Direct Electrodeposition of Porous Graphene Films for Sensitive Detection of Bio-Compounds

Since its discovery, graphene continues to play a big role in the development of low-cost sensors thanks to its unique optical, mechanical, electronic and electrochemical properties. Here, we are going to present a simple approach for the direct electrodeposition of graphene foam from GO solution, providing an effective solution for the electrochemical sensing of redox-active species with high sensitivity. This is superior to previous approaches, in which graphene oxide is often applied to the electrode surface via drop-casting, alleviating its effective surface area and eventually compromising its output current. The present electrochemical method controls the electrostatic interaction between the negatively charged GO sheets and the surface of the electrode for the direct deposition of GO from solution under reducing potentials. This was made possible through the addition of cationic surfactant to GO deposition solution that is shown to improve the adsorption of GO sheets on the electrode surface, allowing for the effective reduction of its oxygen functional groups. This approach leads to the formation of a three-dimensional graphene framework with a very high effective surface area, which is successfully applied for the simultaneous analysis of dopamine (DA), ascorbic acid (AA), and uric acid (UA) with high sensitivity and selectivity. Abnormal levels of DA, AA and UA can lead to some critical diseases, such as Parkinson’s disease, hyperuricemia and leukemia. Therefore, it is considered of great important to develop reliable sensors for the simultaneous analysis of these compounds at physiological conditions. While traditional electrodes cannot distinguish these three biomolecules with an overlapping voltammetric oxidation peak, the new sensor shows three well-defined and completely resolved oxidation peaks along with a remarkable increasing electrooxidation current. Under optimal conditions of differential pulse voltammetry (DPV), the linear ranges for AA, DA, and UA are 2-3500 µM, 0.5-200 µM, and 5-250 µM, respectively. The corresponding detection limit (S/N=3) are 0.22, 0.11, 1.67 µM, respectively. The developed sensor demonstrates high sensitivity, good selectivity, well reproducibility and repeatability. Moreover, the proposed sensor was successfully applied for the simultaneous detection of AA, DA, and UA in real samples with good recovery. This method provides a new route for electrochemical reduction of graphene with a 3D network structure, which is a promising candidate for electrode material and other electrocatalytic applications.