Influence of the N-alkyl chain length on the J-aggregation behavior of a cyanine dye

Red Disperse Azo Dye Side Chains Influence on Polyethylene Terephthalate Dyeing Performances in Supercritical Carbon Dioxide Media

Supercritical carbon dioxide dyeing (SDD) as a dyeing media not only provides a friendly dyeing environment but also significantly increases polymeric dyeing performances ascribed to strong azo dye affinity. Disperse azo dyes have shown to be highly efficient dyeing agents due to their facile coupling synthesis, side chains position, and length tunability to optimize absorption properties. Herein, we first synthesize two series of disperse red azo dyes via a coupling chemical route. Further, we investigate the position of the electron withdrawing group and alkyl chains length impact onto the absorption and color fastness properties. Upon synthesis, ¹H NMR and mass spectroscopy were used to characterize our newly synthesized series dye structure. Also, according to spectroscopic characterization, the functional group positions as well as the alkyl chains length have a major impact on the dye series maximum light absorption wavelength and performance. We have performed SDD dyeing of polyethylene terephthalate woven and determined each dye color fastness, we find that a reduced electron withdrawing effect and alkyl chains increase reduce color-fastness performances. Overall, our dyes exhibited a good resistance against detergent water, perspiration, abrasion, and friction.

Novel carbazole-pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

The synthesis, as well as spectroscopic and thermochemical studies of a novel class of carbazole-4-phenylpyridine co-polymers are described. The synthesis was carried out by a simple and cheaper method compared to the lengthy methods usually adopted for the preparation of carbazole–pyridine copolymers which involve costly catalysts. Thus, two series of polymers were synthesized by a modified Chichibabin reaction, i.e., by the condensation of diacetylated N-alkylcarbazoles with 3-substituted benzaldehydes in the presence of ammonium acetate in refluxing acetic acid. All the polymers were characterized by FTIR, ¹H NMR, ¹³C NMR, UV–vis spectroscopy, fluorimetry, TGA and DSC. The weight average molecular masses (M_w) of the polymers were estimated by the laser light scattering (LLS) technique.

Tunable hydrophobicity in DNA micelles: design, synthesis, and characterization of a new family of DNA amphiphiles

This work describes the synthesis and characterization of a new family of DNA amphiphiles containing modified nucleobases. The hydrophobicity was imparted by the introduction of a dodec-1-yne chain at the 5-position of the uracil base, which allowed precise and simple tuning of the hydrophobic properties through solid-phase DNA synthesis. The micelles formed from these modified DNA sequences were characterized by atomic force microscopy, dynamic light scattering, and polyacrylamide gel electrophoresis. These experiments revealed the role of the quantity and location of the hydrophobic units in determining the morphology and stability of the micelles. The effects of hybridization on the physical characteristics of the DNA micelles were also studied; these results showed potential for the sequence-specific noncovalent functionalization of the self-assembled aggregates.

Specific Cu(2+)-induced J-aggregation and Hg(2+)-induced fluorescence enhancement based on BODIPY

A BODIPY derivative with an -NH(2) and -OH substituted meso-phenyl group is reported, which, under biological conditions, exhibits metal-induced J-aggregation in the presence of Cu(2+) and a specific fluorescence enhancement for Hg(2+).

Kinetics of salt-induced J-aggregation of cyanine dyes

The addition of monovalent, divalent, and trivalent metal ions to three anionic ethyl meso-thiacarbocyanine dyes, an ethyl meso-oxacarbocyanine, and an imidacarbocyanine in aqueous solution at room temperature results in the production of J-aggregates within the range of tens to hundreds of seconds. The rate of formation of J-aggregates correlates with the rate of decay of dimers or monomers and is dependent on the type of metal ion, dye structure, and temperature. The rate of formation of J-aggregates increases as the temperature decreases and the dye and salt concentrations increase, and the rate is highest for trivalent ions and smallest for monovalent ions, independent of the type of anion. The time course of formation of J-aggregates is described in most cases by a sigmoidal curve, and the kinetics and mechanism are discussed within the framework of autocatalysis. Computer simulations reveal that the sigmoidal time dependence is transferred to an exponential-like curve by substantially increasing the rate constant for the noncatalytic step. The reaction pathway into J-aggregates can be switched from dimeric ion pairs as the reactant to monomeric ion pairs, when the rate constant for the catalytic step via the monomer becomes larger with respect to that via the dimer.

Unexpected fluorescence enhancement of naphthylethyl lauryl ether in coaggregation with variant aggregators

Unexpected fluorescence enhancement has been observed during the coaggregation process between naphthylethyl lauryl ether (the fluorescence probe) and vitamin E acetate in aqueous organic binary solutions. Variant aggregators were used to study the influence of structure features on the enhancement. The experiments indicate that a long hydrophobic hydrocarbon chain is of necessity for coaggregation, and a flat group is crucial for the fluorescence enhancement. No enhancement was observed at the absence of coaggregation. The enhancement was attributed to the hindrance of rotations and prolonged life time of the probe by steric hindrance of flat groups in coaggregate. Structure features of aggregates of variant aggregators have also been discussed.