Al2O3nanoparticles were synthesized using laser ablation of an aluminum (Al) target in deionized water. Nd:YAG laser, emitted the light at a wavelength of 1064 nm, was used as a light source. The laser ablation was carried out at different energies of 1, 3, and 5 J. The structure of ablated Al particles suspended in deionized water was investigated using X-ray diffraction (XRD). The XRD patterns revealed that the ablated Al particles transformed intoγ-Al2O3. The morphology of nanoparticles was investigated by field emission scanning electron microscopy (FE-SEM). The FE-SEM images showed that most of the nanoparticles obtained from all the ablated laser energies have spherical shape with a particle size of less than 100 nm. Furthermore, it was observed that the particle size increased with increasing the laser energy. The absorption spectra of Al2O3nanoparticles suspended in deionized water were recorded at room temperature using UV-visible spectroscopy. The absorption spectra show a strong peak at 210 nmarising from the presence of Al2O3nanoparticles. The results on absorption spectra are in good agreement with those investigated by XRD which confirmed the formation of Al2O3nanoparticles during the laser ablation of Al target in deionized water.
This research work undertook a comparative study of the promoting effects of graphene in TiO2 photoanodes. The aim of this work was to investigate the effects of the types and concentration of reduced graphene oxides (rGO) on structure properties and the photovoltaic performance of TiO2 based electrodes. Graphene oxide (GO) was prepared by using modified Hammer’s method. Next, GO was reduced by using two different approaches, which were the chemical reduction with vitamin C and thermal reduction. The latter approach was also carried out in situ during the fabrication and heat treatment processes of the dye-sensitized solar cells (DSSCs). From the results, it was found that the photovoltaic performance of the DSSCs containing the GO/TiO2 electrode, in which the GO phase experienced an in situ thermal reduction, was superior to those containing rGO/TiO2. It was also found that the power conversion efficiency of the DSSCs changed with the concentration of graphene in a nonlinear fashion. The optimum concentrations of graphene, corresponding to the highest PCE values of the GO/TiO2 based DSSC (3.69%) and that of the rGO/TiO2 based cell (2.90%), were 0.01 wt% and 0.03 wt%, respectively.
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