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Effect of intermolecular interaction on excited-state properties of thermally activated delayed fluorescence molecules in solid phase: A QM/MM study
摘要： Recently, thermally activated delayed fluorescence (TADF) molecules have attracted great attention since nearly 100% exciton usage efficiency was obtained in TADF molecules. Most TADF molecules used in organic light-emitting diodes are in aggregation state, so it is necessary to make out the intermolecular interaction on their photophysical properties. In this work, the excited-state properties of the molecule AI-Cz in solid phase are theoretically studied by the combined quantum mechanics and molecular mechanics (QM/MM) method. Our results show that geometry changes between the ground state (S0) and the first singlet excited state (S1) are limited due to the intermolecular π-π and CH-π interactions. The energy gap between S1 and the first triplet excited state is broadened and the transition properties of excited states are changed. Moreover, the Huang-Rhys factors and the reorganization energy between S0 and S1 are decreased in solid phase, because the vibration modes and rotations are hindered by intermolecular interaction. The non-radiative rate has a large decrease in solid phase which improves the light-emitting performance of the molecule. Our calculation provides a reasonable explanation for experimental measurements and highlights the effect of intermolecular interaction on excited-states properties of TADF molecules.
关键词： Hybridized local and charge transfer state,Thermally activated delayed fluorescence,Intermolecular interactions,QM/MM method
更新于2025-09-23 15:21:01
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Carbazole/Benzimidazole-Based Bipolar Molecules as the Hosts for Phosphorescent and Thermally Activated Delayed Fluorescence Emitters for Efficient OLEDs
摘要： A series of carbazole/benzimidazole-based molecules, namely, o-CbzBiz, m-CbzBiz, and p-CbzBiz, were readily synthesized in three steps by integrating carbazole with benzimidazole via the ortho-, meta-, and para-positions of phenyl linked to N-phenyl carbazole. These bipolar molecules exhibited a maximum UV absorption band ranging from 310 to 327 nm and a maximum emission band ranging from 380 to 400 nm. Density functional theory calculations showed that the twist angles between the donor and acceptor moieties of these molecules were from 54.9 to 67.1°. Such a twisted structure hampered the π-electron conjugation within the molecule and resulted in high-lying LUMO levels and triplet energies, which make them suitable to be applied as host materials in OLED devices. Our results showed that a maximum external quantum efficiency (EQE) of OLED reached 21.8% when p-CbzBiz was applied as the host of a green phosphorescent emitter, i.e., Ir(ppy)2(acac). In addition, a maximum EQE of OLED reached 16.7% when o-CbzBiz with the host of a green TADF emitter, i.e., 4CzIPN. Moreover, these devices exhibited lower efficiency roll-off than the CBP-hosted device using the same emitters, which demonstrated the bipolar charge carrier property of carbazole/benzimidazole-based molecules.
关键词： thermally activated delayed fluorescence,bipolar molecules,phosphorescent,carbazole,OLEDs,benzimidazole
更新于2025-09-23 15:21:01
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Enhanced degradation efficiency of mixed industrial effluent by modified nanocomposite photocatalyst under UVLED irradiation
摘要： The aim of this study is to investigate the enhancement of photocatalytic degradation capacity of mixed industrial effluent using a modified activated charcoal/TiO2 nanocomposite catalyst. These nanocomposite catalysts are synthesized by the sol–gel method. The synthesized nanocomposite materials were characterized to confirmed material morphology and size by DLS, FTIR, crystallographic phase analysis (XRD), SEM, UV–Vis spectra, TGA and BET. This modified AC/TiO2 nanocatalyst removal efficiency is evaluated by photocatalytic degradation of mixed industrial effluent under UVLED light irradiation in different time intervals. The results demonstrate that the COD and BOD show 97% and 94% removal, respectively, at 90 min after that the degradation value becomes constant. Photocatalytic degradation of industrial effluent using AC/TiO2 followed pseudo-first-order reaction kinetics, and reaction rate constant was 1.04 × 10?2. Therefore, the performed experiment concludes that removal efficiency enhances to increase reaction time under UVLED irradiation.
关键词： UVLED irradiation,Photocatalytic degradation,Activated charcoal/TiO2 nanocomposite,Mixed industrial effluent
更新于2025-09-23 15:21:01
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Light addressable ion sensing for real-time monitoring of extracellular potassium
摘要： Visualization of ion distribution has broad applications. We report here on a light addressable potassium (K+) sensor where light illumination of a semiconducting silicon electrode substrate results in a localized activation of the faradaic electrochemistry at the illuminated spot. This allows one, by electrochemical control, to oxidize surface bound ferrocene moieties that in turn trigger K+ transfer from the overlaid K+-selective film to the solution phase. The resulting voltammetric response is shown to be K+-selective, where peak position is a direct function of K+ activity at the surface of electrode. This concept was used to measure extracellular K+ concentration changes by stimulating living breast cancer cells. The associated decrease of intracellular K+ level was confirmed with a fluorescent K+ indicator. In contrast to light addressable potentiometry, the approach introduced here relies on dynamic electrochemistry and may be performed in tandem with other electrochemical analysis when studying biological events on the electrode.
关键词： physiological condition,potassium,light activated electrochemistry,ion-selective electrode,potentiometry
更新于2025-09-23 15:21:01
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Light addressable ion sensing for real-time monitoring of extracellular potassium
摘要： Visualization of ion distribution has broad applications. We report here on a light addressable potassium (K+) sensor where light illumination of a semiconducting silicon electrode substrate results in a localized activation of the faradaic electrochemistry at the illuminated spot. This allows one, by electrochemical control, to oxidize surface bound ferrocene moieties that in turn trigger K+ transfer from the overlaid K+-selective film to the solution phase. The resulting voltammetric response is shown to be K+-selective, where peak position is a direct function of K+ activity at the surface of electrode. This concept was used to measure extracellular K+ concentration changes by stimulating living breast cancer cells. The associated decrease of intracellular K+ level was confirmed with a fluorescent K+ indicator. In contrast to light addressable potentiometry, the approach introduced here relies on dynamic electrochemistry and may be performed in tandem with other electrochemical analysis when studying biological events on the electrode.
关键词： physiological condition,potassium,light activated electrochemistry,ion-selective electrode,potentiometry
更新于2025-09-23 15:21:01
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Purine-based thermally activated delayed fluorescence emitters for efficient organic light-emitting diodes
摘要： Organic fluorescent materials possessing thermally activated delayed fluorescence (TADF) characteristics have attracted tremendous attention. Herein, two TADF emitters (1PXZP and 2PXZP) based on a novel biological base acceptor of 9-methylpurine and commonly used donor of phenoxazine (PXZ) have been successfully synthesized and characterized. Both target compounds possess nearly orthogonal configurations to reduce singlet-triplet splitting energy (ΔEST) for remarkable TADF character. The two emitters show good photoluminescence quantum yields (PLQYs), and thus the organic light-emitting diodes employing 1PXZP and 2PXZP as emitters display good performance with maximum external quantum efficiencies of 10.6% and 13.8%, respectively. The efficiencies of 1PXZP based device show nearly no roll-off at 100 cd m-2 luminance due to the short delayed lifetime (τd) of 3.2 μs. This work manifests that the biological base is a promising acceptor for designing TADF materials.
关键词： Thermally activated delayed fluorescence,organic light-emitting diode,aggregation-induced emission,purine
更新于2025-09-23 15:21:01
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Effect of Pulse Energy, Pulse Frequency, and Tip Diameter on Intracanal Vaporized Bubble Kinetics and Apical Pressure During Laser-Activated Irrigation Using Er:YAG Laser
摘要： Objective: Er:YAG laser-activated irrigation (LAI) is an effective method of root canal cleaning, but irrigant extrusion from the apical foramen has been a concern. We aimed to analyze the effects of pulse energy, pulse frequency, and laser tip diameter on intracanal vapor bubble kinetics and periapical pressure generation during LAI with Er:YAG laser. Background: Irrigant vapor bubble kinetics are one of indices of root canal cleaning ef?cacy. However, few studies have compared laser pulse conditions to vapor bubble kinetics, in relation to periapical pressure. Methods: A plastic root canal model (apical diameter 0.50 mm, 6% taper, 20 mm long) was ?lled with distilled water, and LAI with Er:YAG laser (Erwin AdvErl Unit; 30, 50, or 70 mJ; 10, or 20 pulses per second; laser tip R200T or R600T) was performed with the end of the tip ?xed at 15 mm from the root apex. The number, maximum diameter, and velocity of vapor bubbles were analyzed by high-speed video imaging. Pressure generated outside the apical foramen was measured with a pressure sensor. Results: Vapor bubble count and maximum diameter increased signi?cantly with pulse energy, pulse frequency, and tip diameter. Vapor bubble velocity increased signi?cantly with pulse frequency, but not with pulse energy or tip diameter. Periapical pressure increased signi?cantly with pulse energy, pulse frequency, and tip diameter. Conclusions: The pulse frequency was the single factor that signi?cantly affected all the examined parameters (the number, diameter, and velocity) of vapor bubble kinetics together with the periapical pressure.
关键词： Er:YAG laser,vapor bubble maximum diameter,vapor bubble velocity,laser-activated irrigation,vapor bubble count
更新于2025-09-23 15:21:01
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From micro to macro-contaminants: The impact of low-energy titanium dioxide photocatalysis followed by filtration on the mitigation of drinking water organics
摘要： This study evaluated strategies targeting macro- and micro-organic contaminant mitigation using low-energy titanium dioxide photocatalysis. Energy inputs of 1, 2, and 5 kWh m-3 resulted in incomplete oxidation of macro-organic natural organic matter, signified by greater reductions of UV254 and specific ultraviolet UV absorbance (SUVA) in comparison to dissolved organic carbon (DOC). The rate of UV254 removal was 3 orders of magnitude greater than the rate of DOC degradation. Incomplete oxidation improved operation of downstream filtration processes. Photocatalysis at 2 kWh m-3 increased the bed life of downstream granular activated carbon (GAC) filter by 340% relative to direct filtration pretreatment. Likewise, photocatalysis operated ahead of microfiltration decreased fouling, resulting in longer filter run times. Using 2 kWh m-3 photocatalysis increased filter run time by 36 times in comparison to direct filtration. Furthermore, levels of DOC and UV254 in the membrane permeate improved (with no change in removal across the membrane) using low-energy photocatalysis pretreatments. While high-energy UV inputs provided high levels of removal of the estrogenic micro-organics estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynlestradiol (EE2), low-energy photocatalysis did not enhance removal of estrogens beyond levels achieved by photolysis alone. In the cases of E1 and E3, the addition of TiO2 as a photocatalyst reduced degradation rates of estrogens compared to UV photolysis. Overall, process electrical energy per order magnitude reductions (EEOs) greatly improved using photocatalysis, versus photolysis, for the macro-organics DOC, UV254, and SUVA; however, energy required for removal of estrogens was similar between photolysis and photocatalysis.
关键词： granular activated carbon (GAC),estrogens,UV photolysis,dissolved organic carbon (DOC),advanced oxidation process (AOP),natural organic matter (NOM)
更新于2025-09-23 15:21:01
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Synergetic interface and morphology modification to achieve highly efficient solution-processed sky-blue organic light-emitting diodes
摘要： Solution-processed organic light-emitting diodes (OLEDs), especially blue OLEDs, generally suffer from the low efficiency. Herein, we report an efficient approach to achieve high efficiency by synergetic interface and morphology modification with a polymer, Poly(9-vinylcarbazole) (PVK). Sky-blue thermally activated delayed fluorescent (TADF) material, 10-(4-(4,6-diphenyl-1,3,5- triazin-2-yl)phenyl)-10H- spiro[acridine-9,9-fluorene] (SpiroAC-TRZ), is used as the emitter. The incorporation of PVK thin layer at the hole injection layer/emission layer (EML) interface and a small amount of PVK inner the EML modify the carrier behaviors at the interface and improve the EML morphology. As a result, balanced carrier distribution and reduced carrier recombination are realized at the interface and inner the EML. Through these strategies, the maximum external quantum efficiency and current efficiency of the optimal OLED achieve 25.1% and 53.5 cd/A. To the best of our knowledge, the efficiencies are the highest values ever achieved by the solution-processed sky-blue TADF OLEDs.
关键词： Blue organic light-emitting diodes,Thermally activated delayed fluorescence,High efficiency,All-solution process,Film morphology
更新于2025-09-23 15:21:01
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Flexible diphenylsulfone versus rigid dibenzothiophene-dioxide as acceptor moieties in donor-acceptor-donor TADF emitters for highly efficient OLEDs
摘要： Flexible versus rigid molecular structures of donor-acceptor-donor type compounds are investigated with respect to efficiency of thermally activated delayed fluorescence (TADF) by theoretical and experimental approaches. Three highly efficient TADF emitters based on flexible diphenylsulfone and rigid dibenzothiophene dioxide as acceptor units and di-tert-butyldimethyldihydroacridine as donor moiety were designed and synthesized. Despite they showed similar singlet-triplet splitting (0.01-0.02 eV) and high photoluminescence quantum yields in appropriate hosts, maximum external quantum efficiencies as different as 24.1 and 15.9/19.4% were obtained for organic light emitting devices based on these emitters with, respectively, flexible and rigid molecular structures. The high efficiency of the light-emitting compounds with the flexible molecular structure could be traced to the bi-configurational nature of the lowest singlet and triplet states resulting in higher spin-orbit coupling than for molecules with rigid structures. All derivatives showed bipolar charge transport character. High device efficiency with electron mobility of 3×10-5 cm2V-1s-1 and hole mobility of 1.3×10-4 cm2V-1s-1 at the electric field of 5×105 Vcm-1 was recorded for the layer of para-disubstituted diphenylsulfone with flexible molecular structure. This TADF emitter showed an excellent performance in the organic light emitting device, exhibiting a maximum current efficiency, power efficiency, and external quantum efficiency of 61.1 cdA-1, 64.0 lmW-1, and 24.1%, respectively.
关键词： Thermally activated delayed fluorescence,diphenylsulfone,di-tert-butyldimethyldihydroacridine,bipolar charge transport,dibenzothiophene dioxide
更新于2025-09-23 15:21:01