A novel composite of SiO₂-coated graphene oxide and molecularly imprinted polymers for electrochemical sensing dopamine

A novel imprinting route based on graphene oxide (GO) was proposed for preparing a composite of SiO₂-coated GO and molecularly imprinted polymers (GO/SiO₂-MIPs). In this route, SiO₂-coated GO sheets were synthesized in a water-alcohol mixture with sol-gel technique. Prior to polymerization, the vinyl groups were introduced onto the surface of GO/SiO₂ through chemical modification with γ-methacryloxypropyl trimethoxysilane (γ-MAPS), which can direct the selective polymerization on the GO/SiO₂ surface. Then a novel composite of GO/SiO₂-MIPs was successfully obtained by the copolymerization in presence of vinyl groups functionalized GO/SiO₂, dopamine (DA), methacrylic acid and ethylene glycol dimethacrylate. The GO/SiO₂-MIPs composite was characterized by FTIR, TGA, Raman spectroscopy, SEM and AFM. The properties such as special binding, adsorption dynamics and selective recognition ability using differential pulse voltammetry (DPV) were evaluated. The DPV current response of GO/SiO₂-MIPs sensor was nearly 3.2 times that of the non-imprinted polymers (NIPs). In addition, the GO/SiO₂-MIPs sensor could recognize DA from its relatively similar molecules of norepinephrine and epinephrine, while the sensors based on GO/SiO₂-NIPs and vinyl groups functionalized GO/SiO₂ did not have the ability. The GO/SiO₂-MIPs sensor had a wide linear range over DA concentration from 5.0×10^-8 to 1.6×10^-4M with a detection limit of 3.0×10^-8M (S/N=3). The sensor based on this novel imprinted composite was applied to the determination of DA in injections and human urine samples with satisfactory results.