High-temperature solid-state reaction induced structure modifications and associated photoactivity and gas-sensing performance of binary oxide one-dimensional composite system

Abstract

The effects of high-temperature solid-state reactions on the microstructures, optical properties, photoactivity, and low-concentration NO 2 gas-sensing sensitivity of ZnO-SnO 2 core-shell nanorods were investigated. In this study, the ZnO-SnO 2 core-shell nanorods were synthesized through a combination of the hydrothermal method and vacuum sputtering. According to X-ray diffraction and transmission electron microscopy analyses, high-temperature solid-state reactions between the SnO 2 shell and ZnO core materials at 900 C engendered an ultrathin SnO 2 shell layer for transforming into the ternary Zn 2 SnO 4 (ZTO) phase. Moreover, surface roughening was involved in the high-temperature solidstate reactions, as determined from electron microscopy images. Comparatively, the ZnO-ZTO nanorods have a higher oxygen vacancy density near the nanostructure surfaces than do the ZnO-SnO 2 nanorods.The photodegradation of rhodamine B dyes under simulated solar light irradiation in presence of the ZnO-SnO 2 and ZnO-ZTO nanorods revealed that the ZnO-ZTO nanorods have a higher photocatalytic activity than do the ZnO-SnO 2 nanorods. Furthermore, the ZnO-ZTO nanorods exhibited higher gassensing sensitivity than did the ZnO-SnO 2 nanorods on exposure to low-concentration NO 2 gases. The substantial differences in the microstructure and optical properties between the ZnO-SnO 2 and ZnO-ZTO nanorods accounted for the photocatalytic activity and NO 2 gas-sensing results obtained in this study.

Surface crystal feature-dependent photoactivity of ZnO–ZnS composite rods via hydrothermal sulfidation

“…The UV emission band was attributed to the nearest band edge emission originating from the recombination of free excitons of ZnO through an exciton-exciton collision process. 2,6 The green emission band centered at 567 nm was previously attributed to the contribution of the surface defects in ZnO. 2 Notably, the origin of the green emission centered at 520 nm for the ZnO-ZnS-3 composite rods be assigned to the deep states from Zn vacancy in the ZnS crystallites.…”

“…The development of oxide semiconductor photocatalysts for environmental remediation has been widely studied. [1][2][3] Zinc oxide (ZnO) has received global research interest for application as a highly efficient photocatalyst. However, low quantum efficiency, short-range disorder, and photocorrosion continue to affect the performance of ZnO in practical applications.…”

Crystal phase content-dependent functionality of dual phase SnO2–WO3nanocomposite filmsviacosputtering crystal growth

“…A SnO 2 -based composite structure combining SnO 2 with another phase has been widely used in one-dimensional and sphere/particle morphologies to improve gas-sensing properties and dye photodegradation ability. 8,9 However, due to complex synthesis methods, such two-phase structures in thin lms have seldom been reported. SnO-SnO 2 composite thin lms have been shown to possess superior NO 2 sensing ability, and the formation of the SnO-SnO 2 junctions at the thin-lm surface dominates their gas-sensing ability.…”

Surface Morphology-Dependent Functionality of Titanium Dioxide–Nickel Oxide Nanocomposite Semiconductors

“…A larger potential barrier variation was expected in the NST than in the NPT during the gas-sensing tests. This explains the higher gas-sensing response of the NST in this study [2,36]. Moreover, the selectivity of the NST was shown in Figure 7f.…”