Stretchable phosphorescent polymers by multiphase engineering.

Stretchable phosphorescence materials potentially enable applications in diverse advanced fields in wearable electronics. However, achieving room-temperature phosphorescence materials simultaneously featuring long-lived emission and good stretchability is challenging because it is hard to balance the rigidity and flexibility in the same polymer. Here we present a multiphase engineering for obtaining stretchable phosphorescent materials by combining stiffness and softness simultaneously in well-designed block copolymers. Due to the microphase separation, copolymers demonstrate an intrinsic stretchability of 712%, maintaining an ultralong phosphorescence lifetime of up to 981.11 ms. This multiphase engineering is generally applicable to a series of binary and ternary initiator systems with color-tunable phosphorescence in the visible range. Moreover, these copolymers enable multi-level volumetric data encryption and stretchable afterglow display. This work provides a fundamental understanding of the nanostructures and material properties for designing stretchable materials and extends the potential of phosphorescence polymers.

Abnormal thermally-stimulated dynamic organic phosphorescence.

Dynamic luminescence behavior by external stimuli, such as light, thermal field, electricity, mechanical force, etc., endows the materials with great promise in optoelectronic applications. Upon thermal stimulus, the emission is inevitably quenched due to intensive non-radiative transition, especially for phosphorescence at high temperature. Herein, we report an abnormal thermally-stimulated phosphorescence behavior in a series of organic phosphors. As temperature changes from 198 to 343 K, the phosphorescence at around 479 nm gradually enhances for the model phosphor, of which the phosphorescent colors are tuned from yellow to cyan-blue. Furthermore, we demonstrate the potential applications of such dynamic emission for smart dyes and colorful afterglow displays. Our results would initiate the exploration of dynamic high-temperature phosphorescence for applications in smart optoelectronics. This finding not only contributes to an in-depth understanding of the thermally-stimulated phosphorescence, but also paves the way toward the development of smart materials for applications in optoelectronics.

Polymorphism-Dependent Organic Room Temperature Phosphorescent Scintillation for X-Ray Imaging.

Organic phosphorescent scintillating materials have shown great potential for applications in radiography and radiation detection due to their efficient utilization of excitons. However, revealing the relationship between molecule stacking and the phosphorescent radioluminescence of scintillators is still challenging. This study reports on two phenothiazine derivatives with polymorphism-dependent phosphorescence radioluminescence. The experiments reveal that molecule stacking significantly affects the non-radiation decay of the triplet excitons of scintillators, which further determines the phosphorescence scintillation performance under X-ray irradiation. These phosphorescent scintillators exhibit high radio stability and have a low detection limit of 278 nGys-1. Additionally, the potential application of these scintillators in X-ray radiography, based on their X-ray excited radioluminescence properties, is demonstrated. These findings provide a guideline for obtaining high-performance phosphorescent scintillating materials by shedding light on the effect of crystal packing on the radioluminescence of organic molecules.

Narrowband Organic Afterglow via Phosphorescence Förster Resonance Energy Transfer for Multifunctional Applications.

Achieving multicolor organic afterglow materials with narrowband emission and high color purity is important in various optoelectronic fields but remains a great challenge. Here, an efficient strategy is presented to obtain narrowband organic afterglow materials via Förster resonance energy transfer from long-lived phosphorescence donors to narrowband fluorescence acceptors in a polyvinyl alcohol matrix. The resulting materials exhibit narrowband emission with a full width at half maximum (FWHM) as small as 23 nm and the longest lifetime of 721.22 ms. Meanwhile, by pairing the appropriate donors and acceptors, multicolor and high color purity afterglow ranging from green to red with the maximum photoluminescence quantum yield of 67.1% are achieved. Moreover, given their long luminescence lifetime, high color purity, and flexibility, the potential applications are demonstrated in high-resolution afterglow displays and dynamic and quick information identification in low-light conditions. This work provides a facile approach for developing multicolor and narrowband afterglow materials as well as expands the features of organic afterglow.

The facilitating role of phycospheric heterotrophic bacteria in cyanobacterial phosphonate availability and Microcystis bloom maintenance.

BACKGROUND: Phosphonates are the main components in the global phosphorus redox cycle. Little is known about phosphonate metabolism in freshwater ecosystems, although rapid consumption of phosphonates has been observed frequently. Cyanobacteria are often the dominant primary producers in freshwaters; yet, only a few strains of cyanobacteria encode phosphonate-degrading (C-P lyase) gene clusters. The phycosphere is defined as the microenvironment in which extensive phytoplankton and heterotrophic bacteria interactions occur. It has been demonstrated that phytoplankton may recruit phycospheric bacteria based on their own needs. Therefore, the establishment of a phycospheric community rich in phosphonate-degrading-bacteria likely facilitates cyanobacterial proliferation, especially in waters with scarce phosphorus. We characterized the distribution of heterotrophic phosphonate-degrading bacteria in field Microcystis bloom samples and in laboratory cyanobacteria "phycospheres" by qPCR and metagenomic analyses. The role of phosphonate-degrading phycospheric bacteria in cyanobacterial proliferation was determined through coculturing of heterotrophic bacteria with an axenic Microcystis aeruginosa strain and by metatranscriptomic analysis using field Microcystis aggregate samples. RESULTS: Abundant bacteria that carry C-P lyase clusters were identified in plankton samples from freshwater Lakes Dianchi and Taihu during Microcystis bloom periods. Metagenomic analysis of 162 non-axenic laboratory strains of cyanobacteria (consortia cultures containing heterotrophic bacteria) showed that 20% (128/647) of high-quality bins from eighty of these consortia encode intact C-P lyase clusters, with an abundance ranging up to nearly 13%. Phycospheric bacterial phosphonate catabolism genes were expressed continually across bloom seasons, as demonstrated through metatranscriptomic analysis using sixteen field Microcystis aggregate samples. Coculturing experiments revealed that although Microcystis cultures did not catabolize methylphosphonate when axenic, they demonstrated sustained growth when cocultured with phosphonate-utilizing phycospheric bacteria in medium containing methylphosphonate as the sole source of phosphorus. CONCLUSIONS: The recruitment of heterotrophic phosphonate-degrading phycospheric bacteria by cyanobacteria is a hedge against phosphorus scarcity by facilitating phosphonate availability. Cyanobacterial consortia are likely primary contributors to aquatic phosphonate mineralization, thereby facilitating sustained cyanobacterial growth, and even bloom maintenance, in phosphate-deficient waters. Video Abstract.

A resting-state functional magnetic resonance imaging study of altered functional brain activity in cardiac arrest survivors with good neurological outcome.

Purpose: To investigate the spontaneous brain activity alterations in survivors of cardiac arrest (CA) with good neurological outcome using resting-state functional magnetic resonance imaging (rs-fMRI) with amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) methods. Materials and methods: Thirteen CA survivors with favorable neurological outcomes and 13 healthy controls (HCs) were recruited and underwent rs-fMRI scans. The ALFF and ReHo methods were applied to assess the regional intensity and synchronization of spontaneous brain activity. Correlation analyses were performed to explore the relationships between the mean ALFF and ReHo values in significant clusters and clinical parameters. Results: The survivors of CA showed significantly decreased ALFF values in the left postcentral gyrus and precentral gyrus and increased ALFF values in the left hippocampus and parahippocampal gyrus than HCs. Significantly decreased ReHo values were observed in the left inferior occipital gyrus and middle occipital gyrus in the patients. Mean ALFF values in the left hippocampus and parahippocampal gyrus were positively correlated with the time to return of spontaneous circulation (r = 0.794, p = 0.006) in the patient group. Conclusion: Functional activity alterations in the brain areas corresponding to known cognitive and physical impairments were observed in CA survivors with preserved neurological function. Our results could advance the understanding of the neurological mechanisms underlying the residual deficits in those patients.

Timing of brain computed tomography for predicting neurological prognosis in comatose cardiac arrest survivors: a retrospective observational study.

BACKGROUND: To assess the association between relevant brain computed tomography (CT) parameters at different time and neurological prognosis in adult comatose survivors after cardiac arrest (CA). METHODS: A total of 94 CA patients who underwent early and late CT scans (within 24 h and 24 h to 7 d respectively after CA) between January 2018 and April 2020 were enrolled in this retrospective study. According to the Cerebral Performance Category (CPC) score at hospital discharge, the patients were divided into either a good outcome (CPC 1-2) group or a poor-outcome group (CPC 3-5). The grey-to-white matter ratio (GWR) and the proportion of cerebrospinal fluid volume (pCSFV) were measured. In predicting poor outcomes, the prognostic performance of relevant CT parameters was evaluated, and the comparison analysis (expressed as the ratio of parameters in late CT to those in the early CT) of different CT time was conducted. RESULTS: Totally 26 patients were in the good-outcome group, while 68 patients were in the poor-outcome group. The putamen density, GWR, and pCSFV in late CT were significantly lower in the poor-outcome group (P<0.05). The ratios of GWR and pCSFV in the poor-outcome group were significantly decreased according to comparison analysis of different CT time (P<0.05), while there was no significant difference in the ratio of putamen density. GWR-basal ganglia <1.18 in late CT showed the best predictive value. The ratio of pCSFV <0.98 predicted unfavorable neurological outcomes with a sensitivity of 65.9% and a specificity of 93.8% (P=0.001). CONCLUSIONS: Brain CT performed >24 h after CA may be a good choice as a neuroimaging approach to evaluating prognosis. To predict neurological prognosis, comparison analysis of different CT time can be used as another promising tool in comatose CA survivors.

Organic phosphorescent scintillation from copolymers by X-ray irradiation.

Scintillators that exhibit X-ray-excited luminescence have great potential in radiation detection, X-ray imaging, radiotherapy, and non-destructive testing. However, most reported scintillators are limited to inorganic or organic crystal materials, which have some obstacles in repeatability and processability. Here we present a facile strategy to achieve the X-ray-excited organic phosphorescent scintillation from amorphous copolymers through the copolymerization of the bromine-substituted chromophores and acrylic acid. These polymeric scintillators exhibit efficient X-ray responsibility and decent phosphorescent quantum yield up to 51.4% under ambient conditions. The universality of the design principle was further confirmed by a series of copolymers with multi-color radioluminescence ranging from green to orange-red. Moreover, we demonstrated their potential application in X-ray radiography. This finding not only outlines a feasible principle to develop X-ray responsive phosphorescent polymers, but also expands the potential applications of polymer materials with phosphorescence features.

Timing of brain computed tomography for predicting neurological prognosis in comatose cardiac arrest survivors: a retrospective observational study / 世界急诊医学杂志（英文）

@#BACKGROUND: To assess the association between relevant brain computed tomography (CT) parameters at different time and neurological prognosis in adult comatose survivors after cardiac arrest (CA). METHODS: A total of 94 CA patients who underwent early and late CT scans (within 24 h and 24 h to 7 d respectively after CA) between January 2018 and April 2020 were enrolled in this retrospective study. According to the Cerebral Performance Category (CPC) score at hospital discharge, the patients were divided into either a good outcome (CPC 1-2) group or a poor-outcome group (CPC 3-5). The grey-to-white matter ratio (GWR) and the proportion of cerebrospinal fluid volume (pCSFV) were measured. In predicting poor outcomes, the prognostic performance of relevant CT parameters was evaluated, and the comparison analysis (expressed as the ratio of parameters in late CT to those in the early CT) of different CT time was conducted. RESULTS: Totally 26 patients were in the good-outcome group, while 68 patients were in the poor-outcome group. The putamen density, GWR, and pCSFV in late CT were significantly lower in the poor-outcome group (P<0.05). The ratios of GWR and pCSFV in the poor-outcome group were significantly decreased according to comparison analysis of different CT time (P<0.05), while there was no significant difference in the ratio of putamen density. GWR-basal ganglia <1.18 in late CT showed the best predictive value. The ratio of pCSFV <0.98 predicted unfavorable neurological outcomes with a sensitivity of 65.9% and a specificity of 93.8% (P=0.001). CONCLUSIONS: Brain CT performed >24 h after CA may be a good choice as a neuroimaging approach to evaluating prognosis. To predict neurological prognosis, comparison analysis of different CT time can be used as another promising tool in comatose CA survivors.

FMCW lidar multitarget detection based on skeleton tree waveform matching.

Frequency-modulated continuous-wave lidar realizes 4D (three-dimensional space and velocity) imaging of the scene by emitting positive and negative frequency sweep laser signals. The premise of it is to identify the frequency points corresponding to the same target in the positive and negative sweep echo signals. For dechirp receiving, there is usually one peak in the frequency spectrum of the positive and negative sweep signals, respectively. Therefore, it is easy to identify and match the peaks. But in a complex environment, the laser beam will irradiate multiple targets at the same time. In addition, beam scanning and target motion cause the echo spectrum to broaden. The above reasons make it extremely difficult to identify and match peaks in practice. To solve this problem, the waveform-matching algorithm based on the skeleton tree is first applied to multitarget echo pairing. The basic idea of the algorithm is to quantify the target echo hierarchically to generate a skeleton tree. The generation of nodes is based on the relative amplitude of waveform peaks and reflects the characteristics of wave crests nesting. Then the similarity of the signal is determined by comparing the distance between the two signal waveform feature trees. Finally, the waveforms are matched in terms of similarity. To further substantiate the role of the proposed algorithm, imaging experiments and related comparative data for different targets have been completed. The results show that the accuracy of matching processed by the algorithm exceeds 90%, which is improved by about 50% compared with not using the algorithm for the target whose overlapping part accounts for a large proportion of itself.

Enabling long-lived organic room temperature phosphorescence in polymers by subunit interlocking.

Long-lived room temperature phosphorescence (LRTP) is an attractive optical phenomenon in organic electronics and photonics. Despite the rapid advance, it is still a formidable challenge to explore a universal approach to obtain LRTP in amorphous polymers. Based on the traditional polyethylene derivatives, we herein present a facile and concise chemical strategy to achieve ultralong phosphorescence in polymers by ionic bonding cross-linking. Impressively, a record LRTP lifetime of up to 2.1 s in amorphous polymers under ambient conditions is set up. Moreover, multicolor long-lived phosphorescent emission can be procured by tuning the excitation wavelength in single-component polymer materials. These results outline a fundamental principle for the construction of polymer materials with LRTP, endowing traditional polymers with fresh features for potential applications.

Manipulating the Stacking of Triplet Chromophores in the Crystal Form for Ultralong Organic Phosphorescence.

Provided here is evidence showing that the stacking between triplet chromophores plays a critical role in ultralong organic phosphorescence (UOP) generation within a crystal. By varying the structure of a functional unit, and different on-off UOP behavior was observed for each structure. Remarkably, 24CPhCz, having the strongest intermolecular interaction between carbazole units exhibited the most impressive UOP with a long lifetime of 1.06 s and a phosphorescence quantum yield of 2.5 %. 34CPhCz showed dual-emission UOP and thermally activated delayed fluorescence (TADF) with a moderately decreased phosphorescence lifetime of 770 ms, while 35CPhCz only displayed TADF owing to the absence of strong electronic coupling between triplet chromophores. This study provides an explanation for UOP generation in crystal and new guidelines for obtaining UOP materials.

Room-Temperature Phosphorescence from Metal-Free Organic Materials in Solution: Origin and Molecular Design.

Metal-free organic materials with room-temperature phosphorescence (RTP) is hardly achieved in solution owing to the ambiguous underlying mechanism. By combining thermal vibration correlation function rate theory and a polarizable continuum model (PCM) coupled with the Tamm-Dancoff approximation method, concentrating on ß-hydroxyvinylimine boron compounds C-BF2 and S-BF2, we showed that the increased intersystem crossing ( kisc) and radiative decay rates ( kp) are responsible for the strong RTP of S-BF2 in solution. From C-BF2 to S-BF2, the T2 state is increasingly dominated by the n → π* transition, largely enhancing the kisc of S1 → T2 (up to 3 orders of magnitude) and kp of T1 → S0. Impressively, the nonradiative decay rate of T1 → S0 is slightly increased by suppressing the out-of-plane twisting motions. This mechanism is also tenable for several designed RTP molecules through further experimental demonstration, which will pave a new way to design organic materials with single-molecule phosphorescence for applying to organic light-emitting diodes.

Reversible Ultralong Organic Phosphorescence for Visual and Selective Chloroform Detection.

Volatile organic compounds (VOCs) are widespread in our daily life and greatly harmful to human health, as well as to the environment. To date, it remains a formidable challenge to develop a highly sensitive visual system for selective detection of VOCs. Herein, we report on a metal-free organic molecule of 2,4-di(10 H-phenothiazin-10-yl)-1,3,5-triazine (TDP) with ultralong organic phosphorescence (UOP) feature as a visible chemical probe for chloroform detection. In the pristine solid state, this phosphor shows a green UOP with a lifetime of 56 ms after the removal of excitation light source; however, the UOP greatly diminishes when fumed with chloroform, which is ascribed to the variation in both radiative and nonradiative transitions in crystal with embedded chloroform. Remarkably, TDP materials demonstrate great potential as a visual chemical probe for chloroform, showing high sensitivity, excellent selectivity, and good repeatability. The limitation for chloroform detection is as low as 5 ppm. Combining experimental data and theoretical calculations, it is reasoned that the space confinement via intermolecular interactions between chloroform and TDP molecules play a vital role for high selectivity of chloroform detection. These results pave the way toward expanding the scope of organic luminogens with UOP as well as their applications.

Simultaneously Enhancing Efficiency and Lifetime of Ultralong Organic Phosphorescence Materials by Molecular Self-Assembly.

Metal-free organic phosphorescence materials are of imperious demands in optoelectronics and bioelectronics. However, it is still a formidable challenge to develop a material with simultaneous efficiency and lifetime enhancement under ambient conditions. In this study, we design and synthesize a new class of high efficient ultralong organic phosphorescence (UOP) materials through self-assembly of melamine and aromatic acids in aqueous media. A supramolecular framework can be formed via multiple intermolecular interactions, building a rigid environment to lock the molecules firmly in a three-dimensional network, which not only effectively limits the nonradiative decay of the triplet excitons but also promotes the intersystem crossing. Thus, the supermolecules we designed synchronously achieve an ultralong emission lifetime of up to 1.91 s and a high phosphorescence quantum efficiency of 24.3% under ambient conditions. To the best of our knowledge, this is the best performance of UOP materials with simultaneous efficiency and lifetime enhancement. Furthermore, it is successfully applied in a barcode identification in darkness. This result not only paves the way toward high efficient UOP materials but also expands their applications.

The prognostic value of gray-white matter ratio on brain computed tomography in adult comatose cardiac arrest survivors.

BACKGROUND: Recent studies suggested that the gray-white matter ratio (GWR) determined from brain computed tomography (CT) scans may be a reliable predictor of poor neurological outcomes. The aim of study was to evaluate the association between the GWR and the outcomes in adult comatose cardiac arrest (CA) survivors in Chinese. METHODS: A total of 58 CA patients who had CT scans within 72 h of resuscitation between January 2011 and December 2015 were included in this single-center retrospective study. Gray and white matter attenuations (Hounsfield units) were measured, and the GWRs were calculated according to previous studies. The study analyzed the prognostic values of the GWRs in predicting poor outcomes (Cerebral Performance Category 3-5). RESULTS: The attenuation values of gray matter were significantly higher in the good outcome group than in the poor one. All GWRs were significantly higher in the good outcome group (p < 0.05). A GWR (basal ganglia) < 1.18 predicted poor outcomes with a sensitivity and specificity of 50.0% and 87.5%, respectively (p = 0.021). GWR (cerebrum) showed the best predictive performance when CT was performed within 24-72 h (p = 0.003). No significant differences were found between GWR and poor outcomes when CT was performed within the first 24 h. CONCLUSION: Low GWRs which were obtained from brain CT scans in comatose CA patients after restoration of spontaneous circulation were associated with poor neurological outcomes. GWR from brain CT can be a useful parameter for prognostic prediction aiding to an optimal clinical decision process in comatose CA survivors.

Hydrogen-Bonded Organic Aromatic Frameworks for Ultralong Phosphorescence by Intralayer π-π Interactions.

Ultralong organic phosphorescence (UOP) based on metal-free porous materials is rarely reported owing to rapid nonradiative transition under ambient conditions. In this study, hydrogen-bonded organic aromatic frameworks (HOAFs) with different pore sizes were constructed through strong intralayer π-π interactions to enable ultralong phosphorescence in metal-free porous materials under ambient conditions for the first time. Impressively, yellow UOP with a lifetime of 79.8 ms observed for PhTCz-1 lasted for several seconds upon ceasing the excitation. For PhTCz-2 and PhTCz-3, on account of oxygen-dependent phosphorescence quenching, UOP could only be visualized in N2 , thus demonstrating the potential of phosphorescent porous materials for oxygen sensing. This result not only outlines a principle for the design of new HOFs with high thermal stability, but also expands the scope of metal-free luminescent materials with the property of UOP.

Twisted Molecular Structure on Tuning Ultralong Organic Phosphorescence.

Compared to planar carbazole, the molecular conjugation of iminodibenzyl (Id) was destroyed by a C-C bond and a twisted structure was formed, which exhibited blue-shifted ultralong phosphorescence with a lifetime of 402 ms in a crystal under ambient conditions. For the presence of an oscillating C-C bond between the two benzene rings in Id, more than one molecular configuration in the crystal was discovered by X-ray single-crystal analysis. Moreover, its ultralong phosphorescence color changed from blue to green by varying the excitation wavelength in solution at 77 K. Theoretical calculations also confirmed that different molecular configurations had certain impact on the phosphorescent photophysical properties. This result will allow a major step forward in expanding the scope of ultralong organic phosphorescent (UOP) materials, building a bridge to realize the relationship between molecular structure and UOP property.