Visible laser scribing fabrication of porous graphitic carbon electrodes: Morphologies, electrochemical properties, and applications as disposable sensor platforms

Porous graphitic carbon electrodes were fabricated by laser scribing of commercial polyimide tape. The process was performed by a simple one-step procedure using visible wavelength laser irradiation from a low-cost hobbyist laser cutter. The obtained electrodes displayed a highly porous morphology, rich in three-dimensional (3D) interconnected networks and edge planes, suitable for electrochemical sensing applications. Spectral characterization by Raman and X-ray photoelectron spectroscopy (XPS) techniques revealed a crystalline graphitic carbon structure with a high percentage of sp² carbon bonds. Extensive electrochemical characterization performed with outer-sphere [Ru(NH₃)₆]³⁺ and inner-sphere [Fe(CN)₆]⁴⁻, Fe^2+/3+, and dopamine redox mediators showed quasi-reversible electron transfer on the graphitic carbon surface, mainly dominated by a mass diffusion process. Fast heterogeneous electron-transfer rates, higher than similar carbon-based materials and higher than other graphitic carbon electrodes produced by either visible or infrared laser irradiation, were obtained for these electrodes. Thin-layer transport mechanisms occurring in parallel to the main diffusion-limited mechanism were taken into consideration, but overall, the observed enhanced electron-transfer rate effects were ascribed to the large specific surface area of the extended 3D porous network, rich in defects and edge planes. The superior electrocatalytic properties of the fabricated electrodes allowed electrochemical differentiation between the biomarkers ascorbic acid, dopamine, and uric acid in solution. The compatibility of fabricated electrodes with lightweight portable and handheld instrumentation makes such electrodes highly promising for the realization of low-cost disposable sensing platforms for point-of-care applications.