ChemPhotoChem最新文献

Organic materials possessing multiple functional properties such as aggregation induced emission, mechanochromism and acidochromism are rare. In this paper we demonstrate the design of polyfunctional materials using the aggregation quenching chromophore, pyrene. The pyrene derivatives possessing 2,3,3-triphenylacrylonitrile as aggregation induced emission chromophore and phenanthroimidazole or N-phenylcarbazole as auxiliary electron-rich chromophore are designed, synthesized by Suzuki coupling reactions and characterized as aggregation induced emissive mechanochromic materials. Though all the dyes exhibit aggregation induced emission, the dyes containing para-linked 2,3,3-triphenylacrylonitrile and auxiliary chromophore such as phenanthroimidazole or N-phenylcarbazole display mechanochromism. Additionally, the phenanthroimidazole containing dyes show acidochromism attributable to the protonation of phenanthroimidazole moiety.

Two regioisomeric extended tetrathiafulvalenes (TTFs) incorporating diindeno-fused corannulene spacers were synthesized from suitable dione precursors using Horner-Wadsworth-Emmons olefination reactions. Both compounds are strong chromophores with a longest-wavelength absorption that exhibited some degree of charge-transfer character as inferred from solvatochromic behaviors and frontier orbital calculations. The compounds underwent two reversible one-electron oxidations and a quasi-reversible third oxidation during cyclic voltammetry conditions. The mono- and dications had characteristic NIR absorptions and both were EPR active. The dications with potential diradicaloid characters underwent reactions when generated in bulk.

Miniaturization of organic afterglow materials has shown promising application in biomedical and other areas. Current technologies, such as nanoprecipitation, mechanical treatment, and emulsion polymerization, lack the capability of facile control on the morphology and dimension of the miniaturized organic afterglow materials. Here we report the fabrication of organic afterglow nanostructures via block copolymer self-assembly at room temperature. The fabrication is based on two-component design strategy where hydrophobic luminescent emitters with small rate constants of phosphorescence decay or reverse intersystem crossing are designed as the first component. Amphiphilic block copolymers that can form spherical core-shell micelles and worm-like micelles with glassy hydrophobic cores are used as the second component. Upon addition of water into a dimethylformamide solution that contains the two components, the amphiphilic block copolymers self-assemble into well-defined nanostructures and accommodate the hydrophobic luminescent emitters in nanostructure's hydrophobic cores. After switching to pure water by dialysis, room-temperature afterglow nanostructures have been obtained because of the excellent protection of organic triplets by the glassy hydrophobic cores. The afterglow nanostructures exhibit intriguing afterglow mechanism modulated by the types of luminescent emitters, controlled dimensions and morphologies by the structural parameters of the block copolymers.

The reactivity of Cannabigerol (CBG, 1) in organic solvents under photochemical and acid catalyzed conditions has been investigated in detail. The obtained results pointed out the presence of different reaction paths in the photochemical and the acid-catalyzed conditions, with a remarkable selectivity toward the formation of a 2,2-disubstituted-chromane derivative in the first case.

Metal mixed-halide perovskite has demonstrated considerable potential in the development of solution-treated blue light-emitting diodes (LEDs) with high external quantum efficiency, excellent color purity, and tunable wavelength. However, the severe phase segregation of mixed-halide perovskite under bias voltage would lead to the spectral instability of LEDs. Therefore, suppressing phase segregation of Br/Cl perovskite towards spectrally stable blue perovskite LEDs (PeLEDs) is a big challenge. In this work, we systematically explore the influence of perovskite component, preparation conditions, and device structures on the spectral stability of PeLEDs. We have observed that the stable spectra increased the proportion of Cs in the A-site cations, passivator, and the annealing temperature of perovskite films. Finally, we achieve a spectra-stable and high-performance blue PeLED under optimized conditions. Our findings provide important guidance for preparing spectrally stable PeLEDs.

To enhance organic light emitting diode (OLED) performance, host materials with high triplet energies are crucial for confining excitons, despite increasing driving voltages due to the singlet-triplet energy gap. We synthesized sulfonylbis(4,1-phenylene)bis(3,6-disubstituted-9H-carbazole) derivatives as donor-acceptor-donor host materials, namely compounds 3, 5 and 7, with varying fluorination levels. These compounds show moderate singlet-triplet energy splitting and molecular dipole moments, allowing for fine-tuning of hole-transport mobilities, deeper frontier orbital energies, and a red shift in singlet emission while maintaining high triplet energy levels. These adjustments impact a range of physical, electronic and optical properties. The materials exhibit exceptional thermal stability, with decomposition starting above 400 °C and glass transition temperatures over 130 °C. Used with the green TADF emitter DACT-II, these hosts enable reverse intersystem crossing rates between 7.43×10⁴ s⁻¹ and 1.77×10⁵ s⁻¹. While OLEDs using mCP as a reference host achieve a maximum quantum efficiency of 18.5 %, those with host 5 show lower efficiency roll-off, leading to higher external quantum efficiency at brightness levels above 2000 cd/m² without colour shift. The reduced roll-off in devices with host 5 compared to mCP is attributed to effective Förster and Dexter energy transfers to DACT-II at high currents, enhancing light emission pathways.

In recent years, parahydrogen-induced hyperpolarization has become a focus for future medical applications. Similar to the established dynamic nuclear polarization method, a biocompatible bolus from a hyperpolarized sample can be produced for in vivo studies. However, this requires removing toxic hydrogenation catalysts, which inevitably must be used. Additionally, the ratio between the substrate to be hyperpolarized (e. g. pyruvate) and a mandatory catalyst must also be maintained. Even the smallest differences can lead to a reduction in generated signal amplification. In particular, weighing small amounts of catalysts leads to inaccuracies in sample preparations. Fluorescence spectroscopy provides a rapid and sensitive enough approach to determine catalyst concentration. The Ir-IMes metal complexes used in SABRE lead to a quenching of the fluorescence of the solvent, dependent on its concentration. This can be used to quickly estimate the actual concentration in a solution with very small quantities of catalysts. Hence, fluorescence spectroscopy offers a rapid and reliable quality control method for the preparation of samples to be hyperpolarized. In addition, it can also be used as a quality control method to assess filtration efficacy before administration of hyperpolarized samples.

Herein, we have designed aqueous dispersed self-assembled nanostructures with diverse morphologies from the zinc tetraphenyl porphyrin (ZnTPP) monomer employing simple solution-based coprecipitation methods. Detailed morphological studies have been carried out by various electron microscopy techniques. Finally, the structural features were correlated with the underpinning photophysical processes using steady-state and time-resolved spectroscopy. Detailed studies suggest that controlled morphology and highly defined intermolecular interactions affect the overall photoinduced charge transfer process. Based on the fundamental investigations, all these different types of nanostructures have been utilized as photocatalysts for solar hydrogen production without using any cocatalysts, and it was found that the spherical nanostructure exhibits significantly higher H₂ production rates of ∼1682 μ mole/g, which is a few folds higher than other 1D and 2D nanostructured materials. The experimental findings were further supported by the TD-DFT study. Furthermore, the detailed computational studies suggest that the spherical aggregates exhibited a more vital interaction between the ZnTPP molecules, causing significant electronic coupling between bright local excited and charge transfer states, which supports our experimental findings. Finally, we have selectively utilized the oxidative half-reaction for the simultaneous transformation of glycerol to valuable chemicals along with photocatalytic H₂ production through reductive half-reaction.

We have designed and synthesized a novel series of cyanostilbene-based amorphous molecular materials with different methylene chain lengths, BMAC-n (n=3,4,5,6), and investigated their emitting properties in solution and various solid states. All BMAC-n molecules showed solvatochromic fluorescence in solutions. Emission spectra of BMAC-n molecules in the same solution were identical to one another irrespective of the methylene chain length while the spectra in crystalline states depended on their methylene chain length. As in solutions, emission spectra of their spin-coated amorphous films were identical to each other irrespective of the methylene chain length. Emission spectra of rubbed amorphous films prepared by grinding their crystals were identical to those for spin-coated amorphous films; however, comparative studies between spin-coated and rubbed amorphous films indicated that fluorescence quantum yields and photochemical reactivity depend on the preparation method.

The ongoing search for innovative and environmentally friendly luminescent materials coupled with customizable physical and chemical properties at the nanoscale positions carbon dots (CDots) as ideal candidates for photonic applications. However, even today, their rational design for specific applications remains elusive due to the unknown relationship between optical and structural properties. Therefore, this study aims to fill this gap by linking the chemical structure of the precursor and synthetic conditions to the final structural composition of the CDots and, by extension, to their optical properties. The study shows that while CDots are chemically stable, their optical properties, which are determined by the carbonaceous core and surface groups, are highly pH dependent. These properties, together with the long fluorescence lifetimes observed in living cells (>10 ns), make these biomass-derived CDots promising probes for time-resolved fluorescence imaging.