3 research outputs found
Chiral microneedles from an achiral bis(boron dipyrromethene): spontaneous mirror symmetry breaking leading to a promising photoluminescent organic material
Supramolecular self-assembly of a highly flexible and achiral meso bis(boron dipyrromethene) [bis-(BODIPY)] dye straightforwardly yields fluorescent micro-fibers, exhibiting an intriguing anisotropic photonic behavior. This performance includes the generation of chiroptical activity owing to spontaneous mirror symmetry breaking (SMSB). Repetition of several self-assembly experiments demonstrates that the involved SMSB is not stochastic but quasi deterministic in the direction of the induced chiral asymmetry. The origin of these intriguing (chiro)photonic properties is revealed by fluorescent microspectroscopy studies of individual micrometric objects, combined with X-ray diffraction elucidation of microcrystals. Such a study demonstrates that J-like excitonic coupling between bis(BODIPY) units plays a fundamental role in their supramolecular organization, leading to axial chirality. Interestingly, the photonic behavior of the obtained fibers is ruled by inherent nonradiative pathways from the involved push-pull chromophores, and mainly by the complex excitonic interactions induced by their anisotropic supramolecular organization
Ultraviolet–Visible Dual Absorption by Single BODIPY Dye Confined in LTL Zeolite Nanochannels
A new hybrid material with dual UV/vis
light-harvesting ability
has been prepared based on PM546 dye confined in zeolite L nanochannels.
Besides the characteristic vis green-yellow absorption of the dye
in solution, a new band arises due to specific host–guest interactions,
spanning the UV and blue edge of the vis. A chemical reaction takes
place between the PM546 and acid protons from the zeolite, removing
a fluorine atom from the BODIPY and giving rise to the new hypsochromic
absorption. As result, a single dye presents light absorption at two
different wavelengths, as well as a broad fluorescence emission, which
covers a wide part of the vis region through a FRET process
Förster Resonance Energy Transfer and Laser Efficiency in Colloidal Suspensions of Dye-Doped Nanoparticles: Concentration Effects
The donor and acceptor concentration
effects on Förster resonance energy transfer (FRET) and laser
properties of polymer nanoparticles (NPs) highly doped with two dyes
are comprehensively analyzed. Rhodamine 6G (Rh6G, donor) and Nile
Blue (NB, acceptor) are incorporated into anionic methacrylic NPs
∼40 nm in size, in concentrations [Rh6G] = 1–9 mM and
[NB] = 0.5–11 mM. The FRET efficiency is mostly influenced
by the acceptor concentration due to the presence of more available
energy traps and a reduction in the average donor/acceptor distances.
We show that the presence of homo-FRET among donors may give rise
to an enhancement on the net hetero-FRET efficiency mainly when the
concentration of donors exceeds that of the acceptors. When the concentration
of both dyes is raised beyond a given value, the FRET efficiency is
reduced due to the influence of competing quenching processes. Carefully
selected mixtures of Rh6G/NB allow achieving FRET efficiencies as
high as 88% and efficient laser emission in which the excitation/pumping
light has been fully transferred from Rh6G (∼575 nm) to NB
(∼700 nm). Finally, it is shown that, although a higher FRET
efficiency does not guarantee higher acceptor laser efficiencies,
both are mostly affected by the acceptor concentration and the total
amount of dye molecules inside the NPs. This study acquires special
relevance since the use of NPs not only allows achieving FRET efficiencies
much higher than those attainable in liquid solution (88% vs 57%)
but also opens the door to the study of FRET dynamics at concentrations
beyond the solubility limit in liquid solutions and without the undesirable
effects of reabsorption/re-emission processes (at least for the Rh6G/NB
pair)