Preparation of Au nanoparticles in a non-polar medium: obtaining high-efficiency nanofluids for concentrating solar power. An experimental and theoretical perspectiveElectronic supplementary information (ESI) available: General XPS spectrum of the Au nanoparticles synthesized (Fig. S1). Na 1s and O 1s signals obtained from the XPS measurements performed for the Au nanoparticles synthesized (Fig. S2). UV-vis spectra obtained for the nanofluids at zero time and absorbance values at λ = 520 nm for

• Main Authors: Gómez-Villarejo, Roberto, Navas, Javier, Martín, Elisa I, Sánchez-Coronilla, Antonio, Aguilar, Teresa, Gallardo, Juan Jesús, De los Santos, Desiré, Alcántara, Rodrigo, Fernández-Lorenzo, Concha, Martín-Calleja, Joaquín
• Format: Journal Article
• Language: English
• Published: 20.06.2017
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta00986k

This paper presents the preparation of Au nanoparticles in a non-polar medium, which is a fluid composed of the eutectic mixture of biphenyl and diphenyl oxide commonly used in Concentrating Solar Power (CSP) plants. The nanofluids prepared showed enhanced thermal properties, presenting thermal conductivity values 70% higher than those of base fluids, and isobaric specific heat values up to 10% higher. In turn, an increase of up to 36% was observed in their heat transfer coefficient, which is their efficiency as a heat transfer fluid (HTF). Also, the stability of the nanofluids was analysed using UV-vis spectroscopy, and particle size and ζ potential. The nanofluids with lower concentrations agglomerate slowly, which is considered stable for this application. Thus, these nanofluids are a promising, interesting alternative to the HTF often used in CSP plants. Also, molecular dynamics calculations were performed to better understand how the Au-nanofluid behaves in the presence of a surfactant within a temperature range between 50 and 600 K. The isobaric specific heat and thermal conductivity values followed the same experimental tendency. The analysis of the radial distribution functions (RDFs) and spatial distribution functions (SDFs) showed that, as the temperature rose, an exchange took place between the surfactant and diphenyl oxide molecules in the first layer of molecules around the metal. This movement incorporated a directionality that may play a part in the enhanced thermal properties. The surfactant participates as an active component within the Au-nanofluid, contributing to efficient heat transfer processes. Au nanofluids with enhanced thermal properties for use in CSP.