RESUMO
The adverse aggregated-caused quenching (ACQ) problem of most electroluminescent materials existing in highly doped thin films is one of the key factors impeding the commercialization of high-efficiency organic light-emitting diodes (OLEDs) panel. Whereas, by delicately constructing and modulating moderate intermolecular interactions, some aggregates have been demonstrated to present distinct luminescent properties such as tunable emission spectra, improved photoluminescence quantum yields, different emission mechanism and enhanced horizontal transition dipole ratio (Θ) of emitting layer, providing feasible solution for ACQ problem. The luminescence from newly generated emissive state in aggregates is different from the traditional "isolated" molecules in organic electronics and will possess novel properties and applications. Herein, we summarize the different types of intermolecular interactions within emitter aggregates exhibiting distinct luminescent mechanisms, as well as their effects on photoluminescent and electroluminescent properties, offering reliable reference for the advancement of highly efficient OLEDs utilizing aggregated emitters.
RESUMO
Polychlorinated (hetero)arenes have shown great promise for organic optoelectronics applications. However, the harsh synthetic routes for polychlorinated compounds and the possible luminescence quenching from the compact intermolecular π-π stacking induced by chlorine atoms limit their investigations and applications in luminescent materials. Herein, two isomeric polychlorinated polycyclic aromatic hydrocarbon (PAH) compounds JY-1-Cl and JY-2-Cl consisting of rigidified aryl ketones and amine are designed and synthesized under mild conditions through nucleophilic chlorination intermediated by an electron donor-acceptor complex. Among them, as a result of the strong π-π interactions induced by chlorine atoms, JY-2-Cl exhibits bright monomer and dimer emissions with dual thermally activated delayed fluorescence (TADF) characters. Notably, compared with the non-chlorinated compounds, a high photoluminescence quantum yield is maintained after introducing multiple chlorine atoms into JY-2-Cl. The first dual-TADF organic light-emitting diodes are also successfully fabricated with maximum external quantum efficiency as high as 29.1 % by employing JY-2-Cl as emitter. This work presents a new paradigm and synthesis of polychlorinated amine-carbonyl PAHs and demonstrates the great potential of the chlorinated materials for luminescent applications.
RESUMO
Sulfone-embedded heterocyclics are of great interest in organic light-emitting diodes (OLEDs), however, exploring highly efficient narrowband emitters based on sulfone-embedded heterocyclics remains challenging. Herein, five emitters with different sulfur valence state and molecular rigidity, namely tP, tCPD, 2tCPD, tPD and tPT, are thoroughly analysed. With restricted twisting of flexible peripheral phenyl by strengthening molecular rigidity, molecular emission spectra can be enormously narrowed. Further, introducing the sulfone group with bending vibration in low-frequency region that suppresses high-frequency vibration, sharp narrow full-widths at half-maximum of 28 and 25â nm are achieved for 2tCPD and tPD, respectively. Maximum external quantum efficiencies of 22.0 % and 27.1 % are successfully realized for 2tCPD- and tPD-based OLED devices. These results offer a novel design strategy for constructing narrowband emitters by introducing sulfone group into a rigid molecular framework.
RESUMO
Aromatic imide derivatives play a critical role in boosting the electroluminescent (EL) performance of organic light-emitting diodes (OLEDs). However, the majority of aromatic imide-based materials are limited to long wavelength emission OLEDs rather than blue emissions due to their strong electron-withdrawing characteristics. Herein, two novel polycyclic fused amide units were reported as electron acceptor to be combined with either a tetramethylcarbazole or acridine donor via a phenyl linker to generate four conventional fluorescence blue emitters of BBI-4MeCz, BBI-DMAC, BSQ-4MeCz and BSQ-DMAC for the first time. BSQ-4MeCz and BSQ-DMAC based on a BSQ unit exhibited higher thermal stability and photoluminescence quantum yields than BBI-4MeCz and BBI-DMAC based on a BBI unit due to their more planar acceptor structure. The intermolecular interactions that exist in the BSQ series materials effectively inhibit the molecular rotation and configuration relaxation, and thus allow for blue-shifted emissions. Blue OLED devices were constructed with the developed materials as emitters, and the effects of both the structure of the polycyclic fused amide acceptor and the electron donor on the EL performance were clarified. Consequently, a sky-blue OLED device based on BSQ-DMAC was created, with a high maximum external quantum efficiency of 4.94% and a maximum luminance of 7761 cd m-2.
RESUMO
Highly efficient organic thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) emitters for organic light-emitting diodes (OLEDs) generally consist of a twisted donor-acceptor skeleton with aromatic amine donors. Herein, through introducing sulfur atoms into isomeric pentaphene and pentacene frameworks, we demonstrate a set of polycyclic luminophores exhibiting efficient TADF and RTP characters. The incorporation of sulfur atoms confirms a folded molecular plane, while intensifies singlet-triplet spin-orbit coupling. Further, the isomeric effect has a significant effect on the electronic structure of excited state, giving rise to the investigated compounds tunable luminescence mechanisms of TADF and RTP. With efficient triplet harvesting ability, maximum external quantum efficiencies up to 25.1 % and 8.7 % are achieved for the corresponding TADF and RTP OLEDs, verifying the great potential of sulfur-bridged frameworks for highly efficient devices.
RESUMO
BACKGROUND We introduce a minimally invasive technique for the treatment of Raynaud disease - CT-guided percutaneous thoracic sympathetic chain radiofrequency thermocoagulation. MATERIAL AND METHODS Under CT guidance, the radiofrequency needle was punctured from the upper edge of the costotransverse joint to the anterior superior edge of the 4th capitulum costae and the lateral parietal pleura. After sensorial (1.5 mA, 50 Hz) and motorial (1.5 mA, 2Hz) testing to determine that there was no nerve innervation zone with muscle numbness and twitches, radiofrequency coagulation was set at 95°C for 300 s. RESULTS A total of 17 patients were enrolled in the treatment group. All the patients underwent CT-guided percutaneous thoracic sympathetic chain puncture of the needles to the upper edge of the 4th capitulum costae on both sides. The perfusion index (PI) of the fingers began to rise 30 s after radiofrequency thermocoagulation, and the palm temperature (T) began to rise after 90 s. At the end of treatment, PI increased by an average of 4.6-fold, and the T average rose by 3.6°C. Postoperative cold-water stimulation testing could no longer induce Raynaud disease. Follow-up was conducted for 1 to 15 months. Two patients were found to have recurrence at 9 months and 13 months, respectively. CONCLUSIONS CT-guided percutaneous thoracic sympathetic nerve chain radiofrequency coagulation can effectively treat Raynaud disease.
Assuntos
Eletrocoagulação/métodos , Terapia por Radiofrequência/métodos , Doença de Raynaud/terapia , Adulto , China , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ondas de Rádio , Tomografia Computadorizada por Raios X , Resultado do TratamentoRESUMO
Sea sand, a vital sand and gravel resource, is rich in chloride, which causes corrosion of steel reinforcements. This study investigates the effect of the electrochemical chlorine evolution reaction (CER) on the desalination of sea sand. The results indicate that the chlorine removal efficiency (RE) of sea sand increased from 48.76 to 56.40 % under optimal conditions: a current density of 15 mA/cm2, an electrolysis time of 1 min, and a sodium sulphate-supported electrolyte concentration of 0.05 mol/L. After 30 days of resting, the dissolved chlorine content in sea sand was 0.154 %, which was 21.03 % lower than that of the control group. The electrically active chlorine-mediated desalination process demonstrated excellent dechlorination ability, facilitated the transformation of metal and organic chlorine into liquid and gaseous forms, and reduced the slow release of chloride from sea sand. Therefore, CER is expected to be an efficient method for sea sand desalination.
RESUMO
Social media platforms have become inundated with offensive language. This issue must be addressed for the growth of online social networks (OSNs) and a healthy online environment. While significant research has been devoted to identifying toxic content in major languages like English, this remains an open area of research in the low-resource Pashto language. This study aims to develop an AI model for the automatic detection of offensive textual content in Pashto. To achieve this goal, we have developed a benchmark dataset called the Pashto Offensive Language Dataset (POLD), which comprises tweets collected from Twitter and manually classified into two categories: "offensive" and "not offensive". To discriminate these two categories, we investigated the classic deep learning classifiers based on neural networks, including CNNs and RNNs, using static word embeddings: Word2Vec, fastText, and GloVe as features. Furthermore, we examined two transfer learning approaches. In the first approach, we fine-tuned the pre-trained multilingual language model, XLM-R, using the POLD dataset, whereas, in the second approach, we trained a monolingual BERT model for Pashto from scratch using a custom-developed text corpus. Pashto BERT was then fine-tuned similarly to XLM-R. The performance of all the deep learning and transformer learning models was evaluated using the POLD dataset. The experimental results demonstrate that our pre-trained Pashto BERT model outperforms the other models, achieving an F1-score of 94.34% and an accuracy of 94.77%.
RESUMO
Purely organic room-temperature phosphorescence (RTP) materials generally exhibit low phosphorescence quantum yield (ÏP ) and long phosphorescence lifetime (τP ) due to the theoretically spin-forbidden triplet state. Herein, by introducing a donor-acceptor (D-A) skeleton with a phenoxaselenine donor, three nonaromatic amine donor containing compounds with high ÏP and short τP in amorphous films are developed. Besides the enhanced spin-orbit coupling (SOC) by the heavy-atom effect of selenium, the D-A skeleton which facilitates orbital angular momentum change can further boost SOC, and severe nonradiative energy dissipation is also suppressed by the rigid molecular structure. Consequently, a record-high external quantum efficiency of 19.5% are achieved for the RTP organic light-emitting diode (OLED) based on 2-(phenoxaselenin-3-yl)-4,6-diphenyl-1,3,5-triazine (PXSeDRZ). Moreover, voltage-dependent color-tunable emission and single-molecule white emission are also realized. These results shed light on the broad prospects of purely organic phosphorescence materials as highly efficient OLED emitters especially for potential charming lighting applications.
RESUMO
Fast spin-flipping is the key to exploit the triplet excitons in thermally activated delayed fluorescence based organic light-emitting diodes toward high efficiency, low efficiency roll-off and long operating lifetime. In common donor-acceptor type thermally activated delayed fluorescence molecules, the distribution of dihedral angles in the film state would have significant influence on the photo-physical properties, which are usually neglected by researches. Herein, we find that the excited state lifetimes of thermally activated delayed fluorescence emitters are subjected to conformation distributions in the host-guest system. Acridine-type flexible donors have a broad conformation distribution or bimodal distribution, in which some conformers feature large singlet-triplet energy gap, leading to long excited state lifetime. Utilization of rigid donors with steric hindrance can restrict the conformation distributions in the film to achieve degenerate singlet and triplet states, which is beneficial to efficient reverse intersystem crossing. Based on this principle, three prototype thermally activated delayed fluorescence emitters with confined conformation distributions are developed, achieving high reverse intersystem crossing rate constants greater than 106 s-1, which enable highly efficient solution-processed organic light-emitting diodes with suppressed efficiency roll-off.
RESUMO
The cloud-assisted medical Internet of Things (MIoT) has played a revolutionary role in promoting the quality of public medical services. However, the practical deployment of cloud-assisted MIoT in an open healthcare scenario raises the concern on data security and user's privacy. Despite endeavors by academic and industrial community to eliminate this concern by cryptographic methods, resource-constrained devices in MIoT may be subject to the heavy computational overheads of cryptographic computations. To address this issue, this paper proposes an efficient, revocable, privacy-preserving fine-grained data sharing with keyword search (ERPF-DS-KS) scheme, which realizes the efficient and fine-grained access control and ciphertext keyword search, and enables the flexible indirect revocation to malicious data users. A pseudo identity-based signature mechanism is designed to provide the data authenticity. We analyze the security properties of our proposed scheme, and via the theoretical comparison and experimental results we demonstrate that for the resource-constrained devices in the patient and doctor side of MIoT, in comparison with other related schemes, ERPF-DS-KS just consumes the lightweight and constant size communication/storage as well as computational time cost. For the keyword search, compared with related schemes, the cloud can quickly check whether a ciphertext contains the specified keyword with slight computations in the online phase. This further demonstrates that ERPF-DS-KS is efficient and practical in the cloud-assisted MIoT scenario.
Assuntos
Internet das Coisas , Privacidade , Algoritmos , Segurança Computacional , Humanos , Disseminação de InformaçãoRESUMO
Purely organic materials usually exhibit weak spin-orbital coupling (SOC) effect because of the lack of noble heavy metals, and the generation and direct emission from the triplet state is spin-forbidden. This would lead to slow intersystem crossing, long triplet lifetime, and low phosphorescence quantum yield. Herein, strong spin-orbital coupling between singlet and triplet was observed in a "flexible" and twist thianthrene-pyrimidine-based purely organic compound in an amorphous film state, which shows a fast intersystem crossing process and a high phosphorescence rate of 1.1 × 103 s-1. The heavy atom sulfur and nitrogen atoms in the molecule can provide n-π* transition character for efficient spin-orbital coupling. Moreover, the flexible molecule skeleton enables conformational change and molecular vibration in excited states, which was proved to be vital for efficient vibrational spin-orbital coupling. Benefitting from the strong SOC effect, a nondoped purely organic phosphorescence light-emitting diode was fabricated, which achieves a maximum external quantum efficiency of 7.98%, corresponding to an exciton utilization ratio exceeding 87.6%.
RESUMO
The development of white light emitting diodes (WLEDs) holds great promise for replacing traditional lighting devices due to high efficiency, low energy consumption and long lifetime. Metal-organic frameworks (MOFs) with a wide range of luminescent behaviors are ideal candidates to produce white light emission in the phosphor-converted WLEDs. Encapsulation of emissive organic dyes is a simple way to obtain luminescent MOFs. In this review, we summarize the recent progress on the design and constructions of dye encapsulated luminescent MOFs phosphors. Different strategies are highlighted where white light emitting phosphors were obtained by combining fluorescent dyes with metal ions and linkers.
RESUMO
Strategies for developing purely organic materials exhibiting both high efficiency and persistent room-temperature phosphorescence (RTP) have remained ambiguous and challenging. Herein, we propose that introducing an intermediate charge transfer (CT) state into the donor-acceptor binary molecular system holds promise for accomplishing this goal. Guest materials showing gradient ionization potentials were selected to fine-tune the intermolecularly formed CT state when doped into the same host material with a large electron affiliation potential. Such a CT intermediate state accelerates the population of the triplet exciton to benefit phosphorescent emission and decreases the phosphorescence lifetime via quenching the long-lived triplet excitons. As a result, a "trade-off" between a long phosphorescence lifetime (595 ms) and a high phosphorescent quantum yield (27.5%) can be obtained by tuning the host-guest energy gap offset. This finding highlights the key role of CT in RTP emission and provides new guidance for developing novel RTP systems.
RESUMO
The photoinduced reversible ion exchanges in mixed halide perovskites and the resulting luminescent variations make them promising for constructing anti-counterfeiting patterns; however, its understanding in an interfacial view is lacking. In this work, nominal CsPbBr1.5Cl1.5 (CPBC) nanocrystals (NCs) were introduced into macroporous Y2O3:Eu3+ (MYE) to realize emission color variations from red emission of MYE to green emission of halide NCs. The large surface area of MYE helps the formation of Y-Cl/Br bonds which induces fluctuation in the halide composition, while water and intrinsic halogen defects have also been proved to be essential in the reversible ion segregation process. The PL variations of several samples with different pore sizes were investigated upon irradiation of light with different photon energies and excitation power at certain temperatures. According to combined results of density functional theory calculation, the research reveals the presence of two energy barriers that would be overcome correspondingly by the excitation photon and the concentration difference in the ion exchange and recovery process. A photochromic anti-counterfeiting quick response (QR) code was constructed facilely with the perovskite composites. This work provides a deeper understanding from the interfacial aspect and also proposes a feasible strategy to realize reversible PL variation for anti-counterfeiting applications.
RESUMO
The host-guest doping system has aroused great attention due to its promising advantage in stimulating bright and persistent room-temperature phosphorescence (RTP). Currently, exploration of the explicit structure-property relationship of bicomponent systems has encountered obstacles. In this work, two sets of heterocyclic isomers showing promising RTP emissions in the solid state were designed and synthesized. By encapsulating these phosphors into a robust phosphorus-containing host, several host-guest cocrystalline systems were further developed, achieving highly efficient RTP performance with a phosphorescence quantum efficiency (Ï P) of â¼26% and lifetime (τ P) of â¼32 ms. Detailed photophysical characterization and molecular dynamics (MD) simulation were conducted to reveal the structure-property relationships in such bicomponent systems. It was verified that other than restricting the molecular configuration, the host matrix could also dilute the guest to avoid concentration quenching and provide an external heavy atom effect for the population of triplet excitons, thus boosting the RTP performance of the guest.
RESUMO
BACKGROUND: Persistent pain following back surgery called failed back surgery syndrome remains a major treatment challenge. The aim of this study is to evaluate the efficacy and safety of electroacupuncture on relieving back pain in FBSS patients. METHODS/DESIGN: This is a randomized, single-blind, single-site, placebo-controlled trial. A total of 144 eligible FBSS patients will be randomly assigned to the electroacupuncture, manual acupuncture, or sham acupuncture group in a 1:1:1 ratio. Each group will receive 2 treatment sessions per week for 12 weeks. The primary outcome will be low back pain intensity based on the 11-point numerical rating scale (NRS). The secondary outcomes include Oswestry Disability Index (ODI) questionnaire, Beck Depression Inventory-II (BDI-II), Pittsburgh Sleep Quality Index (PSQI), and analgesic consumption. All clinical outcomes will be collected at baseline, during the treatment phase (at 8 and 12 weeks), and at the 16-, 24- and 36-week follow-ups. All data will be analyzed based on the intention-to-treat principle and adverse events will be assessed during the trial. DISCUSSION: This pilot randomized controlled trial will evaluate the efficacy of electroacupuncture for treating failed back surgery syndrome. The outcomes will determine whether electroacupuncture is efficacious in relieving low back pain as well as improving the quality of life in failed back surgery syndrome patients. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2000040144 . Registered on 22 November 2020.
Assuntos
Terapia por Acupuntura , Eletroacupuntura , Síndrome Pós-Laminectomia , Eletroacupuntura/efeitos adversos , Humanos , Medição da Dor , Qualidade de Vida , Ensaios Clínicos Controlados Aleatórios como Assunto , Método Simples-Cego , Resultado do TratamentoRESUMO
Quasi-2D perovskites have long been considered to have favorable "energy funnel/cascade" structures and excellent optical properties compared with their 3D counterparts. However, most quasi-2D perovskite light-emitting diodes (PeLEDs) exhibit high external quantum efficiency (EQE) but unsatisfactory operating stability due to Auger recombination induced by high current density. Herein, a synergetic dual-additive strategy is adopted to prepare perovskite films with low defect density and high environmental stability by using 18-crown-6 and poly(ethylene glycol) methyl ether acrylate (MPEG-MAA) as the additives. The dual additives containing COC bonds can not only effectively reduce the perovskite defects but also destroy the self-aggregation of organic ligands, inducing the formation of perovskite nanocrystals with quasi-core/shell structure. After thermal annealing, the MPEG-MAA with its CC bond can be polymerized to obtain a comb-like polymer, further protecting the passivated perovskite nanocrystals against water and oxygen. Finally, state-of-the-art green PeLEDs with a normal EQE of 25.2% and a maximum EQE of 28.1% are achieved, and the operating lifetime (T50 ) of the device in air environment is over ten times increased, providing a novel and effective strategy to make high efficiency and long operating lifetime PeLEDs.
RESUMO
BACKGROUND: Postherpetic neuralgia (PHN) is one of the most common complications of herpes zoster (HZ). Heritable factors have been found to play a role in various clinical pain symptoms. However, the effect of gene variability on the susceptibility of PHN remains poorly understood. OBJECTIVES: The aim of this study was to evaluate whether genetic variation in pain pathway genes was associated with PHN susceptibility in the Chinese population. STUDY DESIGN: Case-control study. SETTING: Department of Anesthesiology and Pain Medicine in a university hospital. METHODS: Seventy patients with PHN and 111 patients with HZ without developing PHN were enrolled. All patients received standardized antiviral agents and analgesics as needed during the acute phase of HZ. Twenty-four candidate genetic polymorphisms in 12 genes (IL1B, SCN9A, KCNK9, TRPV1, P2RX7, HTR1A, HTR2A, ADRB1, ADRB2, BDNF, COMT, and OPRM1) were genotyped in all patients. Multivariable logistic regression analyses were used to identify genetic variations associated with PHN susceptibility while controlling for potential confounders. RESULTS: Our results suggested that only variation in P2RX7 gene was associated with PHN susceptibility. The P2RX7 rs7958311 AG heterozygous genotype carriers had a decreased risk for PHN in the overdominant model (odds ratio [OR], 0.40; 95% confidence interval [CI], 0.21-0.77; P = 0.005), and codominant model (OR, 0.44; 95% CI, 0.20-0.98; P = 0.045). The P2RX7 rs7958311 GG homozygote genotype was associated with an increased risk for PHN under a recessive model (OR, 2.15; 95% CI, 1.01-4.56; P = 0.046). There were no significant associations between the other 23 single-nucleotide polymorphisms and PHN susceptibility. LIMITATIONS: Lack of validation cohort to verify the findings. CONCLUSIONS: In the present study in the Chinese population, we found purinergic receptor P2X7 rs7958311 may contribute to PHN development after HZ. Future larger independent cohorts are warranted to replicate these initial findings. KEY WORDS: Herpes zoster, postherpetic neuralgia, polymorphisms.
Assuntos
Predisposição Genética para Doença/genética , Neuralgia Pós-Herpética/genética , Receptores Purinérgicos P2X7/genética , Idoso , Povo Asiático/genética , Estudos de Casos e Controles , Feminino , Genótipo , Herpes Zoster/complicações , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Versatile host materials with good chemical stability and carrier-transporting ability are quite responsible for achieving stable solution-processed thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). Herein, we reported three bipolar dendritic hosts with or without the electron-withdrawing pyridine moiety via 6-site-linkages, namely, 3,3'-bis(3,3â³,6,6â³-tetra-tert-butyl-9'H-[9,3':6',9â³-tercarbazol]-9'-yl)-1,1'-biphenyl (mCDtCBP), 3,3â³,6,6â³-tetra-tert-butyl-9'-(6-(3-(3,3â³,6,6â³-tetra-tert-butyl-9'H-[9,3':6',9â³-tercarbazol]-9'-yl)phenyl)pyridine-2-yl)-9'H-9,3':6',9â³-tercarbazole (mCDtCBPy), and 6,6'-bis(3,3â³,6,6â³-tetra-tert-butyl-9'H-[9,3':6',9â³-tercarbazol]-9'-yl)-2,2'-bipyridine (mCDtCBDPy), exhibiting outstanding solubility, thermal stability as well as electrochemical stability. According to the calculation of bond dissociation energy (BDE), photodegradation results, and carrier dynamics evaluation, a significant relationship between device stability and the pyridine-based dendritic hosts was uncovered. Using mCDtCDPy with the highest electron mobility as the host, the solution-processed bluish-green TADF-OLED showed the shortest operational lifetime due to the unbalanced charge fluxes despite its highest anionic BDE for good chemical stability. However, the device based on mCDtCBPy exhibited twice longer lifetime than that based on mCDtCBP in spite of their similar balanced charge transportation, highlighting the importance of higher anionic BDE of the C-N bond in the device degradation process. Our findings unveiled a potential approach to achieve a subtle regulation of chemical stability and carrier transportation for realizing stable solution-processed TADF-OLEDs.