Zhongqiu Hua

NH 3 sensing properties and mechanism of Ru-loaded WO 3 nanosheets

In this paper, WO3 nanosheets were prepared by an acidification method and Ru catalyst was loaded on the surface of nanosheets through a conventional impregnation process. NH3 gas sensors based on the neat and Ru-loaded WO3 nanosheets were fabricated by the scree-printing technique and their sensing properties to NH3 were investigated. The morphologies and surface structures of neat and Ru-loaded WO3 nanosheets were analyzed. It is revealed that WO3 nanosheets have an irregular flake shape and Ru catalyst is found on the surface of nanosheets with an oxided state. It is also found that the sensor response of WO3 is greatly improved by the loading of Ru. Based on the power-law response of oxygen and TPR results, the sensitization mechanism of Ru is explained. It is proposed that the introduction of Ru promotes the catalytic activity of WO3 and in turn modulates the reaction route of NH3 with oxygen adsorbates on the surface, which inhibit the generation of nitrogen oxides and consequently reduces the competitive adsorption with oxygen during the sensor responses.

High-performance photodetectors based on two-dimensional tin(II) sulfide (SnS) nanoflakes

As a kind of two-dimensional (2D) materials, tin sulfides including tin(IV) sulfide (SnS2) and tin(II) sulfide (SnS) have been attracting wide attention because of its earth abundance, low cost, and environment-friendly characteristics as promising photovoltaic and photocatalytic materials. Among them, only SnS is a p-type semiconductor with appealing physical properties. However, its further investigation and functionalization have been hampered by the absence of highly crystallized nanostructures relative to other intensively studied tin sulfides, such as tin(IV) sulfide (SnS2). Herein, high quality 2D SnS is synthesized via the chemical vapor deposition (CVD) method, with a new precursor of stannous oxide (SnO). Its morphology and properties are characterized by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectrometry (EDS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Furthermore, field-effect transistors (FETs) and photodetectors based on such SnS are fabricated using Photolithographic-Pattern-Transfer (PPT) technology. The results show that the as-grown SnS is indeed a p-type semiconductor and exhibits high responsivity (156.0 A W−1), normalized detectivity (2.94 × 1010 jones) and external quantum efficiency (4.77 × 104%) with fast response time (5.1 ms) under illumination of a 405 nm laser. This work demonstrates that 2D SnS holds great promise for next-generation optoelectronic applications.