Scheelite nanostructures Ca 1-2x (Eu,Na) 2x WO 4 (0 < x e 0.135) were prepared from 5 nm Ca 0.968 (Eu,Na) 0.032 WO 4 by hydrothermal treatment. The preparation of 5 nm Ca 0.968 (Eu,Na) 0.032 WO 4 at room temperature and subsequent hydrothermal treatment allow control over chemical compositions and particle size of CaWO 4 -based red phosphors that has not yet possible when using traditional preparation methods. By careful structural and electronic characterization, it is shown that simultaneous substitutions of Eu 3+ and Na + at Ca 2+ sites were possible using this methodology, which allows one to vary the local symmetry surrounding Eu 3+ and moreover the energy transfer from O 2to Eu 3+ and tungstate groups to Eu 3+ for optimum luminescence. As a consequence, the obtained CaWO 4 -based nanocrystals displayed excellent luminescence properties as demonstrated by luminescence lifetimes of milliseconds, abnormally narrowed emissions, and maximum quantum efficiencies of 92%. The results reported in this work show that it is possible to control chemical composition of oxide nanostructures for structural decoration and luminescence property tailoring via codoping aliovalent ions.

Increasing long‐term photostability of BiVO4 photoelectrode is an important issue for solar water splitting. The NiOOH oxygen evolution catalyst (OEC) has fast water oxidation kinetics compared to the FeOOH OEC. However, it generally shows a lower photoresponse and poor stability because of the more substantial interface recombination at the NiOOH/BiVO4 junction. Herein, we utilize a plasma etching approach to reduce both interface/surface recombination at NiOOH/BiVO4 and NiOOH/electrolyte junctions. Further, adding Fe2+ into the borate buffer electrolyte alleviates the active but unstable character of etched‐NiOOH/BiVO4, leading to an outstanding oxygen evolution over 200 h. The improved charge transfer and photostability can be attributed to the active defects and a mixture of NiOOH/NiO/Ni in OEC induced by plasma etching. Metallic Ni acts as the ion source for the in situ generation of the NiFe OEC over long‐term durability.

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.

This work reports on a combinational methodology to CaWO4 nanocrystals of controllable particle sizes for comprehension of particle size dependences of physical properties. Citric acid as a capping molecule restricted the growth of CaWO4 nanocrystals and gave a small particle size of 3.6 nm at room temperature at pH 8, while large particle sizes or the absence of CaWO4 nanocrystals were always observed when the pH value was higher or lower than 8. Hydrothermal treatments over 3.6 nm CaWO4 at high temperatures led to a systematic increase in particle sizes. X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and UV−vis spectroscopy were employed to study the particle size dependences of properties including lattice dimensions, vibrational variations, and transition energies. It is found that, with particle size reduction, CaWO4 nanocrystals showed a lattice expansion, an enhanced structural symmetry, and a red shift in the Au phonon mode. A drastic blue shift of the electronic absorption bands was also observed for the transition of 1A1 → 1T1 in CaWO4 nanocrystals at small sizes, which was explained by taking into account the quantum confinement effect and the enhanced ionicity of W−O bonds.