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Cu2O, a photoactive p‐type semiconductor based on earth‐abundant elements, shows promising features for photoelectrochemical CO2 reduction reaction (PEC CO2RR). However, despite the broad light absorption and appropriate conduction band edge energy, it promptly undergoes photocorrosion in PEC CO2RR conditions. Herein, we evaluate an amine‐functionalized polysiloxane (AF−PSi) as both protective layer and PEC CO2RR promoter via amine‐CO2 adduct formation. Electrochemistry experiments and X‐ray diffraction showed that photostability is significantly enhanced with AF−PSi overlayer. Electrolyses experiments under visible light irradiation indicated selective production of formate with faradaic efficiency of 61 % at low overpotential. Detailed in situ FTIR studies revealed that amine groups bind to CO2 to form carbamate species and that this process is favoured by cathodic polarization, confirming the dual role of AF−PSi layer. [ABSTRACT FROM AUTHOR]

In this study, we report the potential of ethylenediamine (En) in the modification of the morphological, structural, optical and catalytic properties of α-Ag2WO4 crystals decorated with Ag nanoparticles (Ag NPs). Experimental techniques were used to characterize the as-synthesized samples such as X-ray diffraction, Raman, electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and photoluminescence spectroscopy. The results confirmed the efficiency of En in the decoration with the formation of Ag/α-Ag2WO4 crystals and also the modification of α-Ag2WO4 morphology that indicated its influence on the crystal growth mechanism via self-assembly and Ostwald ripening. En affects the degree of order/disorder of the crystalline structures in long and short-ranges. In addition, photoluminescence measurements revealed a blue shift of the optical emission caused by a reduction of oxygen vacancies and an increase in structural disorder due to the En concentration used in the synthesis processes. Regarding the photocatalysis experiments, the reduction in oxygen vacancies also caused a decrease in the photoactivity of α-Ag2WO4 against the rhodamine B dye, thus confirming the relevance of oxygen vacancies for the development of α-Ag2WO4 photocatalysts. [ABSTRACT FROM AUTHOR]

Defect-related luminescent materials have attracted interest because of their excellent optical properties and are considered as a less expensive and nontoxic alternative to commonly used lanthanide-based optical systems. These materials are fundamentally and technologically important for the next generation of full-color tunable light-emitting diodes as well as in the biomedical field. In this study, we report the preparation of α-silver vanadate (α-AgVO 3 , AV) decorated by hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HA) with intense photoluminescence (PL) emissions at various HA/AV molar ratios (1:1-1:1/32) by a simple route based on chemical precipitation. The well-defined diffraction peaks observed by X-ray diffraction were all indexed to the monoclinic AV and hexagonal HA phases. Analysis of the results obtained by Fourier transform infrared spectroscopy reveals the presence of short-range structural order as deduced by the characteristic vibrational modes assigned to AV and HA systems. Characterization by scanning and transmission electron microscopies confirms the presence of AV and HA micro- and nanorods, respectively. UV-vis spectroscopy renders band gap energies of 5.80 eV for HA and in the range 2.59-2.65 eV for pure AV and HA/AV samples. The PL data reveal the presence of broad-band emission profiles, typical of defect-related optical centers in materials. Depending on the molar ratio, the emission can be completely tunable from the blue to red spectral regions; in addition, pure white color emission was obtained. On the basis of these results, we propose an order-disorder model induced by structural and interface defects to explain the PL emissions in the HA/AV system. Moreover, our results show that HA/AV composites have superior bactericidal activity against Staphylococcus aureus (methicillin-resistant and methicillin-susceptible) and can be used as a novel multifunctional material.

In nanotechnology research, significant effort is devoted to fabricating patterns of metallic nanoparticles on the surfaces of different semiconductors to find innovative materials with favorable characteristics, such as antimicrobial and photocatalytic properties, for novel applications. We present experimental and computational progress, involving a combined approach, on the antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) of as-synthesized α-Ag 2 WO 4 samples and Ag nanoparticle composites (Ag NPs)/α-Ag 2 WO 4 . The former included two morphologies: hexagonal rod-like (α-Ag 2 WO 4 -R) and cuboid-like (α-Ag 2 WO 4 -C), and the latter included composites formed under electron beam, Ag NPs/α-Ag 2 WO 4 -RE and Ag NPs/α-Ag 2 WO 4 -CE, and femtosecond (fs) laser irradiation, Ag NPs/α-Ag 2 WO 4 -RL and Ag NPs/α-Ag 2 WO 4 -CL. Direct observations of the arrangement of Ag NPs on the Ag NPs/α-Ag 2 WO 4 composites irradiated with an electron beam and laser, through transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, and field-emission scanning electron microscopy, allow us to investigate the surface morphology, chemical composition, homogeneity, and crystallinity. Therefore, these experimental factors, and in particular, the facet-dependent response of Ag NPs/α-Ag 2 WO 4 composites were discussed and analyzed from the perspective provided by the results obtained by first-principles calculations. On this basis, α-Ag 2 WO 4 -R material proved to be a better bactericidal agent than α-Ag 2 WO 4 -C with minimum bactericidal concentration (MBC) values of 128 and 256 μg/mL, respectively. However, the Ag NPs/α-Ag 2 WO 4 -CL composite is the most efficient bactericidal agent of all tested samples (MBC = 4 μg/mL). This superior performance can be attributed to the cooperative effects of crystal facets and defect engineering. These results on the synthesis and stability of the Ag NPs/α-Ag 2 WO 4 composites can be used for the development of highly efficient bactericidal agents for use in environmental remediation and the potential extension of methods to produce materials with catalytic applications.