Nitrogen and Sulfur Simultaneously Doped Cobalt Oxide-Decorated Hollow Carbon Nanospheres for Electrochemical Detection of Chloramphenicol

Dual heteroatom-doped hollow carbon spheres have increasingly attracted attention in the field of oxygen and hydrogen evolution reactions as catalysts but have not yet been applied to analyte detection. Here, we developed nitrogen and sulfur dual heteroatom-doped hollow carbon spheres (NSCS) using a hard silica template and in situ Co3O4 decoration to obtain CoNSCS nanoparticles for the detection of the chloramphenicol (CAP) drug via electrochemical methods. Different CoNSCS nanoparticles were prepared by varying the concentration of cobalt phthalocyanine to obtain CoNSCS-0.1, CoNSCS-0.2, and CoNSCS-0.3, and their behavior was compared with that of undecorated NSCS. The nanoparticles were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) techniques. Studies revealed the retention of the hollow structure of the NSCS in the presence of Co3O4 decoration. The CoNSCS-0.1 nanoparticles exhibited a higher catalytic CAP reduction rate at a much-reduced overpotential compared to CoNSCS-0.2, CoNSCS-0.3, and the undecorated NSCS, due to the efficient adsorption of CAP on the NSCS structure in the presence of Co3O4 and the involvement of the Co3+ → Co2+ redox transition. The sensor demonstrated a wide linear detection range from 5 μM to 1.65 mM, a limit of detection (LOD) of 1.18 μM, a limit of quantification (LOQ) of 4.36 μM, and a sensitivity of 0.0905 μA μM–1 cm–2 with excellent long-term stability and good reproducibility. The practical applicability of CoNSCS-0.1 was demonstrated using milk, honey, tap water, drinking water, pond water, and CAP capsules, successfully detecting CAP with good signal recovery and renewability.