...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Physical chemistry chemical physics: PCCP >A new method to determine micellar aggregation numbers: positron annihilation lifetime spectroscopy
【24h】

A new method to determine micellar aggregation numbers: positron annihilation lifetime spectroscopy

机译：确定胶束聚集数的新方法：正电子an没寿命谱

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

A new method was developed to measure micellar aggregation numbers (N-ag) by using positron annihilation lifetime spectroscopy (LS), is a similar way as is done in fluorescence quenching experiments. Triplet positronium (o-Ps) is taken as a surrogate to the fluorescent probe, while the quencher is duroquinone, in 0.28 M sodium dodecyl sulfate (SDS) aqueous solution. On the basis of a Poisson distribution of the quencher molecules over the micelles, it is expected that the intensity of those o-Ps atoms decaying in micelles where no quencher molecules are present should decrease exponentially as a function of the quencher concentration and aggregation number, whereas their lifetime, should remain constant. The high oxidation power of the quencher towards Ps is first established in pure dodecane, yielding a reaction rate constant k' = 16.2 l mol(-1) ns(-1). Quantitatively, however, this value would correspond to a solute radius about twice too large, whether the time dependence of the encounter rate coefficient is considered or not. Contrary to expectation, the lifetime of o-Ps trapped in the SDS micelles appears to decrease with increasing duroquinone concentration. This decrease indicates a much smaller overall oxidation rate constant than in dodecane, owing to strong localization of duroquinone near the interface layer. Nevertheless, taking an integral of the LS decay spectra from a time long enough to eliminate the components of lifetimes shorter than tau(4)(0) leads to N-ag = 65 +/- 3, in good agreement with previous determinations. [References: 20]
机译：开发了一种通过使用正电子an没寿命光谱法（LS）测量胶束聚集数（N-ag）的新方法，该方法与荧光猝灭实验中的方法类似。在0.28 M十二烷基硫酸钠（SDS）水溶液中，将三重态正电子（o-Ps）用作荧光探针的替代物，而淬灭剂是度洛醌。根据胶束上淬灭剂分子的泊松分布，可以预见，在不存在淬灭剂分子的胶束中，那些o-Ps原子的衰变强度应根据淬灭剂浓度和聚集数呈指数下降，而它们的寿命应该保持不变。首先在纯十二烷中建立淬灭剂对Ps的高氧化能力，产生的反应速率常数k'= 16.2 l mol（-1）ns（-1）。但是，无论是否考虑相遇速率系数的时间依赖性，该值在数量上都将对应于大约两倍大的溶质半径。与预期相反，捕获在SDS胶束中的邻苯二酚的寿命似乎随着杜罗醌浓度的增加而降低。该降低表明由于十二烷醌在界面层附近的强定位，总的氧化速率常数比十二烷小得多。但是，从足够长的时间中获取LS衰减谱的积分以消除寿命小于tau（4）（0）的分量会导致N-ag = 65 +/- 3，这与先前的确定非常吻合。 [参考：20]

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号