High-Sensitivity and -Selectivity Gas Sensors with Nanoparticles, Nanostructures, and Thin Films

Abstract

Advanced gas sensors fabricated with nanoparticles and thin films of semiconductor metal oxides have been widely used for the detection of toxic, hazardous, and combustible gases and as biomarkers for the safety of human beings, environmental control, and breath analysis. This is certainly due to the simplicity of their synthesis, their low fabrication cost, and their advantageous sensor properties such as high sensitivity (even with small gas concentrations) and long-term stability. Despite these advantages, their limited selectivity and cross-sensitivity to a variety of gases remain challenging issues. Other barriers for the implementation of semiconductor metal oxides are their slow adsorption/desorption kinetics both in response to target analytes and their recovery when these cease. Recent progress in the synthesis of novel nanostructures has revealed that these issues can be overcome by the achievement of superior surface area, the tuning of pore size and pore distribution, the control of morphology, doping (in order to promote the reaction to specific gases), and the formation of metal-oxide-based composites and heterostructures, etc. Accordingly, this Special Issue highlights new achievements in the improvement of gas sensor performance by doping and applying p-n and n-n junctions, and by optimizing synthesis methods for the production of nanoparticles, thin films, nanocomposites, and heterostructures.