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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Excited State Proton Transfer in Ionic Liquid Mixed Micelles
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Excited State Proton Transfer in Ionic Liquid Mixed Micelles

机译：离子液体混合胶束中的激发态质子转移

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Excited state proton transfer (ESPT) of pyranine (8-hydroxypyranine-1.3.6-trisulfonate. HPTS) in room temperature ionic liquid (RTIL) mixed micelles is studied by femtosecond up-conversion. The mixed micelle consists of a triblock copolymer, (PEO)_(20)-(PPO)_(70)-(PEO)_(20) (Pluronic P123), and one of the two RTILs, l-pentyl-3-methyl-imidazolium bromide ([pmim][Br]) andl-pentyl-3-methyl-imidazolium tetra-fluoroborate ([pmim][BF4]). The size and structure of the mixed micelle vary with the relative amount of the RTIL. For [pmim][Br]. the hydrodynamic diameter of the mixed micelle is 26 nm in 0.3 M RTIL and 3500 nm in 3.0 M RTIL. The time constant of initial proton transfer (τ_(PT)) in P123 micelle (65 ps) is 10 times slower than that (5 ps) in water, while the time constants of recombination (τ_(rec)) and dissociation (τ_(diss)) are 2-3 times slower in P123 micelle. On addition of the RTIL. the rate of ESPT is markedly modified. In 0.3 M RTIL-P123 mixed micelle. τ_(PT) is shorter than that in P123 micelle. In the mixed micelle, TpT increases with an increase in the concentration of the RTIL (230 ps in 3 M [pmim][Br] and 55 ps in 0.9 M [pmim][BF4]). This is attributed to large scale penetration of the P123 micelle by RTIL replacing water molecules. The time constants of proton transfer (τ_(PT), τ_(rec), and τ_(diss)) are faster than the slowest component (200-500 ps) of solvation dynamics. It seems that the ultrafast component of solvation (<0.3 ps and <5 ps) is enough for inducing proton transfer. The time constant of the proton transfer (τ_(PT)) in [pmim][BF4] - P123 mixed micelle is longer (~20%) than that in [pmim][Br]-P123 mixed micelle for the same concentration of RTIL. The counterion dependence of ESPT is attributed to the difference in the structure and greater hydrophobicity of the [pmim][BF4].
机译：通过飞秒上转换研究了室温离子液体（RTIL）混合胶束中吡喃（8-羟基吡喃-1.3.6-三磺酸盐.HPTS）的激发态质子转移（ESPT）。混合胶束由三嵌段共聚物（PEO）_（20）-（PPO）_（70）-（PEO）_（20）（Pluronic P123）和两个RTIL之一（1-戊基-3-）组成甲基咪唑鎓溴化物（[pmim] [Br]）和1-戊基-3-甲基咪唑鎓四氟硼酸酯（[pmim] [BF4]）。混合胶束的大小和结构随RTIL的相对量而变化。对于[pmim] [Br]。在0.3 M RTIL中混合胶束的流体动力学直径为26 nm，在3.0 M RTIL中为3500 nm。 P123胶束（65 ps）中初始质子转移的时间常数（τ_（PT））比水中（5 ps）的时间常数慢10倍，而重组（τ_（rec））和离解（τ_（ Diss））在P123胶束中要慢2-3倍。在RTIL上。 ESPT的比率已被明显修改。在0.3 M RTIL-P123混合胶束中。 τ_（PT）比P123胶束中的要短。在混合胶束中，TpT随着RTIL浓度的增加而增加（在3 M [pmim] [Br]中为230 ps，在0.9 M [pmim] [BF4]中为55 ps）。这归因于通过RTIL代替水分子，P123胶束的大规模渗透。质子传递的时间常数（τ_（PT），τ_（rec）和τ_（diss））比溶剂化动力学的最慢成分（200-500 ps）快。看来，溶剂化的超快成分（<0.3 ps和<5 ps）足以诱导质子转移。对于相同浓度的RTIL，[pmim] [BF4]-P123混合胶束中质子传递的时间常数（τ_（PT））比[pmim] [Br] -P123混合胶束中的质子传递时间常数（〜20％）长。 。 ESPT的抗衡离子依赖性归因于[pmim] [BF4]的结构差异和更大的疏水性。

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