Organogels prepared from AOT/4-chlorophenol/m-xylene are immobile in the macroscopic sense, with a well-characterized internal structure. However, the molecular level dynamics inside the gels is not too clear, although a very slow structural relaxation has been reported previously. Using a set of rod-like fluorophores, we find that the rotational mobility of a small guest molecule inside the gel can be extremely fast, indicating presence of sufficiently low-microviscosity domains. These domains consist of m-xylene solvent molecules trapped in the interstices of fiber bundles comprising columnar stacks of 4-chlorophenol surrounded by AOT molecules. However, interstitial trapping of m-xylene does retard its own dynamics, which explains the slow solvent relaxation inside the gels. Hence, the state of m-xylene in the organogel may be characterized as “bound”, in contrast to the “free” state in neat m-xylene. © 2016

DEBABRATA MANDAL

Chemistry

M DANDAPAT

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

Abstract Fluorescence Resonance Energy Transfer (FRET) between donor coumarins (C102 and C153) and acceptor Rhodamine 6G were studied in AOT/4-chlorophenol/m-xylene organogels. The gel comprises a three-dimensional network of fiber bundles trapping the m-xylene solvent. Each fiber is an aggregate of several strands, and each strand consists of a central columnar stack of the phenols, surrounded by AOT headgroups. Our acceptor is ionic so that it was concentrated near the polar center of the strand, while the neutral donors were likely distributed over a wider region. With C153 as donor, clear evidence of FRET (time-constant~100 ps) was found, which indicated that the donor and acceptor may reside in neighboring strands within the same fiber. However, with C102 as donor, FRET probably occurred over an ultrashort, sub-picosecond time-scale suggesting that the donor and acceptor in this case resided in close vicinity. Thus, C102 tends to localize near the polar centre of the strands, compared to the more hydrophobic C153, which prefers to occupy the relatively non-polar peripheral regions of the strands and fibers. © 2015 Elsevier B.V. All rights reserved.

Journal of Luminescence

Fluorescence resonance energy transfer in AOT/4-chlorophenol/m-xylene organogels

Molecular motion of carbocyanine fluorophores DOCI, DODCI and DTDCI were studied in AOT/n-heptane microemulsions containing added polar solvents: water, methanol or acetonitrile. The response varied remarkably depending on the nature of the fluorophore and polar solvent. When the amount of added polar solvent was low, molecular mobility was invariably retarded, due to a combination of electrostatic and hydrophobic forces that induce the guest fluorophore to cling to the AOT molecules of the host reverse micelle. However, at high amounts of added methanol or water, these interactions diminished considerably, causing increase in the mobility of the guest fluorophores up to different extents. © 2014 Elsevier B.V. All rights reserved.

Chemical Physics Letters

Photoisomerization and reorientational mobility of symmetric carbocyanines in AOT/alkane/polar solvent microemulsions

Chitosan hydrogel beads have recently emerged as interesting natural product-based materials capable of accomodating sizeable number of small molecules, opening newer possibilities of biological and industrial applications. However, their efficiency as host media for harboring guest molecules depends critically on the environment they provide to the latter. Fluorescence probing with two types of fluorophores molecules: 8-anilino-1-naphthalene sulfonate (ANS), and three different symmetric carbocyanines, has been employed to unravel the details of the local environment experienced by small guest molecules sorbed by the hydrogel beads, in terms of local polarity and microviscosity. For this purpose, we took advantage of the photophysical properties of these fluorophores. ANS undergoes twisted intramolecular charge transfer, which is remarkably sensitive to medium polarity. On the other hand, the symmetric carbocyanines tend to photoisomerize, which involves large-amplitude torsional motion that is sensitive to the microviscosity of the immediate vicinity. Our results indicate that the guest molecules in the sorbed state encounter a multitude of local environments, ranging from the low polar and high viscous, to high polar and low viscous. While the former is embodied by the chitosan-rich cross-linked polymeric domains, the latter is attributed to the water-filled pores that criss-cross the polymeric network. © 2014 Elsevier B.V.

Journal	Data powered by TypesetSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Publisher	Data powered by TypesetElsevier B.V.
ISSN	1386-1425