Dispersive kinetics: a structural approach to nonexponential processes in disordered media

Siebrand, Willem; Wildman, Timothy A.

doi:10.1021/ar00128a002

Cited by 113 publications

(72 citation statements)

References 30 publications

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“…48 Results and Discussion also observed that the decay of Ru(bpy) 3 2 ÷ in Nafion films cannot be describe by a monoexponential decay model. Figure 1 shows typical decay curves for Ru(bpy) 3 2 ÷ in Nafion at various loading levels; note that these are semilogarithmic plots.…”

Section: Ntis Craandm Dtic T•mentioning

confidence: 78%

Luminescence probe studies of ionomers. 3. Distribution of decay rate constants for tris(bipyridyl)ruthenium(II) in Nafion membranes

Colón¹,

Martin²

1993

Langmuir

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Section: Ntis Craandm Dtic T•mentioning

confidence: 78%

Luminescence probe studies of ionomers. 3. Distribution of decay rate constants for tris(bipyridyl)ruthenium(II) in Nafion membranes

Colón¹,

Martin²

1993

Langmuir

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“…Quite clearly, our data emphasize the need for a better model. In the last few years dispersive kinktic analysis has provided a solid basis for understanding some complex kinetic problems in solid systems (22)(23)(24)(25)(26)(27), notably, the decay kinetics of methyl radicals in methanol glasses (23)(24)(25)(26)(27). This analysis assumes a distribution of rate constants for decay; detailed models are available for a Gaussian distribution of exponential decays.…”

Section: Conclusion and Suggestions For Improved Kinetic Analysismentioning

confidence: 99%

Intrazeolite photochemistry. VI. Diffuse reflectance laser flash photolysis and product studies of diphenylmethyl radicals on solid supports

Kelly¹,

Willsher²,

Wilkinson³

et al. 1990

Can. J. Chem.

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. J. Chem. 68, 812 (1990).Diphenylmethyl radicals have been generated by 266 nm laser excitation of 1,1,3,3-tetraphenylacetone adsorbed on silica gel and included in NaX and Silicalite zeolites and have been studied using diffuse reflectance laser flash photolysis techniques. The spectrum for the radical shows A, , at -335 nm in all three supports and is similar to that in solution. The radicals decay over time scales that vary from hundreds of nanoseconds to minutes and there are indications that some radicals may be decaying on shorter time scales than we can monitor. The efficiency of oxygen quenching increases in going from Silicalite to NaX to silica gel, consistent with the greater accessibility of oxygen to silica gel pores as compared to the narrow channels in Silicalite. Laser dose and ketone loading effects were also examined for the various supports. Potential applications of a kinetic treatment of the data based on dispersive reaction kinetics are also discussed as a means of dealing with the problem of decay kinetics that occur over a wide range of time scales. On a produit des radicaux diphknylmtthyles en excitant, l'aide d'un laser optrant a 266 nm, de la 1,1,3,3-tktraphknylacttone adsorbte sur du gel de silice ou incluse dans des ztolithes de NaX et de Silicalite et on les a ttudits en faisant appel aux techniques de photolyse <> a l'aide de laser i rtflectance diffuse. Le spectre du radical prksente un A, , a environ 335 nm dans chacun des trois supports et il est semblable a celui observt en solution. Les radicaux se dtcomposent a des vitesses qui varient de quelques centikmes de nanosecondes a des minutes; certaines indications nous laissent croire que certains radicaux pourraient se dkcomposer a des vitesses plus rapides que celles que l'on peut mesurer. L'efficacitt du pikgeage par l'oxygkne augmente lorsqu'on passe de la Silicalite au NaX au gel de silice; cet ordre est en accord avec la plus grande disponibilitk de l'oxygkne sur les pores du gel de silice par comparaison avec les canaux Ctroits qui existent sur la Silicalite. Pour divers supports, on a aussi examink les effets de la dose du laser ainsi que de la quantitC de cttone utiliste. On discute aussi des applications potentielles d'un traitement cinttique des donntes bast sur la cinttique de rkactions dispersives cornrne moyen de rksoudre le problkme de la cinktique de dtcompositions qui se produisent a des vitesses trks diffkrentes.

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“…Both these models belong to the class of stretched first order kinetics (Siebrand and Wildman 1986) and are a different way to take into account the accessibility of scissile bonds (Sharples 1954a(Sharples , 1971Wadehra and Manley 1965).…”

Section: Introductionmentioning

confidence: 99%

On the kinetics of cellulose degradation: looking beyond the pseudo zero order rate equation

2007

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The kinetics of cellulose degradation was analysed by means of a two-stage model, characterised by an autoretardant and autocatalytic regime, later tempered by the consumption of glycosidic bonds in the amorphous regions. The proposed model explains the effects on the kinetic equations of different modes of ageing (acid hydrolysis, ageing in ventilated oven or sealed vessels), initial oxidation of cellulose and experimental procedures (with or without reduction of oxidised groups). The autoretardant branch can be analysed in a quantitative way, while the integration of the non-linear autocatalytic branch is allowed in some cases, characterised by the decrease of pH and/or emission of acid volatile organic compounds (VOCs). Most of the controversial results of the literature can be easily explained, but the proposed model offers also a guide for further studies on the kinetics of cellulose degradation.

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Dispersive kinetics: a structural approach to nonexponential processes in disordered media

Cited by 113 publications

References 30 publications

Luminescence probe studies of ionomers. 3. Distribution of decay rate constants for tris(bipyridyl)ruthenium(II) in Nafion membranes

Luminescence probe studies of ionomers. 3. Distribution of decay rate constants for tris(bipyridyl)ruthenium(II) in Nafion membranes

Intrazeolite photochemistry. VI. Diffuse reflectance laser flash photolysis and product studies of diphenylmethyl radicals on solid supports

On the kinetics of cellulose degradation: looking beyond the pseudo zero order rate equation

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