In recent years, complex nanocomposites formed by Ag nanoparticles coupled to an α-Ag2WO4 semiconductor network have emerged as promising bactericides, where the semiconductor attracts bacterial agents and Ag nanoparticles neutralize them. However, the production rate of such materials has been limited to transmission electron microscope processing, making it difficult to cross the barrier from basic research to real applications. The interaction between pulsed laser radiation and α-Ag2WO4 has revealed a new processing alternative to scale up the production of the nanocomposite resulting in a 32-fold improvement of bactericidal performance, and at the same time obtaining a new class of spherical AgxWyOz nanoparticles.

The present joint experimental and theoretical work provides in-depth understanding on the morphology and structural, electronic, and optical properties of ZnWO nanocrystals. Monoclinic ZnWO nanocrystals were prepared at three different temperatures (140, 150, and 160 °C) by a microwave hydrothermal method. Then, the samples were investigated by X-ray diffraction with Rietveld refinement analysis, field-emission scanning electron microscopy, transmission electronic microscopy, micro-Raman and Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and photoluminescence measurements. First-principles theoretical calculations within the framework of density functional theory were employed to provide information at the atomic level. The band structure diagram, density of states, Raman and infrared spectra were calculated to understand the effect of structural order-disorder on the properties of ZnWO. The effects of the synthesis temperature on the above properties were rationalized. The band structure revealed direct allowed transitions between the VB and CB and the experimental results in the ultraviolet-visible region were consistent with the theoretical results. Moreover, the surface calculations allowed the association of the surface energy stabilization with the temperature used in the synthesis of the ZnWO nanocrystals. The photoluminescence properties of the ZnWO nanocrystals prepared at 140, 150, and 160 °C were attributed to oxygen vacancies in the [WO] and [ZnO] clusters, causing a red shift of the spectra. The ZnWO nanocrystals obtained at 160 °C exhibited excellent photodegradation of Rhodamine under ultraviolet light irradiation, which was found to be related to the surface energy and the types of clusters formed on the surface of the catalyst.

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In the present work, the morphology (hexagonal rod-like vs cuboid-like) of an α-Ag 2 WO 4 solid-state material is manipulated by a simple controlled-precipitation method, with and without the presence of the anionic surfactant sodium dodecyl sulfate (SDS), respectively, over short reaction times. Characterization techniques, such as X-ray diffraction analysis, Rietveld refinement analysis, Fourier-transform (FT) infrared spectroscopy, FT Raman spectroscopy, UV−vis spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy (FE-SEM), and photoluminescence emission, are employed to disclose the structural and electronic properties of the α-Ag 2 WO 4 material. First-principles calculations were performed to (i) obtain the relative stability of the six low-index surfaces of α-Ag 2 WO 4 ; (ii) rationalize the crystal morphologies observed in FE-SEM images (using the Wulff construction); and (iii) determine the energy profiles associated with the transformation process between both morphologies induced by the presence of SDS. Finally, we demonstrate a relationship between morphology and photocatalytic activity, evaluated by photodegradation of Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and W cations (local coordination, i.e., clusters) of each surface.