Cooperativity between Dimerization and Binding Equilibria in the Ternary System Laponite-Indocyanine Green-Water

Abstract

Laponite is an artificial nanoclay available in large quantities and at low cost. This marterial represents an efficient and suitable way of delivering hydrophobic vital dyes without the need for chemical functionalization. Laponite is available in large quantities and at low cost, then it would be an efficient way of delivering hydrophobic vital dyes without the need for chemical functionalization. The hydrodynamic diameter of laponite extrapolated to infinite dilution indicates that this clay is completely exfoliated. Furthermore, the hydrodynamic diameter in the laponite-Indocyanine green-water ternary system, at a fixed laponite concentration (2% (m/m)) exhibits a saturation curve. It was found that the extrapolated diameter at dye zero concentration is smaller than in pure water. Absorption spectra with fixed concentration of dye exhibit a red shift of 10–13 nm. On the contrary, the spectra acquired at a constant concentration of laponite do not undergo any displacement. The deconvolution of the spectra with two Gaussian peaks allows to calculate the concentration of the monomeric and dimeric species. The results were interpreted as a synergy between the dye dimerization balance and the dye-laponite binding.

Keywords

• laponite
• indocyanine green
• binding equilibrium
• dimerization equilibrium
• dynamic light scattering