Simple point contact WO3 sensor for NO2 sensing and relevant impedance analysis

Effect of solution concentration on physicochemical and gas sensing properties of sprayed WO3 thin films

“…This unpaired electron in the N atom of NO 2 forms bond with the surface oxygen of WO 3 and subsequently promote the chemisorption. [41]. Thus response towards NO 2 is higher than other gases at moderately low operating temperature.…”

Selectivity of Tungsten Oxide Synthesized by Sol-Gel Method Towards Some Volatile Organic Compounds and Gaseous Materials in a Broad Range of Temperatures

“…Additional advantage related to the assessment of initial kinetics compared to the evaluation of steady-state signal is based on specific features of chemical reactions, which occur during catalytic oxidation based sensing of some here evaluated VOC [46]. Different from the general scheme represented in the Introduction (Equation 7), these reactions proceed through several distinct steps, which are presented below in Equations (12)(13)(14)(15)(16)(17). At higher than room temperatures in the presence of air the majority of gas-or VOC-molecules, which are adsorbed on the metal oxide-based surfaces, are oxygen species (O − ) [47,48].…”

“…When oxygen species are reacting with the reducing organic compounds, then the injection of electrons is narrowing 'the width' of the electron depletion layer, which is leading to the decrease in resistance of sensing layer. Corresponding chemical reactions between analyte-molecules and oxygen species are presented in Equations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) [51,52].…”

“…Among many other oxides, tungsten (VI) oxide (WO 3 ) is a very attractive material due to its relative chemical stability, robustness, inherent electrical conductivity, and good sensitivity towards various gaseous materials including many VOCs [4][5][6]. Various WO 3 -based structures are also used in lithium-ion batteries [7] and solar energy conversion systems [8][9][10][11][12]. The gas-and/or VOC-sensing and photoelectrochemical properties of WO 3 are highly dependent on the deposition method and conditions of sensitive layer formation.…”

Ultra-low NO2 detection by gamma WO3 synthesized by Reactive Spray Deposition Technology

“…Many synthesis procedures have been proposed for producing the WO 3 films for NO and NO 2 sensors. These include spray pyrolysis [31], drop coating [32], co-precipitation [33], sol-gel synthesis [20], plasma-enhance chemical vapor deposition (PECVD) [34], thermal evaporation [13,35], and glancing angle DC magnetron sputtering [36]. In order to have a high productivity, low resistance, and a low power consumption sensor, the current trend is to construct all sensing elements on a chip [37].…”