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.
Different laser dyes (with special interest in boron dipyrromethene) are incorporated as guests into the channels of zeolite L. The resulting doped material is fully characterized by steady‐state and time‐resolved photophysical techniques. The pores of zeolite L are filled with high amounts of dyes, which are exclusively present in their monomeric form and aligned in a preferential orientation, thus generating an organized photoactive material. The ordered disposition of the dye, mostly along the direction of the zeolite L nanochannels, was confirmed by confocal fluorescence microscopy. A careful selection of fluorophores along with controlled loading allows the harvest of light from the entire ultraviolet/visible region for conversion into white light, or alternatively, tuning of the emission in the blue, green, and red regions, owing to the presence of energy‐transfer processes in the antenna systems built up in this work.
Boosted excitation energy transfer in spiranic O-BODIPY/polyarene cassettes, when compared with the parent non-spiranic (flexible) system, is highlighted as a proof for the ability of a new structural design to improve the energy transfer in molecular cassettes.
The donor and acceptor concentration effects on Forster 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).
Hybrid soft materials composed of CdSe-CdS nanorods or "quantum rods" (QRs) and the fluorescent 2,3-didecyloxyanthracene (DDOA) low molecular weight organogelator are obtained through self-assembly. Spectroscopy, microscopy, and rheology studies show that the QRs and DDOA coassemble, thereby stabilizing the organogels. Depending on the QR load and excitation wavelength, single nanofibers (NFs) of the hybrid gel display either sharp polarized red luminescence (under green excitation), or dual perpendicularly polarized blue and red emissions (under UV excitation). Transmission electron microscopy, microspectroscopy, and quantum rod orientation microscopy (QROM) reveal that QRs align along the organogel NFs with order parameters reaching 76% and 87%. This paves the way for obtaining surfaces of QR/NF assemblies yielding sharp red linearly polarized emission. In addition, this work demonstrates that QRs can be used more generally to probe nanostructured soft materials, even nonemissive ones. QROM allows to establish maps of the orientation of single QRs dispersed onto or within a gel network by measuring the polarization of the emission of the individual QRs. As occurs within this work in which QRs and NFs interact, the orientation of each QR reveals information on the underlying nanostructure (such as surface striation, bundle formation, and helicity).
We report the synthesis, and spectroscopic and electrochemical properties of a selected library of novel spiranic O-BODIPYs bearing a phenol-based bi(polyarene) unit tethered to the boron center through oxygen atoms. These dyes constitute an interesting family of arene-BODIPY dyads useful for the development of photonic applications due to their synthetic accessibility and tunable photonic properties. It is demonstrated that the electron-donor capability of the involved arene moiety switches on a non-emissive intramolecular charge transfer (ICT) state, which restricts the fluorescence efficiency of the dyad. Interestingly, the influence of this non-radiative deactivation channel can be efficiently modulated by the substitution pattern, either at the dipyrrin ligand or at the polyarene moiety. Thus, dyads featuring electron-rich dipyrrin and electron-poor polyarene show lower or almost negligible ICT probability, and hence display bright fluorescence upon dual excitation at far-away spectral regions. This synthetic approach has allowed the easy development of low-cost efficient ultraviolet-absorbing visible-emitting cassettes by selecting properly the substitution pattern of the involved key units, dipyrrin and bi(polyarene), to modulate not only absorption and emission wavelengths, but also fluorescence efficiencies.
Here, a method is described for the synthesis of Linde type L (LTL) zeolite under microwave-assisted hydrothermal conditions, and its behavior as a support for heterogeneously catalyzed hydrogen production is detailed. Microwave heating reduces the reaction time and improves the quality of the LTL zeolite crystals in comparison to those obtained using conventional ovens. The size and morphology of zeolite can be fi nely modulated by the composition of the gel and reaction conditions (heating rate, static/dynamic conditions, aging, reaction time, etc). The physicochemical properties of the synthesized LTL zeolites make them appropriate catalyst supports for reforming reactions in which high hydrogen production yields are desired. Therefore, rhodium-and nickel-based bimetallic catalysts are prepared in order to be tested by dry and oxidative biogas reforming processes at 800 °C and atmospheric pressure for hydrogen production. For all the catalysts tested, except for the sodium-exchanged disc-shaped zeolite, hydrogen yields close to the predicted by the equilibrium conversion are reached.
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