Lifetime Decay Curves Research Articles

Long‐lasting phosphorescence properties of Mn2+‐doped Cd2Ge7O16 orange light‐emitting phosphor

AbstractA new phosphor, Cd2Ge7O16:Mn2+, which emits orange‐coloured long‐lasting phosphorescence upon UV light excitation, was prepared by the conventional high‐temperature solid‐state method and its luminescent properties were systematically investigated. X‐ray diffraction, photoluminescence and thermoluminescence spectra and lifetime decay curves were used to characterize the synthesized phosphor. This phosphor is well‐crystallized by calcination at 950 °C for 6 h and shows excellent performance. After irradiation under 258 nm UV light, this phosphor emits a broad band centred at 585 nm and shows obvious long‐lasting phosphorescence. The colour coordinate values of this phosphor are x = 0.56, y = 0.46. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Laser-Induced Phosphorescence for Surface Thermometry in the Afterburner of an Aircraft Engine

In the present work, surface thermometry using a method based on the spectroscopy of inorganic luminescent material was applied in the afterburner of a full-size aircraft jet engine. The technique uses laser-induced emission from thermographic phosphors for nonintrusive remote temperature diagnostics in combustion applications with high sensitivity and accuracy. A phosphor material having suitable temperature sensitivity in the expected temperature range was applied to the surface of interest in the engine afterburner. Phosphorescence radiation was generated using the forth harmonic (266 nm) from a pulsed Nd:YAG laser. The resulting signal was detected with a photomultiplier tube and phosphorescence lifetime decay curves were recorded for various engine loads, including operation of the afterburner. By analyzing the phosphorescence decay, temperature data were acquired through implementation of a regression equation extracted from well-defined calibration measurements on the phosphor used. Quantitative temperature data recorded with a repetition rate of 10 Hz are presented. The laser-induced phosphorescence technique for surface thermometry has proven its applicability in the extremely harsh environment prevailing inside and next to a jet engine operating at full load. (Less)

Characterization of DNA–dye complexes on nanostructure arrays

Abstract The binding of dimethyldiazaperopyrenium dication with Calf Thymus DNA has been studied by atomic force and optical microscopy. We obtained bulk and single dye-intercalating DNA’s fluorescence lifetime decay curves and lifetime distributions. We placed the DNA–dye complexes into different sizes of nanostructures which were prepared on cover glasses using PDMS and UV-curing polyurethane materials. The correlation with dye-intercalating DNA complexes and patterns were observed by acquiring AFM images of nano- and micropatterned cover glasses and DNA–dye complexes. According to the size of channel width, DNA–dye complexes show multiformity. We acquired lifetime images and distributions of dye-intercalating DNA complexes coated on cover glasses using time-correlated confocal fluorescence microscope apparatus. We also obtained information of surface topology and 2D images of fluorescence lifetime at the same area in a continuous series.

Sol–gel-immobilised terbium complexes for luminescent sensing of dissolved oxygen by analysis of emission decayElectronic supplementary information (ESI) available: examples of the analysis of the emission decay data for calibration purposes and examples of data sets and their treatment at different delay times. See http://www.rsc.org/suppdata/nj/b1/b110743g/

Cationic terbium complexes bearing an N-methylphenanthridinium chromophore have been incorporated in sol–gel thin films and their response characteristics analysed with respect to variations in dissolved oxygen concentration. Analysis of the emission lifetime decay curves (547 nm) has allowed a linear calibration model to be defined over an oxygen concentration range from zero to 0.5 mM (H2O, 295 K).

A computer program for the simulation of Boxcar Integrator and Averager system in luminescence decay kinetic experiments

A computer program for simulation of the SR250 Boxcar Integrator & Averager system and a pulsed laser-luminescence spectrometer in excited-state kinetic experiments is presented. This program is very useful for both (1) a quantitative optimization of all instrumental parameters such as the laser repetition rate, gate scan time, gate width, scan width, number of samples averaged and RC time constants from cables, termination and other coupled instruments, in order to minimize the RC distortion on the lifetime decay curves obtained from such experiments; and (2) a direct determination of the best delay time range in the experimental luminescence decay curve where the excited-state lifetime could be extracted with accuracy.

Linear and non-linear approaches to solve the inverse problem: applications to positron annihilation experiments

We present linear and non-linear filters to solve the ill-posed inverse problem and we use them to extract relevant information from positron lifetime and 2D-angular correlation of the annihilation radiation of positrons in solids. A general optimal linear filter is first derived. Then a second linear approach, based on Bayes' theorem, is described. We show that these two linear approaches are indeed equivalent. Two non-linear methods are then discussed. The first is a Bayesian approach which makes use of the maximum entropy principle. The second is an iterative method derived from the general optimal linear filter. Applications of these filtering techniques to positron lifetime decay curves illustrate how lifetimes shorter than the instrumental resolution can be extracted. Finally, we apply the iterative non-linear filter to the problem of the ridge-like Fermi surface on the high temperature superconducting compound YBa 2Cu 3O 7−δ. For the first time a direct measurement of the ridge width through a Brillouin zone is obtained. It is compared with results of band structure calculations.

Physical characterization of cyclosporine binding sites in lymphocytes

The binding of cyclosporine to human peripheral blood lymphocytes (PBLs) was studied by measuring the fluorescence emission spectrum and lifetime of the fluorescent and immunosuppressive cyclosporine derivative dansyl-cyclosporine (DCs). The emission maximum and fluorescence lifetime of DCs were characterized in several solvents. The fluorescence emission maximum and lifetime of DCs increased at a high dielectric constant. The fluorescence lifetime decay curve of DCs was a monoexponential function in all solvents tested. Fluorescence micrographs of lipid vesicles and erythrocytes labeled with DCs exhibit uniform staining patterns, whereas PBLs show heterogeneous DCs labeling. DCs exhibits a relatively low emission maximum (490 nm) in erythrocyte membranes. Such an emission maximum is characteristic of a hydrophobic environment. DCs in PBLs also has a low emission maximum (484 nm). The lifetime of DCs in PBLs required two exponential terms to properly fit the lifetime decay curve and could not be attributed to light scattering. One short component (4.7 +/- 1.0 ns) and a second long component (18.5 +/- 1.0 ns) were resolved from the DCs fluorescence decay curves. Time-resolved anisotropy of DCs in PBLs revealed that the labeled drug was present in an anisotropic environment, consistent with at least some DCs being bound to a membrane. These fluorescence studies suggest that DCs interacts with multiple and/or heterogeneous sites in peripheral blood lymphocytes.

Investigation of Eu(III) Binding Sites on Datura Innoxia Using Eu(III) Luminescence

A pulsed tunable dye laser has been used to obtain excitation spectra and fluorescence decay curves of solid Eu(III)- Datura innoxia and from a series of Eu(III)-containing complexes. Carboxyl and sulfate groups have been demonstrated to be the dominant functional groups for forming binding sites on the cell wall of Datura innoxia at high (≥4) and low (≤3) pH conditions, respectively. The excitation spectra associated with the 7 F0 → 5 D0 electronic transition of Eu(III) luminescence have been used to provide a measure of the electronic structure factors contributing to the interaction between Eu(III) ions and the binding sites on the cell wall of D. innoxia. The noticeably broadened and asymmetric excitation spectra obtained at high pH conditions are ascribed to multiple binding sites. The corresponding lifetime decay curves exhibited a bi-exponential decay. A pK of 4.5 was determined for the binding of Eu(III) to the cell wall at pH ≥4. Kinetic and thermodynamic studies were also undertaken.