The effect of nanoparticles on the liquid–gas surface tension of Bi2Te3nanofluids

This work investigates the effect of size and concentration of nanoparticles on the effective gas–liquid surface tension of aqueous solutions of bismuth telluride nanoparticles functionalized with thioglycolic acid. The gas–liquid surface tension is obtained by solving the Laplace–Young equation under experimentally measured boundary conditions and droplet parameters. The results demonstrate that the gas–liquid surface tension depends on concentration as well as nanoparticle size. Solutions containing 2.5 and 10.4 nm nanoparticle diameters have been tested. For both, a minimum surface tension exists within the range of tested mass concentrations. The largest reduction in the surface tension (>50% versus bulk liquid) occurred for the 2.5 nm nanoparticle nanofluid. Accumulation and assembly of the charged nanoparticles at the liquid–gas interface was assumed to be responsible for the surface tension of the nanofluids investigated in this work.