Hafnium Polystyrene Composite Particles for the Detection of Organophosphate Compound

摘要

Organophosphate (OP) pesticides present a challenge for detection and identification in both the gas and liquid phase. The organophosphate esters are commonly used as persistent pesticides and nerve agents. Thus, it is highly desirable to develop methods for the detection of these compounds. Bragg diffraction of laser light from crystalline colloids of polystyrene spheres is observed for the detection of OPs. This was done by utilizing a simple method for the colloidal crystal arrays (CCA) based on a polystyrene (PS) core and a hafnium oxide (HfO_2) shell sensing composite particles that detects the organophosphorus compound paraoxon (OP) of varying concentrations in aqueous solution. The molecular recognition agent for the sensor is hafnium, which is an inorganic compound that theoretically has an affinity for paraoxon. Energy Dispersive Analysis of X-rays (EDX) was used to characterize the PS coated HfO_2 particles as well as for the confirmation of the presence of hafnium around the polystyrene core. Transmission electron microscopy (TEM) verified the presence of HfO_2 clusters on polystyrene spheres. Reflectance measurements were carried out for varying concentrations of paraoxon from 0.024 ppm to 0.096 ppm, showing a characteristic shift in the reflectance peak from 470 to 483 nm. The peaks wavelength shift from right to left suggested that the distance between the crystals was increasing due to the addition of the concentration of paraoxon. Thus, it acts as a chemical sensor for paraoxon since hafnium has an affinity for phosphate groups. As a result, theoretical matches practical which suggests that hafnium acts as a chemical sensor for paraoxon. It was expressed that by increasing the paraoxon concentration, the reflectance peak increased linearly, making CCA a prospective technique for future chemical sensor research.