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Boosting Efficiency of Near‐Infrared Organic Light‐Emitting Diodes with Os(II)‐Based Pyrazinyl Azolate Emitters
摘要： Tremendous effort has been devoted to developing novel near-infrared (NIR) emitters and to improving the performance of NIR organic light-emitting diodes (OLEDs). Os(II) complexes are known to be an important class of NIR electroluminescent materials. However, the highest external quantum efficiency achieved so far for Os(II)-based NIR OLEDs with an emission peak wavelength exceeding 700 nm is still lower than 3%. A new series of Os(II) complexes (1–4) based on functional pyrazinyl azolate chelates and dimethyl(phenyl)phosphane ancillaries is presented. The reduced metal-to-ligand charge transfer (MLCT) transition energy gap of pyrazinyl units in the excited states results in efficient NIR emission for this class of metal complexes. Consequently, NIR OLEDs based on 1–4 show excellent device performance, among which complex 4 with a triazolate fragment gives superior performance with maximum external quantum efficiency of 11.5% at peak wavelength of 710 nm, which represent the best Os(II)-based NIR-emitting OLEDs with peak maxima exceeding 700 nm.
关键词： N-donor,phosphorescence,osmium,near-infrared emission,organic light-emitting diodes
更新于2025-09-11 14:15:04
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Fast repetition rate fs pulsed lasers for advanced PLIM microscopy
摘要： Simultaneous metabolic and oxygen imaging is promising to follow up therapy response, disease development and to determine prognostic factors. FLIM of metabolic coenzymes is now widely accepted to be the most reliable method to determine cellular bioenergetics. Also, oxygen consumption has to be taken into account to understand treatment responses. The phosphorescence lifetime of oxygen sensors is able to indicate local oxygen changes. For phosphorescence lifetime imaging (PLIM) dyes based on ruthenium (II) coordination complexes are useful, in detail TLD1433 which possesses a variety of different triplet states, enables complex photochemistry and redox reactions. PLIM is usually reached by two photon excitation of the drug with a femtosecond (fs) pulsed Ti:Sapphire laser working at 80 MHz repetition rate and (time-correlated single photon counting) (TCSPC) detection electronics. The interesting question was whether it is possible to follow up PLIM using faster repetition rates. Faster repetition rates could be advantageous for the induction of specific photochemical reactions because of similar light doses used normally in standard CW light treatments. For this, a default 2p-FLIM–PLIM system was expanded by adding a second fs pulsed laser ("helixx") which provides 50 fs pulses at a repetition rate of 250 MHz, more than 2.3 W average power and tunable from 720 nm to 920 nm. The laser beam was coupled into the AOM instead of the default 80 MHz laser. We demonstrated successful applications of the 250 MHz laser for PLIM which correlates well with measurements done by excitation with the conventional 80 MHz laser source.
关键词： oxygen consumption,Ru(II) complexes,phosphorescence lifetime microscopy,Multiphoton microscopy,fast repetition rate excitation,short laser pulses
更新于2025-09-11 14:15:04
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Exciplex-forming derivatives of 2,7-di-tert-butyl-9,9-dimethylacridine and benzotrifluoride for efficient OLEDs
摘要： Strongly medium dependent capability to exhibit not only prompt/delayed thermally-activated fluorescence but also aggregation-induced phosphorescence or exciplex emission is demonstrated either for solutions or for solid samples of acridan-based luminophores. Multicolour emissions of different nature were detected and studied for donor-acceptor derivatives of 2- or 4-(trifluoromethyl)benzene and 2,7-di-tert-butyl-9,9-dimethylacridine containing trifluoromethyl groups in ortho and para positions. For the demonstration of one of possible applications, both compounds were tested in the emissive layers of exciplex-based OLEDs. In the best case, their high maximum current, power and external quantum efficiences of 29.5 cd/A, 29.1 lm/W and 8.2 % respectively were achieved for the device based on exciplex electroluminescence resulting from recombination of intermolecular charge transfer states formed on the interface of electron-donating and electron-accepting molecules used.
关键词： exciplex,acridan,thermally activated delayed fluorescence,room temperature phosphorescence,OLED
更新于2025-09-11 14:15:04
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Neutral heteroleptic cyclometallated Platinum(II) complexes featuring 2-phenylbenzimidazole ligand as bright emitters in solid state and in solution
摘要： A series of 8 neutral cyclometallated platinum(II) complexes featuring 2-phenylbenzimidazole chromophoric ligand and acetylacetonate as ancillary ligand has been synthesized and characterized. The introduction of a variety of substituent on the phenyl ring allows to finely tune the emission wavelength. The emission data reveal high quantum yield in deaerated solution and in bulk solid state (micro-crystalline powder), with values up to an impressive 51%. The emission for all of the complexes is attributed to a mixed 3LC-MLCT state. Both absorption and emission data have been correlated successfully with the redox potentials and the Hammett parameters.
关键词： photophysics,phosphorescence,platinum,organometallic,solid state emission
更新于2025-09-10 09:29:36
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Precise Control of Localized Surface Plasmon Wavelengths Is Needed for Effective Enhancement of Triplet-Triplet Annihilation-Based Upconversion Emission
摘要： In this study, we demonstrate that the localized surface plasmon (LSP) resonance of metal nanoparticles, depending strictly on the generating wavelength of LSP resonance, can have both beneficial enhancement and harmful quenching effects on a triplet-triplet annihilation-based upconversion (TTA-UC) emission. When the LSP resonance band of anisotropic silver nanoprisms spectrally overlapped with the photoexcitation wavelength of a sensitizer and the fluorescence of an emitter, an increase in the photoexcitation efficiency and an acceleration of the radiative decay rate were respectively induced, resulting in an effective enhancement in the TTA-UC emission. Furthermore, the overlapping with the photoexcitation wavelength led to a significant decrease (93%) in the threshold light excitation intensity, which greatly enhances the figure-of-merit in TTA-UC systems. However, when the LSP resonance band overlapped with the phosphorescence band of the sensitizer, the TTA-UC emission was extremely quenched, accompanied by the enhanced phosphorescence and the decreased phosphorescence lifetime. These results suggest that the decrease in the TTA-UC emission is a result of the competition between the triplet-triplet energy transfer to the emitter and the LSP-induced nonradiative energy transfer to the silver nanoprisms from the triplet-excited sensitizer. This discovery of the conflicting effects of LSP resonance provides an important guideline: a precise adjustment of LSP resonance wavelengths is needed for the efficient enhancement of TTA-UC emission. This requirement is different from those of other fluorescence systems such as single downconverted fluorophores and lanthanide-based upconversion nanoparticles.
关键词： solid state,fluorescence,phosphorescence,silver nanoprisms,localized surface plasmon resonance,triplet-triplet annihilation,photon upconversion
更新于2025-09-10 09:29:36
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Hydrogen-Bonded Two-Component Ionic Crystals Showing Enhanced Long-Lived Room-Temperature Phosphorescence via TADF-Assisted F?rster Resonance Energy Transfer
摘要： Molecular room-temperature phosphorescent (RTP) materials with long-lived excited states have attracted widespread attention in the fields of optical imaging, displays, and sensors. However, accessing ultralong RTP systems remains challenging and examples are still limited to date. Herein, a thermally activated delayed fluorescence (TADF)-assisted energy transfer route for the enhancement of persistent luminescence with an RTP lifetime as high as 2 s, which is higher than that of most state-of-the-art RTP materials, is proposed. The energy transfer donor and acceptor species are based on the TADF and RTP molecules, which can be self-assembled into two-component ionic salts via hydrogen-bonding interactions. Both theoretical and experimental studies illustrate the occurrence of effective F?rster resonance energy transfer (FRET) between donor and acceptor molecules with an energy transfer efficiency as high as 76%. Moreover, the potential for application of the donor–acceptor cocrystallized materials toward information security and personal identification systems is demonstrated, benefitting from their varied afterglow lifetimes and easy recognition in the darkness. Therefore, the work described in this study not only provides a TADF-assisted FRET strategy toward the construction of ultralong RTP, but also yields hydrogen-bonding-assembled two-component molecular crystals for potential encryption and anti-counterfeiting applications.
关键词： thermally activated delayed fluorescence,energy transfer,cocrystallization,hydrogen bonding self-assembly,room-temperature phosphorescence
更新于2025-09-10 09:29:36
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Iridium(III) Complex-based Activatable Probe for Phosphorescent/Time-gated Luminescent Sensing and Imaging of Cysteine in Mitochondria of Live Cells and Animals
摘要： This study reports an activatable iridium(III) complex probe for phosphorescence/time-guminescence detection of cysteine (Cys) in vitro and in vivo. The probe, [Ir(ppy)2(NTY-bpy)](PF6), is developed by incorporating a strong electron withdrawing group, nitroolefin, into a bipyridine ligand of the Ir(III) complex. The luminescence of the probe is quenched due to the intramolecular charge transfer (ICT) process, but switched on by a specific recognition reaction between the probe and Cys. [Ir(ppy)2(NTY-bpy)](PF6) shows high sensitivity and selectivity for Cys detection and good biocompatibility. The long-lived emission of [Ir(ppy)2(NTY-bpy)](PF6) allows time-gated luminescence analysis of Cys in cells and human sera. These properties make it convenient for the phosphorescence and time-gated luminescence imaging and flow cytometry analysis of Cys in live samples. The Cys images in cancer cells and inflamed macrophage cells reveal that [Ir(ppy)2(NTY-bpy)](PF6) is distributed in mitochondria after cellular internalization. Visualizations and flow cytometry analysis of mitochondrial Cys levels and Cys-mediated redox activities of live cells are achieved. Using [Ir(ppy)2(NTY-bpy)](PF6) as a probe, in vivo sensing and imaging of Cys in D. magna, zebrafish, and mice are then demonstrated.
关键词： Sensing and Imaging,Time-gated luminescence,Iridium(III) complex,Cysteine,Phosphorescence
更新于2025-09-10 09:29:36
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Self-activated emission and spectral temperature-dependence of Gd8V2O17 phosphor
摘要： Gd8V2O17 was prepared via the facile solid-state reaction. The optical absorption, temperature-dependent luminescence, and decay lifetimes were investigated. Gd8V2O17 has a direct allowed electronic transition with band gap energy of 3.18 eV. Under the excitation of UV light, the phosphor shows the typical self-activated luminescence from the charge transfer (CT) transitions in VO4 3? groups. The emission intensity has a nearly constant value from 10 to 150 K, while it increases above 150 K. And the emission has an abnormal blue-shift with the increase of temperature from 10 to 300 K, so the luminescence color varies from green to blue. Over the whole temperature ranges, the maximum emission wavelength showed a linear dependence on temperature; consequently, the temperature-dependent properties have a potential advantage in luminescence thermometry. The luminescence mechanism was discussed on the proposed two VO4 emission centers and the energy transfer between them.
关键词： Vanadate,Luminescence,Optical materials and properties,Optical thermometry,Phosphorescence
更新于2025-09-10 09:29:36
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Defect-induced Fluorescence of Silica Nanoparticles for Bioimaging Applications
摘要： With biocompatibility, biodegradability, and high functionality, silica nanoparticles (SNPs) have been widely investigated for various biomedical applications. However, lack of optical fluorescence has limited the application of SNPs as a degradable imaging agent. Here, we hydrothermally synthesized fluorescent SNPs by artificially generating optically active defect centers using tetraethyl orthosilicate and (3-aminopropyl)trimethoxysilane. The synthesized SNPs demonstrated strong blue photoluminescence originating from the dioxasilyrane (=Si(O2)) and silylene (=Si:) defect centers with the aid of aminopropyl groups. Furthermore, phosphorescence was observed at 459 nm, indicating the presence of silylene in SNPs. Finally, these SNPs have been successfully utilized as a fluorescent probe for bioimaging of normal, cancer, and macrophage cells.
关键词： silica nanoparticle,silylene,dioxasilyrane,phosphorescence,defect,photoluminescence,bioimaging
更新于2025-09-10 09:29:36
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Ultralong Organic Phosphorescence in the Solid State: the Case of Triphenylene Cocrystals with Halo- and Dihalo-penta/tetrafluorobenzene
摘要： The polycyclic aromatic hydrocarbon (PAH) triphenylene (TP) has been reacted with halo-pentafluorobenzene (XF5, X = Br, I) and 1,4-dihalo-tetrafluorobenzene (X2F4, X = Br, I) to yield the corresponding cocrystals TP·BrF5, TP·Br2F4, TP·IF5, and TP·I2F4 form I. These materials have been synthesized by dissolving TP into an excess of liquid or molten co-former, and single crystals have been grown via seeding chloroform solutions. They have been fully characterized by a combination of techniques including X-ray diffraction, Raman, and luminescence spectroscopy in the solid state. TP·I2F4 form I was found to undergo a single-crystal to single-crystal (SCSC) polymorphic phase transition induced by temperature (when cooled down to 100K) leading to the new form TP·I2F4 form II, which is transformed back into the first structure when brought again at RT. This behavior was confirmed also by Raman spectroscopy. Upon cocrystallization and as a result of the external heavy atom effect, all crystalline materials exhibited bright room temperature phosphorescence clearly visible by naked eye. The latter was almost exclusive for cocrystal TP·I2F4, whereas for TP·Br2F4 both fluorescence and phosphorescence were detected. In TP·Br2F4, the phosphorescence lifetime was of the order of 200 ms, and with the visual outcome of an orange phosphorescence lasting for a couple of seconds upon ceasing the excitation, that makes this compound classifiable as an Ultralong Organic Phosphorescent (UOP) material. The results evidenced the role of the nature of the heavy atom in governing the phosphorescence output from organic cocrystals.
关键词： Room Temperature Phosphorescence,Triphenylene Cocrystals,Ultralong Organic Phosphorescence,Dihalo-tetrafluorobenzene,Halo-pentafluorobenzene
更新于2025-09-09 09:28:46