Chemical pre-reduction and electro-reduction guided preparation of a porous graphene bionanocomposite for indole-3-acetic acid detection

A porous graphene (PG) bionanocomposite of PG, gold nanoparticles (AuNPs) and anti-indole-3-acetic acid (anti-IAA) antibody for sensitive and label-free amperometric immunoassay of IAA was reported. A PG film was produced by a pre-reduction/electrochemical reduction process on a glassy carbon electrode (GCE) and then a homogeneous AuNPs layer electrodeposition on the PG film. The anti-IAA antibody was immobilized onto the AuNPs through electrostatic adsorption and covalent conjugation. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), elecro-chemical impedance spectroscopy (EIS), ultraviolet visible spectroscopy (UV-vis) and differential pulse voltammetry (DPV) were used to characterize the PG film and the stepwise modification of the immunosensor. The electrochemical immunosensor exhibited a wide linear range from 2 x 10(-11) to 2 x 10(-8) g mL(-1) with a detection limit of 0.016 ng mL(-1) (S/N = 3) and showed significant linearity R-2 = 0.9970. In addition, the proposed immunosensor showed acceptable selectivity and has been applied to the determination of IAA in the extract samples of several plant seeds with acceptable relative derivation (%) ranging from -5.25% to 4.24% between the immunosensor and high performance liquid chromatography. The proposed chemical pre-reduction and electro-reduction guided protocol can be extended to the preparation of many other functionalized PG nanocomposite films for wide applications.