scholarly journals Cylindrical aggregates of 5,5',6,6'-tetrachlorobenzimida-carbocyanine amphiphilic derivatives: Structure-related optical properties and exciton dynamics

2006 ◽  
Vol 2006 ◽  
pp. 1-9 ◽  
Author(s):  
A. Pugzlys ◽  
P. R. Hania ◽  
R. Augulis ◽  
K. Duppen ◽  
P. H. M. van Loosdrecht
Keyword(s):  
Linear Dichroism ◽  
Outer Wall ◽  
Basic Structure ◽  
Fluorescence Decay ◽  
Collective Effects ◽  
Absorption Bands ◽  
Time Resolved ◽  
Pump Probe ◽  
Fluorescence Measurements ◽  
Energy Transfers

The static and time-resolved optical response of5,5′,6,6′-tetrachlorobenzimidacarbocyanine chromophore-based tubular double-wall molecular aggregates is studied. The linear dichroism and absorption spectra have the same basic structure for all aggregates investigated essentially showing a set of narrow and highly polarized bands originating from inner and outer wall excitations. The exact positions and strengths of absorption bands are influenced by the choice of side groups and various additives. Time-resolved fluorescence measurements show a substantial speeding of the fluorescence decay upon aggregation, mainly resulting from collective effects. Pump-probe experiments evidence slow inner-to-outer and fast outer-to-inner wall energy transfers between the walls of the tubules.

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.

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.

Time-Resolved Fluorescence Studies of Hematoporphyrin in Different Solvent Systems

1983 ◽  
Vol 38 (1-2) ◽  
pp. 83-89 ◽  
Author(s):  
A. Andreoni ◽  
R. Cubeddu ◽  
S. De Silvestri ◽  
G. Jori ◽  
P. Laporta ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Organic Solvents ◽  
Slow Component ◽  
Fluorescence Decay ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Fluorescence Studies ◽  
Fluorescence Measurements ◽  
Dimeric Form ◽  
Solvent Systems

Time-resolved fluorescence studies of hematoporphyrin in aqueous solution and in different organic solvents are presented. The| observation of two exponential components in the fluorescence decay in aqueous solution reveals the presence of a monomeric and aggregated (probably dimeric) form of the molecule, as confirmed by absorption and fluorescence measurements. The slow component (~ 15 ns in aqueous solution) and the fast one (~ 3.8 ns in aqueous solution) are attributed to monomers and dimers, respectively. Higher aggregated species of hematoporphyrin are also present, which are essentially devoid of fluorescence properties.

Photoinduced intermolecular Charge-Transfer Systems for Optical Limiting

1997 ◽  
Vol 479 ◽  
Author(s):  
X.-L. Wu ◽  
A. A. Heikal ◽  
I.-Y. S. Lee ◽  
M. Bohorquez ◽  
J. W. Perry
Keyword(s):  
Charge Transfer ◽  
Laser Pulses ◽  
Optical Limiting ◽  
Nanosecond Laser ◽  
Absorption Bands ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Intermolecular Charge Transfer ◽  
Ion Absorption ◽  
Donor Acceptor

AbstractPhotoinduced intermolecular charge transfer (PICT) in donor/acceptor systems has been investigated as an approach to the design of new optical limiting (OL) materials. Solution of cyanines or porphyrins (as sensitizers) and viologen derivatives (as electron acceptors) were used in these studies. Picosecond time-resolved fluorescence measurements were carried out to estimate the charge-transfer rate in these donor/acceptor systems. The radical-ion absorption bands were identified using spectroelectrochemistry. Nonlinear transmission measurements with picosecond and nanosecond laser pulses were utilized to determine the effective photo-induced to ground-state absorption cross-section ratio of the sensitizers alone and the sensitizer/acceptor systems. Our studies are consistent with optical limiting by PICT in solution and indicate a substantial radical-ion yield in the systems examined.

Pump-Probe Measurements Using Silicon Nanocrystal Waveguides

2003 ◽  
Vol 770 ◽  
Author(s):  
Nathanael Smith ◽  
Max J. Lederer ◽  
Marek Samoc ◽  
Barry Luther-Davies ◽  
Robert G. Elliman
Keyword(s):  
Probe Beam ◽  
Time Resolution ◽  
Pump Beam ◽  
Silicon Nanocrystals ◽  
Continuous Wave ◽  
Optical Gain ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Measurements

AbstractOptical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.

scholarly journals Architecture of Polyglutamine-containing Fibrils from Time-resolved Fluorescence Decay

2014 ◽  
Vol 289 (39) ◽  
pp. 26817-26828 ◽  
Author(s):  
Christoph Röthlein ◽  
Markus S. Miettinen ◽  
Tejas Borwankar ◽  
Jörg Bürger ◽  
Thorsten Mielke ◽  
...  
Keyword(s):  
Fluorescence Decay ◽  
Time Resolved Fluorescence ◽  
Time Resolved

Investigation on nonlinear dynamics of ZnO using time-resolved pump-probe technique with phase object

2011 ◽  
Author(s):  
Lirong Ge ◽  
Min Shui ◽  
Xiao Jin ◽  
Zhongguo Li ◽  
Yinglin Song
Keyword(s):  
Nonlinear Dynamics ◽  
Phase Object ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Technique

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.

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