LAUSR

Abstract In this study, we experimentally investigated the shape dependent thermal and nonlinear optical properties of water stable ZnO nanostructures. It is important to note that morphology plays a significant role in determining thermo-optic properties of ZnO. The thermal conductivity of colloidal ZnO was measured using a dual beam collinear thermal lens technique. The result shows a 23% enhancement in thermal conductivity of ZnO nanofluid compared to that of base fluid water. The nanofluid with nonspherical ZnOnanoparticles exhibit greater thermal diffusivity than a fluid with spherical nanoparticles. This enhancement in thermal conductivity was explained using the Hamilton – Crosser model based on the formation of nanolayer and interfacial thermal resistance. The third-order nonlinear optical susceptibility and optical limiting properties were investigated using a single beam Z scan technique. All samples showed two photon absorption and a negative nonlinear refractive index which varied with the nanoparticle morphology. Higher dimensional structures showed better optical nonlinearity due to their large surface area, photon scattering and exciton oscillator strength. The Z scan results reveal an increment of three orders of magnitude in third-order susceptibility for the nanoparticles compared to that of bulk ZnO. The nanofluid also exhibits a good optical limiting behaviour. The findings suggest that ZnO nanostructures can be considered as promising candidates for future optoelectronic devices.