Refractometric investigation and analysis of nano-scaled dispersions

Abstract

This work presents the applications of the method of the disappearing diffraction pattern for refractometric measurements and analysis of scattering media. The behavior of the refractive indices of different aqueous dispersions containing metal and polymer particles is studied theoretically and experimentally. Both metallic and latex solutions exhibit linear dependence of the refractive index on the concentration of particles. Values of the specific refractive index increment dn Idc for Co, Fe and Ag nano-dispersions are calculated. Poly(2-ethylhexyl) acrylate and poly(vinyl acetate) latexes with size of particles between 50 and 1300 urn and concentration up to the maximum possible are systematically studied with respect to the properties of the particles -concentration, diameter and refractive index. Empirical relationships are derived for the investigated latexes, describing the dependence of the refractive index of latexes on their properties and on the light wavelength. Such approach could be used to solve the inverse problem of calculating the concentration or the size ofparticles, measuring the refractive index. It is shown that the refractometry provides a simple, easy and accurate way to study and analyze properties of dense nano-and micro-dispersions.

On Total Internal Reflection Investigation of Nanoparticles by Integrated Micro-Fluidic System

“…The maximum discrepancy between them is below the experimental error of 5% for all studied dispersions. Besides, the sensor response is always stronger for the dispersions with higher SRII, as reported in ref . This fact supports the suggestion that δη is mainly caused by the TIR phase changes due to the variation of the fluidic RI.…”

“…The dependence of the ERI, n , on the concentration, c , and the value of their specific RI Increment (SRII), dn/dc , of all dispersions used here have been reported in a recent work . These measurements are made with an automatic refractometer implementing the method of the disappearing diffraction pattern. − It is a modified critical-angle method, which is feasible for dense scattering and turbid media . The precision of the refractometric data is 2 × 10 -4 .…”

“…First, the zeroth diffraction order is of the strongest orders. Moreover, the gradient of η is about 2 times higher compared to that of the ±first diffraction orders, because the −1 and +1 orders are simultaneously exchanging energy with the zeroth order …”

“…The value of N SRII can be determined in two independent ways using the experiments at s and p polarization. The corresponding results, as well the average value N̄ SRII = ( N SRII p + N SRII s )/2 are presented in Table and compared to the reference values . The RI resolution, which corresponds to the calculated effective RI, is given by Δ n = |d(δη calibr )/d(Δ n )| -1 Δ(δη n -part ) = | s r | -1 Δ(δη n -part ), where the derivative d(δη calibr )/d(Δ n ) is found from the calibration experiment and the experimental uncertainty Δ(δη n -part ) from the investigation of the dispersion with nanoparticles.…”