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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photoionization and Ion-Radical Decay of Anthracene in a Water Swollen Nafion Network. Effect of Different Counterions on the SO_3~--Water Clusters
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Photoionization and Ion-Radical Decay of Anthracene in a Water Swollen Nafion Network. Effect of Different Counterions on the SO_3~--Water Clusters

机译：水溶Nafion网络中蒽的光电离和离子自由基衰减。不同抗衡离子对SO_3〜-水团簇的影响

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摘要

The formation of anthracene ion radicals in the H~+-, Na~+-, Fe~(2+)-, and Fe~(3+)-Nafion membrane was established by laser kinetic spectroscopy. The formation of ion radicals was observed to be due to (1) the two photon ionization of the anthracene molecule with the formation of the radical action An~(+·) radical and a fast electron scavenging by H~+, Na~+, Fe~(2+), and Fe~(3+) acting as efficient electron traps in solution and (2) the quenching of the excited anthracene by Fe~(3+) that leads by a redox process to the formation of An~(+·) and Fe~(2+). It is shown that the ensuing kinetics of the ion-radical decay depends on the chemical nature of the traps. The lifetime of ~TAn becomes shorter after Fe~(2+) or Fe~(3+) is introduced in the Nafion. The steady-state anthracene fluorescence is quenched by Fe~(3+) or Fe~(2+) and followed the logarithmic decay law ln(I_0/I) where the decay in solution was seen to be proportional to the [Fe~(3+)] or (Fe~(2+)]. The counterions of SO_3~--water clusters as well as of oxygen in the reaction media strongly affect the kinetics of ion-radical reactions occurring in the Nafion membrane. The counterions and oxygen are suggested to be the traps for the generated electrons in solution. The excited state of An was shown to react with Fe~(3+) through electron transfer. Trilet excited anthracene molecules are quenched by Fe~(3+) and Fe~(2+) with rate constants k_1(Fe~(3+) = (1.9 ± 0.19) * 10~* M~(-1)s~(-1) and k_q(Fe~(2+) = (1.4±0.11) * 10~9 M~(-1)s~(-1). Anthracene ion radicals are formed in the reaction with Fe~(3+) but not with Fe~(2+) on thermodynamic grounds. Fe~(2+) or Fe~(3+) being different chemical species quench with similar rates the An probe inside the Nafion membrane. Treatment of Fe~(3+)-Nafion with NaOH leads to precipitation of iron particles in the membrane having as consequences (1) the decrease of the observed rate for the triplet excited anthracene quenching with a concomitant decrease in the observed An~(+·) yields and (2) a significant decrease of the An~(+·) decay time because of the lowering of the mobility of the iron ions in solution.
机译：通过激光动力学光谱法确定了H〜+-，Na〜+-，Fe〜（2 +）-和Fe〜（3 +）-Nafion膜中蒽离子自由基的形成。观察到离子自由基的形成是由于（1）蒽分子的两个光子电离，形成自由基作用An〜（+·）自由基，并通过H〜+，Na〜+快速清除电子， Fe〜（2+）和Fe〜（3+）充当溶液中的有效电子陷阱，并且（2）Fe〜（3+）淬灭激发的蒽，并通过氧化还原过程导致An〜的形成（+·）和Fe〜（2+）。结果表明，离子自由基衰变的动力学取决于阱的化学性质。在Nafion中加入Fe〜（2+）或Fe〜（3+）后，〜TAn的寿命变短。稳态蒽荧光被Fe〜（3+）或Fe〜（2+）淬灭，并遵循对数衰减定律ln（I_0 / I），其中溶液的衰减与[Fe〜（ 3+）]或（Fe〜（2+）]。SO_3〜-水团簇的抗衡离子以及反应介质中的氧气强烈影响Nafion膜中发生的离子自由基反应的动力学。认为氧是溶液中生成电子的陷阱，An的激发态通过电子转移与Fe〜（3+）反应，三重激发的蒽分子被Fe〜（3+）和Fe〜淬灭。 （2+）具有速率常数k_1（Fe〜（3+）=（1.9±0.19）* 10〜* M〜（-1）s〜（-1）和k_q（Fe〜（2+）=（1.4± 0.11）* 10〜9 M〜（-1）s〜（-1）。在热力学上，与Fe〜（3+）反应生成蒽离子自由基，而与Fe〜（2+）反应则不生成蒽离子自由基。不同化学物种的2+）或Fe〜（3+）以相似的速率淬灭Nafion膜内的An探针。 3 +）-Nafion的NaOH导致膜中铁颗粒的沉淀，其结果是（1）三重激发蒽猝灭的观察速率降低，同时观察到的An〜（+·）产率随之降低，并且（ 2）由于溶液中铁离子迁移率的降低，An〜（+·）衰减时间显着减少。

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