On-Site Visual Detection of Hydrogen Sulfide in Air Based on Enhancing the Stability of Gold Nanoparticles

We have described a simple and low-cost visual method for on-site detection of hydrogen sulfide (H₂S) in air based on the antiaggregation of gold nanoparticles (AuNPs). The bubbling of H₂S into a weak alkaline buffer solution leads to the formation of HS^–, which can stabilize the AuNPs and ensure the AuNPs maintain their red color even in a Tris buffer solution containing 80 mM NaCl with the presence of Tween 80. The stabilization of the AuNPs is attributed to the adsorption of negatively charged S^2– on the AuNPs surface. In contrast, without the bubbling of H₂S, AuNPs aggregate and change color from red to blue. Under optimal conditions, the proposed method exhibits excellent visual sensitivity with a naked-eye detectable limit of 0.5 ppm (v/v), making the on-site detection of H₂S possible. This method also possesses good selectivity toward H₂S over other gases by using a simple SO₂ removal device. The successful determination of the concentrations of H₂S in local air indicates the potential application of this cost-effective method.