Solubilization and Photostabilization in a Sodium Deoxycholate Hydrogel of a Neutral Conjugated Thiophene Oligomer and Polymer

Oligo(3-hexylthiophene-co-1,4-phenylene) and poly(3-hexylthiophene) were solubilized in sodium deoxycholate self-assemblies in water solutions and hydrogels. The oligomer and polymer were incorporated as monomers into the self-assemblies with sodium deoxycholate aggregates, leading to the photoprotection of these neutral conjugated and water insoluble molecules. Dynamic light scattering, rheology and fluorescence experiments established that the deoxycholate aggregation and gel formation properties were not altered with the incorporation of the oligomer or polymer into the deoxycholate self-assemblies, showing that this adaptable host system with some molecular recognition elements is a viable strategy to incorporate neutral conjugated molecules into hydrogels

Dynamics of small molecules within the F127 PEO-PPO-PEO triblock copolymer gel and sol phases studied at the molecular scale

The dynamics of naphthalene derivatives with different hydrophobicities bound to F127 polyethyleneoxide-polypropyleneoxide-polyethyleneoxide (PEO-PPO-PEO) micelles in the gel and sol phases were studied using a quenching methodology for the triplet excited states of the naphthalenes. Studies with triplet excited states probe a larger reaction volume than the volumes accessible when using fluorescent singlet excited states. The use of triplet excited states enables the determination of the dynamics between different compartments of a supramolecular system, which in the case of F127 micelles are the micellar core, the micellar corona and the aqueous phase. This report includes laser flash photolysis studies for the four naphthalene derivatives in the F127 gel and sol phases. The triplet excited states were quenched using the nitrite anion as the quenchers. The association and dissociation rate constants of the naphthalenes from the micelles and the quenching rate constants for the naphthalenes bound to the micelles were determines from the curved quenching plot (observed decay rate constant vs. nitrite concentration)

Paper acidity estimation: application of pH-dependent fluorescence probes

The use of pH-dependent fluorescence probes for paper acidity estimation has been explored. The changes in emission properties of the four probes (quinine bisulphate, fluorescein, pyranine and SNAFL-1, a seminaphthofluorescein dye) in buffer solutions of varying pHs are found to correlate with the respective changes observed for the probes applied on paper samples of varying acidity. The remarkable correlations suggest that the paper acidity ('pHapp') can be inferred by extrapolating the probe behavior on paper samples to that in aqueous solutions of varying pHs. Thus, with a judicious choice of pH-dependent fluorescence probes, a wider range of pH indicators of paper acidity are possible to be developed. This methodology promises a non-destructive alternative to measure acidity of paper

Mechanism of a Disassembly Driven Sensing System Studied by Stopped-Flow Kinetics

Mechanistic studies were carried out on the kinetics for the assembly of a DimerDye (DD12) and the binding of the monomeric DimerDye (DD1) with nicotine in aqueous buffer and artificial saliva. DD12 is non-fluorescent, while monomeric DD1 and DD1-nicotine fluoresce. Binding isotherms were determined from steady-state fluorescence experiments. The report includes measurements of the steady-state fluorescence at pHs 2.2, 6.3 and 12.1, and stopped-flow kinetic data for the homodimerization forming DD12 and DD1-nicotine formation in buffer and artificial saliva. Analysis of the homodimerization kinetics led to the recovery of the association and dissociation rate constants for DD12. These rate constants were used in the global analysis for the coupled kinetics for DD1-nicotine formation, which led to the determination of the association and dissociation rate constants for nicotine binding to DD1.</div