Analysis of the atomic structure of monoclinic BiVO4 reveals its fascinating structure-related dual response to visible light and temperature.Although there have been a few reported studies of its responses to visible light and temperature,an understanding of the effects of quantum size,particle shape or specific exposed facets on its dual responsive properties remains elusive;this is primarily due to the limited availability of high-quality monodisperse nanocrystals with extremely small sizes and specific_(4)exposed facets.Herein,we describe a novel assembly-fusion strategy for the synthesis of mesostructured monoclinic BiVO_(4)quantum tubes with ultranarrow diameter of 5 nm,ultrathin wall thickness down to 1 nm and exposed{020}facets,via a convenient hydrothermal method at temperatures as low as 100℃.Notably,the resulting high-quality quantum tubes possess significantly superior dual-responsive properties compared with bulk BiVO_(4)or even BiVO4 nanoellipsoids,and thus,show high promise for applications as visible-light photocatalysts and temperature indicators offering improved environmental quality and safety.This mild and facile methodology should be capable of extension to the preparation of other mesostructured inorganic quantum tubes with similar characteristics,giving a range of materials with enhanced dual-responsive properties.
In the present paper,we shall rigorously re-establish the result of the single-particle function of a quantum dot system at finite temperature.Unlike the proof given in our previous work(Phys.Rev.B 74 195414(2006)),we take a different approach,which does not exploit the explicit expression of the Gibbs distribution function.Instead,we only assume that the statistical distribution function of the quantum dot system is thermodynamically stable.As a result,we are able to show clearly that the electronic structure in the quantum dot system is completely determined by its thermodynamic stability.Furthermore,the weaker requirements on the statistical distribution function also make it possible to apply the same method to the quantum dot systems in non-equilibrium states.
Raman and luminescence studies on the phase transition of europium orthoniobates(EuNbO4) under high pressure were performed. The pressure dependent Raman spectra revealed that an irreversible phase transition from monoclinic phase to M'-fergusonite phase of EuNbO4 occurred at 7.3 GPa, and the two phases coexisted over a pressure range from 7.3 to 13.7 GPa. An obvious discontinuity on luminescence intensity ratio between 5D0 →7F2 and 5D0→7F1 transitions was observed with increasing pressure, indicating also that a phase transition occurred at 7.3 GPa, which was in agreement with the high pressure Raman spectra data. Meanwhile, the Raman and luminescence spectra in the temperature range of 20–300 K showed the structure stability at low temperatures.
