Improved Charge Transfer for NO2 Gas Sensors by Using 0D SnS Quantum Dot/2D WSe2 Heterostructures

Abstract

A highly sensitive array of two-dimensional (2D) WSe2 nanosheets integrated with zero-dimensional (0D) SnS quantum dots was synthesized by combining liquid-phase exfoliation and wet chemical synthesis methods. The characterization results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) revealed the formation of WSe2/SnS heterostructures, which enable a cyclic and reproducible high gas sensing response. The role allocation of SnS on WSe2 was verified by using density functional theory (DFT) calculations. The result indicates that the top alignment of SnS and the bottom layer of WSe2 act as a gas adsorption layer and carrier conduction layer, respectively. The charge interactions of the heterostructures were systematically explored by monitoring changes in the transferred characteristics at room temperature (27 °C) after introducing 25–100 ppb NO2. The highest sensing response of WSe2/SnS heterostructures toward the NO2 gas was found to be 1.08 at 25 ppb with a LOD of 10.6 ppb. The experimental and simulation results revealed that the charge transfer across the active sites increased after incorporating SnS in the WSe2. The sensing results showed an abrupt and reliable gas response under periodic NO2 gas injection unambiguously achieved by such heterostructures. The sensor also exhibited satisfactory stability and accuracy in selectivity and is not affected by humidity at room temperature. DFT calculations were also used to explain the sensing mechanism and heterojunction for such nanocomposites.