Effect of vitamin B 2 interactions on the optical properties of cadmium selenide quantum dots: experimental and theoretical analysis

Water-soluble cadmium selenide quantum dots (CdSe Qdots) were synthesized using thioglycolic acid (TGA) as a stabilizer in aqueous media and exhibited strong photoluminescence, enabling the detection and quantification of vitamin B2. Dynamic light scattering (DLS) measurements confirmed particle sizes below 10 nm with low polydispersity, while TEM and AFM analyses supported the Qdots morphology and size. UV–Vis spectroscopy revealed a blue-shifted absorption peak relative to bulk CdSe, with an estimated optical band gap of 2.41 eV. The high negative zeta potential (−73.9 mV) indicated successful surface functionalization with TGA, providing colloidal stability via electrostatic repulsion. The fluorescence response of the CdSe Qdots showed a linear correlation with vitamin B2 concentration in the range of 1–11 mg L−1, with a detection limit of 4.11 mg L−1. Complementary density functional theory (DFT) calculations were performed to examine the HOMO–LUMO energy levels of Cd6Se6-TGA alone and in combination with vitamin B2, providing insights into their electronic interactions and binding behavior.