Photoelectrochemical Detection of L-cysteine with a Covalently Grafted ZnTAPc-Gr-based Probe

L-cysteine plays a vital role in organisms, and is an important biomarker for many pathological diseases that seriously affect human health. In the study, a photoelectrochemical (PEC) probe with zinc-tetramine phthalocyanine covalently grafted to graphene oxide (ZnTAPc-Gr) was developed for L-cysteine detection. Graphene oxide (GO) with carboxyl was used to immobilize zinc-tetramine phthalocyanine (ZnTAPc) with amidogen (a graft structure formed by an amide covalent bond), which could firmly immobilize ZnTAPc, thereby improving the photoelectrochemical performance and stability. L-cysteine molecule, an electron acceptor, was specifically recognized by the PEC probe, exhibiting a decrease in the photocurrent signal. Under the optimal experimental conditions, the fabricated PEC probe exhibited excellent performance in L-cysteine analysis within a linear range of 0.25-113 mu M and a detection limit of 11.4 nM. The PEC probe showed high sensitivity, selectivity, and stability. The method described herein provides an effective strategy for PEC probe construction for L-cysteine detection, and can also serve as a promising PEC platform for the analyses of other small molecules.