A high-performance electrochemical sensor for biologically meaningful l-cysteine based on a new nanostructured l-cysteine electrocatalyst.

As a new class of l-cysteine electrocatalyst explored in this study, Au/CeO2 composite nanofibers (CNFs) were employed to modify the screen printed carbon electrode (SPCE) to fabricate a novel l-cysteine (CySH) electrochemical sensor with high performance. Its electrochemical behavior and the roles of Au and CeO2 in the composite toward electro-oxidation of CySH were elucidated and demonstrated using cyclic voltammetry and amperometry techniques for the first time through the comparison with pure CeO2 NFs. More specifically, the Au/CeO2 CNFs modified SPCE possessed greatly enhanced electrocatalytic activity toward CySH oxidation. An ultra high sensitivity of 321 μA mM-1cm-2 was obtained, which is almost 2.7 times higher than that of pure CeO2 NFs, revealing that the presence of Au imposed an important influence on the electrocatalytic activity toward CySH. The detailed reasons on such high performance were also discussed. In addition, the as-prepared sensor showed a low detection limit of 10 nM (signal to noise ratio of 3), a wide linear range up to 200 μM for the determination of CySH, an outstanding reproducibility and good long-term stability, as well as an excellent selectivity against common interferents such as tryptophan, tyrosine, methionine, ascorbic acid and uric acid. All these features indicate that the Au/CeO2 composite nanofiber is a promising candidate as a new class of l-cysteine electrocatalyst in the development of highly sensitive and selective CySH electrochemical sensor.