Study of the thermal diffusivity of nanofluids containing SiO2 decorated with Au nanoparticles by thermal lens spectroscopy

In this work, silicon dioxide (SiO2) spheres and gold nanoparticles (Au) were prepared. The SiO2 was used as a platform to deposit the gold nanoparticles. The SiO2 structures were synthesized employing the Stöber method. Monodisperse spherical particles with mean size of 293 nm were observed by transmission electron microscopy (TEM). The gold nanoparticles were attached to the dielectric platform trough in situ reduction. The UV–Vis spectrum of SiO2–Au showed an absorption band in the visible region associated with the presence of the gold nanoparticles. The TEM micrographs confirmed decorated SiO2 spheres with the metallic nanoparticles of 5 nm in size. Nanofluid concentrations of 0.1–0.6 mg/ml of SiO2 decorated with Au nanoparticles dispersed in water were prepared. The functional groups of SiO2-functionalized spheres were followed by FTIR. The formation of gold nanoparticles was evidenced by UV–Vis spectroscopy. The crystalline structure of SiO2 spheres and SiO2 decorated with Au nanoparticles was determined by XRD. The thermal diffusivity as a function of concentration using the mode-mismatched thermal lens (TL) spectroscopy was studied. The results of TL spectroscopy showed an increase in the thermal diffusivity with an increase of SiO2 decorated with Au nanoparticle concentration in the nanofluid