Room Temperature H2S Sensing by rGO-MoS2 Composite

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.