Nanocomposite of polymerized ionic liquid and graphene used as modifier for direct electrochemistry of cytochrome c and nitric oxide biosensing

In the present work, nanocomposite of polymerized ionic liquid (PIL), poly (1-vinyl-3-ethyl imidazolium) bromide, modified graphene nanosheet (PIL-Gr) was prepared. The PIL-Gr nanosheet composite was evaluated using scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Then, a robust and effective sensing strategy based on the nanocomposite for cytochrome c (Cyt c) immobilization on basal plane graphite (BPG) electrode surface was proposed. Direct electrochemistry and electrocatalysis of immobilized Cyt c were investigated in detail. The cyclic voltammogram results indicated that the PIL-Gr nanocomposite film showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c exhibited an excellent electrocatalytic activity towards the reduction of nitric oxide (NO). The fabricated biosensor exhibited a fast response and a good electrochemical activity for NO with comparable liner range and low detection limit. The low apparent Michaelis-Menten constant indicated the affinity of PIL-Gr and Cyt c. Moreover, the modified electrode displayed a rapid response to NO and possessed good stability and reproducibility. Based on the nanocomposite, a third-generation reagentless biosensor could be constructed for the determination of NO. The present work broadens the applications of graphene and ionic liquid in biosensor field.