A possible optical gauge for supervising particle size in nanofluids

Abstract

We examine theoretically using the ratio between the real and imaginary parts of the effective refractive increment in metallic nanofluids as a particle size monitor. We refer to this ratio as X and show it can be a sensitive gauge of the particles’ size once these are larger than a few nanometers in radius. The parameter X is independent of the particles’ concentration as long as measurements are performed within the independent-scattering regime and it could be a viable candidate for monitoring in real time the growth and generation of nanoparticles during the fabrication processes of nanofluids. We present graphs of X as a function of wavelength for gold, silver and copper nanofluids made of spherical nanoparticles of different radii and suspended in water. We identify the range in wavelengths for which the proposed effective parameter is sensitive to the particle size and analyze whether it is measurable with current instrumentation. We also study the limits in particles’ concentration due to dependent-scattering effects. Effects of particles shape are briefly discussed.