Progress towards chemical gas sensors: Nanowires and 2D semiconductors

There is a great interest in portable gas sensing technologies to provide real-time monitoring of indoor and outdoor air quality as well as the human health diagnostics. One-dimensional metal oxide nanowires have demonstrated improved properties compared to the conventional thick film gas sensors. Furthermore, two-dimensional semiconductor nanomaterials have shown great promise for the development of high performance functional devices owing to their unique physical, chemical and electrical characteristics. Hence, they become one of the most investigated structures for the fabrication of detection systems. Herein, we present an overview of the synthesis and sensing properties of metal oxide nanowires and two-dimensional semiconductor nanostructures such as metal-organic frameworks, graphene and transition metal dichalcogenides. We discuss the current achievements and issues in the preparation of pure, doped and composite materials comprising metal oxide nanowires and two-dimensional semiconductors. Then, we discuss the advances in gas sensing performances of the aforementioned materials considering their morphology, compositions and structure. Afterward, we provide a brief summary along with the opportunities and challenges for future fabrication of high performance and small size gas sensing devices.