Synthesis mechanism and gas-sensing application of nanosheet-assembled tungsten oxide microspheres

Abstract

Nanosheet-assembled tungsten oxide microspheres have been synthesized using rapid sonochemistry followed by thermal treatment. Transient observation of controllable synthesis reveals that the morphological evolution of the product is highly dependent on the ultrasonication time. An assembly mechanism based on oriented attachment and reconstruction is proposed for the sonochemical formation of the nanosheet-assembled microspheres. The obtained samples possess intrinsic nonstoichiometry and a hierarchically porous nano/microstructure, which is beneficial for their utilization in sensing materials and for fast diffusion of gas molecules. The maximum response of the tungsten oxide hierarchical microspheres is 3 times higher than that of commercial nanoparticles for NO 2 gas. The gas adsorption-desorption kinetics during the sensing process were mathematically simulated by a derivative method. The first-principles calculation reveals that the NO 2 molecule is most likely adsorbed at the terminal O 1c site of tungsten oxide, leading to the introduction of new surface states, which are responsible for the intrinsic NO 2 -sensing properties.

Micro-wheels composed of self-assembled tungsten oxide nanorods for highly sensitive detection of low level toxic chlorine gas

“…3(A). 19 Fig. Upon exposure to 500 ppb Cl 2 gas, the resistance of the sensor rapidly increased and reached the saturation values of approximately 0.97, 1.83, 0.87, and 0.29 MU, respectively.…”

A New Facile Synthesis of Tungsten Oxide from Tungsten Disulfide: Structure Dependent Supercapacitor and Negative Differential Resistance Properties

“…Below 1000 cm −1 , the small but sharp peak at 949 cm −1 is indicative of the stretching of short WO bonds and the broad band at around 654 cm −1 is attributed to the stretching modes of OW vibration. In WO 3 the peaks at 949 and 654 cm −1 disappear and a new broad peak arises at around 717 cm −1 for OWO stretching vibrations in the crystal lattice …”

“…In WO 3 the peaks at 949 and 654 cm −1 disappear and a new broad peak arises at around 717 cm −1 for OWO stretching vibrations in the crystal lattice. [40,41] The synthesis of WO 3· H 2 O from WS 2 and its conversion to WO 3 is further established from Raman spectra ( Figure 2c). The precursor material WS 2 powder shows two characteristic peaks at 352 and 422 cm −1 corresponding to E 1 2g (in-plane optical mode) and A 1g (out-of-plane vibration of the sulfur atoms) modes, respectively.…”

Ni-catalysed WO3 nanostructures grown by electron beam rapid thermal annealing for NO2 gas sensing

“…8 that the response of both the Ni-WO 3 NWs and NSh sensor was higher compared to that of the reported WO 3 sensors (for NWs *140 and NSh *157) (Qin et al 2011;Bai et al 2014;Lee et al 1999). This is because of high surface charge depth (Schottky barrier height) owing to the Ni-catalysed high transport of electron density in metal-oxide matrix (Srivastava et al 2012).…”