Spectra and dynamics of an ionic styryl dye in reverse micelles

Probing the reverse micelle environment with a cationic dye by varying oil and water content of micelles

In the present work, spectroscopic properties of crystal violet (CV) within water-in-hexane sodium base (2-ethyl hexyl) sulfosuccinate (AOT) reverse micellar environment was investigated as a function of water contents (W = [H2O]/[AOT] = 6,10) in AOT and also function of mass fraction of nanodroplet (MFD = 0.01, 0.04, 0.07, and 0.1) by using UV/visible, and fluorescence techniques. A deviation in the absorption spectra of crystal violet at the high CV concentration (0.002 M) was observed in the AOT reversed micelles. The Quenching in the emission intensity of crystal violet at high CV concentration and blue shift in λ_max of fluorescence of dye was observed as a function of MFD in AOT RMs. At high concentration of dye, molecules of CV can be reside interfacial region but near core of AOT. At low dye concentration, the CV molecules also can be in interfacial region but far from core. The Stokes shift of CV at high concentration decreased with mass fraction of nano-droplet (MFD), whereas at the low CV concentration, its variation often increased. The ratio of ground state to the excited state dipole moment of crystal violet dye also affected by the change in W values and MFD values. The change in dipole moment and stokes shift indicates the different environment around CV for different W and MFD values.

Switching of emission of a styryl dye in cucurbit[7]uril: a comprehensive experimental and theoretical study

Intriguing colour change and change in fluorescence band of 2-(4-(dimethylamino)styryl)-1-methylpyridinium iodide from nonpolar to polar protic solvent, and also from molecular container cucurbit[7]uril environment to polar protic solvent has been reported here. This interesting colour change of this dye with respect to the medium makes this dye useful as a sensor. Change in spectral characteristics of DASPMI along with change of colour from orange to yellow with increasing polarity of medium is interpreted as due to negative solvatochromatism. Complexations of probe-cucurbit[7]uril (1:1 and 2:1) cause structural change of the probe molecule due to hydrogen bond interaction of cationic part of the dye with CO group of cucurbit[7]uril and the colour change of the solution ensued. On addition of sodium chloride to the inclusion complex the dye is released from cucurbit[7]uril interior with colour of the solution reverted back. Theoretical results show that one carbon atom in the styryl part containing the positive charge gets too close to a carbon atom of cucurbit[7]uril to cause a phenomenal increase of dipole moment by 10X.