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Ag2O was synthesized by the precipitation method and it was used as support to prepare Ag/Ag2O nanocomposites using different sodium citrate volumes to control the size and amount of Ag nanoparticles. Materials were characterized by X-ray powder diffraction, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and nitrogen adsorption–desorption at − 196 °C analyses, respectively. Ibuprofen was selected as a probe molecule and materials were assessed as photocatalysts under simulated visible light irradiation. The SEM and TEM analysis revealed the presence of Ag nanoparticles over Ag2O support showing a size increase as citrate volume increased. By means of DRS analysis a band gap shift was observed, suggesting the formation of metallic silver during Ag impregnation while XPS results proved the co-existence of Ag0 and Ag2O composites. On the other hand, the photocatalysis results revealed the formation of intermediaries during ibuprofen photodegradation. Visible light absorption by Ag nanoparticles produced superoxide anion radicals (due to surface plasmon resonance) that enhanced the formation of intermediaries. The reaction mechanism proposed involves the generation of a Ag/Ag2O heterojunction where the metal acts as an electron scavenger decreasing the recombination of the e−–h+ pair.

In this paper, the gradient temperature and the thermomechanical stresses of a photovoltaic panel has been studied with and without heatsink. For this purpose, a three-dimensional analysis was carried out. Accordingly, a heat transfer analysis was developed. The numerical results show a cooling close to 26.7% with the proposed triangle fins compared with the rectangular fins studied before by another author, and the temperature distribution was determined. With this information, the stress analysis was carried out in order to find the effect on the panel due to the thermomechanical stresses. The aluminium frame was restricted to move freely. The resulting stresses field established the magnitude of the alternative stresses, resulting in a 6.7% drop compared with a reference panel. The guidelines of IEC 61215 have to be take into account. Due to the results obtained, the use of this kind of system in desert conditions is desirable because of its high operational temperature and due to the increase in heat transfer by the fins.

Anatase TiO2 and TiO2 films containing Pt nanoparticles were prepared by sol–gel dip coating method and characterized by X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Further, optoelectronic properties were investigated, showing that for anatase TiO2 films containing Pt nanoparticles there were not changes in the band-gap value in respect to TiO2 films here obtained. However, an increase in the photoresponse and a decrease in resistivity with increase in the Pt % weight (% w) in sol were found. Keywords: TiO2 films, Solar energy, Nanoparticles

ZnO thin films were processed by radio frequency magnetron sputtering at room temperature on p-Si/SiO2 substrates under pure argon (Ar:O2 = 100:0 vol.%) and argon–oxygen mixture (Ar:O2 = 99:1 vol.%) gas environment. Morphological, optical and electrical characteristics of the ZnO films are reported, and they show a clear relationship with the gas mixture employed for the sputtering process. Scanning Electron Microscopy revealed the formation of grains of 15.3 and 19.9 nm average sizes and thicknesses of 59 nm and 82 nm for films growth in pure argon and argon–oxygen, respectively. Photoluminescence measurements at room temperature showed the violet emission band (centered at 3 eV) which was only detected in the ZnO film grown under pure argon. From thermally stimulated conductivity measurements two traps with 0.27 and 0.14 eV activation energies were identified for films grown in pure argon and argon–oxygen mixture, respectively. The trap at 0.27 eV is associated with a level located below the conduction band edge and it is supported by the PL band centered at 3 eV. Both types of ZnO films were used as the active channel layer in thin film transistors with thermal SiO2 as gate dielectric. Field effect mobility, threshold voltage and current ratio were improved in the devices with ZnO channel deposited with the argon–oxygen mixture (99% Ar/1% O2 vol.). Threshold voltage decreased from 25 V to 15 V, field effect mobility and current ratio increased from 0.8 to 2.4 cm2/Vs and from 102 to 106, in that order.

The Ca₃Zr₂S₇ films were deposited by electrodeposition by means of linear voltammetry with a potential applied in the range of -0.1 to -3.0 V vs. SCE. The precursors used for Ca, Zr and S were calcium acetate, zirconium acetate and sodium sulfite, respectively. The films were characterized optically, morphologically and structurally. The presence of Ca, Zr and S elements was verified by energy dispersion spectroscopy analysis. The results of the X-ray diffraction showed the presence of peaks related to a structure belonging to the perovskite family, and the chemical bonds were confirmed by photoelectron spectroscopy emitted by X-rays. The electrical resistivity in the dark and light was also measured. The surface roughness of the Ca₃Zr₂S₇ film was estimated at 3.05 nm with a thickness of 600 nm. It was found that the material absorbs in the visible region of the electromagnetic spectrum with a wavelength of less than 500 nm. The Ca₃Zr₂S₇ film also exhibits ferroelectric properties at room temperature.