Self-Assembly of Ultrathin Nickel Oxysulfide for Reversible Gas Sensing at Room Temperature

Abstract

Two-dimensional (2D) or ultrathin metal sulfides have been emerging candidates in developing high-performance gas sensors given their physisorption-dominated interaction with target gas molecules. Their oxysulfide derivatives, as intermediates between oxides and sulfides, were recently demonstrated to have fully reversible responses at room temperature and long-term device stability. In this work, we explored the micro-scale self-assembly of ultrathin nickel oxysulfide through the calcination of nickel sulfide in a controllable air environment. The thermal treatment resulted in the replacement of most S atoms in the Ni-S frameworks by O atoms, leading to the crystal phase transition from original hexagonal to orthorhombic coordination. In addition, the corresponding bandgap was slightly expanded by ~0.15 eV compared to that of pure nickel sulfide. Nickel oxysulfide exhibited a fully reversible response towards H2 at room temperature for concentrations ranging from 0.25% and 1%, without the implementation of external stimuli such as light excitation and voltage biasing. The maximum response factor of ~3.24% was obtained at 1% H2, which is at least one order larger than those of common industrial gases including CH4, CO2, and NO2. Such an impressive response was also highly stable for at least four consecutive cycles. This work further demonstrates the great potential of metal oxysulfides in room-temperature gas sensing.

Liquid-tin-printed two-dimensional SnO for optoelectronic NO2 gas sensing at room temperature

“…A charge exchange would occur on the surface of two-dimensional materials when exposed to NO 2 gas, which would increase the hole density of SnO and consequently alleviates the electrical resistance of the sensor. [58][59][60] On the one hand, due to the large band gap of SnO, the input energy of light irradiation is not enough to effectively stimulate the generation of photoexcitons to participate in the charge exchange process between the surface of two-dimensional nanomaterials and adsorbable gas molecules. In contrast, the energy input accelerates the desorption of gas molecules on the surface of the material, which is manifested as a reduced response during the response phase.…”

Recent Advances in Functionalization and Hybridization of Two‐Dimensional Transition Metal Dichalcogenide for Gas Sensor

“…[180][181][182] Compared to pure metal chalcogenides, metal oxychalcogenides exhibit modified electronic band structures, while physisorption typically remains the dominant gas adsorption model in their gas-sensing behavior. [183] Also, metal oxychalcogenides are expected to be more durable against selfoxidation because the surface S 2À ions are stabilized by hybridization of the S 3p and O 2p orbitals. [184,185] Although some researches have been studied about the gas-sensing performance of metal oxychalcogenides, detailed sensing mechanism should be studied in more detail.…”

A Room Temperature High‐Performance Visible‐Light‐Assisted NO2 Gas Sensor Based on Ultrathin Zinc Oxysulfide

“…Furthermore, the nanoflakes are of an ultrathin flake-like morphology, depending on their highly transparent features (Figure 1b), which may originate from the high-temperature calcination treatment during the synthesis process (details are presented in the Material Synthesis and Preparation section). [18,29] From energy-dispersive X-ray spectroscopy (EDS) measurements in Figure S2 (Supporting Information), the original zinc sulfide powder is found to be composed of Zn and S atoms only. Given an annealing treatment at 600 °C with a constant airflow supplied, the S atoms of the pure zinc sulfide are largely replaced with O atoms in company with a substantial crystal reconstruction, forming the zinc oxysulfide nanoflakes with the elemental composition of Zn, S, and O as shown in EDS results in Figure 1c.…”

“…[16,17] Physisorption of paramagnetic NO 2 gas molecules over the material surface typically occurs at room temperature or relatively low elevated temperatures, leading to the formation of electric dipoles at the gas-matter interface. [13,18] As a result, the interfacial charge transfer occurs and the electrical resistance of the material is varied, in which the magnitude of such a variation depends strongly on the adsorption energy of NO 2 over the material surface as well as the relative electronic band positions between the material and NO 2 . [13,14,[19][20][21] A wide range of sulfides of metal elements which the oxides also share, including WS 2 , [22] MoS 2 , [23] SnS 2 /SnS, [24] In 2 S 3 , [25] and Ga 2 S 3 /GaS, [26] have been investigated, in which some of them demonstrate fully reversible NO 2 response at room temperature with and without external stimulation (e.g., light and gating).…”

“…The utilization of 3D self-assembly has been proved to favor gas sensing performances over those of randomly stacked low-dimensional nanostructures, owing to its relatively ordered pores and enhanced surface area. [18,20,29] With the excitation of visible light, the electrical resistance of zinc oxysulfide self-assembly deposited over the interdigitated electrode (IDE) substrates is measured in a realtime manner upon the exposure of NO 2 with different concentrations at room temperature. Subsequently, the critical sensing performance parameters of response magnitude, response/recovery time, the limit of detection, and selectivity are extracted.…”