Cresyl Fast Violet in Aqueous Solution: Temperature Dependent Unfolding of Dimer Structure

Molecular interaction of organic dyes in bulk and confined media

Molecular interactions of five thiazine dyes with increasing alkyl substitution have been studied in aqueous and microemulsion media at 303K within a concentration range of (1.35-7.00)x10(-4)M. The dimerization constant (K(d)) values for the five dyes are ranged between 1.761 and 6.258x10(3)lmol(-1) in bulk water media, where as in microemulsion media, K(d)'s are ranged between 1.760 and 4.110x10(3)lmol(-1). Thionine (with no methyl substitution) and azure A (with two methyl substitution) displayed slightly larger K(d) values in microemulsion water pools compared to bulk water while other dyes recorded significant drop in K(d) values. The influence of microemulsion media on the molecular interaction of dyes has been explained in terms of electrostatic and hydrophobic factors. The monomer and the dimer spectra are explained in terms of molecular exciton model and the optical absorption parameters of both the species are reported in bulk and confined media.

Ultrafast T-Jump in Water: Studies of Conformation and Reaction Dynamics at the Thermal Limit

We report the development of ultrafast T-jump with time resolution reaching the fundamental time scale of water thermalization time ( approximately 5 ps). The T-jump heats the bulk water up to 20 degrees C via the overtone absorption of the OH- stretch at 1.5 mum. The example given here shows the application of the methodology, for the first time, and the results demonstrate distinct time scales for solvation, conformational change, and thermal reaction.