Nanostructured carbon electrode modified with N-doped graphene quantum dots-chitosan nanocomposite: a sensitive electrochemical dopamine sensor

A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dotschitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwaveassisted hydrothermal reaction of glucose, and nitrogen doping was realized by introducing ammonia in the reaction mixture. Chitosan incorporation played a significant role towards the selectivity of the prepared sensor by hindering the ascorbic acid interference and enlarging the peak potential separation between dopamine and uric acid. The proposed sensor's performance was shown to be superior to several recently reported investigations. The as-prepared CS/N, GQDs@SPCE exhibited a high sensitivity (i.e. ca. 418 mu AmM cm(-2)), a wide linear range i.e. (1-100 mu M) and (100-200 mu M) with excellent correlations (i.e. R-2 = 0.999 and R-2 = 1.000, respectively) and very low limit of detection (LOD= 0.145 mu M) and limit of quantification (LOQ= 0.482 mu M) based on S/N= 3 and 10, respectively. The applicability of the prepared sensor for real sample analysis was tested by the determination of dopamine in human urine in pH 7.0 PBS showing an approximately 100% recovery with RSD< 2% inferring both the practicability and reliability of CS/N, GQDs@ SPCE. The proposed sensor is endowed with high reproducibility (i.e. RSD= ca. 3.61%),excellent repeatability (i.e. ca. 0.91% current change) and a long-term stability (i.e. ca. 94.5% retained activity).