Temperature dependence fluorescence

Ross D, Gaitan M, Locascio LE (2001) Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. Anal Chem 73 4117-4123 Sammarco TS, Bums MA (1999) ThermocapiUary pumping of discrete drops in microfabricated analysis devices. AlChE J 45 350-366... 

The present experiments are mute as to the timescale on which delocalization may occur. EPR results on Ru(bpy)"5 demonstrate localization of the bpy electron density in this Ru(II)(bpy)2 (bpy )+ species on the EPR timescale, but suggest that delocalization may occur on a timescale only slightly longer. It is possible that either time-resolved EPR or temperature dependent fluorescence depolarization experiments may establish the time-scale of localization in Ru(bpy) +. 

A variety of fiber optic thermometry systems using fluorescence sensors have been discussed or become available over the past years. Most of the earliest systems are based on the temperature-dependent fluorescence intensity of appropriate materials. One such example of an early commercial system is the Luxtron model 1000, shown in Figure 11.2, which utilized europium-activated lanthanum and gadolinium... 

The motions of chromophore groups and of their environment that lead to temperature-dependent fluorescence quenching are those on the nanosecond time scale. Slower motions cannot manifest themselves in effects on the excited-state lifetime (this corresponds to the limit of high viscosity). On the other hand, if the motions are considerably faster (on the picosecond time scale), then they should give rise to static quenching. 

TABLE 27 Adiabatic Photolytic Cycloreversion of Lepidoptereue iu Methylcyclohexane/isopentane upon Excitatiou at 274 um. Temperature Dependent Fluorescence Quantum Yields and Lifetimes [134 ... 

Time resolved synchrotron spectroscopy of excited fluorescence of anthracene single crystals has been published and the time resolved and temperature dependent fluorescence spectra of anthracene and pyrene in both the liquid and crystalline reported states Excimer emission is observed. 

A study of the photochemical addition of 2,3-dimethylbut-2-ene to the furocoumarin derivatives (117-119) has sought to establish an order of reactivity for the cycloaddition of alkenes to the enone double bond. The (2+2) adduct (120) exhibits temperature dependent fluorescence. ... 

A plot of the temperature-dependent fluorescence decay time as a function of 3 MeV proton fluence is shown in Fig. The error bars shown in Fig. 12... 

Figure 6. Temperature dependent fluorescence for a film of pure polystyrene.

Fig. 10.12. Cell for temperature dependent fluorescence EXAFS measurements of liquids wilh soli X-rays. The cell eonsi.sts of holder (1). window flange (2), double-sided flange (.3) containing Ihe liquid sample, blind flange t4). thermocouple (5), cartridge heater (6), copper gaskets (8), screw bolls (9) and polymer coated beryllium window (10). During the experiment, die cell is mounted on the cold linger (7) of a sample maiiipu-lalor I lOHl.

The temperature-dependent fluorescence polarization data for HP in DPPC liposomes loaded with increasing concentrations of Choi have an interesting interpretation. At high concentrations, HP was distributed close to the inner polar headgroups, which was confirmed by a low critical value of phase transition for DPPC at 31°C rather than the typical temperature at T = 41°C. However, when 20% Choi was added a depolarization effect was observed because HP was at the aqueous interface and was not sensitive to changes in the lipid domain. Increasing the Choi concentration further caused a redistribution of HP into the lipid domains and phase transitions were observed. The HP redistribution is attributed to a shift in Choi distribution in DPPC. As expected and observed, further increase in Choi concentration (55%) results in total inhibition of phase transitions in DPPC due to increased rigidity. These studies show that photosensitizers such as HP and PP are important probes in liposomes and mixed liposome systems. 

Optical spectroscopy of Er " doped into bulk AIN ceramics has been reported [296]. The material was prepared by using hot press sintering of AIN with Et203 and (NH4)(ErE4), which yielded fully dense, translucent, hexagonal AIN. The Er concentration was a small fraction of a percent, and resided in multiple sites, with one type of center dominant. A number of the energy levels of Er " were identified for this center. The temperature dependent fluorescence lifetime was probably radiative, with which the stimulated emission and absorption cross section spectra were derived for the " I... 

For temperature measurement by single-dye fluorescence, the temperature sensitivity of a dye, specifically its quantum efficiency, effectively defines the temperature resolution of the measurement itself. Rhodamine B is the most common temperature-dependent fluorescent dye used in both macro- and microscale liquid applications because of its relatively strong temperature sensitivity of 2.3 % in water over a temperature range of 0-120 °C. This dye is also soluble in many other organic solvents, like ethanol, making it a practical choice in a variety of microfluidic applications. Moreover, its absorption spectrum is rather broad (470-600 nm with a peak at 554 nm), meaning it can be readily excited with conventional illumination sources like mercury-arc lamps as well as argon-ion (continuous) and Nd YAG (pulsed) lasers. Further, its emission spectrum is also... 

Temperature measurement at the microscale by single-dye fluorescence was first accomplished by Ross et al. [6] using RhB as the temperature-dependent fluorescent dye and a mercury-arc lamp for illumination. Ross et al. [6] conducted measurements of fluid temperature distributions resulting from Joule heating in a microfluidic... 

Katraro R, Ron A, Speiser S (1979) Photophysical studies of coronene and 1,12-benzperylene. Self-quenching, photoquenching, temperature dependent fluorescence decay and temperature dependent electronic energy transfer to dye acceptors. Chem Phys 42 121-132V... 

Kemnitz K., Yoshihara K. Entropy-driven dimerization ofxanthene dyes in nonpolar solution and temperature-dependent fluorescence decay of dimers. J. Phys. Chan. 1991 95 6095-6104 and... 

T is a constant over the range of temperature investigated. This assumption has often been used when the temperature-dependent fluorescence spectra are characterized by an isoemissive point. In somes cases, is temperature-dependent despite the existence of the isoemissive point (2). Thus, taking the 1 / ratio as proportional to may lead to incorrect conclusions aDOut the matrix mobility. Only transient measurements allow a quantitative determination of the dynamic properties of the probe. 

Fig. 9- Temperature-dependent fluorescence spectra of meso-BIPEE in polybutadiene...

There are many possible explanations as to why the fluorescence intensity is temperature dependent. Fluorescent chromophores generally exhibit a redurtion in their fluorescence intensity with increasing temperature due to the increased thermal energy and the concomitant increase in the rate of the nonradiative decay of the chromophore from the excited state back down to the ground state. Shortened excited states lead to a decrease in the fluorescence intensity with increasing temperature. That the temperature dependence of these decay processes is different above and below Tg seems reasonable, given the fart that polymer dynamics in the two... 

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