Molecularly-imprinted polyaniline nanoparticles for detection of aldrin

Abstract

Molecularly imprinted polymers are a class of new functional materials that bring about selectivity to chemical sensors that is similar to that found in biological systems. The technique enables the creation of artificial recognition cavities within synthetic polymers that can be used in chemical sensors to detect specific analytes. Molecularly imprinted nanostructured materials of defined shape and size show remarkable properties that can be utilized in different fields of analytical chemistry. The work presented in this dissertation is on the preparation, characterization and evaluation of molecularly imprinted polyaniline nanoparticles that can be used to selectively detect aldrin. Molecularly imprinted polyaniline (MI-PANI) nanoparticles were prepared by inverted emulsion polymerization using aldrin as template and aniline as a functional monomer. Materials prepared were characterized using FTIR, UV/VIS and NMR for structural elucidation. AFM and SEM were used for morphological characterization which revealed that the particles prepared were spherical in nature. SEM further showed that the particles had diameters ranging from 500 nm – 1.5 m for MI-PANI compared to a size range of 60 nm – 100 nm for non-imprinted particles. Electrical properties were evaluated using a four-point probe coupled to a source meter. Non-imprinted materials showed an electrical conductivity of 4.149 S/cm that reduced to 0.546 S/cm in MI-PANI. The binding capacity of the imprinted nanoparticles was evaluated via re-binding adsorption experiments and the data fitted into the Langmuir adsorption mathematical model. KD and Bmax were calculated to be 0.6 ng/L and 0.799 ng/L respectively. The selectivity of imprinted nanoparticles was investigated by examining the adsorption characteristics of aldrin and DDT. The distribution co-efficient for DDT and aldrin were found to be 0.76 ng/ng and 1.31 L/ng respectively indicating that MI-PANI exhibited much stronger binding affinity for aldrin than DDT.