Interface chemistry effects in nanofluids: Experimental and computational study of oil-based nanofluids with gold nanoplates

The chemistry of interfaces and its relation with energy storage at and transport through solid–liquid interfaces in heat transfer nanofluids is a very unexplored terrain. Here we discuss how the magnitude of the changes in specific heat and thermal conductivity of the base fluid, upon dispersion of a nanomaterial, depends on the surface chemistry of that nanomaterial. We focus on nanofluids with Au nanoplates from an integrated experimental and theoretical perspective, and compared our findings with those previously reported for nanofluids with Pd nanoplates in the same base fluid. Pd and Au are known to have different surface chemistry, and so are the structures of the solid–liquid interfaces and the thermal properties of these nanofluids. It was experimentally found that for mass fractions in the order of 0.01 wt%, Pd and Au nanoplates provide enhancements of 5.9% and 1.6% in specific heat, and enhancements of 12.5% and 17.9% in thermal conductivity, at 373 K. It was verified using density functional theory and classical molecular dynamics simulations that base fluid molecules can chemisorb on Pd surfaces, but not on Au surfaces. This work suggests that the stronger interactions between species at solid–liquid interfaces, the higher the specific heat enhancements and the lower the thermal conductivity enhancements at high temperature