on Transparent Substrates: Control of Film Microstructure and Photoelectrochemical Water Splitting Performance
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Matus Zelny, Stepan Kment, Radim Ctvrtlik, Sarka Pausova, Hana Kmentova, Jan Tomastik, Zdenek Hubicka, Yalavarthi Rambabu, Josef Krysa, Alberto Naldoni, Patrik Schmuki, and Radek Zboril
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titanium ,anodization ,TiO2 nanotubes ,hardness ,adhesion ,photoelectrochemistry ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
Transfer of semiconductor thin films on transparent and or flexible substrates is a highly desirable process to enable photonic, catalytic, and sensing technologies. A promising approach to fabricate nanostructured TiO2 films on transparent substrates is self-ordering by anodizing of thin metal films on fluorine-doped tin oxide (FTO). Here, we report pulsed direct current (DC) magnetron sputtering for the deposition of titanium thin films on conductive glass substrates at temperatures ranging from room temperature to 450 °C. We describe in detail the influence that deposition temperature has on mechanical, adhesion and microstructural properties of titanium film, as well as on the corresponding TiO2 nanotube array obtained after anodization and annealing. Finally, we measure the photoelectrochemical water splitting activity of different TiO2 nanotube samples showing that the film deposited at 150 °C has much higher activity correlating well with the lower crystallite size and the higher degree of self-organization observed in comparison with the nanotubes obtained at different temperatures. Importantly, the film showing higher water splitting activity does not have the best adhesion on glass substrate, highlighting an important trade-off for future optimization.
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- 2018
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18. Facet‐Control versus Co‐Catalyst‐Control in Photocatalytic H2 Evolution from Anatase TiO2 Nanocrystals
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Shanshan Qin, Lancang Shui, Benedict Osuagwu, Nikita Denisov, Dr. Alexander B. Tesler, and Prof. Patrik Schmuki
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anatase TiO2 ,crystal facet engineering ,Pt co-catalyst ,photocatalytic H2 evolution ,Chemistry ,QD1-999 - Abstract
Abstract Titanium dioxide (TiO2) and, in particular, its anatase polymorph, is widely studied for photocatalytic H2 production. In the present work, we examine the importance of reactive facets of anatase crystallites on the photocatalytic H2 evolution from aqueous methanol solutions. For this, we synthesized anatase TiO2 nanocrystals with a large amount of either {001} facets, that is, nanosheets, or {101} facets, that is, octahedral nanocubes, and examined their photocatalytic H2 evolution and then repeated this procedure with samples where Pt co‐catalyst is present on all facets. Octahedral nanocubes with abundant {101} facets produce >4 times more H2 than nanosheets enriched in {001} facets if the reaction is carried out under co‐catalyst‐free conditions. For samples that carry Pt co‐catalyst on both {001} and {101} facets, faceting loses entirely its significance. This demonstrates that the beneficial role of faceting, namely the introduction of {101} facets that act as electron transfer mediator is relevant only for co‐catalyst‐free TiO2 surfaces.
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- 2022
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19. MoP-protected Mo oxide nanotube arrays for long-term stable supercapacitors
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Bowen, Jin, Seyedsina, Hejazi, Hongqi, Chu, Shiva, Mohajernia, Nguyen, Nhat Truong, Min, Yang, Marco, Altomare, and Patrik, Schmuki
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- 2019
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20. <scp> TiO 2 </scp> Nanotubes and Their Photocatalytic Applications
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Yanyan Song, Kiyoung Lee, Indhumati Paramasivam, Doohun Kim, Benjamin P. Wilson, and Patrik Schmuki
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- 2023
21. Single Atoms in Photocatalysis: Low Loading Is Good Enough!
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Shanshan Qin, Johannes Will, Hyesung Kim, Nikita Denisov, Simon Carl, Erdmann Spiecker, and Patrik Schmuki
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Fuel Technology ,Renewable Energy, Sustainability and the Environment ,Chemistry (miscellaneous) ,Materials Chemistry ,Energy Engineering and Power Technology - Published
- 2023
22. Band gap and Morphology Engineering of Hematite Nanoflakes from an Ex Situ Sn Doping for Enhanced Photoelectrochemical Water Splitting
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Hyo-Jin Ahn, Stepan Kment, Alberto Naldoni, Radek Zbořil, and Patrik Schmuki
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General Chemical Engineering ,General Chemistry - Abstract
In this article, we report a simple ex situ Sn-doping method on hematite nanoflakes (coded as MSnO2-H) that can protect the nanoflake (NF) morphology against the 800 degrees C high-temperature annealing process and activate the photoresponse of hematite until 800 nm wavelength excitation. MSnO2-H has been fabricated by dropping SnCl4 ethanol solution on hematite nanoflakes homogeneously grown over the conductive FTO glass substrate and annealed at 500 degrees C to synthesize the SnO2 nanoparticles on hematite NFs. The Sn-treated samples were then placed in a furnace again, and the sintering process was conducted at 800 degrees C for 15 min. During this step, structure deformation of hematite occurs normally due to the grain boundary motion and oriented attachment. However, in the case of MSnO2-H, the outer SnO2 nanoparticles efficiently prevented a shape deformation and maintained the nanoflake shape owing to the encapsulation of hematite NFs. Furthermore, the interface of hematite/SnO2 nanoparticles became the spots for a heavy Sn ion doping. We demonstrated the generation of the newly localized states, resulting in an extension of the photoresponse of hematite until 800 nm wavelength light irradiation. Furthermore, we demonstrated that SnO2 nanoparticles can effectively act as a passivation layer, which can reduce the onset potential of hematite for water splitting redox reactions. The optimized MSnO2-H nanostructures showed a 2.84 times higher photocurrent density and 300 mV reduced onset potential compared with a pristine hematite nanoflake photoanode. Web of Science
- Published
- 2022
23. DC sputter deposited TiO2 layers on FTO: towards a maximum photoelectrochemical response of photoanodes
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Hyesung Kim, Yue Wang, Nikita Denisov, Zhenni Wu, Štěpán Kment, and Patrik Schmuki
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Abstract
Abstract In this work, we examine the photoelectrochemical response of TiO2 layers prepared by reactive DC sputter deposition on conductive glass (FTO). We show that adequate conditioning of the FTO by a very thin (few nm thick) Ti interlayer and optimizing the sputter parameters, compact TiO2 anatase layers can be produced that reach incident photocurrent conversion efficiencies (IPCE) maxima peaking at 75%. This is outperforming many of the best titania photoanode structures (including high surface area 1D and 3D titania structures). The key role of the interlayer is to promote the crystallization of titania in the anatase form during the annealing process (as opposed to rutile in the interlayer-free case). Without this interlayer, an IPCE maxima of ≈43% is obtained for otherwise identically processed electrodes. The present work thus describes a most simple straightforward approach for fabricating compact, high-efficiency TiO2 (anatase) photoanodes. Graphical abstract
- Published
- 2022
24. Nontoxic Liquid-Infused Slippery Coating Prepared on Steel Substrates Inhibits Corrosion and Biofouling Adhesion
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Alexander B. Tesler, Lucia H. Prado, Ingo Thievessen, Anca Mazare, Patrik Schmuki, Sannakaisa Virtanen, and Wolfgang H. Goldmann
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General Materials Science - Abstract
Wetting of surfaces plays a vital role in many biological and industrial processes. There are several phenomena closely related to wetting such as biofouling and corrosion that cause the deterioration of materials, while the efforts to prevent the degradation of surface functionality have spread over several millennia. Antifouling coatings have been developed to prevent/delay both corrosion and biofouling, but the problems remain unsolved, influencing the everyday life of the modern society in terms of safety and expenses. In this study, liquid-infused slippery surfaces (LISSs), a recently developed nontoxic repellent technology, that is, a flat variation of omniphobic slippery liquid-infused porous surfaces (SLIPSs), were studied for their anti-corrosion and marine anti-biofouling characteristics on metallic substrates under damaged and plain undamaged conditions. Austenitic stainless steel was chosen as a model due to its wide application in aquatic environments. Our LISS coating effectively prevents biofouling adhesion and decays corrosion of metallic surfaces even if they are severely damaged. The mechanically robust LISS reported in this study significantly extends the SLIPS technology, prompting their application in the marine environment due to the synergy between the facile fabrication process, rapid binding kinetics, nontoxic, ecofriendly, and low-cost applied materials together with excellent repellent characteristics.
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- 2022
25. Reactive Deposition Versus Strong Electrostatic Adsorption (SEA): A Key to Highly Active Single Atom co‐Catalysts in Photocatalytic H2 Generation
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Yue Wang, Shanshan Qin, Nikita Denisov, Hyesung Kim, Zdeněk Baďura, Bidyut Bikash Sarma, and Patrik Schmuki
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2023
26. Pt Single Atoms as Co‐Catalysts on CdS‐Sensitized Single‐Crystalline TiO 2 Nanoflakes for Enhanced Visible Light Photocatalytic H 2 Generation
- Author
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Waseem Raza, Alexander B. Tesler, Anca Mazare, Ondrej Tomanec, Stepan Kment, and Patrik Schmuki
- Subjects
Inorganic Chemistry ,Organic Chemistry ,Physical and Theoretical Chemistry ,Catalysis - Published
- 2023
27. Direct and Indirect Effects of Fluorine on the Photocatalytic Performance of Titania‐Based Photocatalysts
- Author
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Si-Ming Wu and Patrik Schmuki
- Subjects
General Energy - Published
- 2023
28. Light‐Induced Agglomeration of Single‐Atom Platinum in Photocatalysis
- Author
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Nikita Denisov, Shanshan Qin, Johannes Will, Bojana Nedić Vasiljevic, Natalia V. Skorodumova, Igor A. Pašti, Bidyut Bikash Sarma, Benedict Osuagwu, Tadahiro Yokosawa, Johannes Voss, Janis Wirth, Erdmann Spiecker, and Patrik Schmuki
- Subjects
Technology ,Mechanics of Materials ,Mechanical Engineering ,ddc:660 ,General Materials Science ,ddc:620 ,ddc:600 - Abstract
Advanced materials 35(5), 2206569 (2023). doi:10.1002/adma.202206569, With recent advances in the field of single-atoms (SAs) used in photocatalysis, an unprecedented performance of atomically dispersed co-catalysts has been achieved. However, the stability and agglomeration of SA co-catalysts on the semiconductor surface may represent a critical issue in potential applications. Here we describe the photoinduced destabilization of Pt SAs on the benchmark photocatalyst, TiO2. In aqueous solutions within illumination timescales ranging from few minutes to several hours, light-induced agglomeration of Pt SAs to ensembles (dimers, multimers) and finally nanoparticles takes place. The kinetics critically depends on the presence of sacrificial hole scavengers and the used light intensity. DFT calculations attribute the light induced destabilization of the SA Pt species to binding of surface-coordinated Pt with solution-hydrogen (adsorbed H atoms), which consequently weakens the Pt SA bonding to the TiO2 surface. Despite the gradual aggregation of Pt SAs into surface clusters and their overall reduction to metallic state, which involves >90% of Pt SAs, the overall photocatalytic H2 evolution remains virtually unaffected., Published by Wiley-VCH, Weinheim
- Published
- 2023
29. Amorphous NiCu Thin Films Sputtered on TiO2 Nanotube Arrays: A Noble-Metal Free Photocatalyst for Hydrogen Evolution
- Author
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Marco Pinna, Angeline Wo Weng Wei, Davide Spanu, Johannes Will, Tadahiro Yokosawa, Erdmann Spiecker, Sandro Recchia, Patrik Schmuki, Marco Altomare, Photocatalytic Synthesis, and MESA+ Institute
- Subjects
Inorganic Chemistry ,hydrogen evolution ,TiO ,Organic Chemistry ,noble-metal free ,UT-Hybrid-D ,TiO2 ,Physical and Theoretical Chemistry ,NiCu alloy ,ddc:600 ,photocatalysis ,Catalysis - Abstract
In this work, NiCu co‐catalysts on TiO2 are studied for photocatalytic hydrogen evolution. NiCu co‐catalyst films are deposited at room temperature by argon plasma sputtering on high aspect‐ratio anodic TiO2 nanotubes. To tune the Ni : Cu atomic ratio, alloys of various compositions were used as sputtering targets. Such co‐catalyst films are found to be amorphous with small nanocrystalline domains. A series of parameters is investigated, i. e., i) Ni : Cu relative ratio in the sputtered films, ii) NiCu film thickness, and iii) thickness of the TiO2 nanotube layers. The highest photocatalytic activity is obtained with 8 μm long TiO2 nanotubes, sputter‐coated with a 10 nm‐thick NiCu films with a 1 : 1 Ni : Cu atomic ratio. This photocatalyst reaches a stable hydrogen evolution rate of 186 μL h−1 cm−2, 4.6 and 3 times higher than that of Ni‐ and Cu‐TiO2, respectively, demonstrating a synergistic co‐catalytic effect of Ni and Cu in the alloy co‐catalyst film.
- Published
- 2022
30. Uncovering the Role of Trioctylphosphine on Colloidal and Emission Stability of Sb-Alloyed Cs2NaInCl6 Double Perovskite Nanocrystals
- Author
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Lukáš Zdražil, Sergii Kalytchuk, Štěpán Kment, Alberto Naldoni, Andrey L. Rogach, Radek Zboril, Patrik Schmuki, and Razi Ahmad
- Subjects
cationic ligand ,NaInCl ,Reaction mechanism ,Photoluminescence ,Materials science ,Nucleation ,Trioctylphosphine ,Ionic bonding ,Cs2NaInCl6 ,Chloride ,double perovskite nanocrystals ,chemistry.chemical_compound ,chemistry ,Nanocrystal ,Chemical engineering ,Oleylamine ,medicine ,photoluminescence ,General Materials Science ,colloidal stability ,Cs ,2 ,6 ,medicine.drug - Abstract
Doping and compositional tuning of Cs(2)AInCl(6) (A = Ag, Na) double perovskite nanocrystals (PNCs) is considered a promising strategy toward the development of light-emitting sources for applications in solution-processed optoelectronic devices. Oleic acid and oleylamine are by far the most often used surface capping ligands for PNCs. However, the undesirable desorption of these ligands due to proton-exchange reaction during isolation and purification processing results in colloidal and structural instabilities. Thus, the improvement of colloidal and optical stability of PNCs represents one of the greatest challenges in the field. Here, we report a trioctylphosphine-mediated synthesis and purification method toward Sb-alloyed Cs2NaInCl6 PNCs with excellent stability and optical features. Nuclear magnetic resonance spectroscopy enabled one to explain the role of trioctylphosphine and to reveal the reaction mechanism during crystal nucleation and growth. Under the optimized reaction conditions, in situ-generated trioctylphosphonium chloride and benzoyl trioctylphosphonium chloride serve as highly reactive halide sources, while benzoyl trioctylphosphonium and oleylammonium cations together with the oleate anion serve as surface capping ligands, which are bound strongly to the PNC surface. The tightly bound ionic pair of oleylammonium oleate and benzoyl trioctylphosphonium chloride/oleate ligands allows one to obtain monodispersed bright-blue-emitting PNCs with high photoluminescence quantum yields exceeding 50% at an optimum Sb content (0.5%), which also exhibit long-term colloidal stability. The approach based on dual cationic ligand passivation of double PNCs opens the doors for applications in other systems with a potential to achieve higher stability along with superior optical properties. Web of Science 13 40 47859 47845
- Published
- 2021
31. Critical factors for photoelectrochemical and photocatalytic H2 evolution from gray anatase (001) nanosheets
- Author
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Shanshan Qin, Nikita Denisov, Xin Zhou, Lukáš Zdražil, Dominik Fehn, Imgon Hwang, Mark Bruns, Hyesung Kim, Karsten Meyer, and Patrik Schmuki
- Subjects
General Energy ,Materials Science (miscellaneous) ,Materials Chemistry ,ddc:620 - Abstract
In recent years, the defect engineering of titania via reduction treatments has shown a high potential for enabling efficient and co-catalyst-free photocatalytic H2 generation from methanol/water solutions. However, defect engineering simultaneously alters several properties of TiO2. Here, we use pristine (white) and hydrogenated (gray) anatase nanosheets with dominant (001) facets. By comparing electrical conductivity, photocurrent spectra, transient photocurrent response, and photocatalytic H2 evolution, we show that the increased conductivity or broad visible light absorption of gray titania is not responsible for its increased activity. Instead, the true bottleneck is the hole transfer rate that is significantly accelerated while using gray instead of white modification. Moreover, the hole transfer reaction causes the accumulation of the reaction products in pure water, hindering the photocatalytic H2 evolution over time. These combined factors explain the superior performance of gray titania over white titania in photoelectrochemical or photocatalytic water splitting.
- Published
- 2022
32. Facile Approach of Direct Sulfidation of FTO to Form Vertically Aligned SnS2 Nanoflake Photoanodes for Efficient Photoelectrochemical Water Splitting
- Author
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Patrik Schmuki, Benedict Osuagwu, Alexander B. Tesler, and Waseem Raza
- Subjects
Materials science ,Chemical engineering ,Materials Chemistry ,Electrochemistry ,Sulfidation ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Water splitting ,Electrical and Electronic Engineering - Published
- 2021
33. Transparent and Low-Loss Luminescent Solar Concentrators Based on Self-Trapped Exciton Emission in Lead-Free Double Perovskite Nanocrystals
- Author
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Oldřich Zmeškal, Razi Ahmad, Štěpán Kment, Michal Otyepka, Jan Pospisil, Sergii Kalytchuk, Patrik Schmuki, Andres Osvet, Radek Zbořil, Marco Altomare, Michal Langer, Lukáš Zdražil, and Christoph J. Brabec
- Subjects
Materials science ,business.industry ,Exciton ,Monte Carlo method ,Energy Engineering and Power Technology ,Lead (geology) ,Nanocrystal ,Photovoltaics ,ddc:540 ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Optoelectronics ,Double perovskite ,Electrical and Electronic Engineering ,business ,Luminescence - Abstract
Luminescent solar concentrators (LSCs) are light-harvesting devices that redirect solar light to an edge-attached photovoltaic cell, and thus, they have high potential to be incorporated directly into buildings’ windows to allow for generating electricity. Perovskite nanocrystals (PNCs) are promising materials for LSCs because their enticing optical properties can be engineered to provide a high photoluminescence (PL) quantum yield (QY) and low overlap between absorption and emission spectra. Replacement of toxic, lead-containing perovskites in LSCs by lead-free PNCs, while retaining high optical efficiency of the device, remains the key challenge, which needs to be overcome to build environmentally friendly solar-harvesting platforms. In this work, we use nanocrystals of Bi-doped Cs2Ag0.4Na0.6InCl6 double perovskites with a self-trapped exciton emission to realize for the first time a transparent, low-reabsorption, lead-free perovskite-based LSC. Fabricated 100 cm2 LSCs show an internal optical quantum efficiency of 21.2% with the corresponding internal concentration factor of 2.7. Monte Carlo (MC) ray-tracing simulations identified the loss caused by nonunity PL QY to be the most significant contribution to the overall efficiency loss. The MC simulations also allowed us to estimate the efficiency of 39.4% for 2,500 cm2 LSCs with hypothetical unity PL. These results demonstrate a significant promise held by Bi-doped lead-free PNCs for LSCs.
- Published
- 2021
34. Graphite-decorated TiO2 nanotubes for enhanced photocatalytic H2 evolution
- Author
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Amara Nasir, Anca Mazare, Alexander Tesler, Shiva Mohajernia, Patrik Schmuki, and Tariq Yasin
- Published
- 2022
35. Pt-single atom decorated TiO2: Tuning anodic TiO2 nanotube structure and geometry toward a high-performance photocatalytic H2 production
- Author
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Xuewen Chen, Shanshan Qin, Nikita Denisov, Song-Zhu Kure-Chu, and Patrik Schmuki
- Subjects
General Chemical Engineering ,Electrochemistry - Published
- 2023
36. Spatially Confined Formation of Single Atoms in Highly Porous Carbon Nitride Nanoreactors
- Author
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Yunpeng Zuo, Yang Chai, Radek Zbořil, Dewei Rao, Tingting Li, Štěpán Kment, Patrik Schmuki, Tianyun Jing, and Ning Zhang
- Subjects
Materials science ,General Engineering ,Nucleation ,General Physics and Astronomy ,02 engineering and technology ,Nanoreactor ,Overpotential ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Catalysis ,Amorphous solid ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Hexafluorophosphate ,General Materials Science ,0210 nano-technology ,Carbon nitride - Abstract
Reducing the size of a catalyst to a single atom (SA) level can dramatically change its physicochemical properties and significantly boost its catalytic activity. However, the massive synthesis of SA catalysts still remains a grand challenge mainly because of the aggregation and nucleation of the generated atoms during the reaction. Here, we design and implement a spatially confined synthetic strategy based on a porous-hollow carbon nitride (p-CN) coordinated with 1-butyl-3-methylimidazole hexafluorophosphate, which can act as a nanoreactor and allow us to obtain metal SA catalysts (p-CN@M SAs). This relatively easy and highly effective method provides a way to massively synthesize single/multiple atoms (p-CN@M SAs, M = Pt, Pd, Cu, Fe, etc.). Moreover, the amorphous NiB-coated p-CN@Pt SAs can further increase the loading amount of Pt SAs to 3.7 wt %. The synthesized p-CN@Pt&NiB electrocatalyst exhibits an extraordinary hydrogen evolution reaction activity with the overpotential of 40.6 mV@10 mA/cm-2 and the Tofel slope of 29.26 mV/dec.
- Published
- 2021
37. Intrinsically Ru-Doped Suboxide TiO2 Nanotubes for Enhanced Photoelectrocatalytic H2 Generation
- Author
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Seyedsina Hejazi, Shiva Mohajernia, Naimeh Naseri, Omran Moradlou, Hamid Mehdipour, Patrik Schmuki, Elham Khorashadizade, and Alireza Z. Moshfegh
- Subjects
Suboxide ,Materials science ,Doping ,technology, industry, and agriculture ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Water splitting ,Hydrogen evolution ,Reduction treatment ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
In the present research, we investigate the synergistic effects of Ru-doping and Ar/H2 reduction treatment on the photoelectrochemical water splitting performance and hydrogen evolution rate of TiO...
- Published
- 2021
38. Mechanical properties of anodic titanium dioxide nanostructures
- Author
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Matej Daniel, Chandrashekhar V. Rode, Mukta Kulkarni, Josef Sepitka, Metka Benčina, Patrik Schmuki, Aleš Iglič, Suresh Gokhale, Niharika Rawat, Ita Junkar, and Anca Mazare
- Subjects
Nanostructure ,Materials science ,Polymers and Plastics ,Scanning electron microscope ,Metals and Alloys ,symbols.namesake ,chemistry.chemical_compound ,chemistry ,Titanium dioxide ,Vickers hardness test ,symbols ,Composite material ,Raman spectroscopy ,Spectroscopy ,Elastic modulus ,FOIL method - Abstract
Highly ordered and uniform titanium dioxide (TiO2) nanotubes (NTs) with different morphologies (15 nm, 50 nm and 100 nm in diameter) were prepared by the electrochemical anodization of Ti substrates. The TiO2 NTs’ surface properties were characterized by X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elastic modulus (E) and the Vickers hardness (HV) of the Ti foil and of the different-morphology TiO2 NTs were evaluated with the nano-indentation technique. E and HV increase with the decreasing length/diameter of the NTs, meaning that NTs with smaller diameters are more resistant to mechanical wear. The elastic modulus of the TiO2 NTs with 15-nm and 50-nm diameters is similar to that of the human bone.
- Published
- 2021
39. Voltage-Switchable Biosensor with Gold Nanoparticles on TiO2 Nanotubes Decorated with CdS Quantum Dots for the Detection of Cholesterol and H2O2
- Author
-
Sung Oh Cho, Muhammad Asim Rasheed, Muhammad Maqbool, Shafqat Karim, Amjad Nisar, Mashkoor Ahmad, Maaz Khan, Patrik Schmuki, Ghafar Ali, and Nilem Khaliq
- Subjects
Materials science ,Nanostructure ,010401 analytical chemistry ,020206 networking & telecommunications ,02 engineering and technology ,01 natural sciences ,Amperometry ,Cadmium sulfide ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Colloidal gold ,Quantum dot ,Electrode ,Titanium dioxide ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,Biosensor - Abstract
A thin layer of gold nanoparticles (Au NPs) sputtered on cadmium sulfide quantum dots (CdS QDs) decorated anodic titanium dioxide nanotubes (TNTs) (Au/CdS QDs/TNTs) was fabricated and explored for the nonenzymatic detection of cholesterol and hydrogen peroxide (H2O2). Morphological studies of the sensor revealed the formation of uniform nanotubes decorated with a homogeneously dispersed CdS QDs and Au NPs layer. The electrochemical measurements showed an enhanced electrocatalytic performance with a fast electron transfer (∼2 s) between the redox centers of each analyte and electrode surface. The hybrid nanostructure (Au/CdS QDs/TNTs) electrode exhibited about a 6-fold increase in sensitivity for both cholesterol (10,790 μA mM-1 cm-2) and H2O2 (78,833 μA mM-1 cm-2) in analyses compared to the pristine samples. The hybrid electrode utilized different operational potentials for both analytes, which may lead to a voltage-switchable dual-analyte biosensor with a higher selectivity. The biosensor also demonstrated a good reproducibility, thermal stability, and increased shelf life. In addition, the clinical significance of the biosensor was tested for cholesterol and H2O2 in real blood samples, which showed maximum relative standard deviations of 1.8 and 2.3%, respectively. These results indicate that a Au/CdS QDs/TNTs-based hybrid nanostructure is a promising choice for an enzyme-free biosensor due to its suitable band gap alignment and higher electrocatalytic activities.
- Published
- 2021
40. Self-assembly and activation of a titania-nanotube based photocatalyst for H2 evolution
- Author
-
Patrik Schmuki, Fan Fu, Gihoon Cha, and Zhenni Wu
- Subjects
Nanotube ,Materials science ,Aqueous solution ,business.industry ,Functional features ,Metals and Alloys ,Nanotechnology ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Semiconductor ,Materials Chemistry ,Ceramics and Composites ,Photocatalysis ,Self-assembly ,Extended time ,business - Abstract
Constructing an efficient photocatalyst for H2 production generally requires the integration of several functional features in and on a semiconductor platform. This is conventionally done by a classic step-by-step synthesis. Here, we report the self-assembly of an amorphous titania nanotube based system when illuminated for extended time in suitable aqueous solutions. Over time, not only photodeposition of a co-catalyst can take place, but also in situ crystallization and morphology changes occur that can provide a higher H2 production than observed for a classically assembled photocatalyst.
- Published
- 2021
41. A drastic improvement in photocatalytic H2 production by TiO2 nanosheets grown directly on Ta2O5 substrates
- Author
-
Benedict Osuagwu, Waseem Raza, Patrik Schmuki, and Alexander B. Tesler
- Subjects
Anatase ,Materials science ,Substrate (chemistry) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Tin oxide ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Titanium dioxide ,Photocatalysis ,General Materials Science ,0210 nano-technology ,Photocatalytic water splitting ,Production rate - Abstract
Titanium dioxide (TiO2) is the most frequently studied semiconducting material for photocatalytic water splitting. One of the favored forms of TiO2 for photocatalytic applications is layers of erected single-crystalline anatase nanosheets (NSs), while the most frequently reported substrate used for its synthesis is a fluorine-doped tin oxide (FTO). Herein we demonstrate that anatase TiO2 NS layers can be similarly grown on a Ta2O5 substrate. We found that a Ta2O5 back contact provides a remarkable improvement of the photocatalytic activity of the TiO2 NSs in comparison to a FTO back contact. The TiO2 NSs on Ta2O5 exhibit a 170-fold increase in photocatalytic H2 production rate than that obtained by TiO2 NSs on FTO substrate. The proposed mechanism reveals that such a drastic enhancement of optimized TiO2 NS arrays on the Ta2O5 substrate is attributed to the blocking nature of Ta2O5 for photo-generated electrons in the TiO2 NSs.
- Published
- 2021
42. A long-term stable aqueous aluminum battery electrode based on one-dimensional molybdenum–tantalum oxide nanotube arrays
- Author
-
Hongqi Chu, Marco Altomare, Min Yang, Patrik Schmuki, Bowen Jin, Gihoon Cha, and Seyedsina Hejazi
- Subjects
Nanotube ,Aqueous solution ,Materials science ,Intercalation (chemistry) ,Oxide ,chemistry.chemical_element ,Electrochemistry ,Redox ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Molybdenum ,Electrode ,General Materials Science - Abstract
Aluminum ion aqueous batteries (AIBs) are among the most promising candidates for high energy density devices due to the multivalent redox processes associated with Al3+ ion intercalation. However, only a few stable AIB electrode materials have been reported so far. MoO3 is a very promising electrode material due to its octahedral layered crystal structure which can accommodate multivalent cation by intercalation. However, the poor electrochemical stability of MoO3 and the sluggish intercalation kinetics of Al3+ ion in Mo oxides electrodes limit its practical application. In this work, we propose a strategy to overcome such shortcomings of MoO3 by fabricating electrodes composed of self-ordered one-dimensional (1D) MoTaOx nanotubes synthesized via electrochemical anodization of Mo-Ta alloy substrates. We show that this approach allows for direct incorporation of Ta in the Mo oxide nanotubes. The resulting MoTaOx nanotubes, composed of octahedral MoO3 and rhombohedral Mo2Ta2O11 phases, exhibit remarkable electrochemical stability and Al-ion storage properties in aqueous electrolytes that are superior to that of pristine Mo oxide or other most efficient electrode materials reported to date. Such MoTaOx nanotube-based electrodes can achieve a specific capacity of 1180 mA h cm-3 (337 mA h g-1, 141 μA h cm-2) at 1.25 A cm-3 (∼0.35 A g-1, 0.15 mA cm-2). More importantly, the capacity retention of such nanotube array electrodes remains above 83% of the initial capacity after 3000 cycles.
- Published
- 2021
43. Photoelectrochemical performance of facet-controlled TiO2 nanosheets grown hydrothermally on FTO
- Author
-
Gihoon Cha, Benedict Osuagwu, Fahimeh Shahvardanfard, Patrik Schmuki, and Nikita Denisov
- Subjects
Photocurrent ,Anatase ,Materials science ,General Engineering ,Bioengineering ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Tin oxide ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Hydrothermal circulation ,0104 chemical sciences ,Faceting ,Chemical engineering ,Electrode ,General Materials Science ,0210 nano-technology ,Single crystal - Abstract
Single crystal anatase TiO2 nanosheets (TiO2-NSs) are grown hydrothermally on fluorine-doped tin oxide (FTO). By systematically changing the hydrothermal conditions such as reaction time, initial concentration of Ti precursor, F precursor, and HCl as an additive, a wide variety of TiO2-NSs, with different morphologies and faceting have been synthesized. For the different morphologies and different facet ratios (anatase S001/S001+101), the photoelectrochemical response is characterized and compared. We find that for photoanodes in neutral electrolytes, the magnitude of the photocurrent depends strongly on the growth parameters, that is, peak IPCEs can vary from 11.7% to 61%. For a wide range of parameters, the key parameter deciding on the photocurrent is the effective electrochemically active area of the electrode. Only for very high facet ratios >91%, the photoresponse can be strongly influenced by faceting – for samples with a S001/S001+101 of 91%, IPCE value of ≈84% is obtained. This work defines not only optimized synthesis conditions for a most effective growth of these single crystalline electrode, but also represents fundamental data for further applications of such electrodes.
- Published
- 2021
44. Hydrogenated anatase TiO2 single crystals: defects formation and structural changes as microscopic origin of co-catalyst free photocatalytic H2 evolution activity
- Author
-
Johannes Will, Markus Stiller, Klaus Götz, Alexander B. Tesler, Erdmann Spiecker, Ewa Wierzbicka, Mingjian Wu, Tadahiro Yokosawa, Tobias Unruh, Ning Liu, Marco Altomare, Patrik Schmuki, Photocatalytic Synthesis, and MESA+ Institute
- Subjects
Anatase ,Materials science ,Renewable Energy, Sustainability and the Environment ,Annealing (metallurgy) ,Brookite ,General Chemistry ,22/4 OA procedure ,Crystallographic defect ,Crystal ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,visual_art ,visual_art.visual_art_medium ,Photocatalysis ,Strontium titanate ,Water splitting ,General Materials Science - Abstract
Herein we systematically investigate the influence of hydrogenation time and temperature on defects formation, structural changes, and co-catalyst free photocatalytic activity for epitaxially grown anatase thin films on strontium titanate single crystals. The photocatalytic activity trend of the anatase epi layers is similar to that of anatase powders and brookite single crystals in reported recent literature, that is, the H2 evolution rate exhibits a typical maximum upon hydrogenation under moderate annealing temperatures (500 °C). By combining surface sensitive X-ray diffraction methods and analytical high-resolution electron microscopy techniques we reveal quantitatively the oxygen loss from the epi-layer ascribed to the hydrogenation (H2 reduction) treatment. We observe specific physicochemical changes associated with the introduction of oxygen vacancies: (i) the formation of a nanoscale strained crystal surface, (ii) the agglomeration of point defects in the bulk of the anatase epi layer, and (iii) a transition towards a Ti2O3 like symmetry at the film surface, i.e. an evident oxygen deficiency at the epi layer surface in particular prominent for the most active sample as a function of the hydrogenation parameters. These extensive experimental findings allow us to propose an empirical model, which links detrimental and beneficial effects of Ti3+ centers and oxygen vacancies in the bulk and at the surface and their abundance to an optimum point defect configuration for water splitting via “grey” anatase.
- Published
- 2021
45. Reduced grey brookite for noble metal free photocatalytic H2evolution
- Author
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Karsten Meyer, Erdmann Spiecker, Mingjian Wu, Ning Liu, Shanshan Qin, Johannes Will, Marco Altomare, Marianna Bellardita, Tobias Unruh, Dominik Fehn, Patrik Schmuki, Tadahiro Yokosawa, Ewa Wierzbicka, Leonardo Palmisano, Wierzbicka E., Altomare M., Wu M., Liu N., Yokosawa T., Fehn D., Qin S., Meyer K., Unruh T., Spiecker E., Palmisano L., Bellardita M., Will J., and Schmuki P.
- Subjects
Anatase ,Materials science ,Renewable Energy, Sustainability and the Environment ,Brookite ,Nanoparticle ,02 engineering and technology ,General Chemistry ,TiO2, brookite, H2 evolution ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Chemical engineering ,Rutile ,visual_art ,Photocatalysis ,engineering ,visual_art.visual_art_medium ,General Materials Science ,Noble metal ,Settore CHIM/07 - Fondamenti Chimici Delle Tecnologie ,0210 nano-technology ,Single crystal - Abstract
Herein we introduce for the first time a reduced “grey” brookite TiO2 photocatalyst, produced by thermal hydrogenation of brookite nanoparticles, that shows a remarkable noble metal free photocatalytic H2 evolution. Its activity is substantially higher than that of other TiO2 polymorphs, i.e. anatase or rutile, comparably sized and activated by hydrogenation under optimized conditions. Along with brookite powders, an oriented brookite single crystal was investigated as a defined surface to confirm the effects of the hydrogenation treatment. By a combination of electron paramagnetic resonance (EPR), electron and X-ray characterization techniques applied to the powders and single crystal, we find that hydrogenation forms in brookite a defective crystalline surface layer rich in Ti3+ states. Amorphization effects, i.e. forming the so called “amorphous shell” as reported in previous work for black anatase TiO2, were not detected. Overall, we provide experimental evidence that hydrogenation forms in brookite a surface strained zone with point defects that are mediators for electron transfer to H2O, leading to a significantly enhanced noble metal free photocatalytic H2 evolution in comparison to anatase.
- Published
- 2021
46. Constructing a photo-enzymatic cascade reaction and its in situ monitoring: enzymes hierarchically trapped in titania meso-porous MOFs as a new photosynthesis platform
- Author
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Junli Guo, Yan-Yan Song, Zhida Gao, Lingling Yang, Patrik Schmuki, and Chenxi Zhao
- Subjects
In situ ,Materials science ,010405 organic chemistry ,Renewable Energy, Sustainability and the Environment ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Enzyme catalysis ,Artificial photosynthesis ,Membrane ,Cascade reaction ,Chemical engineering ,Photocatalysis ,General Materials Science ,Nanoscopic scale ,Visible spectrum - Abstract
A photocatalysis-enzyme coupled system represents a most promising approach towards artificial photosynthesis and a direct use of solar energy for the synthesis of specific organic molecules or fuel. In contrast to extensively explored semiconductor photocatalysts, studies that successfully combine photocatalytic and enzymatic reactions are rare. In the present work we describe a photocatalyst–enzyme coupled approach that relies on the in situ synthesis of a hierarchically porous (hp) metal–organic framework (here using titania-based MIL-125) formed in the nanochannels of a TiO2 membrane. By engineering the nm-scale pore size in the MOF we achieve trapping of active cytochrome C (CytC). Benefiting from the intrinsic photocatalytic activity of the MOF [MIL-125 (Ti)] we develop a functional photocatalyst–enzyme system that is active under visible light. Moreover, the membrane-based architecture allows for in situ triggering and monitoring of the enzymatic reaction. Therefore, the platform represents not only a nanoscale photocatalytic reactor or device but also allows to monitor and understand photocatalytically coupled enzyme reactions.
- Published
- 2021
47. Facet‐Control versus Co‐Catalyst‐Control in Photocatalytic H 2 Evolution from Anatase TiO 2 Nanocrystals
- Author
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Shanshan Qin, Lancang Shui, Benedict Osuagwu, Nikita Denisov, Alexander B. Tesler, and Patrik Schmuki
- Subjects
General Chemistry - Published
- 2022
48. Robust dual cationic ligand for stable and efficient warm-white light emission in lead-free double perovskite nanocrystals
- Author
-
Razi Ahmad, Lukáš Zdražil, Sergii Kalytchuk, Alberto Naldoni, Elmira Mohammadi, Patrik Schmuki, Radek Zboril, and Štěpán Kment
- Subjects
Self-trapped excitons ,Double perovskite nanocrystals ,White-light emission ,Colloidal stability ,Dual cationic ligand ,General Materials Science - Published
- 2022
49. Fluorine Aided Stabilization of Pt Single Atoms on TiO$_2$ Nanosheets and Strongly Enhanced Photocatalytic H$_2$ Evolution
- Author
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Si-Ming Wu, Imgon Hwang, Benedict Osuagwu, Johannes Will, Zhenni Wu, Bidyut Bikash Sarma, Fu-Fei Pu, Li-Ying Wang, Zdenek Badura, Giorgio Zoppellaro, Erdmann Spiecker, and Patrik Schmuki
- Subjects
Technology ,ddc:540 ,General Chemistry ,ddc:600 ,Catalysis - Abstract
ACS catalysis 12, 33 - 41 (2022). doi:10.1021/acscatal.2c04481, Trapping sites in single atom (SA) catalysts are critical to the stabilization and reactivity of isolated atoms. Herein, we show that anchoring of Pt SAs on TiO$_2$ nanosheets is strongly aided by lattice incorporated fluorine species. Tailoring the speciation of fluorine on TiO$_2$ nanosheets is a key factor for uniform and stable dispersion of the Pt SAs and high efficiency in Pt SA co-catalyzed photocatalytic H$_2$ production. Fluorine-stabilized uniformly dispersed Pt SAs on the (001) surface of TiO$_2$ can provide a remarkable photocatalytic activity (a H$_2$ production rate of 45.3 mmol h$^{–1}$ mg$^{–1}$ Pt for 65 mW/cm2 365 nm light). This high (maximized) efficiency can be achieved with a remarkably low loading amount of Pt SAs on TiO$_2$ nanosheets (0.03 wt %), which is far superior to Pt nanoparticles on a TiO$_2$ nanosheet with the same or a higher loading amount. F-stabilized Pt SAs on TiO$_2$ nanosheets also exhibit an excellent stability in long-term photocatalytic reactions., Published by ACS, Washington, DC
- Published
- 2022
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50. Photocatalytic synthesis of oxidized graphite enabled by grey TiO2 and direct formation of a visible-light-active titania/graphene oxide nanocomposite
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Amara Nasir, Anca Mazare, Xin Zhou, Shanshan Qin, Nikita Denisov, Lukas Zdrazil, Štěpán Kment, Radek Zboril, Tariq Yasin, and Patrik Schmuki
- Subjects
graphite ,Organic Chemistry ,graphene oxide ,methylene-blue degradation ,Physical and Theoretical Chemistry ,grey TiO2 ,UV illumination ,Analytical Chemistry - Abstract
Herein we report a one-step, low cost, photocatalytic method for the synthesis of graphene oxide (GO) from commercial graphite using grey TiO2 as a photocatalyst. GO formation is achieved by UV-illumination of a slurry of well-dispersed grey TiO2 and commercial graphite. Light-induced valence-band holes from grey TiO2 then lead to an oxidation and exfoliation of graphite, resulting in the formation of visible-light-active GO. An optimal level of graphite oxidation can be established by controlling the UV illumination time. Moreover, the resulting GO-decorated TiO2 is directly active as a visible-light-active photocatalyst that can, for example, be used for pollution degradation. Web of Science art. no. e202100274
- Published
- 2022
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