Local Dye Concentration and Spectroscopic Properties of Monomer–Aggregate Systems in Hybrid Porous Nanolayers

Abstract

Analysis of absorption, fluorescence, and time-resolved emission spectra of rhodamine 6G in hybrid porous nanolayers at high dye concentration allowed identification of two fluorescent species: monomers and fluorescent aggregates. The method of determination of mean local concentration of aggregates in matrices is proposed based on the energy transfer process between monomers and fluorescent aggregates. Evaluation of aggregate mean local concentration was carried out by comparing the results of Monte Carlo simulation of forward and reverse nonradiative energy transfer between monomers and aggregates with experimental data of fluorescence decay in which monomer and aggregate concentration were treated as best fit parameters.

Photochemistry and Photophysics in Silica-Based Materials: Ultrafast and Single Molecule Spectroscopy Observation

“…Only the caged monomer was observed, and it emits with a longer lifetime than Py in solutions (3 vs 2 ns, respectively), reflecting the rigidity that the matrix imposes on the monomer movement, limiting then its nonradiative processes (Figure B) . Similar behavior was reported for rhodamine dyes. ,,− ,− When R6G (Scheme ) intercalates into solid thin films of laponite (Lap) clay, it tends to self-aggregate, resulting in trapped H- and J-aggregates. , Under very diluted conditions, only the R6G monomer was observed, with an absorption band centered at 528 nm and an emission one at 548 nm. , The average lifetime of the monomer is 4.2 ns, which is slightly longer than in ethanol solution (3.95 ns) and reflects the weak confinement effect on the emission decays of the inorganic nanostructured material. , When R6G concentration increases, H- and J-aggregates are formed. , Their gradual formation is evidenced by the quenching of the fluorescence signal and progressive decrease in the average emission lifetime from 4.2 ns (average lifetime in diluted solutions) to 0.45 ns (average lifetime in concentrated solutions) . These results show that the ratio of H- to J-aggregates increases with the increased dye loading .…”

New Core-Shell Nanostructures for FRET Studies: Synthesis, Characterization, and Quantitative Analysis

“…The Monte-Carlo method has been successfully applied to simulate stochastic processes (for a broad review see [ 41 ]). Mention should be made that in a Monte-Carlo simulation we can obtain not only information on the experimentally accessible observables like the donor fluorescence intensity decay, but also non-measurable quantities, for example the mean number of excitation energy jumps among molecules, the mean squared displacement of excitation energy or the local concentrations of fluorophores in various systems to characterize in depth multistep energy migration [ 35 , 42 , 43 ].…”

“…In this paper we used so called “step by step” method which makes use of the random-number generator for the cyclic formulation of answers to two questions: when any of the given fluorescent processes takes place and what kind of a process it is. The detailed simulation algorithms are based on the Gillespie procedure [ 44 ], further developed and adapted to describe the energy migration and transfer phenomena in disordered concentrated two component systems [ 35 , 36 , 45 , 46 ], uniaxially oriented polymer films [ 47 , 48 ], polypeptides labeled with multiple fluorophores [ 11 , 49 ], porous nanolayers [ 42 , 43 ], and core-shell spherical nanoparticles [ 24 ]. This paper closely follows the algorithm presented in [ 44 ] and modified in [ 24 , 45 ].…”

Fused π-conjugated imidazolium liquid crystals: synthesis, self-organization, and fluorescence properties

“…S52 in ESI, † s ¼ 2.21 ns) indicating the effective trap of excitation energy. 15 It was found from the gure, however, the decay curve excited at 375 nm and monitored at 550 nm (green line) was composed of s ¼ 6.76 ns. The longer lifetime is likely attributable to the excimer-like emission of uorophores.…”