Self-assembled monolayer functionalized metal oxides: a path toward highly selective and low-power consuming gas sensors

Abstract

The emerging functionalization strategy of self-assembled monolayers (SAMs) offers transformative potential for enhancing the performance of nanostructured metal oxides (MOXs)-based gas sensors. Being a 2D-molecular arrangement with a unique structure, polar SAMs tend to modulate the surface charge density and offer distinct surface-specific interactions that lead to enhancement of the sensor performance. This review is focused on highlighting their potential and explores the advancements in SAM-functionalized MOXs, with a particular emphasis on 1D nanostructures such as nanowires and nanotubes. By tailoring the surface chemistry through SAM functionalization, these sensors achieve remarkable improvements in sensitivity, selectivity, and operational temperature, overcoming the persistent challenges of MOX sensors. In addition to the fundamental aspect of SAMs, recent progress in tuning the sensing performance of different 1D-nanostructured MOXs, including SnO₂, ZnO, WO₃, and NiO via SAM functionalization, is systematically reviewed. This review also discusses in detail the underlying sensing mechanism and key findings that underscore the ability of SAMs to offer selective interactions with gas analytes, helping to improve their response dynamics and enable low-temperature operation. Finally, the major challenges are addressed, providing a roadmap for future research. This review presents SAMs as a versatile platform for nanoscale functionalization, advancing the design of energy-efficient and high-performance gas sensors for environmental monitoring and healthcare.