rGO-Modified ZnWO₄/WO₃ Nanocomposite for Detection of NH₃

Abstract

The composite of ZnWO4/12WO3-0.5 wt % rGO was successfully synthesized for the first time by one-step precursor calcination of equimolar W and Zn precursors, followed by loading rGO prepared by hydrazine reduction. The structure, composition, and morphology of the as-synthesized composite were characterized by various spectral analyses. Compared with reported metal-oxide-based NH3 sensors, our sensor can detect low concentrations of NH3, and the method used herein is simple, low-cost, and effective. The composite-based sensor exhibits the highest response of 10.1–20 ppm NH3, which is 3.98 times that of WO3, and has better selectivity and stability at an operating temperature of 140 °C. The improvement is attributed to the synergistic effect of p–n heterojunction formation and rGO decoration; the former creates an additional depletion layer to expand the resistance change in air and gas, while the latter provides more surface active sites to increase gas adsorption and accelerates the electron transfer for enhancing gas-sensing performance. The work has reference value to develop novel metal-oxide-based NH3 sensors.

The influence of advanced materials on the analytical performance of semiconductor-based gas sensors

“…Despite the operating temperature, the excellent sensing mechanism of the probe was attributed to the combined effect of p–n heterojunction construction and rGO decoration, which respectively created more depletion layers to enhance the resistance change and more surface active sites to increase gas adsorption, leading to an improved gas-sensing performance. 50…”

A synergistic approach to enhance sensitivity and selectivity of room temperature operable ammonia gas sensor with humidity assistance using RGO/WO3 nanocomposite

“…Thus, the oxygen atom in H 2 O quickly forms a hydrogen bond with the hydrogen atom of NH 3 . RGO facilitates the defect sites, residual oxygenated functional groups (carbonyl, carboxyl, epoxy, and hydroxyl) and sp 2 linked carbon atom that provides numerous active sites for adsorbing gas and water molecules, thereby enhancing the NH 3 gas sensing performance of metal oxide [61]. Considering this, the sensing mechanism relies on hydrogen bonds between functional groups and defect sites to physisorbed and chemically adsorb NH 3 .…”

“…The captured electrons (charge carriers) then form the chemisorbed oxygen species (O , 10)) [48]. Thus, the captured electrons are returned to the conduction band of WO 3 , enhancing the charge carrier concentration, leading to a decrease in electrical resistance [61][62][63]. The decrease in surface resistivity and increase in conductivity enables to detect the analyte gas.…”

Tailoring NH3 Sensing Responsiveness through Amine Modification of Imine-Based Nanoporous Covalent Organic Polymer

“…Among the different types of gas sensors, chemiresistive sensors are widely investigated because of their easy miniaturization, inexpensiveness, and ease of handling. , Many sensors based on metal oxides (MOs) have been explored for monitoring NH 3 , but these sensors have significant issues such as requiring high operating temperature and lacking selectivity . A composite of ZnWO 4 /12WO 3 -0.5 wt % rGO exhibited an excellent response of 10.1–20 ppm of NH 3 at a temperature of 140 °C . A modified FeVO 4 –SE with 20 mol % NiO showed a very good response to 100 ppm of NH 3 , which was operated at a temperature of 650 °C .…”

“…11 A composite of ZnWO 4 /12WO 3 -0.5 wt % rGO exhibited an excellent response of 10.1−20 ppm of NH 3 at a temperature of 140 °C. 13 A modified FeVO 4 −SE with 20 mol % NiO showed a very good response to 100 ppm of NH 3 , which was operated at a temperature of 650 °C. 14 Recently, scientists have engineered nanoporous covalent organic polymers (nCOPs) to address the limitations of MO sensors employed in the detection of NH 3 gas.…”