Surfactant-Induced Aggregation Patterns of Thiazole Orange: A Photophysical Study

Abstract

The aggregation behavior of the DNA marker dye thiazole orange (TO), has been investigated in two types of surfactant assemblies, namely, premicelles/micelles of sodium dodecyl sulfate (SDS) and pre reverse micelles/reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT). In the case of an SDS/water system, absorption spectral changes of TO signify the formation of H-aggregates and H-dimers of the dye at premicellar concentrations, which subsequently convert to the monomeric form beyond the critical micellar concentration (cmc). Interestingly, the observed changes in the absorption and emission characteristics due to the surfactant-induced formation of H-aggregates/dimers of TO are found to be useful to estimate the surfactant concentration parameters for premicellar aggregation of SDS. In the case of an AOT/n-heptane system, similarly, H-aggregates/dimers are observed at low AOT concentrations, below the cmc. However, in this case, the H-dimers persist even beyond the cmc. This is attributed to the strong tendency of TO for self-aggregation and its favorable electrostatic interactions with the AOT head groups. With increasing water content in the AOT reverse micelles, the hydration of the dye leads to the conversion of H-dimers to the monomeric form. The steady-state fluorescence results are nicely corroborated with those from time-resolved fluorescence studies and demonstrate the interesting behavior of the surfactant-induced aggregation of TO dye.

Spectroscopic characterization and aggregation of azine compounds in different media

“…In addition, we have examined the influence of dye concentration and different solvents on the aggregate formation, since the formation of aggregates modifies the photophysical and photochemical properties of a dye, and therefore affects its ability to act as a PS [16,17]. We have chosen for this study different media such as ethanol and polyethylene glycol (PEG) 400 because they are FDA approved cosolvents for the parenteral dosage form [18,19].…”

Metal-Ion-Mediated Assemblies of Thiazole Orange with Cucurbit[7]uril: A Photophysical Study

“…The new spectrum matches well with that of TO H-dimer. 16,19 An apparent isosbestic point can be discerned around 487 nm, supporting conversion of TO monomers to dimers. With further increase in the CB7 concentration, the 483 nm absorption band starts decreasing and the spectral characteristics revert to the monomeric form of TO, with an isosbestic point around 490 nm.…”

“…This corresponds to the emission from TO H-dimers. 16,19 Beyond ~100 μM CB7 concentration, the fluorescence intensity starts decreasing again and a significant blue shift in the fluorescence spectra can be observed. Although the maximum in the final fluorescence spectrum is not clear due to associated Raman scattering, it appears that the spectral characteristics resemble to a considerable extent to that of TO monomers (maximum ~528 nm).…”

“…We have previously studied surfactant induced aggregation patterns of TO. 16 Recently, specific ion effects have been found to control the organization of this dye. 17 Lau and Heyne have reported the formation of fluorescent H-aggregates of TO in the presence of the host, calix [4]arene sulfonate.…”

New azine compounds as photoantimicrobial agents against Staphylococcus aureus

“…Since aggregation modifies the absorption spectrum and the photophysical and photochemical properties of a dye and affects its ability to act as a PS [18,19], the influence of NRBr concentration in different buffer solutions on the aggregate formation was examined, and these results were then compared with NR dye in identical experimental conditions. Additionally, the acidebase dissociation constant (pK a ), the stability, photostability and octanolewater partition coefficient were evaluated [20e25].…”