SnS2 Quantum Dots Based Optoelectronic Flexible Sensor for Ultrasensitive Detection of NO2 Down to One-ppb.

Transition metal dichalcogenides (TMDs) have gained intense interest for the outstanding optoelectronic, and electrochemical characteristics, utilized as versatile applications like gas sensors and photodetectors. However, TMDs based chemiresistors suffer from poor sensitivity at ppb-level detection and the experimental detection limit fails to reach 1ppb. Here in, SnS2 QDs /graphene nano heterostructure as functional flexible sensors are fabricated for NO2 gas and light detection at room temperature. The semiconductor type of the nanohybrids can be shifted between p-type and n-type by adjusting the proportion of the components, both of which exhibit excellent gas sensing properties. Ppb-level NO2 detection is realized even under room temperature with superior sensitivity (860% to 125ppb) fast response (114s) and recovery (166s). It also demonstrates ultrahigh-sensitive and broadband photo detection in visible region. The photo responsivity can reach to 2.08×103A /W under blue light illumination under room temperature. Especially, the influence of light illumination of different wavelength and intensity on gas sensing performance is studied. 1 mW/cm2 red light greatly enhances the sensitivity up to 5.1 folds and the device performs obvious response to NO2 at concentration as low as 1ppb. Ab initio DFT calculation and band theories are applied to explain the interaction of the components and the effect of the light excitation inducing charge carriers on gas sensing equilibrium.