Zeitschriftenartikel: „Photoinduced charge accumulation“

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Bonn, Annabell G., und Oliver S. Wenger. „Photoinduced Charge Accumulation in Molecular Systems“. CHIMIA International Journal for Chemistry 69, Nr. 1 (25.02.2015): 17–21. http://dx.doi.org/10.2533/chimia.2015.17.

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Kokorin, Alexander I., Tatyana V. Sviridova, Elizaveta A. Konstantinova, Dmitry V. Sviridov und Detlef W. Bahnemann. „Dynamics of Photogenerated Charge Carriers in TiO2/MoO3, TiO2/WO3 and TiO2/V2O5 Photocatalysts with Mosaic Structure“. Catalysts 10, Nr. 9 (04.09.2020): 1022. http://dx.doi.org/10.3390/catal10091022.

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Titania is a widely used photocatalytic material possessing such advantages as low cost and high reactivity under the ultraviolet light illumination. However, the fast recombination of photoexcited charge carriers limits its application. Herein, we have synthesized original nanomaterials with mosaic structures that exhibited well-defined heterojunctions and new properties. Using SEM, XRD, EPR spectroscopy, photocatalytic measurements, and photoinduced pathphysiological activity of these photocatalysts, we studied the processes of charge carrier accumulation in TiO2/MoO3, TiO2/WO3, and TiO2/V2O5 under in situ UV illumination with emphasis on the charge exchange between energy levels of these nanosized semiconductors. It is shown that the accumulation of photoinduced charges occurs in two forms (i) filled electron traps corresponding to Ti4+/Ti3+ levels and (ii) Mo5+ centers, both forms contributing to the photoinduced biocide activity of the samples. This work demonstrates that light exposure of heterostructure photocatalysts with mosaic surfaces produces different types of charge-trapping centers capable of interacting with molecular oxygen yielding peroxo species, which provide long-life light-induced ”self-cleaning” behavior. Such photoaccumulating materials open new opportunities in developing light-driven self-sterilization structures exhibiting a prolonged bactericidal effect up to 10 h after stopping light exposure.

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Bonn, Annabell G., und Oliver S. Wenger. „Photoinduced charge accumulation by metal ion-coupled electron transfer“. Physical Chemistry Chemical Physics 17, Nr. 37 (2015): 24001–10. http://dx.doi.org/10.1039/c5cp04718h.

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Strong Lewis acid/Lewis base interactions between Sc³⁺and superoxide anions permit the light-driven accumulation of two positive charges on oligotriarylamine units with appended Ru(ii) photosensitizers.

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Kamat, Prashant V. „Photoinduced transformations in semiconductormetal nanocomposite assemblies“. Pure and Applied Chemistry 74, Nr. 9 (01.01.2002): 1693–706. http://dx.doi.org/10.1351/pac200274091693.

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Semiconductormetal nanocomposites provide a simple and convenient way to tailor the properties of photocatalysts. Modification of semiconductor surface improves charge separation and promotes interfacial charge-transfer processes in nanocomposite systems. Charge accumulation in the metal layer results in Fermi-level equilibration raising the quasi-Fermi level of the composite close to the conduction band level of the oxide semiconductor. Phototransformations of such compositesincluding morphological changes, interfacial charge-transfer processes and photocurrent generation of TiO2-capped gold colloidsare presented in this review article.

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Ha-Thi, M. H., V. T. Pham, T. Pino, V. Maslova, A. Quaranta, C. Lefumeux, W. Leibl und A. Aukauloo. „Photoinduced electron transfer in a molecular dyad by nanosecond pump–pump–probe spectroscopy“. Photochemical & Photobiological Sciences 17, Nr. 7 (2018): 903–9. http://dx.doi.org/10.1039/c8pp00048d.

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Farran, Rajaa, Long Le-Quang, Jean-Marie Mouesca, Vincent Maurel, Damien Jouvenot, Frédérique Loiseau, Alain Deronzier und Jérôme Chauvin. „[Cr(ttpy)2]3+ as a multi-electron reservoir for photoinduced charge accumulation“. Dalton Transactions 48, Nr. 20 (2019): 6800–6811. http://dx.doi.org/10.1039/c9dt00848a.

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Under visible light irradiation [Cr(ttpy)2]3+ can be reduced twice by a tertiary amine; the photoreduction processes are accelerated in the presence of [Ru(bpy)₃]²⁺ acting as an antenna thanks to an efficient electron transfer reaction from [Ru(bpy)₃]^2+* to [Cr(ttpy)₂]³⁺.

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Zang, Huidong, Yu-Che Hsiao und Bin Hu. „Surface-charge accumulation effects on open-circuit voltage in organic solar cells based on photoinduced impedance analysis“. Phys. Chem. Chem. Phys. 16, Nr. 10 (2014): 4971–76. http://dx.doi.org/10.1039/c3cp54908a.

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8

Schulz, Martin, Nina Hagmeyer, Frerk Wehmeyer, Grace Lowe, Marco Rosenkranz, Bianca Seidler, Alexey Popov, Carsten Streb, Johannes G. Vos und Benjamin Dietzek. „Photoinduced Charge Accumulation and Prolonged Multielectron Storage for the Separation of Light and Dark Reaction“. Journal of the American Chemical Society 142, Nr. 37 (22.08.2020): 15722–28. http://dx.doi.org/10.1021/jacs.0c03779.

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Kuss-Petermann, Martin, und Oliver S. Wenger. „Pump-Pump-Probe Spectroscopy of a Molecular Triad Monitoring Detrimental Processes for Photoinduced Charge Accumulation“. Helvetica Chimica Acta 100, Nr. 1 (12.12.2016): e1600283. http://dx.doi.org/10.1002/hlca.201600283.

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Das, Sushanta K., Navaneetha K. Subbaiyan, Francis D'Souza, Atula S. D. Sandanayaka, Takatsugu Wakahara und Osamu Ito. „Formation and photoinduced properties of zinc porphyrin-SWCNT and zinc phthalocyanine-SWCNT nanohybrids using diameter sorted nanotubes assembled via metal-ligand coordination and π–π stacking“. Journal of Porphyrins and Phthalocyanines 15, Nr. 09n10 (September 2011): 1033–43. http://dx.doi.org/10.1142/s1088424611003951.

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Photoinduced electron transfer processes in self-assembled zinc porphyrin ( ZnP ) or zinc phthalocyanine ( ZnPc ) with semiconducting (7,6)- and (6,5)-enriched SWCNTs were investigated. To bind photosensitizers to SWCNTs, first, pyrene covalently functionalized with a phenylimidazole (Im-Pyr) entity was treated with SWCNTs. Exfoliation of SWCNTs occurred due to π–π stacking of pyrene with nanotubes walls leaving the imidazole entity that was subsequently used to coordinate ZnP or ZnPc in o-dichlorobenzene (DCB). The donor-acceptor nanohybrids thus formed were characterized by TEM imaging, steady-state UV-visible-near IR absorption and fluorescence spectra. Free-energy calculations suggested possibility of electron transfer from the photoexcited ZnP or ZnPc to Im-Pyr/SWCNT(n,m) in the nanohybrids. Consequently, steady-state and time-resolved fluorescence studies revealed efficient quenching of the singlet excited state of ZnP or ZnPc with the rate constants of charge separation (k CS ) in the range of (3–6) × 109 s-1. Nanosecond transient absorption technique confirmed the electron transfer products, ZnP·+←Im-Pyr/SWCNT·- and ZnPc·+←Im-Pyr/SWCNT·- (and opposite charged pairs) having characteristic absorptions with the decay rate constants due to charge recombination (k CR ) in the range of (1.4–2.4) × 107 s-1, corresponding to lifetimes of radical ion-pairs in the 70–100 ns range. The SWCNT·- was further utilized to mediate electrons to hexyl-viologen dication (HV2+) resulting in an electron-accumulation process in the presence of sacrificial electron donor, offering additional proof for the occurrence of photoinduced charge-separation and potential utilization of these materials in light energy harvesting applications. Further, photoelectrochemical cells have been constructed on FTO/ SnO2 electrodes to verify their ability to directly convert light into electricity. An IPCE efficiency of up to 7% has been achieved in case of ZnP←Im-Pyr/SWCNT modified electrode.

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Черемисин, А. Б., und Н. А. Кулдин. „Коррелированное изменение электрических характеристик тонкопленочного полевого транзистора при модификации физических свойств его оксидного полупроводникового канала (InZnO : N)“. Письма в журнал технической физики 44, Nr. 20 (2018): 95. http://dx.doi.org/10.21883/pjtf.2018.20.46811.17293.

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AbstractWe have studied changes in the transmission and current–voltage characteristics of a thin-film field-effect transistor (TFT) during modification of the physical properties of its oxide semiconductor channel based on InZnO:N layer. Modification of the electrical parameters of the device was based on the phenomenon of photoinduced charge accumulation in the semiconductor. It is established that the slopes and intercepts of the capacitance–voltage ( C _G– V _G) and transmission ( I _D– V _G) curves of the TFT under illumination exhibit correlated similar variations. The obtained results justify joint use of the C _G– V _G and I _D– V _G curves in the analysis of peculiarities of the energy band structure of oxide semiconductors.

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El Ghachtouli, Sanae, Régis Guillot, Winfried Leibl und Ally Aukauloo. „Intramolecular photoinduced electron transfer in cobalt(II) chlathrochelate-zinc porphyrin assemblies leading to long-lived Co(I) species“. Journal of Porphyrins and Phthalocyanines 18, Nr. 12 (Dezember 2014): 1125–30. http://dx.doi.org/10.1142/s1088424614500965.

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We report herein the synthesis and characterization of novel cobalt chlathrochelate-zinc porphyrin assemblies. X-ray data and electrochemical studies support the formation and maintenance of these structures both in solid and solution states. Light induced charge accumulation at the cobalt center was realized in the presence of a sacrificial electron donor. The photogenerated Co(I) species was stable in the ms time scale in aqueous medium.

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Xu, Caixia, Jingwen Zhang, Long Xu, Xinyan Ma und Hua Zhao. „Photoinduced charge carriers' accumulation and its impact on random lasing in Nd3+ doped (Pb,La)(Zr,Ti)O3 ceramics“. Journal of Applied Physics 121, Nr. 24 (28.06.2017): 243104. http://dx.doi.org/10.1063/1.4989976.

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Cai, Xingke, Nobuyuki Sakai, Tadashi C. Ozawa, Asami Funatsu, Renzhi Ma, Yasuo Ebina und Takayoshi Sasaki. „Efficient Photoinduced Charge Accumulation in Reduced Graphene Oxide Coupled with Titania Nanosheets To Show Highly Enhanced and Persistent Conductance“. ACS Applied Materials & Interfaces 7, Nr. 21 (19.05.2015): 11436–43. http://dx.doi.org/10.1021/acsami.5b02107.

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Savchuk, Timofey, Ilya Gavrilin, Elizaveta Konstantinova, Alexey Dronov, Roman Volkov, Nickolay Borgardt, Tomasz Maniecki, Sergey Gavrilov und Vladimir Zaitsev. „Anodic TiO₂ nanotube arrays for photocatalytic CO₂ conversion: comparative photocatalysis and EPR study“. Nanotechnology 33, Nr. 5 (12.11.2021): 055706. http://dx.doi.org/10.1088/1361-6528/ac317e.

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Abstract Titania (TiO2) is a widely used semiconductor for the photocatalytic decomposition of organic impurities in air, water and the conversion of CO2 into hydrocarbon fuel precursors. TiO2 in the form of nanotubes arrays is the most attractive for practical use because of the morphological advantages providing more favorable diffusion of photocatalytic reaction products and a low recombination rate of photogenerated electrons and holes. We have carried out a comparative study of the photocatalytic activity of gas-phase conversion of CO2 to hydrocarbon products and the defect properties of multi-walled and single-walled arrays of TiO2 nanotubes. Methanol and methane have been detected in the CO2 photoreduction process. The photocatalytic evolution rate of multi-walled TiO2 nanotubes is twice as fast for methane as for single-walled TiO2 nanotubes after four hours of irradiation and four times faster for methanol. The type and features of the structural defects have been investigated by EPR spectroscopy. For the first time, it has been shown that Ti3+/oxygen vacancy centers are mainly located inside the outer layer of nanotubes, while carbon dangling bonds have been observed directly on the surface of the inner layer. Carbon defects have been found to be the centers of adsorption and accumulation of photoinduced charge carriers. The results are entirely new; they clarify the role of different types of defects in the photocatalytic conversion of CO2 to hydrocarbon compounds and show good prospects for applying TiO2 nanotube arrays.

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Shcherbakova, V. B., T. V. Sviridova, D. V. Sviridov und V. E. Agabekov. „Mechanochemical structural nanoengineering of heterooxide photocatalysts TiO2/ V2O5 capable to accumulating photoinduced charges“. Doklady of the National Academy of Sciences of Belarus 68, Nr. 3 (08.07.2024): 207–13. http://dx.doi.org/10.29235/1561-8323-2024-68-3-207-213.

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The mechanochemical method yielding a composite photocatalyst TiO2/V2O5 of tubular morphology under localized mechanic impact on a mixture of dispersed oxides has been proposed. It has been shown that under contact loading amounting to 25–39 MPa, tubular TiO2 is growing due to bonding of hydrated oxide particles via polycondensation. In the case of a mixture of titania and vanadium oxides, the tubular structure growth is accompanied with dispersing V2O5 particles resulting in the release of free standing lamellae. The mechanochemical activation produces nanоheterojunctions TiO2/V2O5 able to ensure an effective separation of photo-induced charges and their accumulation in redox active V2O5. Employing mechanochemical activation for synthesis of a TiO2/V2O5 composite photocatalyst results in 2.5-fold enhancement of the oxidation activity induced by preliminary photocatalyst exposure.

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Drašković, Isabela, Ivana Fabijanić, Matthias Ferger, Todd B. Marder, Dragomira Majhen und Ivo Piantanida. „Interactions of variously coated gold and silver nanoparticles with a bis(triarylborane) photodyanmic therapy (PDT)-dye; their cellular uptake, cytotoxicity and photo-activity“. Periodicum Biologorum 125, Nr. 1-2 (25.10.2023): 65–74. http://dx.doi.org/10.18054/pb.v125i1-2.23726.

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Background and purpose: Diethynylarene-linked bis(triarylborane) tetracations can be used as probes for fluorimetric and Raman sensing of biomacromolecules, as well as promising theragnostic agents. Among them, bis(triarylborane) fluorophore (TAB3), when bonded to Ag nanoparticles (NP), stood out with specific properties such as Raman signal enhancemen of the TAB3 dye in a cuvette. However, TAB3 dye - nanoparticle composites have not been studied in biological systems. For this reason, questions arose as to whether different types of metal nanoparticles (Au or Ag-based) with different coatings (negatively charged citrate or neutral PVP) could be efficiently stained with the TAB3 dye in a cuvette. The aim of this research was to examine Au and Ag nanoparticles of similar size (20-25 nm) with different stabilizers for their cellular uptake, cytotoxicity in the dark and under visible light radiation, to characterize the interactions of nanoparticles with the TAB3 fluorophore, and to study NP-TAB3 composites in cells, evaluate their intracellular staining, as well as possible photoinduced release and biological activity. Materials and methods: The binding constants of Au- and Ag- based nanoparticles with TAB3 were determined by fluorimetric titrations. The cytotoxic effect of NPs was determined by the survival of A549 cells (MTT assay). Cellular uptake of both NP and NP-TAB3 composites were performed by live cell imaging experiments. Results: The Au- or Ag-based NPs with different coatings bind to the TAB3 with high affinity. These NPs, as well as TAB3-NP complexes, efficiently enter living human cells, accumulating in cytoplasm with no apparent selectivity for a particular organelle. Even prolonged 3-day treatment with the NPs studied did not show any toxic effect on the cells. Bioimaging studies in cells revealed that the TAB3-NP complex does not intracellularly dissociate; the previously reported photo-bioactivity of TAB3 is completely inhibited by binding to NPs. Conclusion: Au- and Ag NPs were non-covalently stained by TAB3, irrespective of the different coatings, with similar binding affinities. Emission from TAB3 is strongly quenched by the NPs, but not completely. Experiments on living human cells revealed that neither free NPs, nor their composites with TAB3, were toxic. Bioimaging studies by confocal microscopy revealed that all NPs efficiently enter living cells within 90 min. Colocalization experiment with simultaneous collection of data in the reflection and fluorescence modes demonstrated that the TAB3 dye remained bound to NPs inside cells. Strong irradiation of TAB3-NP inside cells with a 457 nm laser did not yield any damage to the cells, at variance with our previously shown very strong photo-bioactivity of the TAB3 dye alone. Thus, binding of a chromophore to a nanoparticle can inhibit the chromophore’s ability to undergo photo-induced singlet oxygen production, consequently blocking its photo-bioactivity.

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MIURA, Jin, Fumiyuki INAMURA, Takashi IKUTA, Kenzo MAEHASHI und Kenji IKUSHIMA. „Accumulation of photoinduced carriers at the SiO₂/Si interface observed through graphene transport“. Japanese Journal of Applied Physics, 20.12.2023. http://dx.doi.org/10.35848/1347-4065/ad1778.

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Abstract The accumulation of photoinduced carriers at the SiO2/Si interface was observed via graphene transport. Chemical vapor deposition graphene was transferred to a lightly p-doped silicon substrate with a SiO2 dielectric layer and served as a charge sensor for detecting the accumulation of photoinduced carriers at the SiO2/Si interface. The sample was cooled to 4.2 K to realize an undoped silicon substrate without intrinsic carriers. Photoexcited carriers in the undoped silicon substrate were collected at the SiO2/Si interface via a gate voltage and the carrier polarity was controlled well by the polarity of the gate voltage set during the light illumination. The photoinduced carrier density was determined by the number of photons incident on the silicon substrate with a photon-electron conversion efficiency of about 0.036. These results may provide polarity control of the conduction channel (n- or p-type) in standard Si-MOS structures, paving the way for optically programmable Si-CMOS.

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Zhang, Xianming, Lingyun Li, Bingzhe Wang, Zhipeng Cai, Bohan Zhang, Feng Chen, Guichuan Xing, Kai Li und Songnan Qu. „Donor‐Acceptor Type Supra‐Carbon‐Dots with Long Lifetime Photogenerated Radicals Boosting Tumor Photodynamic Therapy“. Angewandte Chemie International Edition, 22.08.2024. http://dx.doi.org/10.1002/anie.202410522.

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Carbon dots (CDs) have gained significant interest because of their potential in biomedical applications. Nevertheless, developing CDs with efficient photoinduced charge separation for tumor photodynamic therapy (PDT) remains a challenge. This study presents a novel class of supra‐carbon‐dots (supra‐CDs) developed by fusing red emissive CDs with 2,3‐dicyanohydroquinone (DCHQ) via post‐solvothermal treatment. In supra‐CDs, the core, acting as electron donors, is formed by assembled CDs with substantial sp2 domains, the fused interface originating from DCHQ with electron‐withdrawing groups functions as the electron acceptor. This configuration creates the unique donor‐acceptor nanostructure. Upon white light irradiation, the excited electrons from the assembled CDs were transferred to the electron‐withdrawing interface, whereas the photogenerated holes were retained within the assembled CDs as radicals, leading to effective photoinduced charge separation. The separated photogenerated electrons then react with oxygen to generate superoxide radicals. Simultaneously, the photogenerated holes undergo oxidation of crucial cellular substrates. This dual action underscores the exceptional cell‐killing efficacy of supra‐CDs. Moreover, the increased particle sizes (~20 nm) ensure supra‐CDs to exhibit a notable capacity for tumor accumulation via the improved permeability and retention effect, thereby achieving satisfactory anti‐tumor PDT efficacy in a mouse subcutaneous tumor model.

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Zhang, Xianming, Lingyun Li, Bingzhe Wang, Zhipeng Cai, Bohan Zhang, Feng Chen, Guichuan Xing, Kai Li und Songnan Qu. „Donor‐Acceptor Type Supra‐Carbon‐Dots with Long Lifetime Photogenerated Radicals Boosting Tumor Photodynamic Therapy“. Angewandte Chemie, 22.08.2024. http://dx.doi.org/10.1002/ange.202410522.

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Carbon dots (CDs) have gained significant interest because of their potential in biomedical applications. Nevertheless, developing CDs with efficient photoinduced charge separation for tumor photodynamic therapy (PDT) remains a challenge. This study presents a novel class of supra‐carbon‐dots (supra‐CDs) developed by fusing red emissive CDs with 2,3‐dicyanohydroquinone (DCHQ) via post‐solvothermal treatment. In supra‐CDs, the core, acting as electron donors, is formed by assembled CDs with substantial sp2 domains, the fused interface originating from DCHQ with electron‐withdrawing groups functions as the electron acceptor. This configuration creates the unique donor‐acceptor nanostructure. Upon white light irradiation, the excited electrons from the assembled CDs were transferred to the electron‐withdrawing interface, whereas the photogenerated holes were retained within the assembled CDs as radicals, leading to effective photoinduced charge separation. The separated photogenerated electrons then react with oxygen to generate superoxide radicals. Simultaneously, the photogenerated holes undergo oxidation of crucial cellular substrates. This dual action underscores the exceptional cell‐killing efficacy of supra‐CDs. Moreover, the increased particle sizes (~20 nm) ensure supra‐CDs to exhibit a notable capacity for tumor accumulation via the improved permeability and retention effect, thereby achieving satisfactory anti‐tumor PDT efficacy in a mouse subcutaneous tumor model.

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Zhang, Longzhen, Ningfang He, Zhipeng Song, Xin He, Jiahao Guo, Xiaochao Wu, Qingkui Li und Jilin He. „Research on the Fabrication and X‐Ray Detection Performance of MAPbBr₃‐Based 3D/2D Heterojunctions“. physica status solidi (RRL) – Rapid Research Letters, 02.10.2024. http://dx.doi.org/10.1002/pssr.202400243.

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Perovskite materials, renowned for their high mean atomic number, charge carrier mobility–lifetime product, and X‐ray absorption coefficient, have emerged as exceptional candidates for the fabrication of high‐sensitivity X‐ray detectors. Herein, a BA2PbBr4/MAPbBr3 heterojunction is epitaxially grown, with ion migration effectively suppressed through the passivation of surface defects of the 3D heterojunction. Additionally, the presence of an internal electric field within the heterojunction facilitated the extraction and accumulation of photoinduced charge carriers, further enhancing device sensitivity (5964.05 μC Gy−1 cm−2). The fabricated 2D/3D perovskite heterojunction devices show outstanding self‐driven X‐ray detection performance at 0 V mm−1 bias (1195.5 μC Gy−1 cm−2), surpassing that of α‐Se detectors (20 μC Gy−1 cm−2). The proposed method for the fabrication of self‐driven detectors is relatively simple and is therefore expected to contribute to the commercialization of perovskite‐based X‐ray detectors.

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Huang, Xingye, und Jia Guo. „Regulating the Photoisomerization of Covalent Organic Framework for Enhanced Photocatalytic Hydrogen Evolution^†“. Chinese Journal of Chemistry, 03.07.2024. http://dx.doi.org/10.1002/cjoc.202400437.

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Comprehensive SummaryCovalent organic framework (COF) is a desirable platform to tailor electronic properties for improving photocatalytic performances. However, the study on excited‐state configurations that determine photogenerated carrier dynamics has long been neglected. Herein, we concentrate on the molecular design of β‐ketoenamine‐linked COFs to drive their photoisomerization via the excited‐state intra‐molecular proton transfer (ESIPT), which can induce the partial keto‐to‐enol tautomerization and accordingly rearrange the photoinduced charge distribution. We demonstrate that the push‐pull electronic effect of functional side groups attached on the framework linkers is directly correlated with the ESIPT process. The phenylene linkers modified with electron‐withdrawing cyano‐groups reinforce the ESIPT‐induced tautomerization, leading to the in situ partial enolization for extended π‐conjugation and rearranged electron‐hole distribution. In contrast, the electron‐rich linkers limit the photoisomerization of COF and suppress the photoinduced electron accumulation. Thus, the maximum hydrogen evolution rate is achieved by the cyano‐modified COF, reaching as high as 162.72 mmol·g–1·h–1 with an apparent quantum efficiency of 13.44% at 475 nm, which is almost 11.5‐fold higher than those of analogous COFs with electron‐rich linkers. Our work opens up an avenue to control over the excited‐state structure transformation for enhanced photochemical applications.

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Zu, Fengshuo, Dongguen Shin, Emilio Gutierrez‐Partida, Martin Stolterfoht, Patrick Amsalem und Norbert Koch. „Charge Selective Contacts to Metal Halide Perovskites Studied with Photoelectron Spectroscopy: X‐Ray, Ultraviolet, and Visible Light Induced Energy Level Realignment“. Advanced Materials Interfaces, September 2023. http://dx.doi.org/10.1002/admi.202300413.

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AbstractThe electronic properties of metal halide perovskites (MHPs) are crucial for achieving the full potential of MHPs‐based optoelectronic devices, and they are extensively studied by photoelectron spectroscopy (PES). However, there are numerous complexities during PES measurements, which can result in inconsistent experimental data or even misinterpretation of results. Here, it is demonstrated that in the presence of charge selective junctions with MHPs, significant electronic energy level realignment can occur during PES measurements due to the sample excitation with high‐energy photons used in PES, amounting up to over 0.8 eV in the present case. This is caused by unbalanced charge carrier accumulation within the perovskite due to the charge‐selective interface. X‐ray photoelectron spectroscopy further reveals that photoexcitation due to bremsstrahlung, as produced in commonly employed twin‐anode lab‐sources, can readily produce sizable photoinduced shifts of core levels of MHPs films, whereas monochromatized X‐ray lab‐sources (irradiation flux reduced by >50 times by eliminating the bremsstrahlung) induce negligible shifts within the range of presently applied anode powers. The data and measurement conditions presented here are intended to enable others to obtain reliable MHP electronic property information from PES measurements.

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Bruschi, Cecilia, Xin Gui, Pascal Rauthe, Olaf Fuhr, Andreas-Neil Unterreiner, Wim Klopper und Claudia Bizzarri. „Dual Role of a Novel heteroleptic Cu(I) Complex in Visible‐Light‐Driven CO2 Reduction“. Chemistry – A European Journal, 14.05.2024. http://dx.doi.org/10.1002/chem.202400765.

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A novel mononuclear Cu(I) complex was synthesized via coordination with a benzoquinoxalin‐2’‐one‐1,2,3‐triazole chelating diimine and the bis[(2‐diphenylphosphino)phenyl] ether (DPEPhos), to target a new and efficient photosensitizer for photocatalytic CO2 reduction. The Cu(I) complex absorbs in the blue‐green region of the visible spectrum, with a broad band having a maximum at 475 nm (ε = 4500 M‐1cm‐1), which is assigned to the metal‐to‐ligand charge transfer (MLCT) transition from the Cu(I) to the benzoquinoxalin‐2’‐one moiety of the diimine. Surprisingly, photo‐driven experiments for the CO2 reduction showed that this complex can undergo a photoinduced electron transfer with a sacrificial electron donor and accumulate electrons on the diimine backbone. Photo‐driven experiments in a CO2 atmosphere revealed that this complex can not only act as a photosensitizer, when combined with an Fe(III)‐porphyrin, but can also selectively produce CO from CO2. Thus, owing to its charge‐accumulation properties, the non‐innocent benzoquinoxalin‐2‐one based ligand enabled the development of the first copper(I)‐based photocatalyst for CO2 reduction.

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Koysuren, Ozcan, Klodian Dhoska, Hafize Nagehan Koysuren, Irida Markja, Savas Yaglikci, Bilge Tuncel und Elena Bebi. „SiO2/WO3/ZnO based self-cleaning coatings for solar cells“. Journal of Sol-Gel Science and Technology, 06.03.2024. http://dx.doi.org/10.1007/s10971-024-06351-7.

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AbstractThe accumulation of pollution and any kinds of contamination on the glass cover of the solar cell affects the efficiency of the photovoltaic (PV) systems. The contamination on the glass cover can absorb and reflect a certain part of the sunlight irradiation, which can decrease the intensity of the light coming in through the glass cover. With the study, it was planned to develop self-cleaning coatings for the PV systems. It was aimed to prevent or reduce the contamination-induced efficiency loss of the existing PV systems. In the scope of the project, SiO2/WO3 and SiO2/WO3/ZnO composites were coated from their solutions on the glass substrates using a dip-coating technique. WO3 was selected as a photocatalyst semiconductor. Under the UV light irradiation, WO3 could absorb the photons of the UV light, generating the photoinduced charge carriers. The photoexcited charge carriers provide both the photoinduced hydrophilicity on the surface of the coating and the photocatalytic degradation of the organic contaminants accumulated on the surface of the coating, which allows water droplets to spread and flow on the surface of the cover glass to remove the contaminations. However, the recombination rate of the photoexcited charge carriers on the WO3 film was high. In order to suppress the recombination of the photoinduced charge carriers, WO3 was coupled with SiO2 and ZnO. Both of these semiconductors improved the photocatalytic activity of the WO3 film. Although SiO2 has superior features in terms of the light transmission, it was not very effective under UV light as a photocatalyst alone. The widely preferred photocatalyst ZnO was added into the composite film structure to enhance the photocatalytic activity. The self-cleaning mechanism of the film coatings on a solar cell was investigated through the photocatalytic dye removal efficiency on the as-prepared film samples. There was a slight decrease in the light transparency and the solar cell efficiency because of the WO3 content of the composite film. On the other hand, coupling the SiO2/WO3 film with ZnO enhanced the photocatalytic activity, and it suppressed the reduction effect of the WO3 phase on both the light transparency and the solar cell efficiency. The photocatalytic dye removal efficiency was increased to over 90% after 240 min of UVA light irradiation. In addition, the solar cell coated with the SiO2/WO3/ZnO film provided almost the same solar cell efficiency as the uncoated solar cell. The water contact angle measurement also exhibited the photocatalytic degradation of the model contamination on the glass cover of the solar cell under the UVA light irradiation. Graphical Abstract

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Cheng, Cheng, Yonghao Zhu, Zhaohui Zhou, Run Long und Wei-Hai Fang. „Photoinduced small electron polarons generation and recombination in hematite“. npj Computational Materials 8, Nr. 1 (07.07.2022). http://dx.doi.org/10.1038/s41524-022-00814-7.

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AbstractPolarons generally affect adversely the photochemical and photophysical properties of transition metal oxides. However, the excited-state dynamics of polarons are not fully established to date and thus require an atomistic understanding. We focus on α-Fe2O3 with photoexcitation, electron injection, and heterovalent doping as the small polaron models, and conduct simulations of ab initio adiabatic molecular dynamics (AIMD) and nonadiabatic molecular dynamics (NA-MD). The elaborately designed AIMD simulations show that localization of electron at a single Fe site is an adiabatic and ultrafast process within sub-15 fs. Fe2O3 doping with an electron or a Si and Ti dopant forms a localized electron polaron while photoexcitation forms localized electron and hole polarons simultaneously, leading to diverse electron–hole recombination dynamics. NA-MD simulations demonstrate that recombination of an electron polaron created by doping with a delocalized hole at the valence band maximum of α-Fe2O3 takes place around 5 ps, while recombination between a pair of small electron and hole polarons in photoexcited Fe2O3 delays to about 110 ps owing to weak NA coupling and fast decoherence process. The ultrafast formation of small electron polarons in α-Fe2O3 impedes the accumulation of delocalized holes in the valence band that directly participate in water oxidation at photoanodes. The detrimental effect can be partially circumvented in photoexcited Fe2O3 for slowing electron–hole recombination despite polarons may retain low charge mobility. These findings provide a fundamental understanding of the excited-state dynamics of small electron polaron in α-Fe2O3 and may help design efficient transition metal oxides photoanodes.

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Liu, Yang, Ying Zhou, Mohamed Abdellah, Weihua Lin, Jie Meng, Qian Zhao, Shan Yu et al. „Inorganic ligands-mediated hole attraction and surface structural reorganization in InP/ZnS QD photocatalysts studied via ultrafast visible and midinfrared spectroscopies“. Science China Materials, 30.03.2022. http://dx.doi.org/10.1007/s40843-021-1992-3.

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AbstractPhotoinduced carrier dynamical processes dominate the optical excitation properties of photocatalysts and further determine the photocatalytic performance. In addition, as the electrons generally possess a faster transfer rate than holes, hole transfer and accumulation are critical, and they play the key efficiency-limiting step during the photocatalytic process. Therefore, a comprehensive understanding of the dynamics of photogenerated holes and their determining factors in the photocatalytic system is highly essential to rationalize the full catalytic mechanism and develop highly efficient photocatalysts, which have not yet been revealed. In this work, the photoinduced charge carrier dynamics in InP/ZnS quantum dots (QDs) capped with long-chain L-typed ligands (oleylamine) and inorganic ligands (sulfide ion (S2−)) were explored. Time-resolved photoluminescence and femtosecond transient-absorption spectroscopy unambiguously confirmed the ultrafast hole transfer from the InP core to S2− ligands. Moreover, by probing the bleach of vibrational stretching of the ligands with transient midinfrared absorption spectroscopy, the hole transfer time was determined to be 4.2 ps. The injected holes are long-lived at the S2− ligands (>4.5 ns), and they can remove electrostatically attached surfactants to compensate for the spatial charge redistribution. Finally, compared with other inorganic ligands such as Cl− and PO43−, S2− balances the ionic radii and net charge to ensure the optimal condition for charge transfer. Such observation rationalizes the excellent photocatalytic H2 evolution (213.6 µmol mg−1 within 10 h) in InP/ZnS QDs capped with S2− compared with those capped with other ligands and elucidates the role of surface ligands in the photocatalytic activity of colloidal QDs.

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Sreelaya, Vannappilakkal, Shahnaz S. Rohman, Pattiyil Parameswaran und Lakshmi Chakkumkumarath. „An investigation of the excitation wavelength‐dependent dynamic changes in the mechanism of detection of picric acid using pyrene‐based donor‐acceptor systems“. ChemPhysChem, 22.05.2024. http://dx.doi.org/10.1002/cphc.202400264.

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Abstract: Picric acid (PA) is an important industrial feedstock and hence the release of industrial effluents without proper remediation results in its buildup in soil and water bodies. The adverse effects of PA accumulation in living beings necessitate the development of efficient methods for its detection and quantification. Herein, we describe pyrene‐based fluorescent sensors for PA, where pyrene is appended with electron‐withdrawing groups, malononitrile and 2‐(3‐cyano‐4,5,5‐trimethylfuran‐2(5H)‐ylidene) malononitrile (DCDHF). These molecules displayed the typical emission of pyrene monomers, as well as a broad red‐shifted emission resulting from an intramolecular charge transfer (ICT) in the excited state. Both the emissions displayed a turn‐off response to PA with high selectivity and sensitivity and the lowest limit of detection was estimated as 27 nM. To prove the feasibility of on‐site detection, test paper strips were prepared, which could detect PA up to 4.58 picograms. Using a combination of experimental and theoretical studies the mechanism of the detection was identified as primary/secondary inner filter effect, oxidative photoinduced electron transfer, or a combination of both depending on the excitation wavelength. Interestingly, the contribution of each of these mechanisms to the total quenching process varied with a change in the excitation wavelength

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Cruz Neto, Daniel H., Eva Pugliese, Philipp Gotico, Annamaria Quaranta, Winfried Leibl, Karine Steenkeste, Daniel Peláez, Thomas Pino, Zakaria Halime und Minh-Huong Ha-Thi. „Time‐Resolved Mechanistic Depiction of Photoinduced CO2 Reduction Catalysis on a Urea‐Modified Iron Porphyrin“. Angewandte Chemie International Edition, 23.05.2024. http://dx.doi.org/10.1002/anie.202407723.

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The development of functional artificial photosynthetic devices relies on the understanding of mechanistic aspects involved in specialized photocatalysts. Modified iron porphyrins have long been explored as efficient catalysts for the light‐induced reduction of carbon dioxide (CO2) towards solar fuels. In spite of the advancements in homogeneous catalysis, the development of the next generation of catalysts requires a complete understanding of the fundamental photoinduced processes taking place prior to and after activation of the substrate by the catalyst. In this work, we employ a state‐of‐the‐art nanosecond optical transient absorption spectroscopic setup with a double excitation capability to induce charge accumulation and trigger the reduction of CO2 to carbon monoxide (CO). Our biomimetic system is composed of a urea‐modified iron(III) tetraphenylporphyrin (UrFeIII) catalyst, the prototypical [Ru(bpy)3]2+ (bpy = 2,2’‐bipyridine) used as a photosensitizer, and sodium ascorbate as an electron donor. Under inert atmosphere, we show that two electrons can be successively accumulated on the catalyst as the fates of the photogenerated UrFeII and UrFeI reduced species are tracked. In the presence of CO2, the catalytic cycle is kick‐started providing further evidence on CO2 activation by the UrFe catalyst in its formal FeI oxidation state.

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Cruz Neto, Daniel H., Eva Pugliese, Philipp Gotico, Annamaria Quaranta, Winfried Leibl, Karine Steenkeste, Daniel Peláez, Thomas Pino, Zakaria Halime und Minh-Huong Ha-Thi. „Time‐Resolved Mechanistic Depiction of Photoinduced CO2 Reduction Catalysis on a Urea‐Modified Iron Porphyrin“. Angewandte Chemie, 23.05.2024. http://dx.doi.org/10.1002/ange.202407723.

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The development of functional artificial photosynthetic devices relies on the understanding of mechanistic aspects involved in specialized photocatalysts. Modified iron porphyrins have long been explored as efficient catalysts for the light‐induced reduction of carbon dioxide (CO2) towards solar fuels. In spite of the advancements in homogeneous catalysis, the development of the next generation of catalysts requires a complete understanding of the fundamental photoinduced processes taking place prior to and after activation of the substrate by the catalyst. In this work, we employ a state‐of‐the‐art nanosecond optical transient absorption spectroscopic setup with a double excitation capability to induce charge accumulation and trigger the reduction of CO2 to carbon monoxide (CO). Our biomimetic system is composed of a urea‐modified iron(III) tetraphenylporphyrin (UrFeIII) catalyst, the prototypical [Ru(bpy)3]2+ (bpy = 2,2’‐bipyridine) used as a photosensitizer, and sodium ascorbate as an electron donor. Under inert atmosphere, we show that two electrons can be successively accumulated on the catalyst as the fates of the photogenerated UrFeII and UrFeI reduced species are tracked. In the presence of CO2, the catalytic cycle is kick‐started providing further evidence on CO2 activation by the UrFe catalyst in its formal FeI oxidation state.

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Sakaguchi, Yoshifumi, und Kozaburo Tamura. „Fast Photodarkening in Amorphous and Liquid Chalcogenide“. MRS Proceedings 918 (2006). http://dx.doi.org/10.1557/proc-0918-h03-03.

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AbstractTransient photo-induced optical absorption in amorphous and liquid As2Se3 was investigated using a nanosecond pulsed laser and a specially designed optical cell. The measurements have been performed in the second and minute domain and the nanosecond and microsecond domain. From the measurements in the second and minute domain using repeated illumination, we observed the accumulation of photo-induced absorption and the decay after stopping the illumination. The durable photodarkening was also observed after the decay. The accumulated photoinduced change becomes smaller with increasing temperature and approaches to be zero around the glass transition temperature. From the measurements in the nanosecond and microsecond domain, the transient photodarkening in the time domain responded for each pulsed laser was observed. This fast photodarkening was observed even in the liquid state. This is contrast to the cases of the durable photodarkening and the transient photodarkening in the second and minute domain. The origin of the observed photoinduced changes is discussed.

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