Global Analysis of the Fluorescence Decays of N,N‘-Dioctadecyl Rhodamine B in Langmuir−Blodgett Films of Diacylphosphatidic Acids

Abstract

Langmuir-Blodgett multilayer films were prepared from N,N′-dioctadecyl rhodamine B (RB18) diluted in dioleoylphosphatidic acid (DOPA) or dipalmitoylphosphatidic acid (DPPA) with various mixing ratios. Surface pressure-area isotherms of monolayers of the two matrices were recorded. Absorption and fluorescence spectra and fluorescence decays of the multilayer samples of RB18 were further examined. The fluorescence decay curves of RB18 in the multilayer assemblies, determined using time-correlated single photon counting, were analyzed in the framework of several models leading to nonexponential decays: (1) multiexponential decay; (2) Gaussian distribution of rate constants; (3) stretched-exponential decay, characteristic of Förster energy transfer in self-similar fractal-like structures with a fractal dimensionality of <2; and (4) Förster energy transfer in a two-dimensional system accompanied by an unquenched decay. Using the global analysis method, only the decay law for Förster energy transfer in two dimensions accompanied by a monoexponential decay yielded acceptable statistical fits for multilayer assemblies of RB18 and DOPA or DPPA in the concentration range from 0.2 to 5 mol %. While global analysis of nonexponential decay profiles gave adequate parameters over the whole concentration range studied, single-curve analysis yielded less accurate values for the decay parameters, which became physically unacceptable at the highest and lowest dye concentrations studied. For the DOPA multilayer systems the recovered decay parameters suggest a homogeneous distribution of the monomer and dimer molecules. On the other hand, for DPPA multilayer films a demixing leading to a two-phase system is suggested. The phase separation during compression of the mixed DPPA monolayer forms regions where almost exclusively H-like dimers are present and regions where monomers and a small amount of quenching H-like dimers coexist.

Controllable size, shape and morphology of molybdic acid self-aggregated with rhodamine B to construct functional material

“…), which have many oxidation states, especially their low oxidation states oxides or salts show many potential applications in photochromic devices [57], batteries [58][59][60], pigments [61], conductive medium adding in polymers [62] or as reducing reagents, etc. On the other hand, the RhB molecules show strong fluorescent emission at about 580 nm, thus have been fabricated photofunctional materials with other organic compounds [39,63]. Therefore, the RBMA aggregates with the shape or morphology of sphere nanoparticles, disks, hexagonal rods, networks and branches would also show the fluorescent characteristics of RhB molecules.…”

The influence of lead (II) ions introduced into the subphase on the stability of mixed "polyamic acid + surfactant" monolayers and manufacturing of dye-containing Langmuir-Blodgett polymeric films

“…In all of these cases, as well as at compression of the monolayers of N,N'-dioctadecyl rhodamine B perchlorate on pure water and on water containing varying concentrations of sodium n-dodecyl sulfate, studied by Slyadneva et al, 36 competition between dye molecules and surfactants in the monolayers is evident. However, in spite of the absorption spectra in Langmuir -Blodgett films 34 and reflection-absorption spectra in solid-condensed monolayers, 36 our above spectral data give no reliable evidence for dimer formation (see above).Tamai et al 16 reported the spectra of N,N'-dioctadecyl rhodamine B perchlorate in mixed Langmuir-Blodgett films with arachidic acid and methylarachidate, obtained on CdCl 2 -containing subphase, while Ballet et al 31 studied the multilayers of the same dye with diacylphosphatidic acid, obtained from monolayers on aqueous CaCl 2 -containing subphase (in several cases alternated by layers of cadmium arachidate). Comparison of our data with those reported by these authors allows to conclude that phase separation during compression of the mixed monolayers, resulting in dimer formation, is not typical for polymer-based system containing n-heptadecyl rhodamine B.…”

“…31 Each dye-containing monolayer was alternated with three ODA monolayers, prepared on pure aqueous subphase at π = 28 mN m -1 , using the Langmuir trough with two chutes. This allows to attribute the Vis absorption spectrum mainly to the monomeric species of the free rhodamine dye cation or ionic pair with perchlorate anion; the possible dimer formation does not manifest itself markedly, and the 'shoulder' at 520-530 nm is rather of vibrational nature.…”

“…Tamai et al 16 reported the spectra of N,N'-dioctadecyl rhodamine B perchlorate in mixed Langmuir-Blodgett films with arachidic acid and methylarachidate, obtained on CdCl 2 -containing subphase, while Ballet et al 31 studied the multilayers of the same dye with diacylphosphatidic acid, obtained from monolayers on aqueous CaCl 2 -containing subphase (in several cases alternated by layers of cadmium arachidate). Comparison of our data with those reported by these authors allows to conclude that phase separation during compression of the mixed monolayers, resulting in dimer formation, is not typical for polymer-based system containing n-heptadecyl rhodamine B.…”

Time-resolved fluorescence of cationic dyes covalently bound to poly(methacrylic acid) in rigid media

“…The kinetics of long-range electronic energy transfer between molecular probes dispersed in or chemically bound to micro-heterogeneous systems, like surfactant micelles, polymer coils in solution, micro-emulsions, nano-latex particles, and block copolymer micelles, is recognized as an efficient tool to investigate the morphology of those structures as well as their interactions with solutes at a molecular level [21][22][23][24][25][26][27]. The intrinsic distance dependence of the energy transfer process in the dipole-dipole mechanism gives information on the spatial arrangement of the acceptors around the donor, and therefore insights on the structural aspect and interactions of the nano size host particle.…”