A novel fluorescence probe using Brown HT precursor carbon dots for highly selective and ultrasensitive quantitation of potassium ion in some staple food samples

Potassium ions (K⁺) perform a variety of functions in biological systems, including the regulation of blood pressure, enzyme activation, maintenance of muscular strength, regulation of extracellular osmolarity and facilitation of nerve transmission. Thus, a one-step hydrothermal-assisted method was used to prepare small-sized photoluminescent carbon dots (CDs) from Chocolate Brown HT food dye for the first time. The resulting CDs exhibited strong blue emission, with sizes ranging from 1.8 to 3.2 nm (average 2.5 nm) and an estimated quantum yield of 42.76 %. The complex functional groups present on the surface of the CDs enhance their affinity for certain ions. Leveraging the effective fluorescence quenching effect of K⁺, we developed a highly sensitive CD-based fluorescence analytical system with a limit of detection of 0.32 nmol/L. Linearity was established between 1.0 nmol/L and 400 nmol/L. Furthermore, K⁺ detection in staple food samples was accomplished using this sensor. The use of 1200 nmol/L sodium ions as an interfering agent resulted in an error of less than 5 %. To validate the accuracy of the proposed method, the results were compared to those obtained using flame atomic emission spectroscopy as a reference method, yielding recovery values ranging from 97.69 % to 103.19 %.