Influence of dipole moment of capping molecules on the optoelectronic properties of ZnO nanoparticles

Thiol-stabilized zinc oxide nanoparticles were synthesized via an aqueous route under moderate temperature to obtain better crystalline material. The work has been focused to study the effect of molecular dipole moment on optoelectronic properties of these nanoparticles. Three different organic thiols such as 1-thioglycerol, thioglycolic acid and 2-mercaptoethanol possessing different dipole moment were used as capping molecules. These nanoparticles were characterized by X-ray diffraction, optical absorption, photoluminescence, energy dispersive analyses of X-ray, infrared spectroscopy and scanning electron microscopy. X-ray diffraction results revealed that as-synthesized zinc oxide nanoparticles had pure hexagonal wurtzite structure and 2-mercaptoethanol capping gives smallest particle size. Colloids of these nanoparticles clearly emit violet color under ultraviolet light irradiation. The role of dipole moment and its orientation on ZnO surface has been investigated. It has been observed that a static electric field due to dipole moment on these nanoparticles significantly affects the photoluminescence properties.