Well-dispersed cobalt phthalocyanine nanorods on graphene for the electrochemical detection of hydrogen peroxide and glucose sensing

Cobalt phthalocyanine nanorods were non-covalently absorbed onto graphene (Gr) through a one-step microwave radiation-assisted synthesis, and a novel cobalt phthalocyanine nanorod-graphene nanocomposite (nanoCoPc-Gr) was obtained. The formation of nanoCoPc on the surface of Gr was characterized by UV spectroscopy, IR spectroscopy and high-resolution transmission electron microscopy (HRTEM). HRTEM demonstrated that the nanorods were well-dispersed on the surface of Gr. The electrochemical performance of this type of nanocomposite was further investigated. NanoCoPc-Gr accelerates the electron transfer, and a glassy carbon electrode modified with the complex exhibits excellent electrocatalytic activity towards hydrogen peroxide (H2O2). Based on the electrocatalytic oxidation towards hydrogen peroxide, an amperometric enzyme electrode sensitive to glucose is also described, which was achieved by the immobilization of glucose oxidase onto the nanoCoPc-Gr electrode. The proposed glucose biosensor displayed good amperometric response characteristics towards glucose in a 0.1 M buffer solution, such as a low overpotential (+500 mV vs. SCE), a fast amperometric response (approximately 3 s), a good linearity (R = 0.9999) with the concentration range from 1.67 × 10−5 M to 1.60 × 10−3 M, and a low detection limit of 1.46 × 10−5 M (S/N = 3).

Schematic representation showing the formation of cobalt phthalocyanine nanorods (nanoCoPc) on graphene (Gr) and schematic illustration of glucose sensing on the surface of ®Nafion/GOD/nanoCoPc-Gr/GCEThe nanocomposite of nanoCoPc-Gr was formed according to two main processes. The large conjugated system of Gr caused the formation of CoPc macrocycles on its surface via π–π stacking interactions. Then CoPc molecules aggregated to form nanorods through the same π–π accumulation effect, and the final nanoCoPc-Gr was obtained.The mechanism of glucose sensors is based on monitoring of hydrogen peroxide (H2O2). Glucose oxidase (GOD) can oxidize β-D-glucose into gluconic acid, accompanied by the consumption of O2 and the liberation of H2O2. Subsequently, H2O2 diffuses into the layer of nanoCoPc-Gr, and gets oxidized. The nanoCoPc-Gr acts as a catalyst to reduce the oxidation overpotential of H2O2 on the electrode. The response of H2O2 is used to indirectly evaluate the glucose concentration in the solution.Figure optionsDownload as PowerPoint slide