Probes phosphorescent

A similar phenomenon may be observed even when BrNp is free to diffuse into and out of the CD bucket. Turro et al. have modified 4-BrNp with protecting, (n-alkyl)trimethylammonium detergent groups [300], Although cationic phosphorescent probes 5 are quenched efficiently by oxygen and Co(NH3)g+ in aque-... 

If we estimate the time required for S-T mixing and recombination for a radical pair to be 100 ns( and the lifetime of the plvaloyl radical at 31°C to be v6 ps(i5., we can estimate the rate constant for the exit of t-butyl/plvaloyl radicals from HDTCl micelles to be on the order of 10 -10 sec . This Is nicely In line with exit rates of small phosphorescent probe molecules from similar micelle systems. 

The rates of diffusion of solutes and surfactants in and out of micelles have been measured using photophysical techniques. The most commonly used method is to measure the deactivation of excited states of the probe by added quenchers, which are only soluble in the aqueous phase. The measurement of either the decrease in emission intensity or a shortening of the emission lifetime of the probe can be employed to determine exit and entrance rates out of and into micelles 7d). The ability of an added quencher to deactivate an excited state is determined by the relative locations and rates of diffusion of the quenchers and excited states. Incorporation of either the quencher or excited state into a surfactant allows one to determine the rates of diffusion of surfactants. Because of the large dynamic range available with fluorescent and phosphorescent probes (Fig. 3), rates as fast as... 

Song, B., Wang, G.L., and Yuan, J.L. (2005) A new europium chelate-based phosphorescence probe specific for singlet oxygen. Chemical Communications, 3553—3555. 

In an effort to examine the scope of the message in a bottle strategy and to develop phosphorescent pH sensors with longer excitation wavelengths, the case of 5 is examined. In contrast to sensor 3 which had a maximum extinction coefficient of 5300 M-lcm l at 283nm in methanol, 5 possesses the corresponding value of 15300 M"Icm l at 325nm. The quaternary salt 6 and other 1-bromo, 4-alkanoyl naphthalene derivatives were previously employed by Turro as phosphorescent probes of... 

The MLCs have several advantages over the phosphorescent probes. In contrast to phosphorescence, the luminescence from MLCs can be measured in the presence of dissolved oxygen. The MLCs are only partially quenched by ambient oxygen, whereas phosphorescence is usually completely quenched. Additionally, there are relatively few phosphorescent probes, but there are numerous MLCs (Chapter 20). 

As well as linear spectroscopy, the nonlinear spectroscopic techniques of electroabsorption, third harmonic generation and two-photon absorption have all been deployed to investigate other excited states. In addition, phosphorescence probes and photoinduced absorption have been used to investigate the triplet states. In view of the spectral shifts arising from disorder and variations in the chemical structures, these investigations reveal a remarkably consistent picture for PPP, PFO, and PPV. 

The required accuracy for < ) depends, of course, on the purpose of the measurement.) Protein motions with < ) values greater than this will probably require that a longer-lived extrinsic fluorophore (e.g. pyrene) be attached to the molecule. Motions on the microsecond to second timescales can be monitored using phosphorescent probes (see Section 4.2). 

Eosin and its derivatives show weak room temperature phosphorescence and are particularly useful as phosphorescent probes for measuring the rotational properties of proteins and other biomolecules in solution and in membranes. Also useful for FRET studies and fiuorescence recovery after photobleaching (FRAP) measurements of diffusion. 

The rate constants of the phosphorescent probe s exit from cetyltrimethyl-ammonium chloride micelles were determined by Bolt and Turro [155]. The logarithm of the rate constant is a linear function of the number of the carbon atoms in the probe molecule. The apparent activation energy of the exit process is 9 kcal/mole. 

Electron transfer rates between adrenaline and related benzene diols and complexes of iron(III) with some substituted 1,10-phenanthrolines have been reported [67] in surfactant systems. In cationic systems the reactions take place in the aqueous phase and reaction rates are lower than they are in simple aqueous systems, but in anionic surfactant systems the reaction rates are enhanced, reactions probably taking place at the micellar interface. The rates of exit and entrance of aromatic compounds from and into micelles have recently been studied using phosphorescence decay measurements [68] exit rate constants of aromatic hydrocarbons are of the order of 10 to 10 s " S whereas values of 10 to 10 (moll ) s have been reported for intramicellar energy transfer processes. Release of aromatic phosphorescence probes from micelles followed by their deactivation in the aqueous phase is hence expected to be an important mode of deactivation of the triplet state [69]. Kinetic schemes for triplets that are partitioned between aqueous and micellar phases are considered for the cases of single occupancy and double occupancy of the micellar units. 

Promethazine sensing devices based on MIPs include an MIP-based potentiometric sensor which was reported to be applicable in the concentration range of 5.0 X 10" - 1.0 X 10 M, with an LOD 1.0 X 10 M [409] and an MIP-modified carbon phase electrode with two linear response ranges of 4 x 10 -lx 10 M and 1 x 10 - 1 X 10" M and a detection limit of 2.8 x 10 M [381]. Propranolol detection has also been reported through MIP-based phosphorescent probes using tetrabromobisphenol A and diphenylmethane 4,4 -diisocyanate as functional monomers in tetrahydrofuran [380], and an MIP-based ion-selective sensor with a narrow linearity range of 10 -10" M [360]. 

A. Alvarez, J.M. Costa, R. Pereiro and A. Sanz-Medel, Reusable phosphorescent probes based on molecularly imprinted polymers for the determination of propranolol in urine. Sens. Actual B-Chem., 168 370-375,2012. 

A related cell-permeable, cyclometalated iridium(III) complex, [Ir(2-C6H4-quinoline)2(H20)2] OTf, is a phosphorescent probe for cell imaging by preferentially staining the cytoplasm of both live and dead cells with a bright luminescence. ... 

This facilitates the relative importance of radiationless decay by internal conversion or by quenching through collision with traces of impurities. Consequently, phosphorescence is rarely observable in fluid media. An important exception is in the case of ketones which have lowest energy - (mr ) triplet excited states (4). Here photon emission occurs at rates of 10 to 10 sec , fast enough to compete with solvent or impurity quenching if care is taken to deoxygenate the samples and purify the solvents. For molecules such as acetone, acetophenone, benzo-phenone, biacetyl and benzil, phosphorescence is readily observed in fluid solution at ordinary temperatures with (1/e) lifetimes of 50-500 ys. Heavy atoms promote phosphorescence rates. Dibromoacetonaph-thone (5), with a lowest (TnT ) triplet state is a useful phosphorescence probe of micellar systems. There is a whole literature on heavy-atom induced room-temperature phosphorescence applications in analytical chemistry (6),... 

Erythrosin has also been used as a phosphorescence probe to assess the effects of photopolymerization on surfactant vesicle surface morphology (40). 

The relationship between segmental and group motion in solid polymers and the rates of diffusion of small molecules suggests that diffusion measurements might be used to detect the transitions associated with the occurrence of this type of motion, and indeed this turns out to be the case. One of the most sensitive measurements of the occurrence of solid-phase transitions is obtained by observing the quenching of phosphorescent probes in solid polymers by the diffusion of oxygen. 

The detection of transition regions in polystyrene by this technique have been shown to be relatively independent of the nature of the phosphorescence probe. For example,... 

Luminescent probes can be divided into two groups fluorescence probes and phosphorescence probes. Fluorescence is an emission of light associated with... 

Both delay and acquisition times have to be chosen carefully in order to maximise SNR. For instance, a too long delay time cuts out the most intense emission from the phosphorescent probes and a too long acquisition time leads to noise integration at the end of the probe decay. If the decay is a single exponential function, the phosphorescence signal... 

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