Preparation of molecularly imprinted polymer coated quantum dots to detect nicosulfuron in water samples

A novel dual-function material was synthesized by anchoring a molecularly imprinted polymer (MIP) layer on Mn-doped ZnS quantum dots (QDs) via a sol-gel process using 3-aminopropyltriethoxysilane (APTES) as a functional monomer, tetraethoxysilane (TEOS) as cross-linker, and nicosulfuron as template through a surface imprinting method. The amino groups in the APTES interact with the functional groups in the template molecules to form a complex through hydrogen bonding. The energy of the QDs was transferred to the complex, resulting in the quenching of the QDs and thus decreasing the fluorescence intensity, which allowed the nicosulfuron to be sensed optically. Fluorescence intensity from MIP-coated QDs was more strongly quenched by nicosulfuron than that of the non-imprinted polymer, which indicated that the MIP-coated QDs which acted as a fluorescence probe could selectively recognize nicosulfuron. Under the optimal conditions, it can detect down to 1.1 nmol L(-1) of nicosulfuron, and a linear relationship has been obtained covering the concentration range of 12-6000 nmol L(-1). The recoveries were in the range from 89.6 to 96.5 %, and the relative standard deviations were in the range of 2.5-5.7 %. The present study established a new strategy to combine inorganic (Mn-doped ZnS QDs)-organic MIPs, which is successfully applied to determine nicosulfuron in water samples.