Organophosphate Nerve Agent Sensor Based on Polystyrene Core and Zirconium Shell Colloidal Crystal Array

Abstract

A simple method has been developed for the preparation of colloidal crystal arrays (CCA) based on a polystyrene (PS) core and a zirconia (ZrO2) shell sensing microgel that detects the organophosphorus compound paraoxon at parts per million (ppm) concentrations in aqueous solution. The molecular recognition agent for the sensor is zirconia (ZrO2), which has a chemical affinity for paraoxon. Colloidal crystal arrays based on these core-shell particles were prepared by a simple gasket method at room temperature. Transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDX) was used to characterize the PS-coated ZrO2 particles. TEM analysis confirmed two distinct morphologies of the core-shell particles, while the EDX analysis confirmed the presence of zirconium around the polystyrene core. TEM confirmed the presence of ZrO2 clusters on polystyrene spheres. Reflectance measurements were carried out for varying concentrations of paraoxon from 0.024 to 0.096 ppm, showing a characteristic shift in the reflectance peak from 468 to 488 nm. The shift in the peak wavelength from right to left suggested that the distance between the crystals or lattice spacing increased due to addition of paraoxon. Thus, it acts as a chemical sensor for paraoxon since zirconia has an affinity for the phosphate group of paraoxon. It was demonstrated that by increasing paraoxon concentration, the reflectance peak increased linearly, making CCA a potential candidate for future chemical sensor applications.