Fluorometric determination of hydrogen sulfide via silver-doped CdS quantum dots in solution and in a test strip

Silver-doped CdS quantum dots capped with mercaptoacetic acid (CdSAg-MAA QDs) were prepared and are shown to be a quenchable fluorescent probe for hydrogen sulfide (H₂S). The optimized approach exhibits a linear response in the 0.01 to 500 μM H₂S concentration range and a 3.0 nM detection limit (RSD = 0.54 % for n = 5 at 10 nM of H₂S). The estimated endogenous H₂S levels in local wastewater were 45.4 μM and 48.7 μM and the assays were not responsive to various ions often present in water and wastewater. The method gave recoveries ranging from 98 to 102 % for the analysis of acidified wastewater spiked with H₂S. Consequently, a simple colorimetric test strip was prepared by impregnating the filter paper with a mixture of CdSAg-MAA QDs and chitosan. The test strip exhibited good selectivity and sensitivity for the quantitation of H₂S in local wastewater samples. [Figure not available: see fulltext.]