Scalable WS₂-Graphene Hybrids for Ultralow NO₂ Concentration Detection

This work presents a facile approach for fabricating hybrid heterostructures of tungsten disulfide (WS₂), synthesized via atmospheric pressure chemical vapor deposition (APCVD) and commercial graphene. A simple airbrushing technique, with nitrogen (N₂) as the carrier gas, was employed to fabricate the sensors. The morphological and structural characterizations of the hybrid material revealed a sheet-like synthesis of edge-enriched 2D WS₂ decorated with multilayer graphene nanomaterial. The gas-sensing properties of the pristine and hybrid materials were evaluated for nitrogen dioxide (NO₂) at various operating temperatures. The hybrid sensor with a WS₂ to graphene ratio of 3:1 demonstrated exceptional sensitivity to ultralow NO₂ concentrations (10 ppb) at a remarkably low operating temperature of 100 °C, outperforming both the graphene and WS₂ counterparts. Additionally, the sensor's responses to CO, H₂, C₆H₆, and NH₃ were examined to assess its selectivity. The sensor was tested under different relative humidity conditions (RH at 25 °C; 25%, 50%, and 75%). The sensor response nearly doubled at RH = 50%, highlighting its potential for practical applications in selective NO₂ detection. The sensor responses eventually reached saturation at 75% RH. In addition, the manuscript provides a detailed discussion of the NO₂ gas sensing mechanism.