Energy transfer and formation of exciplex between thiacyanine and acridine orange facilitated by anionic biopolymers and synthetic polymers

Subpicosecond Kerr-gate spectrofluorometry

This chapter describes an experimental layout for time and spectrally resolved fluorescence measurements with femtosecond time resolution based on Kerr gating. The combination of data recorded using different Kerr media allows a temporal dynamic range from ~100 fs to several nanoseconds. Simultaneous analysis of multiple datasets is described.

Exciplex fluorescence emission from simple organic intramolecular constructs in non-polar and highly polar media as model systems for DNA-assembled exciplex detectors

Organic intramolecular exciplexes, N-(4-dimethylaminobenzyl)-N-(1-pyrenemethyl)amine (1) and N'-4-dimethylaminonaphthyl-N-(1-pyrenemethyl)amine (2), were used as model systems to reveal major factors affecting their exciplex fluorescence, and thus lay the basis for developing emissive target-assembled exciplexes for DNA-mounted systems in solution. These models with an aromatic pyrenyl hydrocarbon moiety as an electron acceptor appropriately connected to an aromatic dimethylamino electron donor component (N,N-dimethylaminophenyl or N,N-dimethylaminonaphthyl) showed strong intramolecular exciplex emission in both non-polar and highly polar solvents. The effect of dielectric constant on the maximum wavelength for exciplex emission was studied, and emission was observed for 1 and 2 over the full range of solvent from non-polar hydrocarbons up to N-methylformamide with a dielectric constant of 182. Quantum yields were determined for these intramolecular exciplexes in a range of solvents relative to that for Hoechst 33,258. Conformational analysis of 1 was performed both computationally and via qualitative 2D NMR using (1)H-NOESY experiments. The results obtained indicated the contribution of pre-folded conformation(s) to the ground state of 1 conducive to exciplex emission. This research provides the initial background for design of self-assembled, DNA-mounted exciplexes and underpins further development of exciplex-based hybridisation bioassays.

Principal Component Analysis of the Absorption Spectra of the Dye Thiacyanine in the Presence of the Surfactant AOT: Precise Identification of the Dye-Surfactant Aggregates

Spectral change of a cationic dye 3,3'-diethylthiacyanine iodide (THIA) in the presence of an anionic surfactant AOT has been presented. The THIA-AOT system exhibits blue-shifted metachromasia at AOT concentrations below its critical micellar concentration (CMC) and is thought to be due to the aggregation of electrostatically bound dye-AOT complex (DS). Metachromasia is gradually reversed to the monomeric band (peak at 425 nm) by AOT above its CMC. Principal component analysis (PCA) method has been applied for spectral analysis; the results show that the metachromatic peaks at 377 and 366 nm originate, respectively, from trimer and hexamer of the dye associated with AOT. From PCA, the molar absorption coefficient spectra of the individual absorbing components and the equilibrium constants for the systems, monomer right harpoon over left harpoon trimer and hexamer right harpoon over left harpoon monomer below and above CMC of AOT, respectively, have also been obtained. The micellar aggregation number of AOT obtained from PCA is found to be 16 which is in good agreement with the literature value.