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A Global Scenario on the Dynamics of Excited State Proton Transfer of Pyranine in the Mixed Micellar Assemblies: Role of Water Accessibility in the Probe Location +
Author(s) -
Das Ishita,
Halder Mintu
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201800361
Subject(s) - pyranine , micelle , chemistry , sodium dodecyl sulfate , cationic polymerization , ionic bonding , excited state , proton , photochemistry , chemical engineering , chromatography , aqueous solution , polymer chemistry , organic chemistry , ion , biochemistry , physics , quantum mechanics , membrane , nuclear physics , engineering
Excited state proton transfer (ESPT) dynamics of pyranine (HPTS) is explored in mixed micellar aggregate of pluronic F127 micelles and Na‐dodecyl sulfate (SDS) employing steady state and time resolved fluorescence. HPTS shows two proton transfer (PT) time constants in both F127 and F127‐SDS micelles. The slow ∼1.05 ns component in F127 micelles is attributed to PT occurring in the corona phase; whereas, the bulk water‐like variant (∼160 ps) arises from the probe in water exposed micellar periphery. Addition of SDS upto some low concentration in F127 produces mixed micelles due to SDS‐monomer incorporation. The slower ESPT time constant becomes ∼670 ps in the mixed micellar system (∼1.5 times faster than in neat), whereas, the faster one gets ∼140 ps. It is known that association of SDS in F127 micelles enhances water penetration in the corona region, thus this increased hydration speeds up the ESPT. The chosen photoacid, in principle, can anticipate changes in the microenvironment of the mixed micelles via modulation of its ESPT. In spite of similar hydration enhancements in both cationic and anionic mixed micelles, it is observed that the modification pattern of the ESPT in mixed anionic is opposite to that of mixed cationic. A rationale of such contrasting ESPT responses in these differently charged composites is presented. In addition to copolymeric micelles, some mixed systems formed with other nonionic‐ionic combinations are also explored to cast a more generalized picture