Facile synthesis of 3D porous nitrogen-doped graphene as an efficient electrocatalyst for adenine sensing

In this work, a simple, low-cost and eco-friendly strategy for fabricating the three-dimensional porous nitrogen-doped graphene (3D-N-GN) is demonstrated by combining the hydrothermal assembly and freeze-drying process without using any framework support. The desired features for 3D-N-GN, such as rich macroporosity, nitrogen-doping structure and high active surface area have been confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical techniques, respectively. In comparison with two-dimensional graphene (2D-GN) and nitrogen-doped graphene (2D-N-GN), 3D-N-GN makes a more negative shift in the oxidation peak potential of adenine together with a remarkable increase in the oxidation peak current, highlighting the importance of the nitrogen-doping and 3D construction of the graphene-based support for improving the electrocatalytic performance. It also indicates that 3D-N-GN can be used as an efficient electrocatalyst for adenine sensing. Furthermore, the sensing conditions are optimized and the resulting sensor displays excellent analytical performance in the detection of adenine at low concentrations ranging from 0.02 to 1.20 μM, with a detection limit of 8 nM. Finally, this proposed method not only exhibits preferable reproducibility, stability and adequate sensitivity, but also demonstrates good efficiency in the detection of adenine in biological fluids.