A “signal-on” cathodic photoelectrochemical biosensor based on Cu-MOF@Cu₂O heterostructure for L-cysteine detection

Cathodic photoelectrochemical (PEC) sensor has attracted extensive attention as a convenient and efficient detection method. In this study, a “signal-on” cathodic PEC sensor based on Cu-MOF modified Cu₂O heterostructure (Cu-MOF@Cu₂O) has been successfully constructed for L-Cysteine (L-CySH) detection. Compared with Cu-MOF and Cu₂O, the photocurrent response of Cu-MOF@Cu₂O heterostructure are significantly enhanced due to the improved visible light capturing ability and photoelectric conversion efficiency. For the detection of L-CySH, L-CySH can be coupled to the electrode surface via Cu[sbnd]S bond and further oxidized by copper ions (Cu²⁺) to form L-Cystine (L-CySSyC). Then, the L-CySSyC serves as the electron acceptor to scavenge the photogenerated electron of Cu-MOF@Cu₂O, resulting in the increase of photocurrent response. The linear concentration range for L-CySH detection is 0.5–500.0 μM, and the detection limit is 0.32 μM. Furthermore, this sensor also has been obtained satisfactory results for L-CySH detection in real urine samples.