Recent progress in intrinsic and stimulated room-temperature gas sensors enabled by low-dimensional materials

Room temperature (RT) gas sensors based on low-dimensional materials have rapidly attracted wide attention in various automation control systems and particularly in the Internet of Things (IoT) platforms due to their unbeatable advantages such as low fabrication cost and power consumption, compactness, long-term stability, and high sensitivity over the conventional temperature enabled gas sensing applications. Therefore, significant efforts have been recently devoted to exploring the alternative assisted methods from the aspects of intrinsic gas sensing properties of low-dimensional nanomaterials and external stimuli to drive the gas sensing performance without relying on a high temperature. In this review, we summarise the enhancing strategies of low-dimensional materials such as nanostructure optimisation, surface functionalisation and heterostructure formation with a comprehensive discussion of their room-temperature gas sensing mechanism. Moreover, the external stimuli approaches including voltage biasing, and UV and visible light excitons are also carefully examined with an insightful discussion of their impacts on the gas sensing performance. Finally, the current challenges and further improvements of the introduced methods are illustrated and the prospects of the emerging techniques are discussed.