Circular Dichroism and Derivative Spectra Study of the Excitonic Aggregation of Pinacyanol by Aerosol-OT

Abstract

Different structures are proposed for the complexes formed from the interaction between the cationic cyanine dye 1, 1’-diethyl-2, 2’-carbocyanine chloride (Pinacyanol chloride) and the anionic surfactant sodium bis (2-ethylhexyl) sul- fosuccinate (Aerosol-OT) in ethanol-water solutions. UV/vis and electronic circular dichroism (CD) spectra provide tools to study the concentration and solvent dependence of this interaction. The aggregation spectra of the dye are dominated by a strongly blue-shifted, sharp and single visible band, which appears at concentrations much below the critical micelle concentration (cmc) of Aerosol-OT. Above the cmc, the spectra in pure aqueous solution indicate disso- ciation into monomer and dimer species, and the system becomes completely empty of chirality. Two different CD spectra with a distinct isosbestic point are observed for complexes with different surfactant to dye ratios. Both the addi- tion of ethanol (more than 7.5%) and increasing the temperature retards the metachromatic process between the dye and Aerosol-OT. By using the peakFit program, the two overlapping excitonic absorption bands together with the optically inactive absorption band for one spectrum (the most optimal one) at a specific Aerosol-OT concentration were sepa- rated

Synthesis and characterisation of far-red fluorescent cyanine dye doped silica nanoparticles using a modified microemulsion method for application in bioassays

“…However significant absorption was observed at 475 nm. In a separate study Khouri et al also observed a band at 475 nm for a red cyanine dye when surfactant was added, which was assigned to dye surfactant aggregation [35]. For FR670 a slightly higher absorption band at 670 nm combined with a small peak at 475 nm was observed but the total amount of dye loaded was still significantly lower than that obtained using alternative methods (see supporting information, Fig.…”

α-Lipoic Acid in Soluplus ® Polymeric Nanomicelles for Ocular Treatment of Diabetes-Associated Corneal Diseases

“…CMC for AOT and Soluplus have been reported to be 2.4 mM and 6.6 Â 10 À5 mM, respectively. 34,35 The concentrations of each surfactant/copolymer chosen for the study were well above those values, and ranged between 0.4 and 2 mM for Soluplus and 4 and 20 mM for AOT. Soluplus micelles had an average size of 69.9 (standard deviation [SD] 4.9 nm) and polydispersity index of 0.15 ± 0.02 with a narrow distribution, whereas AOT micelles had average size of 528.3 (SD 16.4 nm) and polydispersity index of 0.59 ± 0.07 with a width distribution (Table 1).…”

Pinacyanol chloride forms mesoscopic H- and J-aggregates in aqueous solution – a spectroscopic and cryo-transmission electron microscopy study

“…Similarly, weak bands emerged upon the interaction of PCYN with polymers, 15,22 b-amyloid fibrils 20 or micelles of the cationic surfactant sodium bis-(2-ethylhexyl) sulfosuccinate (Aerosol-OT) in aqueous solutions. 18 Aqueous PCYN iodide solutions containing 200 mM NaCl also showed similar bands. 24 Due to their general appearance in the long-wavelength side of the monomer spectrum they were ascribed to J-aggregates.…”

“…Aggregation causes a blue-shift of the absorption band due to the formation of dimers 23 and higher H-type aggregates. 22 In contrast to PIC-Cl, which shows very strong J-aggregation, the evolution of J-aggregates for PCYN was in fact believed to occur in a few studies, 18,22,24 but until now has not been conclusively demonstrated.…”

“…Pinacyanol chloride (1,1 0 -diethyl-2,2 0 -carbocyanine chloride, PCYN-Cl, Chart 1) is a homologue of PIC and differs from it only in the length of the alkene bridge between the two quinoline moieties, which is longer by two methine units for PCYN. PCYN has been used as a redox indicator to monitor peroxide activation, 11 a saturable absorber, mode-locker, sensitiser in imaging technology, 12,13 a diagnostic tool for the study of polysaccharides, [14][15][16] to determine physicochemical properties of micelles 17,18 and vesicles, 19 as well as to probe fibrillization of the b-amyloid peptide. 20 Most of the applications of PCYN utilize the strong binding of the cationic dye to anionic colloids, which promotes aggregation.…”