Room Temperature H₂S Sensing by rGO-MoS₂ Composite

Abstract

Diagnosis of diseases by analyzing the constituents of breath or mouth vapor, owing to its ease of operation, is emerging as a promising alternative to the existing diagnostics. H ₂ S is one of the known biomarkers of hepatocellular carcinoma. This work reports detection of H ₂ S using reduced graphene oxide (rGO) and molybdenum disulfide (MoS ₂ ) composite. rGO was synthesized by thermally reducing graphene oxide that was obtained using modified Hummers' method and MoS ₂ nanoflakes were synthesized using a facile liquid exfoliation technique. The composite was synthesized by mixing the two nanomaterials in specific proportion and ultrasonicating the dispersion. The 2-D morphologies of all the intrinsic nanomaterials and the composite were confirmed using electron microscopies. The bandgaps of rGO, MoS ₂ , and rGO-MoS ₂ composites were found to be 4.1, 1.7, and 2.2 eV, respectively, when studied using ultraviolet-visible spectroscopy. All the nanomaterials were tested exhaustively for 5–54 ppm of H ₂ S at room temperature. The rGO exhibited 0.5%–1.5% response toward 13–54 ppm H ₂ S while the responses of MoS ₂ and rGO-MoS ₂ composite were found to vary between 20%–50% and 15%–33%, respectively, for 5–54 ppm H ₂ S at room temperature. The incorporation of rGO in the MoS ₂ network led to stabilization of the baseline resistance of the sensors, which was otherwise varying largely in case of intrinsic MoS ₂ . The composite was found to be fast with the response times varying from 21 to 50 s and the recovery time was found to vary from 10 to 33 s for 5–54 ppm H ₂ S at room temperature. The composite also exhibited excellent selectivity toward the target gas.