RESUMEN
In this work, we reported the fabrication and characterization of CaWO4:Ln3+/Na+ (Ln = Nd, Er, and Yb) core/shell microspheres via a facile hydrothermal method in the presence of citric acid and PVP. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectra, and photoluminescence. It's found that citric acid could modulate the nucleation and growth of CaWO4 nanocrystals and enable the co-incorporation of Na+ and Ln3+ (Ln = Nd, Er, and Yb) into CaWO4 lattice. Meanwhile, PVP controlled the assembly of CaWO4 nanocrystals into a core/shell spherical structure. All CaWO4:Ln3+/Na+ (Ln = Nd, Er, and Yb) core/shell microspheres exhibited intense near-IR luminescence. In comparison with CaWO4:Ln3+/Na+ nanocrystals, the self-assembled core/shell nanoarchitechtures showed highly enhanced IR luminescent properties due to the depressing of surface energy-loss.
RESUMEN
This work reports on the preparation of a noble-metal-free and highly active catalyst that proved to be an efficient and green reductant with renewable capacity. Nitridation of a silent Ta1.1O1.05 substrate led to the formation of a series of TaOxNy hollow nanocrystals that exhibited outstanding activity toward catalytic reduction of nitrobenzenes under ambient conditions. ESR and XPS results indicated that defective nitrogen species and oxygen vacancies at the surfaces of the TaOxNy nanocrystals may play synergetic roles in the reduction of nitrobenzenes. The underlying mechanism is completely different from those previously reported for metallic nanoparticles. This work may provide new possibilities for the development of novel defect-meditated catalytic systems and offer a strategy for tuning any catalysts from silent to highly reactive by carefully tailoring the chemical composition and surface defect chemistry.
RESUMEN
This work reported on the synthesis of a series of nitrogen doped Ca2Nb2O7 with tunable nitrogen content that were found to be efficient and green noble-metal-free catalysts toward catalytic reduction of p-nitrophenol. XPS and ESR results indicated that the introduction of nitrogen in Ca2Nb2O7 gave rise to a large number of defective nitrogen and oxygen species. Defective nitrogen and oxygen species were found to play synergetic roles in the reduction of p-nitrophenol. The underlying mechanism is completely different from those reported for metallic nanoparticles. Moreover, the more negative conduction band edge potential enabled nitrogen doped Ca2Nb2O7 to show photo-synergistic effects that could accelerate the reduction rate toward p-nitrophenol under UV light irradiation. This work may provide a strategy for tuning the catalytic performance by modulating the chemical composition, electronic structure as well as surface defect chemistry.