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Extracellular biosynthesis of Cu2-xSe nanocrystallites with photocatalytic activity
摘要： Semiconductor Cu2-xSe nanospheres were successfully biosynthesized based on bioreduction of SeO3 2? into Se2? by the selenite-reducing bacterium, Pantoea agglomerans. The Cu2-xSe nanospheres had excellent crystallinity with a face-centered cubic structure and an average diameter of 80 nm. Composition and oxidation states analysis using X-ray photoelectron spectroscopy and X-ray energy dispersive spectroscopy followed by optical characterization using ultraviolet-visible and Fourier transform infra-red spectroscopy confirmed that the biosynthesized Cu2-xSe nanospheres were capped by proteins. The extracellular proteins which mediated biosynthesis were visualized by excitation–emission matrix fluorescence spectroscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis revealed that the molecular masses of proteins were about 110, 50, 38, 35 and 25 kDa. The biosynthesized Cu2?xSe nanospheres showed an excellent and stable photocatalytical activity under sunlight irradiation in the degradation of methylene blue for four cycles. This study put forward a green and toilless way to manufacture copper selenide nanoparticles using a biological process.
关键词： Biosynthesis,Photocatalytical activity,Cu2-xSe,Extracellular proteins
更新于2025-09-23 15:21:21
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Temperature Dependence of the Lattice Parameters of Cu2?–?xSe (0.03 ≤ x ≤ 0.23) Powders Fabricated by Mechanochemical Synthesis
摘要： The Cu2 – xSe (0.03 ≤ x ≤ 0.23) powders fabricated by mechanochemical synthesis have been studied by X-ray diffraction. The in situ study has been carried out for the temperature dependences of the lattice parameters, the structures, and the phase compositions of the powders in the temperature range 25–350°C. The powder compositions are shown to differ from the charge compositions and are shifted to lower copper concentrations. The estimation of peak half-widths of the cubic β phase indicates an increase in the structure imperfection after the phase transition from the α phase to the β phase of Cu2 – xSe at ~140°C. It is shown that the superpositions of the subtraction solutions (copper vacancies) and interstitials solutions (copper atoms in interstitial sites), whose proportion is changed as a function of temperature and the deviation from stoichiometry, are in the thermodynamic equilibrium in the copper selenide solid solution at room temperature. The change in the slope of the dependence of the lattice parameter of the powder Cu2 – xSe samples on the composition (0.03 ≤ x ≤ 0.23) in the temperature range 25–350°C enables the suggestion that interstitial copper atom concentration increases with temperature and deviation from stoichiometry.
关键词： phase transition,lattice parameters,mechanochemical synthesis,Cu2 – xSe,X-ray diffraction,thermodynamic equilibrium
更新于2025-09-23 15:21:01
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An in situ inward etching strategy for constructing a p-p heterojunction Cu2S/Cu2-xSe material based on brass as an effective counter electrode for quantum dot sensitized solar cells
摘要： Composite counter electrode Cu2S/Cu2-xSe nanosheets based on brass are fabricated by an in situ inward etching method using Cu(OH)2 nanotubes as a template. Due to superior electrocatalytic activity towards the polysulfide electrolyte, the quantum dot-sensitized solar cells constructed with Cu2S/Cu2-xSe counter electrodes deliver a considerable power conversion efficiency of 6.10% under 1 sun illumination, which is a 22% enhancement compared to that of Cu2S/brass (5.00%). According to the results of BET testing, solid-state J-V measurements and transient photocurrent measurements, the enhanced electrocatalytic activity is attributed to two aspects: one is the larger surface active area, which provides more active sites for the electrolyte, and the other is the formation of a p-p heterojunction for more effective electron transfer in the counter electrode. In addition, the band energy structure of the Cu2S/Cu2-xSe heterojunction is further investigated to understand the behavior of interfacial electron transfer. Finally, the outstanding electrochemical catalytic activity and stability of the Cu2S/Cu2-xSe counter electrode are proved by electrochemical impedance spectroscopy, Tafel polarization and cyclic voltammetry results for symmetric dummy cells, demonstrating that the Cu2S/Cu2-xSe composite is a desirable material as a counter electrode for quantum dot sensitized solar cells.
关键词： Cu2S/Cu2-xSe CE,Electrochemical catalytic activity,QDSCs,p-p heterojunction,Stability
更新于2025-09-11 14:15:04