Growth morphologies, phase formation, optical & biological responses of nanostructures of CuO and their application as cooling fluid in high energy density devices

Abstract

Different nanoscale objects of CuO have been synthesized by a simple chemical route where the Cu(OH)₂ nanostructures were first synthesized by the alkaline hydrolysis of Cu(NO₃)₂·3H₂O using NaOH as a base and the synthesized precipitate was subsequently annealed at a temperature of 130 °C. The alkaline content (pH) of the solutions during the hydrolysis process was varied to tailor the morphologies and dimensions of the nanostructures, consequently a series of fascinatingly shaped nanostructures, e.g. seeds, ellipsoidal, rods and leaves were obtained. Topographical characteristics along with the mechanism behind the structural variation have been rationalized by XRD, FTIR, SEM and HRTEM investigations. Optical performance of these samples provided simultaneous emission in the visible bands of blue, green, yellow and red, which were correlated to the size, shape and structural defects of these nano-scaled objects. The toxicity of these nanostructured materials were also put into perspective and it was found that the leaf shaped particles were the most toxic among the various shapes of nano-CuO. Finally the synthesized particles, when applied as nanofluids (water medium) showed their ability to enhance the thermal conductivity of water to a noticeable degree (above 40%) at high temperatures, even at very small concentrations, bespeaking their applicability in cooling fluids.