Recognition principle of Cu2+-imprinted polymers—Assessing interactions by combined spectroscopic and mass-sensitive measurements

Generating molecularly imprinted polymers for metal ions follows slightly different pathways than in the case of larger analytes, because geometric features of the analyte itself play only minor role, but coordination spheres should be important. Hence elucidating the interactions leading to recognition is increasingly important for such systems. For this purpose, we have focused on spectroscopic characterization and sensor analysis of copper ion imprints. FT-IR studies revealed that in preparing ion-imprinted polymers for copper (Cu2+-IIP) only N-vinyl-2-pyrrolidone (NVP) interacts with copper ions via both its carbonyl group and the lone pair of the nitrogen atom. In contrast to this, the carbonyl band of ethylene glycol dimethacrylate (EGDMA) remains unaltered by the presence of the template ion. Complexation via NVP can further be confirmed by UV–vis studies resulting in an absorption band at 309 nm with an extinction coefficient of 13,182 L mol−1 cm−1. Feasibility of imprinting and successful transfer of the recognition motive is confirmed by quartz crystal microbalance (QCM) measurements. These sensors show pronounced selectivity of copper in comparison of Na+ (possessing poor complex ability) thus further confirming the interaction model proposed.

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