Electrochemically deposited p-phenylenediamine-derived coating on graphite for nucleobase detection

A simple electrochemical sensing interface based on a p-phenylenediamine (pPD)-derived coating deposited on a graphite electrode was investigated for the individual and simultaneous detection of DNA nucleobases. The electroactive coating was obtained by cyclic potential scanning from -0.3 to +1.0 V vs. Ag/AgCl and characterized by scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy and Raman spectroscopy. Combined electrochemical, morphological, and spectroscopic results supported the formation of an adherent pPD-derived layer on the graphite surface, while XRD indicated preservation of the crystalline structure of the graphite substrate. Potential scan-rate (v) studies yielded a slope of approximately 0.42 for the log Ip - log v relationship, indicating contributions from charge propagation and ion transport within the deposited layer rather than a purely surface-confined process. The modified electrode exhibited concentration-dependent responses toward adenine (A), cytosine (C), guanine (G) and thymine (T), with cyclic voltammetric calibration coefficients of 0.99253, 0.98773, 0.97416 and 0.98191, respectively. Individual oxidation responses were observed at approximately 1.05, 1.38, 0.72 and 1.14 V for adenine, cytosine, guanine and thymine, respectively. In mixed solutions, the corresponding responses occurred at approximately 0.87, 1.22, 0.60 and 1.04 V, while preserving the oxidation sequence G < A < T < C. These results provide proof-of-concept evidence that a comparatively simple pPD-derived graphite interface can provide concentration-dependent nucleobase responses and electrochemical discrimination of the four DNA nucleobases in a multicomponent system.