Photothermal properties of a nanofluid containing graphene oxide-copper nanoparticle hybrid materials prepared by using Paramignya trimera extract

Abstract

This study reports the green synthesis, characterization, and photothermal performance of graphene oxide–copper nanoparticle (GO–CuNP) hybrid nanofluids. The hybrid materials were fabricated using graphene oxide (GO) as a template and Paramignya trimera (P. trimera) extract as a reducing and stabilizing agent, producing uniformly distributed Cu nanoparticles (∼8.5 nm) on GO sheets. The prepared nanofluids (0.01–0.04 vol%) exhibited enhanced thermal conductivity and optical absorption compared with deionized water. The thermal conductivity increased by 4–15% in the temperature range 30–55 °C. Zeta potential analysis revealed values of 38.5, 32.6, 30.8, and 26.2 mV, indicating good colloidal stability up to 0.03 vol% and moderate stability with incipient aggregation at 0.04 vol%. Under AM 1.5 solar irradiation, the GO–CuNP nanofluids demonstrated photothermal conversion efficiencies of 35–62%, which are higher than those of nanofluids containing GO and CuNPs only. This was attributed to synergistic plasmonic–graphenic absorption and improved heat transport within the hybrid structure. These findings highlight the potential of hybrid nanofluids as efficient solar-absorbing media for solar thermal applications.