Green synthesis of fluorescent carbon quantum dots from field horsetail Equisetum Arvense L and fluorimetric detection of Pd2+ ions

The study presents a comprehensive phytochemical analysis of A. caucasicus, examining both the leaf and flower parts of this plant. The Fluorescent carbon quantum dots (CQDs) were synthesized via a hydrothermal method using field horsetail (Equisetum arvense L.) as a green carbon source at 180 °C. The resulting CQDs were characterized by various techniques, including UV–Vis absorption spectroscopy, fluorescence spectroscopy, fourier-transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). Under UV illumination at 365 nm, the CQDs displayed intense blue fluorescence. The effects of 32 different metal ions, including Li⁺, Na⁺, K⁺, Ag⁺, NH₄⁺, Tl⁺, Ba²⁺, Be²⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Pb²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Zn²⁺, Sr²⁺, Cr³⁺, Au³⁺, Y³⁺, Al³⁺, V³⁺, Bi³⁺, B³⁺, Sc³⁺, Sb³⁺, Ti⁴⁺, Se⁴⁺, Mo⁶⁺, W⁶⁺, and Pd²⁺, on the fluorescence properties of the CQDs were systematically investigated using fluorescence spectrophotometry. Among them, Pd²⁺ ions caused significant fluorescence quenching. Based on this response, a sensitive and straightforward fluorometric sensing strategy was developed for detecting Pd²⁺ in tap water. The method showed a good linearity over the concentration range of 0.5 to 15.0 μM, with a detection limit of 50.2 nM and a quantification limit of 150.6 nM. The applicability of the method was further validated through spiking experiments, yielding satisfactory recoveries at various concentrations. The approach also demonstrated excellent reproducibility, with a relative standard deviation (RSD) consistently below 2.3%.