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White-light emitting (WLE) polymers have attracted continuous attention for their promising applications in solid-state lighting, flexible display and related fields. However, achieving dual-emission and pure white-light emission in a single-component polymer is still challenging. In this study, a brominated single-component polymer BrOD-TFB was designed and synthesized, which shows dual-emission and white light emission properties in solution and room-temperature phosphorescence (RTP) in thin films. The dual-emission properties can be tuned by concentration, solvent polarity, and excitation energy. Spectral analyses and theoretical calculations reveal that the origin of the high-energy emission band (HEB) is intramolecular charge transfer (ICT) along the polymer chain, whilst the low-energy emission band (LEB) originates from the excited-state related to the intra-chain and inter-chain C-Br⋯π interactions as demonstrated by the single-crystal structure of the model compound. Appropriate control of the formation and the destruction of the halogen-assisted interactions can initiate white-light emission in the single-component polymer. More interestingly, by dispersing BrOD-TFB (0.1 wt%) in a non-emissive, colorless and transparent polymer, the characteristics of this white-light emission can be fully demonstrated while exhibiting unexpected RTP properties, with photoluminescence quantum efficiency (ΦPL) of up to 23% and CIE coordinates of (0.32, 0.32).

Luminophores usually suffer from luminescent quenching when introduced into a polymer backbone or side chain, which leads to the inefficient luminescence or even no luminescence of the polymer. In this work, alicyclic imide rings were found to be capable of balancing the donor-acceptor properties between the rigid spacer and the aggregation-induced emission-active fluorophore in light-emitting polymers. Along with the nonplanar and rigid emitter, the suppressed intramolecular charge-transfer effect and interchain disturbance can efficiently preserve the luminescence characteristics of the active center, resulting in high solid-state photoluminescence quantum yields of up to 89%. The amorphous polyimides exhibit excellent thermal properties, such as high glass transition temperature (Tg) values (398 °C) and high thermal decomposition temperature (Td) values (538 °C). As far as we know, these luminescent polymer materials are of excellent heat resistance with the highest luminescence efficiency reported. The results have significant impact for the precise prediction of the optical properties of light-emitting polymers by appropriate monomer design, providing controllable ways for synthesizing high thermal stability polymeric materials with efficient fluorescence properties.

Supplemental Digital Content is available in the text., Right ventricular outflow tract obstruction (RVOTO) is a rare cause of hemodynamic instability in the intensive care unit (ICU) after cardiac surgery. We report the first cases of RVOTO diagnosed in the ICU using continuous right ventricular pressure waveform monitoring. Our 2 cases reflect both mechanical and dynamic causes of obstruction, each of which require different approaches to treatment. Inotrope use can exacerbate RVOTO caused by dynamic etiology, whereas surgery is usually the treatment of choice for mechanical obstructions. Inability to recognize RVOTO or the correct etiology can lead to hemodynamic compromise and poor outcomes.

High-performance low-k and low-loss circuit materials are urgently needed in the field of microelectronics due to the upcoming Fifth-Generation Mobile Communications Technology (5G Technology). Herein, a facile design strategy for non-fluorinated intrinsic low-k and low-loss polyimides is reported by fully considering the secondary relaxation behaviors of the polymer chains. A new amorphous non-fluorinated polymer (TmBPPA) with a k value of 2.23 and a loss tangent lower than 3.94 × 10−3 at 104 Hz has been designed and synthesized, which to the best of our knowledge is the lowest value amongst the non-fluorinated and non-porous polymers reported in literature. Meanwhile, TmBPPA exhibits excellent overall properties, such as excellent thermostability, good mechanical properties, low moisture absorption, and high bonding strength. As high-performance flexible circuit materials, all these characteristics are highly expected to meet the present and future demands for high density, high speed, and high frequency electronic circuit used in 5G wireless networks.

An original design strategy for the preparation of polymers with a low dielectric constant is presented. The key to this design strategy is taking the most advantage of the secondary relaxation beh...

A dithienylethene molecule involving carborane clusters shows remarkable fatigue resistance and high contrast visual colour changes when irradiated with alternating ultraviolet and visible light. The fluorescence of this assembly can be switched on and off when irradiated in the solid state but not in the solution state.

Pulsatile flow of the portal vein has been implicated as an indicator of right ventricular dysfunction in cardiac patients. In patients with significantly elevated right atrial pressure, pulsatile venous flow may be transmitted to the portal, splenic, renal, and femoral veins. We describe the evolution of these echocardiographic findings in four patients with constrictive pericarditis (CP) undergoing pericardiectomy with simultaneous hemodynamic waveform and cerebral oximetry monitoring in the operating room and in the intensive care unit.Patient 1 presented classic signs of CP, including equalization of left and right diastolic pressures, a "square root" sign on the diastolic portion of the right ventricular pressure curve, and elevated right atrial pressure. Preoperative transesophageal echocardiography showed a hyperdynamic left ventricle and dilated right ventricle with abnormal pulsatile waveforms in the portal and splenic veins. Surgical decompression of the pericardium gradually normalized the Doppler waveforms. Increased venous return following pericardiectomy during surgery in patients 2 and 3 and during the postoperative period in patient 4 resulted in right ventricular (RV) failure due to significantly increased preload. Venous pulsatility was also observed in the portal, splenic, and femoral veins.In patients with CP, changes in hemodynamic and echocardiographic signs of RV dysfunction are rapidly reflected by changes in peripheral venous velocities. Identifying signs of splanchnic and peripheral vascular venous congestion could help identify patients at higher risk of developing postoperative complications following pericardiectomy.RéSUMé: OBJECTIF : Le flux pulsatile de la veine porte a été impliqué comme indicateur de dysfonctionnement ventriculaire droit chez les patients de chirurgie cardiaque. Le flux veineux pulsatile pourrait être transmis aux veines porte, splénique, rénale et fémorale chez les patients présentant une pression auriculaire droite significativement élevée. Nous décrivons l’évolution de ces observations échocardiographiques chez quatre patients atteints de péricardite constrictive (PC) bénéficiant d’une péricardectomie avec monitorage simultané de la forme d’onde hémodynamique et de l’oxymétrie cérébrale en salle d’opération et à l’unité de soins intensifs. CARACTéRISTIQUES CLINIQUES: Le patient 1 présentait des signes classiques de PC, y compris l’égalisation des pressions diastoliques gauche et droite, un signe de « racine carrée » sur la partie diastolique de la courbe de pression ventriculaire droite, et une pression auriculaire droite élevée. L’échocardiographie transœsophagienne préopératoire a montré un ventricule gauche hyperdynamique et un ventricule droit dilaté, avec des formes d’onde pulsatiles anormales dans les veines porte et splénique. La décompression chirurgicale du péricarde a progressivement normalisé les formes d’onde Doppler. L’augmentation du retour veineux suivant une péricardectomie, survenue pendant la chirurgie chez les patients 2 et 3 et en période postopératoire chez le patient 4, a entraîné une défaillance ventriculaire droite (VD) due à l’augmentation significative de la précharge. La pulsatilité veineuse a également été observée dans les veines porte, splénique et fémorale. CONCLUSION: Chez les patients atteints de péricardite constrictive, les changements dans les signes hémodynamiques et échocardiographiques de dysfonctionnement du VD sont rapidement reflétés par des changements dans la vélocité veineuse périphérique. L’identification des signes de congestion veineuse splanchnique et vasculaire périphérique pourrait aider à identifier les patients présentant un risque plus élevé de manifester des complications postopératoires après une péricardectomie.

A series of rigid nonconjugated polyimide (PI)-based thermally activated delayed fluorescence (TADF) polymers were reported for the first time, based on a "TADF-Linker-Host" strategy. Among of which, the TADF unit contains a typical TADF luminous core structure, the "Host" unit exhibits effective conjugation length that endows polyimide with high triplet energy, and the "Linker" unit has an aliphatic ring structure to improve solubility and inhibits intramolecular charge transfer effect. All the TADF polymers exhibit high thermal stability (Tg >308.7 °C) and refractive index (1.76-1.79). Remarkably, highly-efficient polymer light-emitting diodes (PLEDs) based on the polymers are successfully realized, leading to a maximal external quantum efficiency of 21.0 % along with low efficiency roll-off. Such outstanding efficiency is amongst the state-of-the-art performance of nonconjugated PLEDs, confirming the effectiveness of structural design strategy, providing helpful and valuable guidance on the development of highly-efficient fluorescent polymer materials and PLEDs.

Supplemental Digital Content is available in the text., Objectives: To report the use of common femoral vein Doppler interrogation as a simple technique to diagnose right ventricular dysfunction. Design: Case report. Setting: Cardiac surgical ICU. Patients: Postoperative cardiac surgical patients. Interventions: Common femoral pulsed-wave and color Doppler examination associated with hepatic, portal, and renal venous Doppler measurement were obtained in both patients and before and after treatment in patient number 1. In addition, right ventricular pressure waveform examination was obtained in patient number 2. Measurements and Main Results: The technique to obtain common femoral venous Doppler is described. Two cases of patients presenting with right ventricular dysfunction and fluid overload with portal and renal venous congestion in the perioperative period undergoing complex multivalvular cardiac surgery are presented. Hemodynamic waveform monitoring was performed alongside echocardiographic, hepatic, and renal venous flow Doppler assessment, and spectral Doppler profiles of the common femoral veins were examined. Those findings were useful in confirming our diagnosis and guiding our response to treatment. An algorithm was developed and tested on two additional hemodynamically unstable patients. Conclusions: Doppler examination of the common femoral vein is a simple, fast, and noninvasive technique that could be useful to rule in the presence of right ventricular dysfunction with venous congestion and help guide the management of such patients.

Prolonging the phosphorescence lifetime of pure organic phosphorescent materials by a methyl-substitution strategy is described. We present a chemical strategy for improving the phosphorescence lifetime of triplet excitons under ambient conditions by incorporating methyl groups into the chemical structures. This is observed by a long-lived phosphorescence lifetime of up to 0.83 s detected for methylated 9-(4-(mesitylsulfonyl)phenyl)-9H-carbazole (3M), compared to 0.36 s for 9-(4-(phenylsulfonyl)phenyl)-9H-carbazole (0M) without any methyl groups. Additionally, enhanced phosphorescence efficiency can be obtained at an appropriate methylation degree, because of the smaller ΔEST (singlet and triplet energy gap) and ΔETT* (normal phosphorescence and long-lived phosphorescence energy gap). A comprehensive investigation on the packing mode in the crystalline state reveals that the methyl groups occupy the free volume and result in a suppression of non-radiative decay, accounting for the enhanced phosphorescence lifetime.

Extending the spectral response from the ultraviolet (UV) to the visible-light range and enhancing the UV-light stability are two remaining challenges for the development of perovskite solar cells (PSCs). Lanthanide complexes show a broad absorption range in the UV region and can down convert UV-light into visible-light; thus, they are potentially able to improve the device performance of PSCs. Herein, we report the fabrication of PSCs with a novel samarium (Sm)-based down conversion nanomaterial, Sr2CeO4:Sm3+ (SCOS). In comparison to the control device without a SCOS layer, the SCOS-coated device shows an enhancement of 11.4% in photocurrent and 16.2% in average power conversion efficiency (PCE), due to the harvesting and re-emitting of UV-light in the visible range through the SCOS layer. Significantly, the SCOS-coated devices retain 50% of their initial PCE for 60 hours under continuous UV-light illumination and even after 60 days of storage under ambient environment conditions, whilst for the control device the longevity is 15 hours and 26 days, respectively. The results suggest that the SCOS layer makes an important contribution in terms of both enhanced photovoltaic performance and prolonged device stability by reducing photo-loss and photo-degradation.

Thienyl containing triarylethylene derivatives, namely 2ThDpF and 3ThDpF, with photochromic properties have been designed and synthesized. These new photochromic molecules with simple chemical structures show fast-response and striking photochromic behaviors in the solution-state, in the solid-state and in polymer films. Based on 2ThDpF, a real-time and repeatable photoresponsive surface was fabricated. Upon UV-light irradiation for 1 minute, most of the 2ThDpF nano-aggregates on the SiO2 substrate changed from cone-shaped to hump-shaped and the contact angles of a water droplet drastically increased from 43° to 95° simultaneously. The surface morphology and wettability can easily be reverted by white-light irradiation for 5 minutes. The key issues to affect the real-time morphology and wettability changes are also discussed in-depth based on single-crystal analyses and TDDFT calculations. Therefore, these triarylethylene derivatives with simple molecular structures are attractive in the areas of photochromism and photoresponsive surfaces.

Thermally activated delayed fluorescence (TADF) emitters can harvest singlet and triplet excitons for light emission to afford highly efficient organic light-emitting diode (OLED) devices, especially for all-TADF white OLEDs (WOLEDs). However, the majority of TADF emitters suffer from concentration quenching effects and require complicated doping techniques for device fabrication. Herein, we demonstrate a yellow TADF emitter that enables non-doped OLED systems, which is beneficial for the simplification of the OLED device structure and fabrication. The non-doped yellow OLED achieves a maximum external quantum efficiency (EQE) of 16.7% at a high luminance of 3600 cd m−2, in which such a high magnitude is rarely reported. More significantly, by the combination of the yellow TADF emitter with a blue TADF emitter, a fully non-doped emissive layer (EML) strategy has been demonstrated for the fabrication of an all-TADF WOLED, in which the non-doped yellow and blue TADF emissive layers are closely stacked together without any interlayers. The fully non-doped WOLEDs show a maximum EQE of up to 19.8%, along with high quality white-light emission. This is the first report regarding the fully non-doped all-TADF WOLEDs, and the presented design strategy provides a universal route towards the fabrication of simple and efficient WOLEDs.

The persistent room-temperature phosphorescence (RTP) of purely organic materials in the solid state has recently attracted much research interest and found promising, rapid and visual applications by the naked eye, after the removal of the excitation source. However, almost all reported organic persistent RTP processes are induced by using a UV-light irradiation source. In this report, persistent RTP with an emission lifetime as long as 0.15 s which can be induced not only by photoirradiation but also by mechanical action is presented, which merges mechano-induced luminescence and persistent RTP together. It is found that such persistent RTP is produced through intermolecular electronic coupling (IEC) of units with different excited state configurations. Interestingly, there are two different crystals with and without mechano-induced persistent RTP which can be grown from this organic material, as such a new type of mechano-luminescence (ML) is strongly dependent on their intermolecular interactions. Furthermore, the intensity of such mechano-induced persistent RTP can be increased by lowing the temperature as well, similar to that of photo-induced persistent RTP. Notably, these two crystals exhibit a ML enhancement and ML “turn on”, respectively, with decreasing temperature. Therefore, such mechano-induced persistent RTP provides an example of new types of organic luminescent materials, which is a missing jigsaw piece of organic luminescence and important for both fundamental research and practical applications of both persistent RTP and ML of organic materials.

This study provides a reliable strategy to tune the mechanoluminescent colors by adjusting the weak intermolecular interactions., A new mechanoluminescent material (4-(diphenylamino)phenyl)(4-(diphenylphosphanyl)phenyl)methanone (CDpP), which displays tunable mechanoluminescent emission colors, has been designed and successfully synthesized. CDpP shows two distinct mechanoluminescent colors (blue and green) in different crystalline states. Single-crystal analyses and femtosecond transient emission studies reveal that the striking tunable mechanoluminescence properties of CDpP mainly originate from the different C–H···π interactions in the crystal structures. CDpP crystals with more C–H···π interactions show blue mechanoluminescence (ML), and the emission is attributed to the locally excited (LE)-state because the twisting process for the excited state is restricted by C–H···π interactions. Conversely, CDpP crystals with fewer C–H···π interactions display green ML, in which the red-shifted emission band originates from the twisted intramolecular charge transfer (TICT) excited state because the diphenylamine moiety is relatively free to rotate. The manipulation of weak intermolecular interactions in the crystalline state is a useful and reliable strategy for the tuning of the ML emission wavelengths.

Since the realization in 2011 that most aggregation-induced emission (AIE) molecules exhibit mechano-responsive luminescence (MRL), research regarding the MRL of AIE molecules has drawn much attention, and this area has been expanding tremendously. As one of the most extensively studied AIE cores, tetraphenylethylene (TPE) has been widely used to construct MRL molecules. This review will focus on recent advances in MRL of TPE derivatives with AIE properties, including a brief history of mechano-responsive AIE-active materials, mechanistic studies on MRL, mechano-responsive luminogens based on TPE, mechano-responsive luminogens containing multiple AIE-active units, mechano-memory chromism and mechanoluminescence of TPE derivatives. Moreover, this review will give a perspective on the possible opportunities and future challenges that exist in this research area.

Thermally activated delayed fluorescence (TADF) emitters have aroused serious attention for their use in organic light-emitting diodes (OLEDs). However, TADF emitters providing both doped and non-doped OLEDs with high device performance are rare. In this work, we present a yellow TADF emitter (OPDPO) meeting the above requirements. The OPDPO-based doped OLEDs show a maximum external quantum efficiency (EQE) of 26.7%, which is amongst the highest ever reported for doped yellow TADF-based OLEDs. The EQE remains as high as 22.1% at a luminance of 1000 cd m−2. Meanwhile, the OPDPO-based non-doped OLEDs afford a maximum EQE of 16.6% at a high luminance of 3600 cd m−2, which is amongst the best performances of non-doped yellow TADF-based OLEDs. Moreover, simple and efficient white OLEDs are implemented by combining a blue conventional fluorescent emitter with either a doped or non-doped OPDPO emissive layer, confirming the universal applications of OPDPO in high-performance OLEDs.

Warm-white organic light-emitting diodes (WOLEDs) fabricated with hybrid fluorescence-based emitters, consisting of traditional fluorescence and thermally activated delayed fluorescence (TADF) emitters can achieve high efficiency without the use of expensive organometallic phosphors. However, most of these types of OLEDs require complicated fabrication techniques, especially host–guest doping systems and multiple interlayers. Herein, an efficient design strategy for hybrid fluorescence WOLEDs is presented, in which a traditional blue fluorescence emitter is simply stacked together with a yellow TADF emitter without any interlayers. Due to the high triplet excited state of the chosen blue emitter, its intrinsically non-radiative triplet excitons can be efficiently utilized for light emission, by exoergic transfer to the adjacent yellow TADF emitter. Following this idea, a maximum external quantum efficiency of 20.8% at a high luminance of 400 cd m−2 is achieved for a fully non-doped WOLED when using a blue fluorescent emitter with the aggregation-induced emission property. This strategy provides a universal approach for the fabrication of highly-efficient fluorescence–TADF hybrid WOLEDs based on the fully non-doped device configuration.

Soft luminescent materials are attractive for optoelectronic applications, however, switching dominant chromophores for property enrichment remains a challenge. Herein, we report the first case of a soft organic molecule (DOS) featuring selective expression of chromophores. In response to various external stimuli, different chromophores of DOS can take turns working through conformation changes, exhibiting full-colour emissions peaking from 469 nm to 583 nm from ten individual single crystals. Dynamic triplet-exciton behaviours including thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), mechanoluminescence (ML), and distinct mechano-responsive luminescence (MRL) can all be realized. This novel designed DOS molecule provides a multifunctional platform for detection of volatile organic compounds (VOCs), multicolour dynamic displays, sensing, anticounterfeiting, and hopefully many others.

Small energy gap boosts dual-channel triplet harvesting via TADF and UOP, which suppresses long-lived triplet concentration quenching. An infrared laser (808 nm) is able to induce persistent emission under ambient conditions., Due to inefficient molecular design strategies, two-photon-excited ultralong organic room temperature phosphorescence (TPUOP) has not yet been reported in single-component materials. Herein, we present an innovative design method by dual-channel triplet harvesting to obtain the first bright TPUOP molecule with a lifetime of 0.84 s and a quantum efficiency of 16.6%. In compound o-Cz the donor and acceptor units are connected at the ortho position of benzophenone, showing intramolecular space charge transfer. Therefore, the two-photon absorption ability is improved due to the enhanced charge transfer character. Moreover, the small energy gap boosts dual-channel triplet harvesting via ultralong thermally activated delayed fluorescence and H-aggregation phosphorescence, which suppresses the long-lived triplet concentration quenching. Through two-photon absorption, a near-infrared laser (808 nm) is able to trigger the obvious ultralong emission under ambient conditions. This research work provides valuable guidance for designing near-infrared-excited ultralong organic room temperature phosphorescence materials.

An ortho-substituent design strategy promoting steric hindrance has afforded excellent AIE-TADF emitters, and high-efficiency TADF-OLEDs have been subsequently demonstrated., Thermally activated delayed fluorescence (TADF) materials have opened a new chapter for high-efficiency and low-cost organic light-emitting diodes (OLEDs). Herein, we describe a novel and effective design strategy for TADF emitters which includes introducing a carbazole donor unit at the ortho-position, at which the donor and acceptor groups are spatially in close proximity to guarantee the existence of intramolecular electrostatic attraction and through-space charge transfer, leading to reduced structural vibrations, suppressed non-radiative decay and rapid radiative decay to avoid excited state energy loss. As a result, a green TADF emitter (2Cz-DPS) showing high solid-state photoluminescence quantum efficiency (91.9%) and excellent OLED performance was produced. Theoretical simulations reveal that the non-adiabatic coupling accelerates the reverse intersystem crossing of 2Cz-DPS, resulting in a state-of-the-art non-doped OLED with an extremely high external quantum efficiency of 28.7%.

A carbazole containing triphenylethylene derivative (TrPEBCar) has been designed and synthesized, which combines aggregation-induced emission (AIE), piezochromism and photochromism together. In the crystalline state, an intensive emission band at 448 nm was detected. After pressing the crystalline solid, a [crystalline–amorphous] morphological transition takes place, in which the resulting amorphous state of TrPEBCar exhibits a different color and a red-shifted emission band at 470 nm. Photochromic behavior of TrPEBCar is achieved by utilizing a stilbene-type intramolecular photocyclization in the crystalline state. In addition, we report for the first time morphology-dependent photochromism, in which the photochromic properties of TrPEBCar are only observed in the crystalline state but not in the amorphous state. Therefore, the methods of pressing/fuming and heating/fuming act as gates to switch the photochromic properties by changing the aggregation states between the crystalline and amorphous states. By combining the piezochromic properties with the photochromic properties, the ON/OFF states of TrPEBCar can easily be observed by the different colors and emission properties. The triphenylethylene derivative with simple molecular structure provides a new approach for gated photochromic materials with both switch and indicator.

In this study, loosely packed crystals with the building blocks of aggregation induced emission (AIE)-active TPE-MN molecules were constructed with the assistance of intermolecular hydrogen bonding. The AIE properties of the compound TPE-MN were studied. From single crystal analyses, a sandwich-like crystal structure with tightly packed areas (TPE moieties) and loosely packed areas was observed. Nevertheless, the TPE-MN crystals display non-emissive properties in the loosely packed crystalline state. Differential scanning calorimetry (DSC) studies, powder X-ray diffraction analyses and various photophysical studies further reveal that the loosely packed crystal structure can provide enough space for significant molecular rotations and vibrations to occur, which leads to emission quenching. By breaking the loosely packed crystal structure with mechanical force or UV irradiation, the emission band with a maximum at ca. 562 nm can be turned on. These results can serve as a basis for constructing multi-responsive materials with turn-on emissive properties.

Dynamic right ventricular outflow tract obstruction is rare in the cardiac surgical population. Significant obstruction developing in the perioperative period can contribute to systemic hemodynamic instability. We describe 2 cases of dynamic right ventricular outflow tract obstruction that developed immediately after separation from cardiopulmonary bypass, due to temporary right ventricular epicardial pacing. Both patients had systemic hypotension which improved once ventricular pacing was discontinued. We discuss the recognition of right ventricular outflow tract obstruction as a contributing factor to hemodynamic instability, as well as the importance of identifying the underlying cause such as to institute appropriate management in these patients.

Mechanoluminescence (ML) materials are environmentally friendly and emit light by utilizing mechanical energy. This has been utilized in light sources, displays, bioimaging, and advanced sensors. Organic ML materials are strongly limited to application by in situ unrepeatable ML. Now, in situ solar-renewable organic ML materials can be formed by introducing a soft alkyl chain into an ML unit. For the first time, the ML from these polycrystalline thin films can be iteratively produced by simply recrystallizing the fractured crystal in situ after a contactless exposure to sunlight within a short time (≤60 s). Additionally, their ML color and lifetime can be also easily tuned by doping with organic luminescent dyes. Therefore, large-area sandwich-type organic ML devices can be fabricated, which can be repeatedly used in a colorful piezo-display, visual handwriting monitor, and sensitive optical sensor, showing a lowest pressure threshold for ML of about 5 kPa.

We have synthesized a series of fluorene-based fluorophores, in which a central fluorene core has been modified with different peripheral arylene vinylene substituents that are able to activate aggregation-induced emission (AIE) characteristics. 9,9-Dioctylfluorene doubly end-capped at the 2,7-positions with triphenylethene groups, such as 4-(2,2-diphenylvinyl)phenyl (F1-(2,2)-HTPE) and 4-(1,2-diphenylvinyl)phenyl (F1-(1,2)-HTPE) were synthesized and compared to the tetraphenylethene analogue (F1-TPE). Both F1-(2,2)-HTPE and F1-(1,2)-HTPE glow with a deep blue fluorescence in THF solution with emission maxima (λem) of 426 and 403 nm, respectively. The λem slightly red-shifts in the solid-state to 458 nm for F1-(2,2)-HTPE and 437 nm for F1-(1,2)-HTPE. The fluorescence quantum yields (oF) of F1-(2,2)-HTPE (oF=35.1 %) and F1-(1,2)-HTPE (oF=26.2%) were found to be higher in solution compared to the near quenching of F1-TPE (oF=0.1%). Consequently, this results in weaker AIE-stability of F1-(2,2)-HTPE (αAIE=1.5) and F1-(1,2)-HTPE (αAIE=1.9) compared to F1-TPE (αAIE=125), suggesting that four phenyl groups are necessary for efficient AIE-activity of these fluorene bridged arylene vinylene type materials. In addition, decreasing the steric hindrance around the arylene vinylene moiety by removal of a phenyl ring is another method to decrease the AIE characteristics, in a similar manner to the commonly known "phenyl-locking". Non-polar triphenylethenes are poorer AIE materials than their tetraphenylethene analogues. Replacing the hydrogen atom of F1-(2,2)-HTPE with a cyano group affords fluorene end-capped with 2,3,3-triphenylacrylonitrile (F1-TPAN), which boosts the AIE-effect to αAIE=90.5 and red-shifts the solid-state emission (λem=528 nm) with near quenching in THF solution (oF=0.12%). X-ray crystallographic analysis of F1-TPAN indicates that the introduction of cyano groups can not only diminish the intramolecular steric hindrance in comparison of F1-TPE, but also improve the molecular cohesion ability via multiple CH···N interactions.

We report a flexible multifunctional aromatic polyimide (BTDBPI) that shows yellow–green fluorescence with high photoluminescence quantum yield (PLQY) of 30% in the film state. The nonvolatile “write once–read many” (WORM) characteristic in a memory device with the configuration of ITO/BTDBPI/Au indicates that BTDBPI possesses organic semiconductor behavior. Moreover, polymer light-emitting diodes (PLEDs) with the structure of ITO/PEDOT:PSS/BTDBPI/TPBI/Mg–Ag exhibits an interesting dual-emission phenomenon that originates from the electroluminescence (EL) of the BTDBPI nanometer film (yellow–green, 525 nm) and TPBI (deep blue, 380 nm), demonstrating that BTDBPI shows both the charge-transporting and EL properties.

Truly stretchable electronics, wherein all components themselves permit elastic deformation as the whole devices are stretched, exhibit unique advantages over other strategies, such as simple fabrication process, high integrity of entire components and intimate integration with curvilinear surfaces. In contrast to the stretchable devices using stretchable interconnectors to integrate with rigid active devices, truly stretchable devices are realized with or without intentionally employing structural engineering (e.g. buckling), and the whole device can be bent, twisted, or stretched to meet the demands for practical applications, which are beyond the capability of conventional flexible devices that can only bend or twist. Recently, great achievements have been made toward truly stretchable electronics. Here, the contribution of this review is an effort to provide a panoramic view of the latest progress concerning truly stretchable electronic devices, of which we give special emphasis to three kinds of thin film electronic and optoelectronic devices: (1) thin film transistors, (2) electroluminescent devices (including organic light-emitting diodes, light-emitting electrochemical cells and perovskite light-emitting diodes), and (3) photovoltaics (including organic photovoltaics and perovskite solar cells). We systematically discuss the device design and fabrication strategies, the origin of device stretchability and the relationship between the electrical and mechanical behaviors of the devices. We hope that this review provides a clear outlook of these attractive stretchable devices for a broad range of scientists and attracts more researchers to devote their time to this interesting research field in both industry and academia, thus encouraging more intelligent lifestyles for human beings in the coming future.

A general approach for the synthesis of dibenzofulvene-based derivatives is demonstrated. The bisanthracene modified dibenzofulvene (F-DAn) exhibits efficient piezofluorochromic properties with the fluorescence reversibly altered between green (536 nm) and red (620 nm) under external stimuli.

In this report, we integrated a photoswitchable quencher, a highly emissive yet pH sensitive fluorophore, and a water-soluble polymer with controlled hydrophilicity into a functional nanosystem. The photoswitching quencher is based on dithienylethene (DTE) unit, while the pH-sensitive emitter is naphthalimide (NI) unit and the water-soluble polymer is obtained from polymerization of N-isopropylacrylamide (NIPAM). Together, these three units create a novel super-resolution lysosome highlighter, although individually none can function as a lysotracker. Because the emitter is sensitive to pH, the resulting polymer becomes highly fluorescent in acidic lysosomes. In addition, photoswitching regulates the fluorescence on and off and thus enables super-resolution localization of fluorescent polymers with sub-40 nm spatial resolution in imaging subcellular organelles. Thus, the concept presented here, including the photoswitchable DTE-pH-sensitive NI dyad, is promising to guide the development of future-generatio...

A general approach to the design and synthesis of a new series of geminal-substituted tetraarylethene (g-TAE) chromophores with aggregation-induced emission (AIE) properties has been developed via Corey–Fuchs reaction and subsequent Suzuki/Stille coupling reactions. To demonstrate the synthetic simplicity and versatility of this approach, fluorophores with diverse electronic characteristics have been synthesized. The validation of the geminal structure and bulky steric effect on the bond lengths and dihedral angles is further confirmed by the X-ray crystallography of three chromophores. With respect to single crystals of 2,2′-(2,2-diphenylethene-1,1-diyl)-dinaphthalene (DPDN2), 1,1′-(2,2-diphenylethene-1,1-diyl)-dinaphthalene (DPDN1), and 9,9′-(2,2-diphenylethene-1,1-diyl)dianthracene (DPDAn), intensive cofacial π–π stacking is absent in their molecular packing. The pseudopolymorphism of DPDAn crystals associated with different photoluminescence properties is investigated. In comparison to the solvent-fre...

We report on the reversible fluorescence switching of biodegradable nanoparticles of spiropyran-terminated poly(e-caprolactone) (SP-PCL) for super-resolution fluorescence imaging. SP-PCL was synthesized via ring-opening polymerization using hydroxyl-containing SP derivative as the initiator. SP-PCL solution in THF or dioxane exhibits fast photochromism from colorless to blue upon UV irradiation due to the transformation of SPs in SP-PCL into merocyanines (MCs). Although both SP-PCL solution and MC-PCL solution do not fluoresce, SP-PCL nanoparticle dispersion fabricated via nanoprecipitation in aqueous media, in which SP molecules were embedded into the hydrophobic PCL matrix, displays considerable green emission at 530 nm at an excitation wavelength of 420 nm. Upon

In this paper, the bromination of carbazole has been controlled and then subsequent mono, di, tri and tetra-bromocarbazoles have been subjected to Suzuki cross-coupling to yield a series of carbazole-tetraphenylethene (TPE) materials with varying numbers of peripheral TPE groups. Accompanied by 2,7-dibromo-carbazole, five new Cz-TPE materials are successfully synthesized. All the Cz-TPEs are non-fluorescent in THF and emit strong blue-green fluorescence in aggregate states (fw = 90%) and thin films because of their aggregation induced emission (AIE) nature. In THF (10−5 M) solution, all the Cz-TPEs emit deep blue fluorescence after UV irradiation and we find that the more the TPE groups, the slower the enhancement of fluorescence. In thin films (40 nm), the emission maximum blue shift decreases and finally becomes non-emissive after about 1.5 h of UV irradiation for all the Cz-TPEs. We suppose these optical properties are attributed to photo-induced irreversible changes of TPE to diphenylphenanthrene derivatives. The photo-oxidation process for Cz-1TPE has been investigated and proved by HPLC analysis, 1H NMR and LS-MS. Electrochemical properties of all the Cz-TPEs are investigated by cyclic voltammetry and with UV-absorption spectra, and their energy levels are calculated. Finally, we applied the Cz-TPEs to organic light emitting diode (OLED) devices by the spin coating deposition process with OLED devices configuration: ITO/PEDOT (40 nm)/Cz-TPEs (50 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm). All EL devices emit blue-green light with a maximum luminance (Lmax) of 2858, 1353, 986, 2088 and 1129 cd m−2, a maximum current efficiency (ηc,max) of 3.5, 4.9, 3.1, 3.1 and 5.5 cd A−1, a maximum power efficiency (ηP,max) of 2.1, 3.9, 2.2, 1.8 and 3.1 lm W−1 and a turn on voltage (Von) of 3.5, 3.5, 3.3, 3.6 and 4.2 V for Cz-1TPE, Cz-2TPE, Cz-3TPE, Cz-4TPE, Cz-2TPE (2,7), respectively.

Two heavy atom-free white-light emitting luminophores exhibit fluorescence–phosphorescence dual-emission and are multi-stimuli responsive at room temperature., Two heavy atom-free luminophores (SHB2t and SDB2t) with simple molecular structures have been synthesized via Suzuki coupling reactions in which both display white-light emission with prompt fluorescence and room temperature phosphorescence (RTP) in the solid state. The impressive RTP of the luminophores is produced by a synergistic effect of the strong intermolecular hydrogen bonding in addition to the spin–orbit coupling of the sulfonyl oxygen atoms and the moderate singlet-triplet energy gaps (ΔE ST). These factors facilitate the intersystem crossing (ISC) process to generate triplet excitons in which the molecular conformations become immobilized to effectively suppress radiationless decay. Under the stimuli of mechanical force and solvent vapor, the RTP of SHB2t and SDB2t can be simply turned off and on by breaking and reforming the robust hydrogen bonding, which leads to remarkable and reversible mechanochromism between white and deep-blue emission. Moreover, two different thermochromic processes have been observed for the pristine and ground samples of SDB2t, in which a tricolor switching system between white, deep-blue and blue emission has been successfully achieved through the sequential control of grinding, heating and fuming. From detailed studies we have determined that the mechanism for the thermochromism of SDB2t is correlated with the rearrangement of the white-light emitting molecules to a new packing mode without RTP emission.

Organic materials that exhibit thermally activated delayed fluorescence (TADF) are an attractive class of functional materials that have witnessed a booming development in recent years. Since Adachi et al. reported high-performance TADF-OLED devices in 2012, there have been many reports regarding the design and synthesis of new TADF luminogens, which have various molecular structures and are used for different applications. In this review, we summarize and discuss the latest progress concerning this rapidly developing research field, in which the majority of the reported TADF systems are discussed, along with their derived structure–property relationships, TADF mechanisms and applications. We hope that such a review provides a clear outlook of these novel functional materials for a broad range of scientists within different disciplinary areas and attracts more researchers to devote themselves to this interesting research field.

The hole-transporting material 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA) is widely used as a host in phosphorescent organic light-emitting diodes (PhOLEDs). Based on the unipolar TCTA, we synthesized a novel bipolar host material, (9-(4-(bis(4-(9H-carbazol-9-yl)phenyl)amino)phenyl)-9H-carbazol-3-yl) diphenylphosphine oxide (TCTAPO) by directly imparting an electron-transporting diphenylphosphine oxide moiety to TCTA. It was found that TCTAPO can be used as an ideal versatile host for blue, orange, and white PhOLEDs due to its high triplet energy (ET = 2.83 eV), high glass transition temperature (Tg = 165 °C), and bipolar charge-transporting ability. The maximum power efficiencies of 40.7 and 43.7 lm/W were achieved in the blue and orange PhOLEDs with FIrpic and (fbi)2Ir(acac) as the blue and orange dopants, respectively. Furthermore, the single-emitting-layer white organic light-emitting diode (WOLED) based on the emitter of TCTAPO:FIrpic:(fbi)2Ir(acac) exhibited a maximum current efficiency of 43.7 ...

Hierarchical mesostructures of poly(e-caprolactone)-b-poly(ethylene oxide)-b-poly(e-caprolactone) (PCL-PEO-PCL) triblock copolymers have been grown from evaporation-induced self-assembly directed by alkali metal ions. The self-assembly process began with a dilute homogeneous solution of the triblock copolymers in a mixture of tetrahydrofuran (THF) and water. THF preferentially evaporated under reduced pressure and induced the formation of amphiphilic polymer micelles. The spherical polymer micelles formed both in deionized water and NaOH aqueous solution. However, different mesostructures were discovered during the film depositing process for scanning electron microscopy observation. The polymer micelles were observed for the deposition sample in deionized water while sisal-like hierarchical mesostructures resulted from the film deposition of polymer micelles in NaOH aqueous solution. The sisal-like mesostructures and their formation process were observed through scanning electron microscopy, transmission electron microscopy, fluorescent microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Detailed study revealed that during evaporation-induced self-assembly of PCL-PEO-PCL amphiphilic triblock copolymer directed by alkali metal ions, the sodium ions and polymer micelles increasingly concentrated in NaOH aqueous solution and the solvent quality for the diblock progressively decreased, which resulted in the stronger coordination between alkali metal ions and PEO ligands in the block copolymer and PEO segment crystallization.

Four-arm star-shaped PCL polymers are synthesized using iPT as initiator for the controlled ROP of CL at 25–40 °C. The number-average molecular weights of the star-shaped Ti(O-PCL)4 with narrow molecular weight distributions are proportional to the molar ratios of monomer to initiator. The four-branch star-shaped structures of Ti(OPCL)4 are confirmed through polymer hydrolysis monitoring by GPC, which indicates that the stability of the Ti—O bond in the core of the star-shaped polymer chain increases with the increase of polymer molecular weights. The star-shaped Ti(O-PCL)4 can act as a macroinitiator for successive block copolymerization with d,l-Lactide in bulk at 60 °C.

Photosensitive fluorescent probes have become powerful tools in chemical biology and molecular biophysics, which are used to investigate cellular processes with high temporal and spatial resolution. Accordingly, photosensitive fluorescent probes, including photoactivatable, photoconvertible, and photoswitchable fluorophores, have been extensively developed during the past decade. The photoswitchable fluorophores have received much attention because they highlight cellular events clearly. This minireview summarizes recent advances of using reversibly photoswitchable fluorophores and their applications in innovative bioimaging. Photoswitchable fluorophores include photoswitchable fluorescent proteins, photoswitchable fluorescent organic molecules (dyes), and photoswitchable fluorescent nanoparticles. Several strategies have been developed to synthesize photoswitchable fluorophores, including engineering combination proteins, chemical synthesis, polymerization, and self-assembly. Here we concentrate on polymer nanoparticles with optically switchable emission properties: either fluorescence on/off or dual-alternating-color fluorescence photoswitching. The essential mechanisms of fluorescence photoswitching enable different types of photoswitchable fluorophores to change emission intensity or wavelength (color) and thus validating the basis of the fluorescence on/off or dual-color photoswitching design. Generally the possible applications of any fluorophores are to label biological targets, followed by specific imaging. The newly developed photoswitchable fluorophores enable super-resolution fluorescence imaging because of their photosensitive emission. Finally, we summarize the important area regarding future research and development on photoswitchable fluorescent nanoparticles.

The synthesis and liquid crystal behaviour of light‐emitting trimeric liquid crystals consisting of three mesomorphic moieties connected by aliphatic spacers are reported. The combination of an aromatic light‐emitting central core and two cholestanyl (dihydrocholesteryl) groups induces a helical liquid crystalline phase with circularly polarised photoluminescence and electroluminescence. These segmented trimers are designed to possess a high glass transition temperature below which the structure of liquid crystalline phases can be fixed. The effects of odd and even spacers, spacer length and the presence of large lateral substituents on the liquid crystal behaviour and the glass transition temperature of these trimers were studied. Electroluminescence from a segmented liquid crystalline trimer is reported for the first time.

Liquid-crystal (LC) gels are normally used as insulating, scattering media in LC displays. Organic solar cells generate electrical power by the separation of photocreated electrons and holes at the interface between electron-donating and electron-accepting organic semiconductors. We combine these two technologies to create a new type of plastic solar cell. The efficiency of solar cells can be improved by enlarging the interface area to maximize charge separation and by vertically separating the two materials to provide different paths for electrons and holes to the electrodes. We use a new electron-donating, visible-light absorbing, LC gel to form a surface with nanometer-sized grooves with a large interface area to an overlying electron-accepting layer. This forms a photovoltaic cell, which exhibits a monochromatic power conversion efficiency of 0.6 % at an incident intensity of 45 mW cm. Improvements will provide low-cost, robust solar cells compatible with plastic electronics and roll-to-roll processing. Most organic photovoltaics use either main-chain conjugated polymers, often in conjunction with fullerenes, or low-molecular-weight glasses, achieving power-conversion efficiencies up to 4.2 %. Charge separation is achieved in solar cells by ionization of the photogenerated exciton at a heterointerface between electron-donating material with a low ionization potential (IP) and electron-accepting species with a high electron affinity (EA). The diffusion length of the exciton before recombination is of the order of 100–200 A, so that distributed, rather than planar, heterointerfaces have been used to maximize charge separation. These have been formed by phase-separated blends of electron-donating and electronaccepting organic materials. The bulk-distributed heterojunctions are formed randomly and do not guarantee a continuous pathway for charge carriers to the electrodes. The required vertical segregation of the blend materials can be obtained by surface treatment or in diffuse bilayer photovoltaics. A blend of an electron-donating columnar LC, hexabenzocoronene, and an electron-accepting perylene dye vertically segregates spontaneously to give an efficient photovoltaic effect. Unfortunately, the spatial scale of the phase separation cannot be controlled reproducibly in these devices. Another problem for phase-separated configurations is poor stability of the domain size lowering the device efficiency. To date the photovoltaic effect has only been demonstrated with calamitic LCs via an ionic mechanism, although electronic photoconductivity has been well researched. Polymerizable LCs, with two polymerizable groups attached through flexible aliphatic spacers to an aromatic core, are attracting interest as organic semiconductors for electroluminescence and organic transistors. Their advantages include spontaneous self-assembly, relatively high charge mobility (1 × 10 cm V s), easy deposition by spin-coating or ink-jet printing and lithographic photopatterning to form multilayer polymer networks. We now report the use of reactive mesogens in a novel way to demonstrate a new approach to photovoltaics. Liquid-crystalline gels are formed from a homogeneous mixture of a reactive mesogen and a non-polymerizable LC. Polymerization results in controlled phase separation of the two components and the formation of a polymer network matrix around the nematic droplets. To date, transparent LC gels have typically been used in direct-view reflective displays, switchable polarizers, directional reflectors, and so forth. Polymerization-induced phase separation of a homogeneous mixture of a LC and a polymer-forming material brings the concept of a paintable display closer. A key step in our new approach is the use of mixtures of hole-transporting reactive mesogens with a low IP and analogous LCs with the same aromatic core to form an electron-donating LC gel. An ideal LC composite photovoltaic is illustrated in Figure 1. It has a vertically separated, large-area interface between electron-donating and electron-accepting layers providing complete pathways for transport of holes and electrons. An electron-blocking polymer network of the electron-donating reactive mesogen is deposited first on an electrode surface by spin-coating from solution and then crosslinking in order to provide a high open circuit. A mixture of the same electron-donating reactive mesogen and the corresponding non-polymerizable analogue are then deposited in a similar C O M M U N IC A TI O N S

We report the synthesis of a red light‐emitting and photopolymerizable smectic liquid crystal (reactive mesogen). We investigate the suitability of polymer networks formed from smectic reactive mesogens for use in organic light‐emitting diodes (OLEDs). The use of mixtures of smectic reactive mesogens is shown to lower the processing temperature for the fabrication of OLEDs to room temperature. We also report efficient energy transfer from a nematic polymer network host to a smectic light‐emitting dopant and polarized emission from a polymer network formed from an aligned smectic reactive mesogen.

We report a systematic study of charge transport in a range of low-molar-mass and extended (having at least six aromatic rings) nematic liquid crystals, some of which are reactive mesogens, with a high degree of shape anisotropy, i.e., the length-to-width (aspect) ratio is exceptionally high. We demonstrate that the hole mobility is independent of the macroscopic, but not microscopic, ordering of the nematic and isotropic phases of these nematic liquid crystals with a long, rigid, and extended aromatic molecular core, because no discontinuity is observed at the transition between these phases. A room-temperature mobility of up to 1.0 × 10-3 cm2 V-1 s-1 is obtained in the nematic phase, which is attributed to the short intermolecular distances between the highly polarizable but rigid long aromatic cores. We show that the intermolecular separation can be easily fine-tuned by changing the lateral and terminal aliphatic groups of these nematic liquid crystals. Hence, the charge mobility can be varied by up to...

We report the results of a systematic study of the structure–mesomorphic behaviour relationships of a diverse range of light‐emitting liquid crystals, but especially nematic 2,7‐disubstituted‐9,9‐dialkylfluorenes. The dependence of the mesomorphic behaviour and transition temperatures on the nature and length of the terminal chains, the nature, position and number of lateral substituents and the number and nature of aromatic rings with and without heteroatoms in the central core is studied. The results of these studies are used to design polymerizable, light‐emitting crystals (reactive mesogens) with a nematic phase having a high clearing point and a melting point below room temperature for facile OLED fabrication.