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Photochromic kinetics

The compound was found to have excellent photochromic and fluorescence properties in solution. The photochromic kinetics showed the cyclization processes is zero order and the cycloreversion is first order. [Pg.140]

Most photochromic compounds undergo large stmctural changes while being transformed from the uncolored to the colored form. This property has been used to examine the pore si2e of polymers by utili2ing the relationship of pore si2e and the kinetics of the photochromic response (46). [Pg.165]

Optical lithography, in compound semiconductor processing, 22 193 Optically active citronellol, 24 506 Optically transparent porous gel-silica, 23 75, 76 Optical materials nonlinear, 17 442-460 second-order nonlinear, 17 444—453 third-order nonlinear, 17 453-457 Optical memory, photochromic material application, 6 602 Optical microscopy, 16 467-487 history of, 16 467-469 in kinetic studies, 14 622 liquid immersion, 15 186 Optical mode density, 14 849, 850-852 Optical multichannel analyzers (OMAs), 23 143... [Pg.649]

Addition of 20-25% (v/v) ethylene glycol, known to stabilize native protein structures, has often been found to be a convenient measure also for phytochrome. Absorption spectroscopy showed that the additive does not cause any loss of Pr fcf Pfr photochromicity, and the lifetimes and amplitudes of the Pj components [108] as well as the kinetic parameters of the absorption decays of 1 qq and I200 [113] at 272-297 K (Table 3) were hardly affected either. This is in accord with a confinement of the sequence Pr - I700 - Ibi t0 the phytochromobilin-binding protein domain without... [Pg.261]

Photoinduced unimolecular reactions often have kinetics of the order of ps. One example of isomerization in ps times is shown in Figure 8.9. This is the photochromic reaction of a spiropyran. The photoinduced process takes place... [Pg.262]

Figure 1 shows a typical curve obtained for most photochromic systems. In the dark, there should be no absorbance by the colored form of the photochrome. At time, ti, the exciting radiation is turned on which immediately causes conversion of the initial molecule, X, into its colored form Y. The absorbance of Y builds up to a maximum value with time until a steady-state concentration is reached in the reaction, X Y. When the exciting radiation is shut off, the colored form Y reverts to X at a rate dependent on the kinetics of the dark reactions. [Pg.277]

T. Hayashi, K. Maeda, and M. Takeuchi, Kinetic study of the photochromism of 2,2, 4,4, 5,5 -hexaphenyl-l,l -biimidazolyl with electron spin resonance. Bull. Chem. Soc. Jpn. 1964, 37, 1717. [Pg.142]

An additional step in the cascade reaction scheme is the quenching of the sensitizer triplet state with relatively low-concentration radicals (Fig. 1.5) (Papper et al 1999, 2000 Papper and Likhtenshtein, 2001). The entire investigated reaction that is shown in Fig. 1.5 is the sequence of the four kinetic processes and serves as a basis for the spin-triplet-photochrome labeling technique. This technique combines the three types of biophysical probes stilbene photochrome probe, triplet probe and stable nitroxide-radical spin probe, which depresses the sensitiser exited triplet state. [Pg.13]

The triplet-photochrome labeling method has been used to study very rare encounters in a system containing the Erythrosin B sensitiser and SITC photochrome probe (Mekler and Likhtenshtein, 1986). Both types of the molecules were covalently bound to a-chymotrypsin. The photoisomerisation kinetics was monitored by fluorescence decay of the frans-SITS. The rate constants of the triplet-triplet energy transfer between Erythrosin B and SITS (at room temperature and pH 7) were found k,r = 2 xlO7 NT s-1 and ktT = 107 M V. It should be emphasized that the concentration of the triplet sensitiser attached to the protein did not exceed 10 7 M in those experiments, and the collision frequencies were close to 10 s 1 which are 8-9 orders of magnitude less than those measured with the regular luminescence or ESR techniques. [Pg.14]

A recurring theme throughout the book is the importance of the medium in which the photochromic compound is incorporated. The medium can strongly influence or control the kinetics of the thermal back reaction when it occurs, the color of the species formed in the forward photochemical reaction, and other properties of the photochromic process. [Pg.3]

In chapter 7, special emphasis has been placed on the synthesis of representative polycyclic quinones and their photochromic behavior, including the spectral, kinetic, and fatigue characteristics of such systems. Potential applications are focused on recording and multiplication of images, optical memories, and gradation masking. [Pg.7]

D. Kuhn, H. Balli, and U. E. Steiner, Kinetic study of the photodecoloration mechanism of an inversely photochromic class of compounds forming spiropyran analogues, J. Photochem. Photo-biol.A Chem., 61, 99-112(1991). [Pg.77]

M. A. Halberstam and M. B. Gordin, Kinetics of reversible photochromic reactions in the series of 1,5-disubstituted 3,3-dimethyl-6 -nitro-8 -bromospiro-[(2 /7,l -benzopyran)-2,2 -indolines], Photo-... [Pg.78]

M. B. Gordin, and M. A. Gal bershtam, Kinetics of the darkening [Note fading is meant] of several photochromic spiropyrans, Kinet. Catal, 12, 688-689 (1971). [Pg.78]

C. Lenoble and R. S. Becker, Photophysics, photochemistry and kinetics of photochromic 27 -pyrans... [Pg.138]

K. Ulrich, H. Port, and P. Bauerle, Photochromic thiophene fulgide absorption spectra and kinetics... [Pg.204]

Irradiation of the photochromic DHI 7 gives rise to the colored forms 8 and 9. The thermal back or fade reaction 9 —> 7 (i.e., the 1,5-electrocyclization), can be easily studied kinetically using UV spectroscopy. The rate constant k thus determined can be converted by the equation ... [Pg.236]

All photochromic anthrapyridones and anthrapyridines were characterized by a reversible change of their spectra under UV and visible light, but the kinetic processes have not been investigated. Kinetic data are lacking at present. [Pg.301]

As in the case of the photochromic quinones discussed earlier, the kinetics of the photochromic transformations for phenoxypyrazoloanthrones were determined by the irradiation intensity that activated the initial or photoinduced form41,42... [Pg.302]

An analysis of the kinetic characteristics of photochromic quinones showed that the photochromic transformations of methylnaphthoquinone, alkyl- and acyloxyan-thraquinones in solution at room temperature were observed in the microsecond range. As a consequence, these compounds may be of theoretical interest in the future. The photochromic aryloxyanthraquinones are characterized by a lifetime of the photoinduced form that reaches several minutes in solution and several hours in polymer films at room temperature, which makes them acceptable for a number of applications. In this regard, of special interest are photochromic naphthacenequi-... [Pg.303]


See other pages where Photochromic kinetics is mentioned: [Pg.161]    [Pg.334]    [Pg.33]    [Pg.20]    [Pg.139]    [Pg.58]    [Pg.286]    [Pg.249]    [Pg.152]    [Pg.928]    [Pg.75]    [Pg.142]    [Pg.143]    [Pg.143]    [Pg.312]    [Pg.14]    [Pg.57]    [Pg.63]    [Pg.82]    [Pg.161]    [Pg.185]    [Pg.201]    [Pg.205]    [Pg.299]    [Pg.309]    [Pg.312]    [Pg.313]    [Pg.314]   
See also in sourсe #XX -- [ Pg.140 ]




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