Andrea Buzády

Time-resolved study of intramolecular energy transfer in Eu3+, Tb3+/β-diketone/o-phenanthroline complexes in aqueous micellar solutions

Abstract We found that by adding Phen to the Eu3+/TTA complexes, the luminescence intensity of Eu3+ can be increased very much. The Phen is bounded to the complexes and can be found not only in the first coordination sphere. It is an efficient shield against the quenching processes and opens a new IMET channel towards the Eu3+. Concerning the ligands, only the S1 excited state plays a role in the IMET.

Phase-fluorimetry study on dielectric relaxation of human serum albumin.

The dielectric relaxation (DR) of human serum albumin (HSA) was studied by the method of phase-fluorometry. The protein environment of the single tryptophan in HSA shows a relatively low-speed DR of sub-ns characteristic time. This relaxation can be measured as a decaying red-shift of the time-resolved fluorescence emission spectra. The details of calculations of time-emission matrices (TEM) and comparison to the fluorescence data of the reference solution of N-acetyl-L-tryptophanamide (NATA) are also presented.

Sensitized luminescence of the Eu3+/La3+/cinnamic acid mixed complex: comparison to the Eu3+/Gd3+/cinnamic acid mixed complex

Abstract The photoluminescence properties of europium and lanthanum mixed complexes with cinnamic acid are described. The maximum emission intensity is found to be at about 80% Eu 3+ /20% La 3+ content at room temperature. The roles of intramolecular and intermolecular energy transfer processes are discussed. Comparison to photoluminescence properties of Eu 3+ /Gd 3+ /cinnamic acid mixed complexes is given. A slight photochemical degradation of the samples is found, the degree of which depends on the Eu 3+ /La 3+ ratio.

Sensitized luminescence of Eu3+/Gd3+/cinnamic acid mixed complex

Abstract The photoluminescence of europium and gadolinium mixed complexes with cinnamic acid is investigated at room temperature. The maximum emission intensity is found to be at 70% Eu 3+ /30% Gd 3+ content. The probable ways of energy transfer processes are discussed on the basis of spectroscopic data. Photochemical degradation of the sample is found, the degree of which depends on the Eu 3+ /Gd 3+ ratio.

TIME-RESOLVED LUMINESCENCE OF EU(III)/THENOYLTRIFLUOROACETONE/SURFACTANT SYSTEMS IN AQUEOUS SOLUTIONS

Abstract Temporal developing of photoemission of Europium(III)-Thenoyltrifluoroacetone complex in micelle solutions was investigated. From steady-state fluorescence and phosphorescence excitation, steady-state and time-resolved emission spectra and decay curves it was found that not only 5D0 triplet level but 5D1 triplet level of Europium(III) also plays role in the energy transfer from the ligand to the Europium(III) ion.

Phase-fluorometry study on dielectric relaxation of acrylodan-labeled human serum albumin

Dielectric relaxation (DR) of acrylodan-labeled human serum albumin (HSA/AC) was studied by phase-fluorometry. A non-monoexponential behavior of both the total fluorescence--and the DR decays has been found. The protein environment of the fluorescent marker shows DR times ranging from the pico to nanosecond timescale. In fluorescence emission decays measured on the red side of the fluorescence spectrum a time constant (<10 ps) affected by a negative preexponential was found supporting the existence of DR of the excited states.

ENHANCED FLUORIMETRIC DETERMINATION OF SAMARIUM WITH DIBENZOYLMETHANE AND DIPHENYLGUANIDINE BY GADOLINIUM

Abstract The fluorescence of Sm-dibenzoylmethane (DBM)-diphenylguanidine (DPG) system was enhanced by about two to three orders of magnitude when it was excited in the presence of Gd in ethanol-water solution. The excitation and emission wavelegths were 390 nm and 652 nm, respectively. The fluorescence intensity was a linear function of the concentration of Sm in the range of 1.0 × 10−9–2.0 × 10−6 M. The fluorescence mechanism of the system is discussed.

Sensitivity Test of Derivative Matrix Isopotential Synchronous Fluorimetry and Least Squares Fitting Methods

Determination of concentrations of spectrally overlapping compounds has special difficulties. Several methods are available to calculate the constituents’ concentrations in moderately complex mixtures. A method which can provide information about spectrally hidden components in mixtures is very useful. Two methods powerful in resolving spectral components are compared in this paper. The first method tested is the Derivative Matrix Isopotential Synchronous Fluorimetry (DMISF). It is based on derivative analysis of MISF spectra, which are constructed using isopotential trajectories in the Excitation-Emission Matrix (EEM) of background solution. For DMISF method, a mathematical routine fitting the 3D data of EEMs was developed. The other method tested uses classical Least Squares Fitting (LSF) algorithm, wherein Rayleigh- and Raman-scattering bands may lead to complications. Both methods give excellent sensitivity and have advantages against each other. Detection limits of DMISF and LSF have been determined at very different concentration and noise levels.

Subpicosecond Transient Signal Spectroscopy of Prodan in Dimethylformamide Solution

We report a pump–probe experiment revealing the temporal evolution of subpicosecond evolution of Prodans excited‐state absorption in dimethylformamide. Also, we present calculation of the first spectral moment of this spectral band and estimation of different relaxation components on the subpicosecond time scale.

Relation Between Fluorescence Decays and Temporal Evolution of Excited States

A differential equation system describing the temporal evolution of excited substates and fluorescence emission were tested using a DOPRI algorithm. The numerical solutions show that there is significant difference in the measurable parameters according to the type of connectivity among the excited substates. In the globally connected case, the fluorescence emission exhibits a double exponential behavior, and the first moment of the emitted spectrum decays with stretched exponential characterized by β < 1. In the diffusive case the fluorescence emission cannot be always fitted with double exponential, and the first moment of the emitted spectrum may decay with stretched exponential characterized by β > 1. Details of modeling and the possibilities of drawing conclusions are also presented.