Adsorption and detection of praseodymium ion by ion-imprinted polymer with ultra-low sensitivity

A novel kind of carbon dot (CD) was prepared by one-step hydrothermal microwave assisted method using L-tryptophan and L-tartaric acid as raw materials. Monodisperse poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres were utilized as the matrix, with praseodymium (Pr) ion (Pr³⁺) as the template, methacrylic acid as the functional monomer, and 5-amino-8-hydroxyquinoline (5-AHQ) acts as the ligand. A composite microsphere of ion-imprinted polymer (IIP) and CD (noted CD@IIP) was prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). For comparison, IIP without CD (Pr-IIP) and non-imprinted polymer (NIP) were also prepared. Through static adsorption experiments, it was  determined that the saturated adsorption amount of CD@IIP is 47.19 mg g^-1, that of Pr-IIP is 54.49 mg g^-1, while that of NIP is only 24.32 mg g^-1. Dynamic adsorption experiments showed that the equilibrium of three kinds of materials was reached within 30 min. Particularly, CD@IIP could emit two fluorescence peaks at 325 nm and 421 nm under ultraviolet irradiation, and exhibited excellent selectivity and fluorescence quenching effect on Pr³⁺. The fluorescence response of Pr³⁺ in the range 0-400 μmol L^-1 was determined by ratiometric fluorescence method, offering a two-stage model and robust linear regression coefficient. These results demonstrated that CD@IIP exhibited selective adsorption ability for Pr³⁺, and a sensitive, rapid and simple method for detection of Pr³⁺ was successfully developed.