Synthesis of carbon dots based on chitosan and melamine and their application in detecting vanadate (V) anions

Vanadium (V) is considered a microelement of great industrial, environmental, biological, and pharmacological importance. Vanadium-containing complexes have been widely used as biologically active compounds. Outside cells, vanadium exists in the form of the vanadate anion, while inside cells, it primarily exists as the tetravalent vanadyl cation. Both a deficiency and an excess of vanadium in the human body can lead to various diseases. Therefore, the aim of this study is to detect vanadium ions using fluorescent carbon dots, which are capable of rapid and sensitive detection. In this study, carbon dots synthesized from chitosan and melamine were used as fluorescent reagents. Fluorescent carbon dots (C-dots) were synthesized by hydrothermally treating 99.95% pure chitosan with melamine at 180 °C for 5 h, followed by freeze-drying in a lyophilizer, and purification using high performance liquid chromatography (HPLC). These dots were found to emit bright green fluorescence. The formation of green fluorescence is associated with the incorporation of nitrogen into the carbon materials, which were then used for the detection of vanadium ions. The C-dots and their complexation with vanadium were fully characterized by infrared spectroscopy and spectrofluorometry.