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In this work, cerium-and nickel-codoped ZnS nanoparticles were obtained by a sonochemical method for 20 min. The nanoparticles were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and microscopy electronic transmission (MET). The electrical properties are estimated through I-V curves and the antimicrobial activity was analyzed against E. coli (gram-negative) and S. aureus (gram-positive) bacteria using the diffusion disk methodology. The diffractograms indicate the obtaining of cubic structure ZnS for the pure sample, whereas the doped samples present the cubic and hexagonal structures of the ZnS. The bandgap reduced from 3.60 to 3.52 eV, for pure and codoped samples. I-V curves indicate an increase in resistivity with doping, being more evident for samples containing cerium. Antimicrobial activity increased as doping occurred, where the codoped sample showed the best results. Even for the low amount of dopant (1 mol%), the antimicrobial activity can be increased by about 50% for the codoped sample, compared to the pure ZnS. Thus, it is known that the doping of ZnS with cerium and nickel provides the stabilization of the hexagonal metastable phase, which acts to restrict electronic mobility and, consequently, improves the antimicrobial response of the material.

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Zinc-doped CuO powders were obtained by microwave-assisted hydrothermal processing at 140°C for 30 min then decorated with silver by photodeposition and characterized by x-ray diffraction (XRD) analysis, field-scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) spectroscopy region for E gap estimation. The photocatalytic activity of the powders was measured using methylene blue dye. To provide further information on the influence of the process variables on the photocatalytic activity, a 2 3 factorial design was carried out with three central points, using the amounts of zinc and silver and the stirring time under UV radiation as variables. The XRD patterns indicated ZnO precipitation when 8% Zn was added. SEM micrographs showed that the CuO had predominantly nanoplate morphology, with loss of the regular aspect of the ends and increased thickness on addition of zinc atoms. The photocatalytic activity results showed that addition of zinc and silver increased the photocatalytic activity of pure CuO. According to the factorial design, the stirring time of the CuO powder in contact with AgNO 3 solution was the most significant variable affecting the photocatalytic properties, with longer time being detrimental due to an increase in the size of the silver nanoparticles.