Dependence of Size of Liquid Phase Pulsed Laser Ablated ZnO Nanoparticles on pH of the Medium

Abstract

Highly transparent, luminescent, chemically pure and biocompatible zinc oxide (ZnO) nanoparticles (NPs) without any surfactants were synthesized by liquid phase-pulsed laser ablation (LP-PLA) of sintered ZnO pellets. Transmission electron microscopic study confirms the formation of crystalline ZnO nanoparticles. The size of the nanoparticles increases when oxygen is bubbled in the liquid during ablation and it remains same on bubbling with nitrogen. The yellow luminescence from ZnO NPs is due to the oxygen vacancies. The emission color can be tuned from yellow to bluish violet by suppressing the oxygen vacancies on bubbling oxygen during the ZnO ablation. The NPs were also grown by LP-PLA under surfactants free acidic and basic medium and the surface charge of the NPs provided the repulsive force between NPs which suppressed the growth through coagulation. These luminescent and nontoxic ZnO nanoparticles will find applications in biomedical imaging and cancer detections.