Self-affinity of AuNPs on polyethyleneimine (PEI) functionalized polypyrrole-derived carbon nanotubes hybrid nanocomposite: A novel interference-free electrochemical sensing platform for caffeine detection

Heterogeneous composite materials have drawn considerable attention for their synergistic effects and are anticipated to provide high-performance electrochemical sensing. In the present study, a simple, sensitive, and selective electrochemical sensor for the determination of caffeine (CAF) was developed by using carbon-rich polypyrrole nanotubes (PPy NTs) derived carbon nanotubes (PPy CNTs) via direct pyrolysis strategy without structural degradation loaded with AuNPs by in situ chemical route via hydrogen bonding with polyethyleneimine (PEI) to obtained [email protected] NTs and [email protected] CNTs hybrid nanocomposites. Subsequently immobilized on a glassy carbon electrode (GCE) to construct [email protected] NTs/GCE and [email protected] CNTs/GCE electrochemical sensors that could be directly used to measure caffeine in beverages and pharmaceuticals using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Interestingly, [email protected] CNTs modified sensors showed exceptional electrocatalytic effects on CAF oxidation with a significantly increased peak current (∼4.5-fold) than an [email protected] NTs/GCE sensor. The electrode material exhibited linear responses in the concentration ranges 50 nM to 500 µM and 10 nM to 10 mM with detection limits of 14.2 and 2.8 nM (S/N = 3) for the [email protected] NTs/GCE and [email protected] CNTs/GCE, respectively. The fabricated electrode displayed a low detection limit, wide linear range, excellent selectivity, stability, and high reproducibility (2.37 % RSD for seven prepared sensors). The proposed method was successfully applied to determine caffeine in actual samples such as tea, coffee, and energy drinks without sample pretreatments, with recoveries ranging from 92.36 to 117.1 %. Therefore, the present electrode has excellent potential for sensitive and straightforward determination of caffeine in actual samples.