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Enhanced Emission in Self‐Assembled Phenyleneethynylene Derived π‐Gelators
Author(s) -
Das Gourab,
Thirumalai Rajasekaran,
Vedhanarayanan Balaraman,
Praveen Vakayil K.,
Ajayaghosh Ayyappanpillai
Publication year - 2020
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202000173
Subject(s) - chromophore , materials science , fluorescence , transmission electron microscopy , quantum yield , self assembly , stacking , excimer , lamellar structure , photochemistry , tetraphenylethylene , nanotechnology , aggregation induced emission , optics , organic chemistry , chemistry , composite material , physics
Optical properties of π‐systems are of great significance for a wide range of applications in materials and biology. Aggregation and self‐assembly induced emission are one of such phenomena. Herein, the self‐assembly induced modulation of the emission of p ‐phenyleneethynylene (PE) chromophores bearing linear achiral ( 1 ) or branched chiral ( 2 ) alkoxy chains is reported. Self‐assembled structures of both 1 and 2 from n ‐decane exhibit enhanced emission with fluorescence quantum yield ( Φ F ) values of 0.34 and 0.25, respectively, whereas these molecules are less‐emissive in chloroform ( Φ F = 0.02). Transmission electron microscopy and fluorescence microscopy studies reveal the formation of entangled blue‐emissive fibers for 1 and supercoiled helical blue‐emissive fiber bundles for 2 . At higher concentrations (8.8 × 10 −3 m for 1 and 23.6 × 10 −3 m for 2 ) in n ‐decane, intense blue‐emitting gels are formed. Significant shift in the emission toward longer wavelength can be seen from solution state to aggregates to the gel state. The wide‐angle X‐ray scattering and fluorescence data indicate that the interdigitated lamellar assembly with weaker π‐stacking and the resultant restriction of rotation of the PE chromophores are responsible for the enhanced emission of the self‐assembled gel state.