Unveiling the Power of Surfactant-Based Carbon Dots: Ultrasensitive Detection of Cadmium in Tap and Drinking Water Samples

This study introduces a novel approach for transforming the cationic surfactant, cetyltrimethylammonium bromide (CTAB), into fluorescent carbon dots (CDs) capable of detecting cadmium ions at ultralow concentrations. The current approach involves preparing CDs through hydrothermal process at various pH levels. The CDs synthesized using pH 10, CTAB-CDs-10, exhibited the highest fluorescence quantum yield (QY), 14.22%. UV-Vis spectroscopy helped identify specific peaks between 210 and 300 nm, corresponding to the π–π* transitions of the aromatic C=C bonds. Transmission electron microscopic (TEM) analysis verified the uniform spherical morphology with a particle size < 2.45 nm. FT-IR analysis confirmed the presence of C=C stretching vibrations. The Box–Behnken (BB) Design was used to reconnoiter the influence of three variables on the response parameter: the F0/F ratio. The best performance could be achieved at a pH of 9, after only 300 s, and a temperature of 50 °C. The developed CTAB-CDs-based nanoprobe showed an ON–OFF behavior when came in contact with cadmium (II) and demonstrated high sensitivity with a limit of detection as low as 0.06 µM (0.007 ppm) over a wide linear range of 2–103 µM. Validation tests confirmed the applicability of the CTAB-CDs-based nanoprobe for detecting cadmium (II) in tap and drinking waters with high accuracy and precision.