Hierarchical Cu@Cu_xO nanowires arrays-coated gold nanodots as a highly sensitive self-supported electrocatalyst for L-cysteine oxidation

The sensitivity, selectivity, and stability of an electrochemical sensor for detecting small biomolecules can be significantly upgraded through properly controlling the morphology and chemical structure of electrocatalyst. Herein, we fabricated a unique hierarchical nanostructure based on Cu@Cu_xO nanowires (NWs) array uniformly depositing with a layer of gold nanoparticles (2-3 nm) through a simple electroless deposition process. The Au-Cu@Cu_xO NWs hybrid was successfully applied as a novel binder-free self-supported biosensor towards L-cysteine detection with low limit of detection (1.25 μM), wide linear detection range (1.25 μM-1.94 mM), long-term stability (four weeks), and excellent selectivity. In addition, the hybrid-based sensor accurately detected L-cysteine in real samples. It was found that the obtained nanostructure with the formation of strong interaction between Au and Cu phase produces synergistic effects, which improve exposed electroactive site number, accelerate charge transfer rate, and increase surface area, thereby boosting the sensing performance. The results open a potential way to develop electrochemical sensor for efficiently detecting not only L-cysteine but also other small molecules with high sensitivity, accuracy, stability, and cost-effectiveness in health care and disease diagnosis.