Multilayered and Chemiresistive Thin and Thick Film Gas Sensors for Air Quality Monitoring

Selective detection of gases such as nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), and various volatile organic components (VOCs) is necessary for air quality monitoring. Detection of hydrogen (H2) is equally important as it is a flammable gas and poses serious threat of explosion when exposed to oxygen gas. We have studied the sensing characteristics of these gases using thin film deposited by chemical solution deposition as well as relatively thicker films deposited by atmospheric plasma spray (APS) process. The chapter starts with the sensing mechanism of chemiresistive sensors followed by the definition of gas sensing parameters. Subsequently, we have demonstrated selective NO2 sensing characteristics of zinc oxide-graphene (ZnO-G) multilayered thin film followed by CO and H2 sensing characteristics of ZnO thin film and SnO2 thick film. Cross-sensitivity among CO and H2 gases has been addressed through the analysis of conductance transients with the determination of activation energy, Ea, and heat of adsorption, Q. The concepts of reversible and irreversible sensing have also been discussed in relation to CO and H2 gases. CO2 sensing characteristics of LaFe0.8Co0.2O3 (LFCO)-ZnO thin film have been elucidated. Interference from CO has been addressed with principal component analyses and the ascertaining of Ea and Q values. Additionally, the variation of response with temperature for each gas was simulated to determine distinct parameters for the individual gases. Further, VOC sensing characteristics of copper oxide (CuO) thin film and WO3-SnO2 thick film were investigated. Principal component analysis was performed to discriminate the gases in CuO thin film. The interaction of WO3-SnO2 thick film with various VOCs was found to obey the Freundlich adsorption isotherm based on which Ea and Q values were determined

Electrophoretically Deposited ZnFe2O4-Carbon Black Porous Film as a Superior Negative Electrode for Lithium-Ion Battery

This article reports ZnFe2O4 (ZFO) based negative electrodes for a lithium-ion battery, which is synthesized using a simple autocombustion technique and coated onto copper current collectors using the electrophoretic deposition technique. The use of electrophoretic deposition to manufacture the electrodes results in the significant improvement of electrochemical properties of ZFO, which is achieved without the use of any complex processing steps or costly additives like graphene, CNT, etc. The electrophoretically fabricated electrodes possess a porous microstructure with uniform carbon black distribution. Such a microstructure and carbon black distribution successfully tackles the issues related to the low electronic conductivity and volumetric fluctuation based delamination. These electrodes deliver a stable reversible specific capacity of 560 mAh g(-1) at a specific current rate of 0.5 A g(-1), which is retained for 100 cycles. The electrodes also exhibit a specific capacity of 330 mAh g(-1) at a high specific current rate of 3.5 A g(-1). Electrophoretic deposition, thus, represents a simple and cost-effective route to fabricate negative electrode coatings with superior electrochemical properties