Two-Photon Absorption Properties of Chromophores in Micelles: Electrostatic Interactions
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- 作者：Semere Bairu ; Guda Ramakrishna
- 刊名：Journal of Physical Chemistry B
- 出版年：2013
- 出版时间：September 12, 2013
- 年：2013
- 卷：117
- 期：36
- 页码：10484-10491
- 全文大小：469K
- 年卷期：v.117,no.36(September 12, 2013)
- ISSN：1520-5207
文摘
Two-photon absorption (2PA) cross sections of neutral Coumarin 485 (C485) and anionic Coumarin 519 (C519鈥?/sup>) solubilized in Triton X-100 (Tx-100, neutral), sodium dodecyl sulfate (SDS, anionic), and cetyltrimethylammonium bromide (CTAB, cationic) are reported. The objective of the study is to probe the influence of local electrostatic fields in micelles on the 2PA properties of chromophores. The 2PA measurements have shown that the cross sections of neutral C485 are unchanged in different micellar environments, although the local micropolarities of chromophores are different. On the other hand, the 2PA cross sections of C519鈥?/sup> are unchanged or slightly decreased in Tx-100 and SDS micelles when compared to water while 100% increase in 2PA cross sections was observed for C519鈥?/sup> in CTAB micelles. The enhancement in 2PA cross section is attributed to the electrostatic fields arising in the Stern layer of CTAB, where C519鈥?/sup> is solubilized. The titration measurements have shown that the 2PA enhancement is due to the organized medium only and not because of the simple association of C519鈥?/sup> and the quaternary ammonium group of CTAB. From the analysis, local electric field of 0.7 卤 0.3 MV/cm is estimated for the Stern layer of CTAB.