Exciton-Driven Chemical Sensors based on Excitation Dependent Photoluminescent Two Dimensional SnS

Excitation wavelength dependent photoluminescence (PL) in two-dimensional (2D) transition metal chalcogenides enables a strong excitonic interaction for high-performance chemical and biological sensing applications. In this work, we explore the possible candidates in the domain of post-transition metal chalcogenides. Few-layered 2D p-type tin monosulfide (SnS) nanoflakes with sub-micrometer lateral dimensions are synthesized from the liquid phase exfoliation of bulk crystals. Excitation wavelength dependent PL is found and the excitonic radiative lifetime is more than one order enhanced compared to that of bulk counterpart due to the quantum confinement effect. Paramagnetic NO2 gas is selected as a representative to investigate the exciton-driven chemical sensing properties of 2D SnS. Physisorption of NO2 results in the formation of dipoles on the surface of 2D SnS, causing the re-distribution of photoexcited charges in the body and therefore modifying PL properties. For practical sensing applications, 2D...