Abstract
A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dots–chitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwave-assisted 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 µA mM cm−2), a wide linear range i.e. (1–100 µM) and (100–200 µM) with excellent correlations (i.e. R2 = 0.999 and R2 = 1.000, respectively) and very low limit of detection (LOD = 0.145 µM) and limit of quantification (LOQ = 0.482 µM) 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).
Highlights
Dopamine is among the very important neurotransmitters ensuring inter-neuronal communication in the human central nervous system [1]
The latter are sensitive, rapid, simple and cost-effective, their major drawback lies in the interference of uric acid and ascorbic acid that always coexist with dopamine in biological fluids, with the oxidation potentials of all three being very similar [2,13]
The prepared quantum dots showed a monodispersed, spherical shape with a size ranging between approximately 3 and 4 nm as revealed from the transmission electron microscope (TEM) image shown in figure 1 which is in the typical range of nitrogen-doped graphene quantum dots [49]
Summary
Dopamine is among the very important neurotransmitters ensuring inter-neuronal communication in the human central nervous system [1]. Due to its fascinating electroactivity [11], dopamine determination has been extensively studied by various electrochemical methods [12] The latter are sensitive, rapid, simple and cost-effective, their major drawback lies in the interference of uric acid and ascorbic acid that always coexist with dopamine in biological fluids, with the oxidation potentials of all three being very similar [2,13]. These interfering species might cause poor reproducibility and selectivity if their oxidation products accumulate on the electrode surface resulting in its fouling [14]. The real challenge is to develop a sensor that is reliable, selective and sensitive, and economical and practical
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