Light-assisted Schottky barrier enhancement for selective detection of l-cysteine using Ni/Cu2O/Ag nanocubes†

L-Cysteine (L-Cys), a sulfur-containing amino acid, plays a crucial role in various biological processes. Rapid and accurate detection of L-Cys in the human body is significant for clinical diagnosis and drug analysis. However, classic electrochemical sensing mechanisms are usually based on redox reactions, and substances with similar redox properties in the serum can easily interfere with the detection process. In this study, we present a novel approach for the detection of L-Cys using Schottky barriers of Ni/Cu₂O/Ag nanocubes. The electrode exhibits excellent selectivity towards L-Cys due to the specific interaction between Cu₂O and L-Cys through the formation of Cu–S bonds. The Schottky barrier at the Cu₂O/Ag interface, formed due to the difference in work functions, impedes electron transfer and can be modulated by the adsorption of charged L-Cys molecules. The introduction of light irradiation enhances the barrier modulation capability, resulting in improved sensitivity. Experimental results demonstrate that the Ni/Cu₂O/Ag electrode exhibits a linear response to L-Cys concentration within 0–2400 nM at pH 3.0 and pH 7.0, with a low detection limit of 11.86 nM. The electrode shows excellent performance in real sample analysis, exhibiting high recovery rates and low relative standard deviations. The light-assisted barrier enhancement mechanism provides a new avenue for the development of highly selective and sensitive electrochemical sensors.