Effects of Production Methods on the Particle Morphology and Properties of Aqueous Au Nanofluids

In this study, the effects of nanofluid production methods on the particle morphology and properties of aqueous gold (Au) nanofluids are investigated using chemical reduction (referred as Turkevich method). Sonication method is used to provide energy for the production of Au nanofluids. Applied energy to the production of nanofluids and temperature of the reduction reaction are two main parameters in the production of aqueous Au nanofluids, affecting the particle size and dispersion state of Au nanofluids even though same production method is used. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) are used to characterize particle size, shape and distribution. The thermal conductivities of Au nanofluids are measured by the custom-made transient hot wire system. Uncertainty of the measurements is less than ±1.5%. The pH and electrical conductivities are also measured by commercial products in this study. Temperature range of measuring properties is 10–30 °C. Experimental results show that production methods can affect the particle morphology and transport properties of Au nanofluids. Sizes of produced Au nanoparticles are 20–40 nm depending on the production methods and parameters. Through characterization and experimental results of Au nanofluids, we found the optimum conditions for production of aqueous Au nanofluids which have high thermal conductivity, small particle size and well dispersed characteristics.