New Approach for Porous Chitosan–Graphene Matrix Preparation through Enhanced Amidation for Synergic Detection of Dopamine and Uric Acid

[Image: see text] Amide-functionalized materials have emerged as promising nonprecious catalysts for electrochemical sensing and catalysis. The covalent immobilization of chitosan (CS) onto graphene sheet (GS) (denoted as CS–GS) has been done via higher degree of amidation reaction to develop an electrochemical sensing matrix for simultaneous determination of dopamine (DA) and uric acid (UA). The enhanced amidation between CS and GS has not been reported previously. However, electrochemical results have revealed that the CS–GS enhances the electrocatalytic performance in terms of the oxidation potential and peak current due to the higher degree of amide functionalization compared to that of CS/GS, which has a lower amidation. Differential pulse voltammetry-based studies have indicated that the CS–GS matrix works at a lower detection limit (0.14 and 0.17 μM) (S/N = 3) and over a longer linear range (1–700 and 1–800 μM), with a comparatively higher sensitivity (2.5 and 2.0 μA μM(–1) cm(–2)), for DA and UA, respectively. In addition, the CS–GS matrix demonstrates good selectivity toward the detection of DA and UA in the presence of a 10-fold higher concentration of AA and glucose. The as-prepared three-dimensional porous CS–GS also endows selective determination toward DA and UA in various real samples.