Fluorescence Quenching and Solvation Processes of Fluorenone and 4-hydroxyfluorenone in Binary Solvents

2003 ◽  
Vol 58 (2-3) ◽  
pp. 144-156 ◽  
Author(s):  
M. Jozefowicza ◽  
J. R. Heldt ◽  
J. Karolczak ◽  
J. Heldt
Keyword(s):  
Hydrogen Bond ◽  
Photophysical Properties ◽  
Equilibrium Constants ◽  
Mixed Solvents ◽  
Emission Spectra ◽  
Fluorescence Decay ◽  
Binary Solvents ◽  
Time Resolved ◽  
Decay Times ◽  
Fluorescence Light

Steady state and time-resolved spectroscopic measurements of fluorenone and 4-hydroxyfluorenone dissolved in binary nonpolar, polar and polar protic mixed solvents have been performed at room temperature. The absorption and emission spectra show that, apart from the free molecules, hydrogen bond complexes exist in the ground and excited states in the mixed solvents used. The data obtained were used to determine the stoichiometric equilibrium constants. The fluorescence decay data point that in the binary used solutions the radiation appears from an assembly of luminescence centers emitting fluorescence light of different wavelengths and decay times. Molecules forming simple hydrogen bond complexes (with fluorenone) show different photophysical properties from those where a proton-relay complex (with 4-hydroxyfluorenone) is established.

Synthesis and Photophysical Properties of a Conformationally Flexible Mixed Porphyrin Star-Pentamer

2009 ◽  
Vol 62 (7) ◽  
pp. 692 ◽  
Author(s):  
Toby D. M. Bell ◽  
Sheshanath V. Bhosale ◽  
Kenneth P. Ghiggino ◽  
Steven J. Langford ◽  
Clint P. Woodward
Keyword(s):  
Energy Transfer ◽  
Photophysical Properties ◽  
Fluorescence Decay ◽  
High Yield ◽  
Free Base ◽  
Time Resolved ◽  
Zinc Porphyrin ◽  
Relative Contribution ◽  
Synthetic Strategy ◽  
Decay Times

The synthesis of a porphyrin star-pentamer bearing a free-base porphyrin core and four zinc(ii) metalloporphyrins, which are tethered by a conformationally flexible linker about the central porphyrin’s antipody, is described. The synthetic strategy is highlighted by the use of olefin cross metathesis to link the five chromophores together in a directed fashion in high yield. Photoexcitation into the Soret absorption band of the zinc porphyrin chromophores at 425 nm leads to a substantial enhancement of central free-base porphyrin fluorescence, indicating energy transfer from the photoexcited zinc porphyrin (outer periphery) to central free-base porphyrin. Time-resolved fluorescence decay profiles required three exponential decay components for satisfactory fitting. These are attributed to emission from the central free-base porphyrin and to two different rates of energy transfer from the zinc porphyrins to the free-base porphyrin. The faster of these decay components equates to an energy-transfer rate constant of 3.7 × 109 s–1 and an efficiency of 83%, whereas the other is essentially unquenched with respect to reported values for zinc porphyrin fluorescence decay times. The relative contribution of these two components to the initial fluorescence decay is ~3:2, similar to the 5:4 ratio of cis and trans geometric isomers present in the pentamer.

Novel Electric Responsive Columnar Liquid Crystals based on Perylene Tetra sec-alkyl Ester Derivatives

2013 ◽  
Vol 66 (6) ◽  
pp. 692 ◽  
Author(s):  
Lei Wang ◽  
Qing Cui ◽  
Xiao-Fang Chen ◽  
Yang Li ◽  
Zheng-Qiang Li ◽  
...  
Keyword(s):  
Electric Field ◽  
Molecular Orbital ◽  
Indium Tin Oxide ◽  
Photophysical Properties ◽  
Mixed Solvents ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Mirror Image ◽  
Alkyl Ester ◽  
Fluorescence Emission Spectra

A series of novel perylene tetra sec-alkyl ester compounds were successfully designed and synthesised. The photophysical properties were investigated and the UV absorption and fluorescence emission spectra displayed a mirror-image relationship. The compound PS8 showed the highest fluorescent quantum yield, while the fluorescence of PS8 was quenched in the aggregated state in mixed solvents. Moreover, the electrochemical properties of the perylene derivatives were studied to determine the molecules’ highest occupied molecular orbital and lowest unoccupied molecular orbital levels by cyclic voltammetry. The most important result was that PS8 exhibited a columnar phase at room temperature and was responsive to an electric field. PS8 could perpendicularly orient to an applied electric field. In addition, highly oriented face-on alignment was achieved on indium tin oxide-covered glass by thermal annealing.

scholarly journals Probing Local Environments by Time-Resolved Stimulated Emission Spectroscopy

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Ana Rei ◽  
Graham Hungerford ◽  
Michael Belsley ◽  
M. Isabel C. Ferreira ◽  
Peter Schellenberg
Keyword(s):  
Emission Spectroscopy ◽  
Sol Gel ◽  
Fluorescence Emission ◽  
Local Environment ◽  
Fluorescence Decay ◽  
Stimulated Emission ◽  
Binary Solvents ◽  
Time Resolved ◽  
Local Environments ◽  
Lower Viscosity

Time-resolved stimulated emission spectroscopy was employed to probe the local environment of DASPMI (4-(4-(dimethylamino)styryl)-N-methyl-pyridinium iodide) in binary solvents of different viscosity and in a sol-gel matrix. DASPMI is one of the molecules of choice to probe local environments, and the dependence of its fluorescence emission decay on viscosity has been previously used for this purpose in biological samples, solid matrices as well as in solution. The results presented in this paper show that time-resolved stimulated emission of DASPMI is a suitable means to probe the viscosity of local environments. Having the advantage of a higher time resolution, stimulated emission can provide information that is complementary to that obtained from fluorescence decay measurements, making it feasible to probe systems with lower viscosity.

Concentration and Temperature Dependence of Laurdan Fluorescence in Glycerol

2003 ◽  
Vol 58 (9-10) ◽  
pp. 581-588 ◽  
Author(s):  
K. A. Kozyra ◽  
J. R. Heldt ◽  
J. Heldt ◽  
M. Engelkec ◽  
H. A. Diehl
Keyword(s):  
Steady State ◽  
Time Distribution ◽  
Emission Spectra ◽  
Fluorescence Decay ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Fluorescence Decay Time ◽  
Laurdan Fluorescence ◽  
Vibrational Equilibrium

Steady-state and time-resolved fluorescence measurements have been performed on Laurdan, dissolved in viscous glycerol, as functions of temperature and concentration. The results indicate spectral heterogeneity of the Laurdan solution. The fluorescence decay time distribution is attributed to radiative deexcitation of spatial conformational forms of locally excited (LE) and charge transfer (CT) states, the S1(CT)EQ state being in thermodynamic and vibrational equilibrium. The lifetimes and contributions of the different fluorescence modes depend on concentration and temperature. The excitation and emission spectra show discontinuous changes with increase of the Laurdan concentration.We suppose that the observed changes are caused by the formation of Laurdan micelle aggregates.

Time resolved fluorescence of aqueous tryptophan

1978 ◽  
Vol 56 (5) ◽  
pp. 743-745 ◽  
Author(s):  
D. M. Rayner ◽  
A. G. Szabo
Keyword(s):  
Exponential Decay ◽  
Emission Spectra ◽  
Fluorescence Decay ◽  
Time Resolved Fluorescence ◽  
Decay Function ◽  
Time Resolved ◽  
Exponential Decay Function

The fluorescence decay of aqueous tryptophan is shown to be described by a two exponential decay function whose components have life-times of 3.14 ns and 0.51 ns. These components are assigned as the solvent equilibrated 1La and 1Lb, states respectively. The time-resolved emission spectra are presented and can be resolved into two spectra with λmax at 350 nm and 335 nm corresponding to these two states.

scholarly journals 2-aminopurine as a fluorescent probe of DNA conformation and the DNA–enzyme interface

2015 ◽  
Vol 48 (2) ◽  
pp. 244-279 ◽  
Author(s):  
Anita C. Jones ◽  
Robert K. Neely
Keyword(s):  
Fluorescent Probe ◽  
Fluorescence Intensity ◽  
Photophysical Properties ◽  
Fluorescence Decay ◽  
Structural Isomer ◽  
Time Resolved ◽  
Use Of Time ◽  
Fluorescence Measurements ◽  
Natural Base ◽  
Decay Parameters

AbstractNearly 50 years since its potential as a fluorescent base analogue was first recognized, 2-aminopurine (2AP) continues to be the most widely used fluorescent probe of DNA structure and the perturbation of that structure by interaction with enzymes and other molecules. In this review, we begin by considering the origin of the dramatic and intriguing difference in photophysical properties between 2AP and its structural isomer, adenine; although 2AP differs from the natural base only in the position of the exocyclic amine group, its fluorescence intensity is one thousand times greater. We then discuss the mechanism of interbase quenching of 2AP fluorescence in DNA, which is the basis of its use as a conformational probe but remains imperfectly understood. There are hundreds of examples in the literature of the use of changes in the fluorescence intensity of 2AP as the basis of assays of conformational change; however, in this review we will consider in detail only a few intensity-based studies. Our primary aim is to highlight the use of time-resolved fluorescence measurements, and the interpretation of fluorescence decay parameters, to explore the structure and dynamics of DNA. We discuss the salient features of the fluorescence decay of 2AP when incorporated in DNA and review the use of decay measurements in studying duplexes, single strands and other structures. We survey the use of 2AP as a probe of DNA-enzyme interaction and enzyme-induced distortion, focusing particularly on its use to study base flipping and the enhanced mechanistic insights that can be gained by a detailed analysis of the decay parameters, rather than merely monitoring changes in fluorescence intensity. Finally we reflect on the merits and shortcomings of 2AP and the prospects for its wider adoption as a fluorescence-decay-based probe.

Optical Properties and Characterization of Eu3+ Activated Pmma:Paac Copolymer Samples: Eu Concentration Effects

1999 ◽  
Vol 560 ◽  
Author(s):  
R. Sosa F. ◽  
M. Flores ◽  
R. Rodríguez T. ◽  
A. Munoz F.
Keyword(s):  
Optical Properties ◽  
Emission Spectra ◽  
Spectroscopic Properties ◽  
Fluorescence Decay ◽  
Polymerization Process ◽  
Concentration Effects ◽  
Visible Absorption ◽  
Properties And Characterization ◽  
Decay Times ◽  
Fluorescence Decay Times

ABSTRACTSamples of Eu3+ -activated PMMA:PAAc copolymers were prepared in order to investigate their spectroscopic properties. The densities, refractive indices, UV-Visible absorption and emission spectra and fluorescence decay times were obtained experimentally. These data were used in conjunction with Judd-Ofelt theory to calculate the spontaneous emission probabilities and branching ratios, as a function of the europium content. The range of the concentration was 0.1 to 2.5 % mol. Our results are combined with previous information on the optical properties of rare-earth activated polymers in order to get a better understanding of the role played by the Eu3+ ions on the polymerization process in our samples.

Tyrosine and tyrosinate fluorescence of S-100b. A time-resolved nanosecond fluorescence study. The effect of pH, Ca(II), and Zn(II)

1989 ◽  
Vol 67 (4-5) ◽  
pp. 179-186 ◽  
Author(s):  
R. J. Turner ◽  
R. S. Roche ◽  
R. S. Mani ◽  
C. M. Kay
Keyword(s):  
Metal Ion ◽  
Tertiary Structure ◽  
Emission Spectra ◽  
Fluorescence Decay ◽  
Time Resolved Fluorescence ◽  
Fluorescence Study ◽  
Time Resolved ◽  
Effect Of Ph ◽  
Class A ◽  
Long Lifetime

The properties of the tyrosine and tyrosinate emissions from brain S-100b have been studied by nanosecond time-resolved fluorescence at emission wavelengths in the range 305 to 365 nm. The effect of pH on the fluorescence has been studied at pH 6.5, 7.5, and 8.5 for the Ca(II) apo and holo forms of the protein, and for the apo and holo forms in the presence and absence of Zn(II) at pH 7.5. The fluorescence decay is biexponential at pH 8.5 and triexponential at pH 6.5 and 7.5. The three components of the decay have wavelength and metal ion dependent lifetimes in the ranges 0.06 to 1.05 ns, 0.49 to 3.76 ns, and 3.60 to 14.5 ns. The observation of a long lifetime component at wavelengths characteristic of emission from tyrosinate suggests that in class A proteins this may be a useful diagnostic of the environment of tyrosine in their native structures. The time-resolved emission spectra provide evidence for efficient, subnanosecond protolysis of the excited state of the single tyrosine (Tyr17) under all conditions studied except in 6 M guanidium chloride in which the protein shows only emission from tyrosine (λem 305 nm), suggesting that the tyrosinate emission is a property of the tertiary structure of the native protein. The Zn(II)-dependence of the fluorescence is fully consistent with the earlier suggestion that Tyr17 is near the Zn(II) binding site and remote from the high affinity Ca(II) binding site.Key words: S-100b, time-resolved fluorescence, tyrosinate fluorescence, time-resolved emission spectra.

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