Analysis of Local Charge Distribution on the Surface of Molecularly Imprinted Polymer Films

Abstract

Molecularly imprinted polymers (MIPs) are synthetic molecular recognition materials that have attracted attention in recent years due to their high selectivity, stability, reusability toward target analytes, and versatility in various analytical applications. The electrochemical properties of MIPs largely depend on the surface morphology and the nature of charge distribution at the electrode-polymer and polymer-solution interphase boundaries. The study of local surface charges of MIPs allowed us to evaluate the heterogeneity of the surface, the nature of active centers, and the influence of synthesis conditions on the electrical characteristics of the polymer layer. Modern scanning probe microscopy methods, in particular scanning force microscopy (SFM), allowed us to study the surface of MIPs at the nanoscale, simultaneously analyzing its morphology and charge distribution, which provides a comprehensive study of processes at the electrode-polymer interface. Local charges on the surface of polyimides were investigated in the electromechanical response mode. For this purpose, a conductive TiN probe of a scanning microscope was used. A voltage was applied between it and the copper electrode of a planar amperometric sensor on which a polymer film was synthesized. For the non-imprinted polymer, changing the polarity on the probe did not result in a change in the SFM image or charge distribution. A different picture was observed for the molecularly imprinted polymer. When the negative pole was connected to the probe, the charge distribution was similar to that for the non-imprinted polymer. When reversing polarity, it was found that the entire surface of the MIP was covered with local charges.