'Excimer’ fluorescence III. Lifetime studies of 1:2-benzanthracene derivatives in solution

1964 ◽  
Vol 277 (1369) ◽  
pp. 270-278 ◽  
Keyword(s):  
Light Source ◽  
Fluorescence Yield ◽  
Response Functions ◽  
Fluorescence Lifetimes ◽  
Concentrated Solutions ◽  
Excimer Fluorescence ◽  
Methyl Derivatives ◽  
Excimer Formation ◽  
Lifetime Studies ◽  
Monomer Fluorescence

Observations were made of the fluorescence lifetimes of 1:2-benzanthracene and fourteen of its methyl derivatives in dilute deoxygenated cyclohexane solutions. 1:2-benzanthracene and its 5-, 6- and 10-methyl derivatives were also studied in more concentrated solutions. The time response functions of the monomer and excimer fluorescence components were measured by two independent methods, namely the phase and modulation fluorometer and the pulsed light source techniques. The quantum efficiency of the monomer fluorescence in dilute solutions, and the relative excimer/monomer fluorescence yield I D I M in concentrated solutions, were also observed. The results are analyzed to determine the rate parameters of monomer and excimer fluorescence and of excimer formation and dissociation. It is found that only about half the collisions between excited and unexcited monomers result in excimer formation. This behaviour differs from that of pyrene and it is indicative of weaker excimer interaction in the 1:2-benzanthracene derivatives. The factors determining I D I M are discussed.

‘Excimer’ fluorescence - VIII. Lifetime studies of 1,6-dimethyl naphthalene

1966 ◽  
Vol 291 (1425) ◽  
pp. 244-256 ◽  
Keyword(s):  
Reaction Scheme ◽  
Pure Liquid ◽  
Intersystem Crossing ◽  
Lifetime Data ◽  
Fluorescence Lifetimes ◽  
Temperature Dependent ◽  
Concentrated Solutions ◽  
Excimer Fluorescence ◽  
Solute Interactions ◽  
Lifetime Studies

Observations were made by the pulsed light source method of the fluorescence lifetimes of 1, 6-dimethyl naphthalene solutions of 10 -4 to 6⋅4 M (pure liquid) in n -heptane from 200 to 295°K, and in cyclohexane and phenylcyelohexane at 295°K. The design and characteristics of discharge lamps containing various gases are described. For dilute solutions up to ca . 1M the lifetime data are consistent with the established monomer/excimer reaction scheme with rate parameters which are independent of concentration. For more concentrated solutions the rate parameters, notably those of internal quenching, are concentration dependent. In dilute n -heptane solution (and in the pure liquid, for which the values are in parentheses) the respective monomer and excimer rate parameters are k fM = 5x10 6 s -1 and k fD = 1⋅4 x 10 6 s -1 (2⋅2 x 10 6 s -1 ) for fluorescence, and k 0 iM = 11⋅6 x 10 6 s -1 and k 0 iD = 5⋅1 x 10 6 s -1 (4⋅2 x 10 6 s -1 ) for the temperature-independent component of intersystem crossing. The respective monomer and excimer temperature-dependent intersystem crossing rate parameters, which are influenced by solvent-solute interactions, have frequency factors of k ' iM = 2⋅7 x 10 8 s -1 and k ' iD = 6⋅0 x 10 9 s -1 (3⋅2x10 10 s -1 ) and activation energies of W iM = 0⋅11 eV and W iD = 0⋅16 eV (0⋅19 eV). Evidence is presented that k fM / k 0 iM = k fD / k 0 iD and that the excimer triplet state is dissociated. The excimer binding energy of B = 0⋅26 ± 0⋅05 eV agrees with previous spectral data.

‘Excimer’ fluorescence - X. Spectral studies of 9-methyl and 9, 10-dimethyl anthracene

1966 ◽  
Vol 291 (1427) ◽  
pp. 570-582 ◽  
Keyword(s):  
Transition Probabilities ◽  
Entropy Change ◽  
Radiative Transition ◽  
Fluorescence Yield ◽  
Concentration Quenching ◽  
Spectral Studies ◽  
Quantum Yields ◽  
Excimer Fluorescence ◽  
Excimer Formation ◽  
Monomer Fluorescence

The monomer and excimer fluorescence spectra and quantum yields of solutions of 9-methyl anthracene and 9-10-dimethyl anthracene in several solvents were observed as a function of concentration and temperature ( T ). The monomer and excimer fluorescence quantum efficiencies, the molar excimer/monomer fluorescence yield K , and the Stern–Volmer concentration quenching parameter K' , were determined at room temperature. K was observed as a function of T , and the excimer binding energy B evaluated. At high T, K for a given solute is independent of the solvent, indicating that B , ∆ S , the entropy change on excimer formation, and ( k fD ) 0 /( k fM ) 0 , the ratio of the excimer and monomer radiative transition probabilities in vacuo , are solvent-independent molecular properties. It is proposed that the excimer structure of any compound is similar to that of two adjacent molecules in the crystal lattice, with a reduced intermolecular spacing, and that the excimer fluorescence polarization is that of the 1 L a — 1 A monomer fluorescence. This model accounts for the different types of photodimerization behaviour in the meso -substituted anthracenes. It is proposed that all concentration quenching in aromatic hydrocarbons is due to the formation of excimers and/or stable photodimers.

'Excimer’ fluorescence II. Lifetime studies of pyrene solutions

1963 ◽  
Vol 275 (1363) ◽  
pp. 575-588 ◽  
Keyword(s):  
Binding Energy ◽  
Light Source ◽  
The Other ◽  
Collision Process ◽  
Excimer Fluorescence ◽  
Diffusion Controlled ◽  
Excimer Formation ◽  
The Difference ◽  
Lifetime Studies ◽  
Modulated Light

Measurements have been made of the concentration dependence of the rise and decay time characteristics of the monomer and excimer fluorescence of deoxygenated solutions of pyrene in cyclohexane at temperatures from 293 to 340 °K. Two independent methods were employed, one using a pulsed light source and a pulse-sampling oscilloscope, and the other a modulated light source and a phase and modulation fluorometer. In conjunction with observations of the monomer and excimer fluorescence quantum efficiencies, the results have been analyzed to determine the six rate parameters which describe the behaviour of the system. Values of 6.8 x 10 -7 and 0.9 x 10 -7 s are obtained for the radiative lifetimes of the monomer and excimer, respectively. Excimer formation is shown to be a diffusion-controlled collision process, in which every collision between excited and unexcited molecules is effective. From the difference in the activation energies for excimer dissociation and formation, the excimer binding energy is found to be 0.34eV.

'Excimer’ fluorescence VI. Benzene, toluene, p -xylene and mesitylene

1965 ◽  
Vol 283 (1392) ◽  
pp. 83-99 ◽  
Keyword(s):  
Binding Energy ◽  
Steric Hindrance ◽  
Fluorescence Spectra ◽  
Potential Model ◽  
Excimer Fluorescence ◽  
Benzene Toluene ◽  
Methyl Derivatives ◽  
Excimer Formation ◽  
Excitation Conditions

Observations were made of the fluorescence spectra of cyclohexane and n -hexane solutions of benzene, toluene, p -xylene and mesitylene and of the pure liquids as a function of concentration and temperature under standard excitation conditions. Excimer fluorescence is observed in benzene, toluene and mesitylene, and there is evidence for excimer formation in p -xylene. The data are analysed to determine the fluorescence quantum efficiencies, the rate parameters and other properties of the monomer-excimer systems. The following values are obtained for the excimer binding energy B ; benzene, 0.22 eV; toluene, 0.17 eV; p -xylene, > 0.11 eV; and mesitylene, 0.12 eV. The results are consistent with the excimer potential model, and the reduction in B in the methyl derivatives is attributed to steric hindrance.

‘Excimer’ fluorescence VII. Spectral studies of naphthalene and its derivatives

1965 ◽  
Vol 284 (1399) ◽  
pp. 551-565 ◽  
Keyword(s):  
Fluorescence Spectra ◽  
Entropy Change ◽  
Spectral Studies ◽  
Pure Liquid ◽  
Methyl Ethyl ◽  
Excimer Fluorescence ◽  
Mean Values ◽  
Fluorescence Characteristics ◽  
Excimer Formation ◽  
Monomer Fluorescence

The fluorescence spectra of solutions of naphthalene and fourteen of its methyl, ethyl, dimethyl and trimethyl derivatives were observed as a function of molar concentration c at 20 °C and as a function of temperature from 20 to -70 °C. All the compounds show similar excimer fluorescence characteristics with mean values of the excimer binding energy B = 0.28 ± 0.03 eV and of the excimer interaction energy V' m = 0.765 ± 0.03 eV, with the exception of 1,8-dimethyl naphthalene (B = 0.14 eV) in which excimer formation is sterically hindered. The monomer fluorescence quantum efficiencies and ionization potentials were also determined. The fluorescence spectra of liquid 1,6-dimethyl naphthalene and its solutions in three solvents were observed, and the rate parameters and the entropy change ∆ S on excimer formation were determined, B and ∆ S (= -19.1 cal mole -1 deg -1 ) have similar values in the pure liquid and in cis -decalin and dilute ( c ≤ 1 m) cyclohexane solutions, but slight differences occur in n -heptane and concentrated (c > 1 m ) cyclohexane solutions.

scholarly journals Unfolding of Helical Poly(L-Glutamic Acid) in N,N-Dimethylformamide Probed by Pyrene Excimer Fluorescence (PEF)

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1690
Author(s):  
Weize Yuan ◽  
Remi Casier ◽  
Jean Duhamel
Keyword(s):  
Glutamic Acid ◽  
Local Density ◽  
Guanidine Hydrochloride ◽  
Racemic Mixture ◽  
Excimer Fluorescence ◽  
Excimer Formation ◽  
Blob Model ◽  
Α Helix ◽  
The Relationship ◽  
Pyrene Excimer Formation

The denaturation undergone by α–helical poly(L-glutamic acid) (PLGA) in N,N-dimethylformamide upon addition of guanidine hydrochloride (GdHCl) was characterized by comparing the fluorescence of a series of PLGA constructs randomly labeled with the dye pyrene (Py-PLGA) to that of a series of Py-PDLGA samples prepared from a racemic mixture of D,L-glutamic acid. The process of pyrene excimer formation (PEF) was taken advantage of to probe changes in the conformation of α–helical Py-PLGA. Fluorescence Blob Model (FBM) analysis of the fluorescence decays of the Py-PLGA and Py-PDLGA constructs yielded the average number (<Nblob>) of glutamic acids located inside a blob, which represented the volume probed by an excited pyrenyl label. <Nblob> remained constant for randomly coiled Py-PDLGA but decreased from ~20 to ~10 glutamic acids for the Py-PLGA samples as GdHCl was added to the solution. The decrease in <Nblob> reflected the decrease in the local density of PLGA as the α–helix unraveled in solution. The changes in <Nblob> with GdHCl concentration was used to determine the change in Gibbs energy required to denature the PLGA α–helix in DMF. The relationship between <Nblob> and the local density of macromolecules can now be applied to characterize the conformation of macromolecules in solution.

‘Excimer’ fluorescence I. Solution spectra of 1:2-benzanthracene derivatives

1963 ◽  
Vol 274 (1359) ◽  
pp. 552-564 ◽  
Keyword(s):  
Quantum Yield ◽  
Crystal Lattice ◽  
Excited States ◽  
Concentration Dependence ◽  
Fluorescence Spectra ◽  
Excimer Fluorescence ◽  
Relative Quantum Yield ◽  
Relative Quantum ◽  
Different Types ◽  
Excimer Formation

Observations have been made of the concentration dependence of the fluorescence spectra of solutions of 1:2-benzanthracene and fifteen of its hydrocarbon derivatives. All of the compounds, except the 9,10-dim ethyl derivative, exhibit dim er emission at higher concentrations. The lower excited states, 1 L b and 1 L a , satisfy Förster’s conditions for fluorescent dim er formation. The factors determining the relative quantum yield of excimer fluorescence are discussed. The different types of crystal fluorescence spectra shown by the compounds are explained in terms of excimer formation in the crystal lattice.

Excimer fluorescence - XI. Solvent-solute energy transfer

1968 ◽  
Vol 303 (1472) ◽  
pp. 85-95 ◽  
Keyword(s):  
Energy Transfer ◽  
Molecular Diffusion ◽  
Dissociation Rate ◽  
Excimer Fluorescence ◽  
Transfer Distance ◽  
Diffusion Migration ◽  
Benzene Toluene ◽  
Excimer Formation ◽  
Alkyl Benzenes

The rate parameters of solvent-solute energy transfer and of oxygen-solvent quenching have been determined for solutions of 2, 5-diphenyloxazole in benzene, toluene, p -xylene and mesitylene. The role of excited molecules and excimers in transfer to the solute molecules is considered in terms of the Voltz relations, which include the Förster critical transfer distance, the molecular diffusion coefficients, and the solvent excitation migration coefficient. It is proposed that the migration is due to excimer formation and dissociation, and that the energy transfer occurs by a diffusion/migration-controlled collisional process. Dilution of the solvent decreases the migration, but increases the transfer distance, so that the transfer efficiency remains practically constant. The excimer formation and dissociation rate parameters in the pure alkyl benzenes are evaluated.

Autoregressive-Model-Based Fluorescence-Lifetime Measurements by Phase-Modulation Fluorometry Using a Pulsed-Excitation Light Source and a High-Gain Photomultiplier Tube

2009 ◽  
Vol 63 (11) ◽  
pp. 1256-1261 ◽  
Author(s):  
Tetsuo Iwata ◽  
Ritsuki Ito ◽  
Yasuhiro Mizutani ◽  
Tsutomu Araki
Keyword(s):  
Light Source ◽  
Phase Modulation ◽  
High Gain ◽  
Ar Model ◽  
Fluorescence Lifetimes ◽  
Excitation Light ◽  
Pulsed Excitation ◽  
Model Based ◽  
Analysis Technique ◽  
Load Resistor

We propose a novel method for measuring fluorescence lifetimes by use of a pulsed-excitation light source and an ordinary or a high-gain photomultiplier tube (PMT) with a high-load resistor. In order to obtain the values of fluorescence lifetimes, we adopt a normal data-processing procedure used in phase-modulation fluorometry. We apply an autoregressive (AR)-model-based data-analysis technique to fluorescence- and reference-response time-series data obtained from the PMT in order to derive plural values of phase differences at a repetition frequency of the pulsed-excitation light source and its harmonic ones. The connection of the high-load resistor enhances sensitivity in signal detection in a certain condition. Introduction of the AR-model-based data-analysis technique improves precision in estimating the values of fluorescence lifetimes. Depending on the value of the load resistor and that of the repetition frequency, plural values of fluorescence lifetimes are obtained at one time by utilizing the phase information of harmonic frequencies. Because the proposed measurement system is simple to construct, it might be effective when we need to know approximate values of fluorescence lifetimes readily, such as in the field of biochemistry for a screening purpose.

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