Hydrophilic polymer/polypyrrole/graphene oxide nanosheets with different performances in electrocatalytic applications to simultaneously determine dopamine and ascorbic acid

Hydrophilic polymers (HP) functionalized polypyrrole/graphene oxide nanosheets (HP/PPy/GO) were successfully prepared by covalently modifying polyacrylamide (PAM), polyacrylic acid (PAA) and polyvinylpyrrolidone (PVP) on the surface of PPy/GO nanosheets containing vinyl groups. Besides significantly improving the dispersivity of PPy/GO in water, the different chemical properties among the three HP with different hydrophilic groups further resulted in the different performances of the obtained electrochemical biosensors (PAM/PPy/GO, PAA/PPy/GO and PVP/PPy/GO modified glassy carbon electrodes (GCEs)) in electrocatalytic applications to simultaneously determine dopamine (DA) and ascorbic acid (AA). PAM/PPy/GO and PAA/PPy/GO modified GCEs exhibited good electrochemical responses to distinguish DA from AA in their mixture at certain concentrations, which cannot be achieved by the PVP/PPy/GO modified GCE, due to their different chemical properties among the three HP with different hydrophilic groups. Particularly, compared to PAA/PPy/GO, PAM/PPy/GO can act as a good steady electrode material with good selectivity and sensitivity that can simultaneously determine the two substrates in their mixture at lower concentrations, which may be due to the different chemical properties between the electron-donating amide groups and electron-withdrawing carboxyl groups. The different electronic effects of the amide group and carboxyl group resulted in the difference in the transmission capability of electrons released from the oxidation reaction of DA and AA. Therefore, PAM/ PPy/GO modified GCE can act as a good electrochemical sensor with high sensitivity and selectivity for DA and AA.