An asymmetric BODIPY triad with panchromatic absorption for high-performance red-edge laser emission

© The Royal Society of Chemistry 2015. A rational design of an unprecedented asymmetric cassette triad based entirely on BODIPY chromophores allows efficient light harvesting over the UV-vis spectral region, leading to a bright and stable red-edge laser emission via efficient energy-transfer processes.Peer Reviewe

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

A FRET analysis of dye diffusion in core/shell polymer nanoparticles

In this paper we show that dye distributions within polymer core/shell nanoparticles (NPs), grown in multiple steps, are controlled not only by the synthesis route, but are also governed by dye diffusion between core and shell, resulting in dye distributions completely different from the targeted ones. We show that Förster Resonance Energy Transfer (FRET) dynamics can be used as a spectroscopic measure to determine the particular dye profiles along the NPs and thus to uncover the presence of dye diffusion. Finally, to confirm the previous results and with the aim to have a clearer understanding of the diffusion processes within core/shell NPs (equilibrium and transient dye distributions, time scales, etcetera), we analyze the behaviour predicted by existing diffusion models and infer that the dye diffusion is already finished at the end of the shell growth. This journal is © the Partner Organisations 2014.Peer Reviewe

Emission properties of dye-doped cationic nanoparticles: Size, surfactant and monomeric composition effects

© The Royal Society of Chemistry 2015. Cationic nanoparticles (NPs) demonstrate advantages over similar anionic systems in relevant applications such as nanocarriers and biomarkers. To harness their unique properties and full potential in bioimaging, a clear understanding of the factors controlling the emission performance of dye-doped cationic NPs, especially under drastic pumping conditions such as those involved in high-resolution microscopy, is required. Herein, we present, for the first time, a comprehensive analysis of the photophysical and laser properties of Rhodamine 6G (Rh6G) doped cationic NPs in colloidal suspensions and self-assembled monoliths. Composition and morphological parameters such as dye content, weigh proportion of NPs in the solution, NPs size, dielectric constant of the surrounding medium, monomeric composition, and surfactant structure, have been mapped. The fluorescence capacity of Rh6G is mainly ruled by the size of the NP, as well as by its monomer and surfactant composition. The laser properties are more sensitive to compositional changes, since laser efficiencies ranging from 50% to 0% (no lasing) are measured. Hence, a most careful selection of monomers and surfactants must be carried out in order to boost their emission and photonic properties.Peer Reviewe

Focusing on charge-surface interfacial effects to enhance the laser properties of dye-doped nanoparticles

The synthesis of nanoparticles (NPs) for which only a single property is modified in a controlled manner is a challenge due to the fact that several physicochemical parameters are entangled. This letter assesses, from both experimental and theoretical points of view, the critical dependence on the charged-surface interfacial effect of the laser behavior in photonic nanomaterials based on dye-doped latexes without interference from other physicochemical parameters. When the dye and the NPs have similar charge nature, strong electrostatic repulsion prevents the dye molecules from being directly adsorbed in the surface and maintains the dye homogeneously distributed inside the NP, thus reducing deleterious interfacial effects. The highly homogeneous inner morphology leads to at least two-fold laser behavior enhancement of Rh6G in cationic NPs as compared with their anionic counterparts, and at least three-fold enhancement over Rh6G behavior in water solution. © 2014 Astro Ltd.Peer Reviewe

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). © 2014 American Chemical Society.Peer Reviewe

Tailoring the molecular skeleton of Aza-BODIPYs to design photostable red-light-emitting laser dyes

1 pagIn this article the design and characterization of a set of novel red-light-emitting laser aza-BODIPY dyes is reported. The applied synthetic method allows an exhaustive and versatile functionalization of both the dipyrrin core and the boron bridge. From the analysis of the photophysical and laser signatures, we determine the suitable modifications of the chromophoric backbone necessary to modulate the emission spectral region, efficiency and photostability under a strong irradiation regime. These dyes are endowed with efficient fluorescence and laser emission, and are particularly outstanding in terms of their high photostability, a key parameter to guarantee long-lasting emission in any (bio)technological application. The herein-reported results support, for the first time, the viability of aza-BODIPYs as tunable red laser dyes. In fact, the laser performances of some of the tested aza-BODIPYs surpass those of commercially available laser dyes in the same spectral region.This work was supported by the Spanish Ministerio de Economia y Competitividad (MAT2017‐83856‐C3) and Gobierno Vasco (IT912‐16

Towards Efficient and Photostable Red-Emitting Photonic Materials Based on Symmetric All-BODIPY-Triads, -Pentads, and -Hexads

The development of efficient and stable red and near-IR emitting materials under hard radiation doses and/or prolonged times is a sought-after task due to their widespread applications in optoelectronics and biophotonics. To this aim, novel symmetric all-BODIPY-triads, -pentads, and -hexads have been designed and synthesized as light-harvesting arrays. These photonic materials are spectrally active in the 655–730 nm region and display high molar absorption across UV–visible region. Furthermore, they provide, to the best of our knowledge, the highest lasing efficiency (up to 68 %) and the highest photostability (tolerance >1300 GJ mol) in the near-IR spectral region ever recorded under drastic pumping conditions. Additionally, the modular synthetic strategy to access the cassettes allows the systematic study of their photonic behavior related to structural factors. Collectively, the outstanding behavior of these multichromophoric photonic materials provides the keystone for engineering multifunctional systems to expedite the next generation of effective red optical materials.We gratefully acknowledge the Spanish Ministerio de Economia yCompetitividad for financial support (projectsCTQ201566702-R, MAT2017-83856-C3-1-P and 3-P). We also thank the Ministerio de Ciencia InnovacijnyU niversidades (project RTI2018-094862-B-I00) and the Gobierno Vasco for financial support (project IT912-16)and for apredoctoral fellowship to E.A.Z. The authors thank SGIker of UPV/EHU for technical support with the computational calculations, which were carried out in the “arina” informatic clus

A Palette of Efficient and Stable Far-Red and NIR Dye Lasers

© 2020 by the authors.The disposal of long-wavelength-emitting sources is of paramount relevance in technology and biophotonics due to the low interference with the surroundings that these kinds of far-red and near-infrared radiations hold. As a result of the continued efforts carried out during the last few years by our research group to design new boron-dipyrromethene (BODIPY) dyes with improved photonic performance, two approaches were tested to develop a new generation of organic dyes able to display efficient and long-lasting laser emission in both target spectral regions. On the one hand, the annulation of aromatic benzofuran at the dipyrrin backbone leads to conformationally restricted dyes yielding photostable and bright laser emission beyond 600 nm at the far-red spectral region. On the other hand, a more pronounced shift to longer wavelengths reaching 725 nm at the near-infrared region is feasible, while keeping a reasonably high laser efficiency and tolerance to prolonged and intense pumping, based on aza-BODIPYs bearing peripheral aryl rings. These two complementary strategies yield a library of laser-emitting compounds comprising the 600–725 nm spectral region. Moreover, their laser performance is better than the commercially available dye lasers active in this spectral window.This research was funded by the Spanish Ministerio de Economia y Competitividad (MINECO), grant number MAT2017-83856-C3-1-P, 2-P and 3-P, and Gobierno Vasco, grant number IT912-16.Peer reviewe