Abstract
Extensive research studies are being carried out to significantly improve the sensing characteristics of pesticide sensors (chlorpyrifos, organophosphates (OP)) especially at ultra low concentrations using advance fabrication and characterization techniques. We report feasibility study of pesticide sensing, using nanostructured zinc oxide (ZnO) and acetylcholinesterase (AChE) immobilized ZnO films, at ultra low concentrations (10 to 1000 ppb). ZnO nanoparticles (NPs) were synthesized by non-aqueous sol-gel method. Reduced glutathione (GSH) was coated on as-synthesized ZnO NPs by physical mixing. FESEM observation revealed spherical particles of about 10-20 nm in diameter having fairly uniform shape distribution. Thick films of these powders were printed on pre-printed electrodes using conventional screen printing technique. AChE was immobilized on the films by physical adsorption method. It is found that bare ZnO NPs are insensitive to pesticides while GSH coated ZnO NPs exhibit monotonous increase of sensitivity as a function of OP concentration over the wide range (10 ppb to 1000 ppb) with sensitivity of 2.1 mu A/ppm/cm(2), detection limit of 3 ppb and regression coefficient of 0.92. Electrochemical measurement indicated that sensors can be used for few times due to the known inhibitory nature of OP and AChE reaction.