A laser-based “green” synthesis of nanoparticles (NPs) was used to manufacture goldNPs in water. The light source is a Ti:Sapphire laser with 30 fs FWHM pulses, 800 nm meanwavelength, and 1 kHz repetition rate. The method involves two stages: (1) pulsed laser ablationin liquids and (2) photo-fragmentation (PF). Highly pure and well-dispersed NPs with a diameterof 18.5 nm that can be stored at room temperature without showing any agglomeration over aperiod of at least 3 months were produced without the need to use any stabilizer. Transmittancespectra, extinction coefficient, NPs agglomeration dynamics, and thermal conductivity of thenanofluids obtained were analyzed before and after being submitted to thermal cycling and comparedto those obtained for commercial gold/water suspensions. Optical properties have alsobeen investigated, showing no substantial differences for thermal applications between NPs producedby the laser ablation and PF technique and commercial NPs. Therefore, nanofluids producedby this technique can be used in thermal applications, which are foreseen for conventionalnanofluids, e.g., heat transfer enhancement and solar radiation direct absorption, but offering theopportunity to produce them in situ in almost any kind of fluid without the production of anychemical waste.
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