"Quantum dots: Perspectives in next-generation chemical gas sensors" ‒ A review.

Advances in gas sensing devices are urgently needed to reduce air pollution and control human health. In this regard, the progress in the development of low-dimensional semiconductor structures may revolutionize the concept of conventional gas sensors. The confinement of charge carriers in one or more spatial dimensions leads to the unique electrical and optical properties of semiconductor materials. Quantum dots, where the electron-hole pairs are confined in all three dimensions, offer new insights into the properties of materials. The research on quantum dot chemical sensors has become one of the rapidly developing fields in contemporary sensing technologies. The structures comprising quantum dots have shown promising sensing performance indicating that they are emerging as a new class of materials for application in chemiresistive devices. However, the QD-based structures are only beginning to be integrated into the monitoring systems. The experimental findings suggest that intensive studies need to be performed for deeply understanding the influence of synthesis procedures and additive materials on the sensing performance of quantum dots. Moreover, the response and selectivity of the materials should be analyzed considering the band gap changes in quantum dots as the size is varied. This paper provides an overview of the progress in the research of semiconductor quantum dots for application in chemical gas sensors. Advances in the fabrication and functionalities of metal oxide, chalcogenide and carbon quantum dots are highlighted. The effect of precursor materials and preparation methods on the structural features, chemical nature, size reduction and electronic properties of quantum dots are considered to examine their sensing performance. Afterward, a brief summary and outlook for the field are provided, along with the achievements and issues that are important for future studies.