Enhanced Organophosphate sensing response of thermally diffused copper doped ZnO nanowires

Abstract

Organophosphate (OP) based pesticides are continuously used above their lethal dosage for enhancement of the agricultural harvest. Consequently, the residues of these toxic pesticides in environment cause several chronic diseases and leads to an ultimate death in living entities. Therefore, real-time detection of these pesticides is very much essential to reduce the environmental health hazards. Thus, an effort has been made to improve the sensing behavior of aqueous grown ZnO nanowires (NWs) by thermal diffusion of RF sputtered Cu atoms in ZnO NWs by annealing at various temperatures in argon ambient. FESEM images have depicted the randomly oriented high density ZnO NWs for the annealed samples. XRD patterns for both thermally diffused Cu-doped and as-grown ZnO NWs have indicated the presence of c-axis oriented single crystalline (002) peak, which is found to be consistent with the high resolution transmission electron microscopy (HRTEM) and selected area diffraction pattern (SAED) results. Micro-Raman spectroscopy has shown E2 modes at about 96 cm-1 and 437 cm-1,which corresponds to the wurtzite structure of ZnO. Photoluminescence spectra have shown the appearance of strong peaks at 3.35 eV and 2.75 eV. OP sensing response at room temperature have shown significant enrichment in the conductivity around three orders with a faster response time (<1 sec) in Cu-doped ZnO NWs.