Weibin Zhang

Controlled synthesis and enhanced luminescence of BiOCl:Eu3+ ultrathin nanosheets

BiOCl:Eu3+ ultrathin nanosheets were synthesized through a facile solvothermal method with the assistance of polyvinyl pyrrolidone. The ultrathin nanosheets showed a size ranging from 50–100 nm and a height of 2.9 nm, which is about four [Cl–Bi–O–Bi–Cl] layers. In addition, the luminescence properties and mechanism were investigated in detail, and compared with that of the nanoplate. It was found that the luminescence intensity for the BiOCl:Eu3+ ultrathin nanosheet was 6 times stronger than that of the nanoplate. Importantly, the oxygen vacancies act as a luminescence centers, and there was effective energy transfer from BiOCl ultrathin nanosheets to Eu3+ ions. In BiOCl:Eu3+ ultrathin nanosheets, white-light emission was observed under near-ultraviolet (NUV) excitation. These BiOCl:Eu3+ ultrathin nanosheets exhibit great potential as color-emitting phosphors for white light-emitting diode applications.

First-principle study of the structural, electronic, and optical properties of SiC nanowires

We preform first-principle calculations for the geometric, electronic structures and optical properties of SiC nanowires (NWs). The dielectric functions dominated by electronic interband transitions are investigated in terms of the calculated optical response functions. The calculated results reveal that the SiC NW is an indirect band-gap semiconductor material except at a minimum SiC NW (n = 12) diameter, showing that the NW (n = 12) is metallic. Charge density indicates that the Si–C bond of SiC NW has mixed ionic and covalent characteristics: the covalent character is stronger than the ionic character, and shows strong s–p hybrid orbit characteristics. Moreover, the band gap increases as the SiC NW diameter increases. This shows a significant quantum size and surface effect. The optical properties indicate that the obvious dielectric absorption peaks shift towards the high energy, and that there is a blue shift phenomenon in the ultraviolet region. These results show that SiC NW is a promising optoelectronic material for the potential applications in ultraviolet photoelectron devices.

Correlation between lateral size and gas sensing performance of MoSe2 nanosheets

We demonstrate a facile synthetic method to prepare lateral size controlled molybdenum diselenide (MoSe2) nanosheets using liquid phase exfoliated few-layer MoSe2 nanosheets as a starting material. By precisely controlling the centrifugation condition, preparation of MoSe2 nanosheets with a narrow size distribution ranging from several hundred nanometers to several micrometers could be realized. The accurate size control of MoSe2 nanosheets offers us a great opportunity to examine the size dependent sensing properties. The sensing test results demonstrate that the MoSe2 nanosheets provide competitive advantages compared with conventional graphene based sensors. A tradeoff phenomenon on sensing response and recovery as the lateral size of MoSe2 nanosheets varies is observed. First principles calculations reveal that the ratio of edge-surface sites is responsible for this phenomenon. The correlation between the lateral size and gas sensing performance of MoSe2 nanosheets is established.

FIRST-PRINCIPLES STUDY OF Ti-CATALYZED HYDROGEN ADSORPTION ON LiB (001) SURFACE

Ti-doped LiB (001) is a promising material for hydrogen storage. The adsorption of H2 is greatly enhanced by doping Ti into LiB (001), change the electronic structures of the surface Li, B atoms. After H2 is adsorbed on the surface, the Ead of the (H2)n@Ti/LiB (001) system is considered. It is around -0.22 eV/H2 to -0.31 eV/H2, which is close to the target specified by U.S. Department of Energy. The nature of the bonding between Ti and H2 is due to the H 1s, Ti 4s and B 2s orbital hybridization. In addition, Ti 3d orbital is hybridized strongly with B-2p orbital, resulting in more stable Ti/LiB (001) system. These results are verified by the electron density distribution intuitively. It is found that the system can adsorb up to four H2 at ambient temperature and pressure. Therefore, the Ti-doped LiB (001) would be a promising hydrogen storage material. Such optimal molecular hydrogen adsorption system makes H2 adsorption feasible at ambient conditions, which is critical for practical applications.

Theoretical investigation on the low-lying electronic states of beryllium antimonide

The Λ-S electronic states with respect to the lowest four dissociation limits of BeSb are investigated theoretically on the icMRCI + Q level employing basis set of quintuple-ζ quality. The geometrical parameters, potential energy curves, vibrational energy levels, spectroscopic constants for the twelve Λ - S states are obtained, analyzed and compared with those of the Beryllium-VA group diatomic family species where data are available. The permanent dipole moments, transition dipole moments, Einstein emission coefficients, radiative lifetimes and Franck-Condon factors for interested Λ - S states are also derived. Further assessments of the spin-orbit coupling effect are performed for states associated with the first two dissociation asymptotes of BeSb. Four Λ - S states split into seven Ω states, and some of the PECs are distorted significantly through the spin-orbit coupling effect, which is similar to its isovalent diatomics BeAs. In consideration of potential risks of manipulating beryllium-containing species directly, the information associated with molecular structures, spectroscopic parameters as well as transition properties that provide in this paper is anticipated to serve as guidelines for further researches of BeSb.

Fe-doped Bi4O5Br2 Visible Light Photocatalyst: A First Principles Investigation

This study employed first principles calculations to investigate Fe-doped Bi4O5Br2 as a potential photocatalyst with high efficiency. Based on formation energy calculation, the Fe atoms prefer to r...