Optically Transparent Electrodes Modified with Sulfide Ion‐Covered CdS Quantum Dots for Sensitive Photoelectrochemical Detection of Sulfhydryl‐Containing Compounds

Abstract

AbstractA sensitive and selective photoelectrochemical sensor has been developed. Negatively charged, citrate‐capped CdS quantum dots (QDs) are assembled layer‐by‐layer onto indium tin oxide (ITO) electrodes precoated with positively charged poly(diallyldimethylammonium chloride). By exposing the modified photoelectrochemical electrodes to a Na2S solution, QDs can be covered with excess S2− ions. The weakly bound S2− ions are easily replaceable with a sulphydryl‐containing analyte, and the photocurrent decrease is proportional to the analyte concentration. The detection limit is 0.4 nM for cysteine with a linear range of 1.0–100.0 nM. The level of cysteine in human serum samples has been quantified.