Facile and green synthesis of graphene oxide by electrical exfoliation of pencil graphite and gold nanoparticle for non-enzymatic simultaneous sensing of ascorbic acid, dopamine and uric acid

Pencil graphite is electrochemically exfoliated to obtain few layered graphene oxide (GO) in hydrochloric acid (HCl, HGO), sodium hydroxide (NaOH, NGO) and phosphate buffer saline (PBS, pH 7.4, PGO) media at a constant potential (+7.0 V) without ionic liquid for the first time. Thus, obtained graphene oxide is deposited (by drop casting and electro reduction) onto a glassy carbon electrode (GCE). Following this, gold nanoparticles (AuNP) are electro deposited to form a GO-AuNP composite for simultaneous discrimination of dopamine (DA), ascorbic acid (AA) and uric acid (UA) at pH 7.4. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques reveal well separated oxidation peaks for DA, AA and UA. The sensor surfaces are characterized by ultraviolet visible (UV-vis), photoluminescence (PL), X-ray diffraction (XRD), contact angle goniometry (CA) and scanning electron microscopy (SEM) techniques. DA, AA and UA are studied individually to evaluate the dynamic ranges and lowest detection limits of the sensor by the DPV method. Concentrations of DA, AA and UA in real samples viz., dopamine injection, vitamin C tablets and human urine are evaluated.