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

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.