Direct Electrochemistry of Cytochrome c Based on Poly(diallyldimethylammonium Chloride)‐ Graphene Nanosheets/Gold Nanoparticles Hybrid Nanocomposites and Its Biosensing

A novel biosensor was developed by entrapping cytochrome c (Cyt c) in thin films of the room temperature ionic liquid (RTIL) containing nanocomposites of poly(diallyldimethylammonium chloride)‐graphene nanosheets‐gold nanoparticles (PDDA‐Gp‐AuNPs) at a 11‐mercaptoundecanoic acid‐6‐mercapto‐1‐hexanol modified gold electrode. The synthesized PDDA‐Gp‐AuNPs hybrid nanocomposites were characterized by UV‐vis spectroscopy, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The PDDA‐Gp‐AuNPs nanocomposites could increase the effective surface of the electrode, enhance the fixed amount of Cyt c on the electrode surface, promote the electron transfer and facilitate the catalytic activity of Cyt c. The RTIL could provide a biocompatible microenvironment to keep Cyt c biological activities, act as an effective mediator to immobilize a large number of Cyt c on the electrode and have good conductivity to improve electron transfer. Therefore, the resultant electrode exhibited good electrochemical performance and electrocatalytic activity. It could be used for electrochemical detection of H₂O₂ with rapid response, high sensitivity, wide linear range and low detection limit, as well as good stability, repeatability and selectivity. The sensor might be promising for practical application.