For nanofluids with GNP 300, electrical conductivity increases to about 21 μS/cm for a mass percentage of 0.1%, while electrical conductivity of water is about 2 μS/cm. The enhancement in electrical conductivity check details was determined by

the formula [((σ − σ 0) × 100)/σ 0] where ‘σ 0’ refers to the electrical conductivity of base fluid and ‘σ’ that of nanofluid. The maximum enhancement of around 950% was observed at 25°C which was for GNP 300. Through the results, it could be seen that electrical conductivity was enhanced by increasing mass percentage along with decreasing specific surface area. Figure 12 Electrical conductivity ( σ ) of GNPs. Conclusions Stability and thermophysical properties of GNP nanofluids have been studied systematically, and the following conclusions could be drawn from the results. The nanofluids of GNPs prepared by ultrasonication were stable for a long period of time. Detailed measurements were carried out to determine the effect of particle mass concentration, specific surface area, and temperature on the thermophysical properties of GNP nanofluid. The rate of increase

in thermal conductivity of nanofluids is found to be very significant at higher specific surface area of GNPs due to factors like stability, homogeneity, and rate of agglomeration. The maximum percentage buy LXH254 of enhancement in thermal conductivity was obtained at 27.64% for the loading of 0.1 wt.% of GNP 750 at 35°C. The shear rate of nanofluids increased when higher specific surface areas and concentration of GNPs were used. It can be inferred that GNP nanofluids could be a useful and cost-effective material for heat transfer applications along with the development of a facile approach to a large-scale production of aqueous GNP dispersions without any surfactant stabilizers. Nomenclature A absorbency b optical

path (cm) c molar concentration Methamphetamine (mol/dm3) GNPs graphene nanoplatelets I transmitted light intensity I i incident light intensity k bf thermal conductivity of base fluid k nf thermal conductivity of nanofluids k p thermal conductivity of the particle TEM transmission electron microscopy; wt.% weight percentage 2D two-dimensional ϕ particle volumetric fraction ϵ molar absorptivity, L (mol−1 cm−1) Acknowledgements This research work has been financially supported by High Impact Research (MOHE-HIR) grant UM.C/625/1/HIR/MOHE/ENG/45, IPPP grant PV113/2011A, and Malaysian FRGS national grant FP007/2013A. The author wishes to thank the Bright Sparks unit (University of Malaya) for the additional financial H 89 research buy support. References 1. Ma W, Yang F, Shi J, Wang F, Zhang Z, Wang S: Silicone based nanofluids containing functionalized graphene nanosheets. Colloids Surf A Physicochem Eng Asp 2013, 431:120–126.CrossRef 2. Choi SUS, Eastman J: Enhancing Thermal Conductivity of Fluids with Nanoparticles. Lemont, IL: Argonne National Lab; 1995:99–105. 3.