Nonionic
surfactant modulated aggregation induced emission enhancement
(AIEE) of Dimethyl-2,5-bis(4-(methoxyphenyl)amino)terephthalate (DBMPT)
has been investigated. DBMPT exhibits unidirectional aggregated growth
with nonionic triton X-100 (TX-100) to produce highly luminescent
nanorods, the dimensions and emission intensities of which are controlled
by concentration of DBMPT. Energy transfer from perylene-3,4,9,10-tetracarboxylic
acid dianhydride (PTAD) to these nanorods in aqueous medium produces
pure white light emission with the CIE chromaticity coordinates (0.33,
0.36) and a significantly high quantum yield of 35%. Gelation of the
system with agarose yields a bright white light emitting gel. Both
these factors demonstrate an excellent potential for application of
this system in light harvesting and as an advanced material for organic
electronic devices.
Dimethyl-2,5-bis(4-methoxyphenylamino)terephthalate (DBMPT) is a water-insoluble fluorogenic molecule, which has been rendered water-soluble in physiological conditions, by the addition of triblock copolymers (TBPs), P123 (PEO 19 PPO 69 PEO 19 ), and F127 (PEO 100 PPO 65 PEO 100 ). DBMPT-TBP mixed aggregates, formed in the process, exhibit significant aggregation-induced enhancement of emission, with nanosecond fluorescence lifetimes. Dynamics involved in suppression of nonradiative pathways and consequent enhancement of fluorescence are followed by femtosecond transient absorption and time-resolved fluorescence spectroscopic techniques. Interestingly, shapes of the aggregates formed with the two TBPs are found to be very different, even though they differ only in the length of hydrophilic blocks. DBMPT-P123 aggregates are micrometer-sized and spherical, while DBMPT-F127 aggregates form nanorods. Evolution of their morphologies, as a function of TBP concentration, is monitored using cryo-TEM, FESEM, and fluorescence lifetime imaging microscopy. Fluorescence lifetime distribution provides useful insight into microheterogeneity in these mixed aggregates. Excellent cell permeability is observed for DBMPT-F127 nanorods, in contrast to DBMPT-P123 microspheres. These fluorescent nanorods exhibit the ability to mark lipid droplets within the cell and hence bear the promise for application in intracellular imaging.
Dimethyl-2,5-bis[4-(methoxyphenyl)amino] terephthalate
(DBMPT)
exhibits aggregation-induced enhancement of emission with Tween 40
and formation of nanorods with strong orange fluorescence. These nanorods
disrupt fibrils of human serum albumin and lead to partial refolding
of the protein, as monitored by circular dichroism and thioflavin
T (ThT) fluorescence. The resultant milieu emits white light, the
mechanism of which is explored in this study. It is established that
direct excitation of the acceptor plays a significant role, even though
Förster resonance energy transfer (FRET) is found to be operative
to some extent. A decrease in the fluorescence intensity and lifetime
of ThT with progressive addition of DBMPT, which is often used as
the sole indicator of FRET, is ascribed to the disruption of the fibrils
by the nanorods.
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