CONICET | Buscador de Institutos y Recursos Humanos

ABSTRACT: The effect of near-criticality upon the properties ofdilute solutions of attractive solutes has been previously studied onlyusing pure solvents close to the vaporliquid critical point. Theexperimental difficulties that plague this thermodynamic region havesomewhat obscured the interpretations of the results. Consequently,the coupling of long-range critical fluctuations with short-rangeintermolecular interactions is still a matter of debate. We developeda new strategy consisting of studying the changes in the solvationshell of probe molecules dissolved in a binary solvent mixture close toits lower consolute critical point. The study is based on UVvisabsorption and fluorescent emission measurements of the solvatochromic and thermochromic effects of two dyes, Reichardt?s Dyeand Nile Red, dissolved in mixtures of lutidinewater. The results show unambiguously the existence of a subtle change in thecomposition of the near-critical solvent surrounding the probe molecules with respect to the bulk composition, thus we concludethat the coupling of long-range fluctuations with short-range interactions is now firmly established.