For some decades, the scientific community has been looking for alternatives to the use of fossil fuels that allow for the planet’s sustainable and environmentally-friendly development. To do this, attempts have been made to mimic some processes that occur in nature, among which the photosystem-II stands out, which allows water splitting operating with different steps to generate oxygen and hydrogen. This research presents promising results using synthetic catalysts, which try to simulate some natural processes, and which are based on Au@ZnO–graphene compounds. These catalysts were prepared by incorporating different amounts of gold nanoparticles (1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%) and graphene (1 wt.%) on the surface of synthesized zinc oxide nanowires (ZnO NWs), and zinc oxide nanoparticles (ZnO NPs), along with a commercial form (commercial ZnO) for comparison purposes. The highest amount of hydrogen (1127 μmol/hg) was reported by ZnO NWs with a gold and graphene loadings of 10 wt.% and 1 wt.%, respectively, under irradiation at 400 nm. Quantities of 759 μmol/hg and 709 μmol/hg were obtained with catalysts based on ZnO NPs and commercial ZnO, respectively. The photocatalytic activity of all composites increased with respect to the bare semiconductors, being 2.5 times higher in ZnO NWs, 8.8 times higher for ZnO NPs, and 7.5 times higher for commercial ZnO. The high photocatalytic activity of the catalysts is attributed, mainly, to the synergism between the different amount of gold and graphene incorporated, and the surface area of the composites.
Hollow magnetite microspheres have been synthesized by a simple process through a template-free hydrothermal approach. Hollow microspheres were surface modified by coating with a silica nanolayer. Pristine and modified hollow microparticles were characterized by field-emission electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, FT-IR and Raman spectroscopy, and VSM magnetometry. The potential application of the modified hollow magnetite microspheres as a drug carrier was evaluated by using Rhodamine B and methotrexate as model drugs. The loading and release kinetics of both molecules showed a clear pH and temperature dependent profile.Graphical abstractHollow magnetite microspheres have been synthesized. Load-release experiments with Rhodamine-B as a model drug and with Methotrexate (chemotherapy drug used in treating certain types of cancer) demonstrated the potential applications of these nanostructures in biomedical applications.
Different amount of gold nanoparticles (1, 3, 5, 10 wt%) were deposited on the surface of synthesized titanium oxide nanowires (TiO 2 NWs) and Degussa P25 (TiO 2 -P25). The results evidenced the presence of small and dispersed gold particles on the surface of TiO 2 NWs and TiO 2 -P25 and an increase in the specific surface area of all the composites. The photocatalytic activity was characterized by measuring the hydrogen production by water splitting, using UV-vis radiation. Au@TiO 2 NWs catalysts showed the highest production of hydrogen (1,436 µmol hg −1 ), with a gold loading of 10 wt%, while in the case of Au@TiO 2 -P25 the hydrogen production was slightly lower (800 µmol hg −1 ), with a gold loading of 5 wt%. The enhancement in the hydrogen production was 11.5 times higher than that reported by the TiO 2 NWs catalyst (125 µmol hg −1 ) and 5.2 times higher than the TiO 2 -P25 (154 µmol hg −1 ). The activity of the catalysts was found to be dependent both on the surface area of the composites and on the amount of gold.
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