Aqueous Nanofluids based on Thioglycolic acid-coated copper sulfide nanoparticles for heat-exchange applications

We report the one-pot synthesis of an aqueous nanofluid (NF) with improved thermal conductivity and with high colloidal stability. The thermal conductivity showed an increase of 38% (relative to the base fluid) for NF with a volumetric fraction (φ) of 0.06%, and the NF was stable for over 900 days in the stationary state. e. Aqueous NF based on thioglycolic acid (TGA) - coated copper sulfide nanoparticles (NPCu(2-x)S) was synthesized by the chemical reduction method. The NPCu(2-x)S characterization by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicated the formation of copper(I) sulfide. Transmission electron microscopy (TEM) allowed the morphology to be characterized and the size of the nanomaterials obtained, with an average diameter of 5.4 ± 1.9 nm. Zeta potential and dynamic light scattering were used to evaluate the colloidal stability of NF, where the NF showed −29 mV and 23 nm, respectively, for the NF in slightly basic pH. The colloidal stability by DLS in function of the temperature showed minor variations of the hydrodynamic diameter (Dh) under heating/cooling cycles; the Dh increased with increased temperature, but the process was reversible, as was shown in the cooling step, and did not indicate the absence of aggregation or dissolution of the NPCu(2-x)S present in the aqueous NF. •Synthesis and characterization of NF based on highly dispersible Cu(2-x)S NP.•Thermal conductivity were evaluated by the hot wire method.•Nanofluid showed high colloidal stability, evaluated by DLS and zeta potential.•The stability was evaluated by DLS vs. temperature (heating and cooling cycles).