Thiacyanine Dye Research Articles

Spectroscopic studies of β-cyclodextrin-complexed cyanine dyes

We have studied the interaction of a homologous series of symmetrical thiacyanine dyes (DTCI, DTDCI, DTTCI) with β-cyclodextrin. From absorption spectra we infer that all three dyes form β-CD complexes, either as dye cation monomer or dimer. Higher aggregates, e.g. H-aggregates, are observable in water alone for both DTDCI and DTTCI, as is well-known. The H-aggregate formed from DTTCI in water provides evidence of a unique pathway for thermalization of photoexcitation energy; excited aggregate ejects excited dye monomer. β-CD complexes of all three dyes exhibit technologically useful levels of second-order hyperpolarizability, measured by Hyper-Rayleigh scattering, and we assign the non-linear optical response to dimer complex. Second-order scattering is observed, however, only when the saturation concentration of dye monomer in water is exceeded; at lower concentrations we infer that complexes do not form. Computational modelling, carried out for DTCI, suggests that the dimer forms endergonically with a structure that both locks in a significant degree of bond alternation, as well as allowing considerable freedom for torsional relaxation.

Determination of nucleic acids by near-infrared fluorescence quenching of hydrophobic thiacyanine dye in the presence of Triton X-100.

A near-infrared (near-IR) fluorescence quenching method was developed for the determination of nucleic acids in aqueous solution by using a cationic heptamethylene thiacyanine as a probe. The near-IR cationic cyanine showed maximum excitation and emission wavelengths at 800 and 825 nm, respectively, in the presence of Triton X-100; the fluorescence of the cyanine could be greatly quenched by DNA. The calibration graphs were linear over the range of 10-400 ng/mL for CT (calf thymus) DNA and over the range 5-400 ng/mL for FS (fish sperm) DNA under optimal conditions. The corresponding detection limits were 5.2 ng/mL for CT DNA and 2.5 ng/mL for FS DNA. The relative standard deviation (n = 8) was 3.1% for 75 ng/mL CT DNA and 2.2% for 75 ng/mL FS DNA, respectively. Preliminary research showed that the fluorescence quenching might be ascribed to the formation of dye aggregate facilitated by DNA.

Structure determination of thiacyanine dye J-aggregates in thin films: Comparison between spectroscopy and wide angle X-ray scattering

The structural properties of J-aggregates in thin films were studied by wide-angle synchrotron X-ray scattering, UV/VIS absorption and fluorescence spectroscopy and time-correlated single photon counting. The system of investigation was the cyanine dye (C33H32N2O6S4−·HN(CH2CH3)3+; 2-{3-[1-(3-sulfopropyl)-naphtho-[1,2-d]thiazol-2(1H)-yliden]-2-ethyl-1-propen-1-yl}-1-(3-sulfo-propyl)-naphtho-[1,2-d] thiazolium-betain·triethylammonium salt) incorporated into a Na-polystyrene-sulfonate (PSSNa) matrix. It could be shown that, depending on the preparation conditions, it is possible to create either a monomer phase or a J-aggregate phase in PSSNa films. Both could optically be distinguished through their typical bathochromic shift of the J-aggregate band in the UV/VIS spectra. Wide angle X-ray scattering experiments confirm intermolecular distances of 7 A in the J-aggregate and an angle of inclination of 20°. Out of optical studies, the angle of inclination was determined to be around 30°. A more detailed interpretation of the wide angle X-ray scattering signals suggests that 80% of the formed J-aggregate consists of dimers and 20% of a helical arrangement with a diameter of ca. 16 A. The used stacking model was built out of mono-cis conformer units which were confirmed to be the most stable conformation by DFT calculations (6-31G* basis set, BeckeLyp functional).

ABSORPTION SPECTRA SIMULATION OF PERSISTENCE-TYPE CYANINE DYE AGGREGATES IN LB FILMS

Simulation of the absorption spectra of the 2D persistence-type molecular aggregates consisting of the combination of oxacyanine dye (S9) and thiacyanine dye (S11) is being considered. These aggregates are modeled by square matrix structure in the extended dipole approximation. The simulation takes into account the vector properties of the transitional dipole moment, its orientation, diagonal disorder and the composition of the aggregate. Good fit with the experiment is obtained for dipole tilt angle θ=40°, dipole moment μ=8.1 D and the disorder parameter of 450 cm -1 for various molar fractions of dyes.

Excitation energy transfer between J-aggregates in layer-by-layer alternate assemblies

The layer-by-layer alternate assemblies incorporating two kinds of cyanine dyes have been fabricated by the alternate adsorption technique. In order to examine excitation energy transfer between J-aggregates, a thiacyanine dye has been employed as the donor and thiacarbocyanine dyes as the acceptor. It is confirmed that these dye combinations form the mixed J-aggregate in the alternate assemblies. From steady-state fluorescence spectra of the molecular assemblies, the occurrence of efficient energy transfer from the donor J-aggregate to the acceptor J-aggregate has been demonstrated. The experimentally obtained rate constant of energy transfer kET in the Stern–Volmer kinetics of the order of 1013nm2molecules−1s−1 is interpreted in terms of exciton migration and trapping in the mixed J-aggregate. The difference in kET between various combinations of cyanine dyes is not inconsistent with an exponential energy gap law.

Lattice Structure of Mesoscopic Rod-like J Aggregates of Thiacyanine Dye Characterized by Atomic Force Microscopy

Abstract We characterized the lattice structure of mesoscopic rod-like J aggregates of thiacyanine dye on mica possessing similar morphological and spectroscopic characteristics with those in bulk solution. The structure showed a staircase molecular arrangement.

Luminescence Properties of the Mixed J-Aggregate of Two Kinds of Cyanine Dyes in Layer-by-Layer Alternate Assemblies

The layer-by-layer alternate assemblies incorporating two kinds of cyanine dyes have been fabricated by alternately adsorbing a cationic polyelectrolyte and anionic cyanine dyes on the quartz plate. A thiacyanine dye (dye I) was employed as the donor and two kinds of thiacarbocyanine dye having a meso-alkyl groupm-ethyl (dye II), m-methyl (dye III)as the acceptor. The mole fraction of the acceptor in the mixed J-aggregate, χ, was varied from 0 to 1. It is confirmed that these dye combinations form the mixed J-aggregate in the alternate assemblies. From steady-state fluorescence spectra of the molecular assemblies, excitation energy transfer from the donor J-aggregate to the acceptor J-aggregate is observed, whose kinetics obeys the Stern−Volmer relationship. The experimentally determined rate constant of energy transfer, kET, is fairly large, indicating efficient energy transfer due to exciton migration through the donor J-aggregate. The relative fluorescence quantum yield and the fluorescence lifetime of the acceptor aggregate decrease with increasing χ, implying the considerable self-quenching of acceptor fluorescence. The relative change of the coherent size of the dye II aggregate has been estimated from the J-band line width and the radiative decay rate constant. It is found that the coherent size of the dye II aggregate is increased by a factor of 4−5 with increasing χ from 0.008 to 1.

Exciton Annihilation in J-Aggregates Probed by Femtosecond Fluorescence Upconversion

Femtosecond fluorescence upconversion was used to study the excited-state dynamics of two-dimensional J-aggregates of a thiacyanine dye. At high intensities the excited-state population decay is faster than exponential and the decay is intensity dependent. A singlet−singlet exciton annihilation decay mechanism is consistent with the observed behavior. A value of 4 × 1012 molecule s-1 is calculated for the exciton annihilation constant γ. Exciton annihilation measurements reported in the literature for J-aggregates of several cyanine dyes are recast into the same units for comparison. The physical state of these J-aggregates is elucidated to explore the relationship between the magnitude of the exciton annihilation constants and the liquid-crystalline nature of these aqueous colloidal systems. Attempts to time-resolve spectral features related to intraband relaxation in the excited excitonic states of the thiacyanine J-aggregate prior to annihilation indicate that these relaxation processes are faster than 100 fs at room temperature.

Adsorption of Thiacyanine Dyes on Silver Halide Nanoparticles: Study of the Adsorption Site

Silver halide particles were synthesized in a water-in-oil microemulsion consisting of AOT (sodium bis-2ethylhexylsulfosuccinate)/n-heptane/water. Different molecules of thiacyanines were adsorbed on these particles. These molecules can be adsorbed on the particles by two main sites of adsorption: either by an interaction between the sulfur atom and the silver ion or by a Coulombic interaction between the nitrogen atom and the halide ion. To distinguish the two adsorption sites, particles with different excesses of charge have been used. It has been concluded that the adsorption site depends on the structure of the molecules: the sulfur is more reactive in the presence of an electron donor moiety and more for the thiacarbocyanine than for the thiacyanine. The adsorption between the sulfur and the silver ion is also more favorable on the silver bromide particles than on the silver chloride particles.

Complex formation between symmetrical thiacyanine dyes and aromatic heterocycles: evidence for molecular recognition

Complexes between three thiacarbocyanine dyes and imidazole, Im, benzimidazole, Bz, and 2-methylbenzimidazole, 2-MeBz, have been detected by perturbation of the dyes' fluorescence. In some cases 1 : 2, as well as 1 : 1 complexes, can be observed. This assignment has been confirmed by time-resolved laser flash spectroscopy, detected by transient absorption spectroscopy. Based on a preconception of complex geometry, we selected a series of α,ω-bis(2-benzimidazolyl)alkanes of chain length n, as complexing agents which we anticipated might exhibit molecular recognition towards the cyanine chromophores. A modicum of molecular recognition was indeed observed when ( n−4) matched the number of carbon atoms in the polymethine chain of the dye. Computational chemical studies using the Merck molecular force field and AM1 semi-empirical molecular orbital calculation were carried out to elucidate complex structure. Geometry of the Im and Bz complexes turned out to be quite different. The calculated geometry of the latter complexes turned out to be incompatible with the anticipated basis for molecular recognition. The computational studies suggested the basis for dye-complexing agent interaction in the ground state to be principally electrostatic, i.e., with little or no dispersion or charge transfer contributions.

Layer-by-layer self-assembly of polyelectrolyte and water soluble cyanine dye

We have fabricated multilayer assemblies consisting of cyanine dye and polyelectrolyte by means of alternate adsorption method. In this study we used two kinds of water soluble thiacyanine dyes and poly(diallyldimethylammonium chloride) (PDDA) as polycation. Anionic cyanine dye molecules were adsorbed onto the positively charged surface of PDDA layer, giving rise to the J-aggregate. The sequential alternate adsorption yielded the PDDA-(dye/PDDA) n assemblies ( n, repeating number). UV-vis spectroscopy measurements indicated that peak absorbance at the J-band increased linearly with the increasing adsorption cycles. These results demonstrate the advantage of the alternate adsorption method for investigating J-aggregate-containing multilayer assemblies.

Memory Effect of Thiacyanine Dye in LB Film

Memory Effect of Thiacyanine Dye in LB Film

Influence of Substituents on the Association of Thiacyanine Dyes

Influence of Substituents on the Association of Thiacyanine Dyes

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

The fluorescence of thiacyanine (THIA) dye is greatly enhanced on binding to polyanions due to the reduction in internal conversion of the excitation energy of the dye. Glycosaminoglycans (chondroitin sulphates (CS) A, B and C; heparin) and the synthetic polyanion poly(vinylsulphate) (PVS), in addition to enhancing the fluorescence of THIA, facilitate the formation of an exciplex between excited THIA and cool acridine orange (AO), both bound to the polymers. Of the three chondroitin sulphates, chondroitin sulphate C (CSC) is the most efficient in enhancing the fluorescence of THIA and facilitating the formation of an exciplex. The efficiency of heparin in this respect is comparable with that of CSC,and poly(vinyl sulphate) is even more efficient. In 20% (v/v) ethanol the association constant of THIA—CSC is reduced to one-tenth of its value in water. Aqueous ethanol also partially inhibits exciplex formation between the two dyes bound to chondroitin sulphates, although the effect is less prominent in the case of CSC.

Dye fluorescence kinetics of Langmuir-Blodgett films

In this paper fluorescence decay is applied to investigations of perylene aggregate formation in ω-tricosenoic acid LB films and aggregate of thiacyanine dye in LB films. The complicated decay law of fluorescence of perylene and the extremely short lifetime (approx. 500 ps) of the excited thiacyanine dye in LB films is investigated. The kinetic fluorescence characteristics were measured by a time-correlated single photon technique.

ChemInform Abstract: Electronic Structure of Thiacyanine Dyes (I) in the Solid State

ChemInform Abstract: Electronic Structure of Thiacyanine Dyes (I) in the Solid State

Electronic structure of thiacyanine dyes in the solid state

Electronic structure of thiacyanine dyes in the solid state

Energy transfer in monolayers with cyanine dye Sheibe aggregates

A monolayer of an oxacyanine dye organized in Scheibe aggregates is doped with a thiacyanine dye (e.g., one molecule of the guest per 104 molecules of the host). Strong energy transfer from the excited host to the guest takes place at room temperature, the efficiency decreasing with lowering temperature T. The rate of energy transfer is proportional to T. A simple model of the excited state is discussed based on a coherent exciton extending over a certain domain. The exciton moves over the aggregate, occasionally reaching the vicinity of an acceptor molecule. The domain size of the exciton is inversely proportional to the absolute temperature T. As a consequence, the lifetime of the exciton is proportional to T, and therefore the energy transfer efficiency is proportional to T.

Correlation of reduction potentials of cyanine dyes with their orbital energies

The relationship between the reduction potential and calculated electron affinities of some thiacyanine dyes is examined. The results show that there is an excellent correlation between these two parameters of the dyes.

Fluorescence Behavior and Energy Transfer of Cyanine Dyes Bound to Bilayer Membranes of Double-Chain Ammonium Amphiphiles

Abstract Negatively-charged cyanine dyes are bound specifically to aqueous bilayer membranes of double-chain ammonium amphiphiles, as reflected in their absorption spectra. The quantum yield of the fluorescence emission of a trimethine-thiacyanine dye is remarkably enhanced (up to 0.64) when the dye is bound to crystalline bilayer membranes of certain double-chain ammonium amphiphiles. The fluorescence intensity diminished drastically with the liquid crystalline bilayers. Efficient energy transfer is noted from an oxacyanine to the thiacyanine dye in the crystalline membrane matrix. The efficiency decreases by the membrane phase transition to the liquid crystalline state. These results are discussed in terms of specific dye binding and concentration of dyes at the membrane surface.