Label-free femto molar level electrochemical dopamine sensor based on amorphous carbon-coated pencil graphite electrode

A new promising low-cost amorphous carbon pencil graphite electrode (APGE) based electrochemical sensor for ultra-low-level detection of dopamine (DA) is proposed. The presence of high sp³ carbon atoms in amorphous carbon drives the strong adsorption of DA molecules by lowering their activation energy. The topography of the APGE electrode characterized by SEM confirmed the successful coating of amorphous carbon on the pencil graphite electrode, and the coating thickness on the bare electrode was optimized by cyclic voltammetry studies. The electrochemical surface area calculation further revealed that a 2-layer APGE was suitable for calibrating dopamine on the APG electrode. With optimized deposition voltage and time, the anodic sweeping voltammetry (ASV) technique was used for the sensing measurements. This APG electrode demonstrated sufficient potential for highly selective detection of dopamine down to 3.98 fM concentration with a sensitivity of 0.3874 μA fM⁻¹ cm⁻². The sensor also offered excellent selectivity in the presence of other interfering bio-analytes.