Review on Porosity Control in Nanostructured Semiconducting Metal Oxides and Its Influence on Chemiresistive Gas Sensing

Abstract

Nanostructured semiconducting metal oxides (SMOs) hold the potential for playing a critical role in gas-sensing applications due to their interconnected nanograins, large surface area, and shorter diffusion length. The rational introduction of ubiquitous porosity in SMOs can enhance gas/air diffusion as well as the accessibility of nanograins and reactive sites. Although much work has been researched for adopting highly porous nanostructured SMOs to enhance gas sensing, no comprehensive review on porosity control has yet been presented. In this review, the latest porosity control methods for SMOs, structural properties, and their gas-sensing results are reported. Finally, perspective on porosity control methods and future directions are provided for further development and research of porous SMO-based gas-sensing nanomaterials.

Oxidation-enabled SnS conversion to two-dimensional porous SnO2 flakes towards NO2 gas sensing

“…They show interlinked tiny nanoparticles, large specific surface areas and abundant sizetunable pores and are often capable of improving the overall performance of gas sensors because of the quick diffusion, surface adsorption and high reactivity of NO 2 /O 2 gas molecules as well as the rapid charge transduction among cross-linking nanoparticles. 9,[13][14][15]25,26 The template method has been shown to be one of the most efficient strategies to induce porosity, through which tunable pore size and density are created by removing one or more of the components of Sn-bearing template materials by means of annealing, pyrolysis, oxidation, and etching. 13,15,[25][26][27][28][29][30] For example, tin chalcogenides (e.g., SnS 2 and SnSe) have been used as self-sacrificial templates to prepare porous SnO 2 materials through thermal annealing or oxidation to remove chalcogen elements.…”

Bismuth Molybdate Nanorods Derived from a Metal–Organic Framework for Triethylamine Gas Sensors

“…The origin of resistive metal oxide semiconductor (MOS) gas sensors can be traced back to 1962 when a ZnO film exhibited electrical property changes in the presence of different gases such as CO 2 , benzene, and ethyl alcohol . As devices designed for monitoring the concentration of various gases, MOS sensors have been widely used because of their high sensitivity, lower cost, and simple fabrication and miniaturization. − The general working principle of resistive sensors is that, in clean air, oxygen is adsorbed on their surface, changing the electronic configuration of nanostructured MOS and increasing electrical resistance . In the presence of a reducing gas target, electrons are released in the MOS, resulting in a diminution of the electrical resistance proportional to the analyte concentration.…”

“…9−11 The general working principle of resistive sensors is that, in clean air, oxygen is adsorbed on their surface, changing the electronic configuration of nanostructured MOS and increasing electrical resistance. 12 In the presence of a reducing gas target, electrons are released in the MOS, resulting in a diminution of the electrical resistance proportional to the analyte concentration.…”

Metal–organic framework-derived metal oxides for resistive gas sensing: a review

“…[44][45][46][47][48][49][50][51][52][53] In addition, the large surface area and permeable structure of metal oxides derived from MOFs create a wealth of adsorption sites and pathways, allowing for effective gas-molecule interactions. [54][55][56][57][58] As a consequence, gas detection applications experience enhanced sensitivity and swift response times. [59][60][61][62][63] The remarkable chemical stability and manageability of metal oxides derived from MOFs have enabled the creation of custom sensing materials for certain gases.…”