Tracer diffusion in nanofluids measured by fluorescence correlation spectroscopy

Nanofluids exhibit some intriguing thermal properties, and have great potential to increase efficiency in various heat technological applications in micro- and nano-technology. Recent studies on mass transport in nanofluids yielded some interesting but controversial results. In this communication, we report the tracer diffusion of fluorescent dye in different nanofluids. Measurements were performed using fluorescence correlation spectroscopy (FCS). Nanoparticle concentration in the nanofluid varied up to 1.7 vol%, and the diffusion coefficient of fluorescent dye was measured. Our results showed no significant changes in diffusion of dyes in the concentration range used, and the results indicate that more research is needed to completely understand the diffusion in nanofluids. This communication brings upon the powerful FCS technique for the first time to study the dynamics of nanofluids.