Isostructural doping for organic persistent mechanoluminescence.

Mechanoluminescence, featuring light emission triggered by mechanical stimuli, holds immense promise for diverse applications. However, most organic Mechanoluminescence materials suffer from short-lived luminescence, limiting their practical applications. Herein, we report isostructural doping as a valuable strategy to address this challenge. By strategically modifying the host matrices with specific functional groups and simultaneously engineering guest molecules with structurally analogous features for isostructural doping, we have successfully achieved diverse multicolor and high-efficiency persistent mechanoluminescence materials with ultralong lifetimes. The underlying persistent mechanoluminescence mechanism and the universality of the isostructural doping strategy are also clearly elucidated and verified. Moreover, stress sensing devices are fabricated to show their promising prospects in high-resolution optical storage, pressure-sensitive displays, and stress monitoring. This work may facilitate the development of highly efficient organic persistent mechanoluminescence materials, expanding the horizons of next-generation smart luminescent technologies.

Dual-channel mechano-phosphorescence: a combined locking effect with twisted molecular structures and robust interactions.

Organic mechanoluminescence materials, featuring dual emission and ultralong phosphorescence characteristics, exhibit significant potential for applications in real-time stress sensing, pressure-sensitive lighting, advanced security marking techniques, and material breakage monitoring. However, due to immature molecular design strategies and unclear luminescence mechanisms, these materials remain rarely reported. In this study, we propose a valuable molecular design strategy to achieve dual-channel mechano-phosphorescence. By introducing the arylphosphine oxide group into a highly twisted molecular framework, enhanced intra- and intermolecular interactions could be achieved within rigid structures, leading to dual-channel mechanoluminescence with greatly promoted ultralong phosphorescence. Further investigations reveal the substantial boosting effect of intra- and intermolecular interactions on mechanoluminescence and ultralong phosphorescence properties by locking the highly twisted molecular skeleton. This work provides a concise and guiding route to develop novel smart responsive luminescence materials for widespread applications in material science.

Multilaminate Energy Storage Films from Entropy-Driven Self-Assembled Supramolecular Nanocomposites.

Composite materials comprising polymers and inorganic nanoparticles (NPs) are promising for energy storage applications, though challenges in controlling NP dispersion often result in performance bottlenecks. Realizing nanocomposites with controlled NP locations and distributions within polymer microdomains is highly desirable for improving energy storage capabilities but is a persistent challenge, impeding the in-depth understanding of the structure-performance relationship. In this study, a facile entropy-driven self-assembly approach is employed to fabricate block copolymer-based supramolecular nanocomposite films with highly ordered lamellar structures, which are then used in electrostatic film capacitors. The oriented interfacial barriers and well-distributed inorganic NPs within the self-assembled multilaminate nanocomposites effectively suppress leakage current and mitigate the risk of breakdown, showing superior dielectric strength compared to their disordered counterparts. Consequently, the lamellar nanocomposite films with optimized composition exhibit high energy efficiency (>90% at 650 MV m-1), along with remarkable energy density and power density. Moreover, finite element simulations and statistical modeling have provided theoretical insights into the impact of the lamellar structure on electrical conduction, electric field distribution, and electrical tree propagation. This work marks a significant advancement in the design of organic-inorganic hybrids for energy storage, establishing a well-defined correlation between microstructure and performance.

Effects of the elongated needling combined with routine acupuncture therapy in the patients with post-stroke hemiplegia and central pain： a randomized controlled trial. / èŠ’é’ˆé€åˆºè”åˆä½“é’ˆæ²»ç–—å¯¹ä¸­é£ŽåŽåç˜«ä¼´ä¸­æž¢æ€§ç–¼ç—›æ‚£è€ çš„ä¸´åºŠç–—æ•ˆè§‚å¯Ÿï¼šéšæœºå¯¹ç §è¯•éªŒ.

OBJECTIVES: To investigate the effects of the elongated needling at the points of hand and foot yang meridians and the Governor Vessel combined with the routine acupuncture therapy on pain, balance function and muscle strength of the patients with post-stroke hemiplegia and central post-stroke pain (CPSP), and to investigate whether its therapeutic mechanism is related to antioxidant damage. METHODS: Ninety-four patients with post-stroke hemiplegia and CPSP admitted from March 2020 to September 2021 were divided into a trial group (47 cases, 1 cases dropped out) and a control group (47 cases 3 cases dropped out). In the control group, the rehabilitation exercise combined with routine acupuncture therapy was used, and in the trial group, on the base of the treatment as the control group, the elongated needling at the points of hand and foot yang meridians and the Governor Vessel was supplemented. In the two groups, the treatment was given once daily, and 1 course of treatment was composed of 14 days, a total of 6 courses were required in the trial. Separately, before treatment, and 1, 2 and 3 months after treatment, between two groups, the score of visual analogue scale (VAS) and that of Berg balance scale (BBS), as well as muscle strength were compared；the neural function was evaluated using the national institutes of health stroke scale (NIHSS) and the serum contents of nitricoxide synthase (NOS), superoxide dismutase (SOD) and malondialdehyde (MDA) were detected by ELISA in the patients. RESULTS: Compared with those before treatment, VAS score and NIHSS score were all decreased (P<0.05) in the trial and the control group after 1 month, 2 months and 3 months of treatment, and BBS score was increased (P<0.05)；and the case proportion of muscle strength grade 4 and 5 was higher (P<0.05) in the trial group. In the control group, the proportion of grade 4 increased after treatment for 2 months (P<0.05), and that of grade 4 and 5 increased after treatment for 3 months (P<0.05). The serum contents of NOS and SOD were increased (P<0.05), and MDA was decreased (P<0.05) after 3 months of treatment in the two groups. In comparison with the control group at the same time point, VAS score and NIHSS score were lower (P<0.05), BBS score higher (P<0.05) and the muscle strength grade was improved (P<0.05, P<0.01) after 1, 2 and 3 months of treatment, respectively；and the serum contents of NOS and SOD increased (P<0.05), and MDA decreased (P<0.05) after 3 months of treatment in the trial group. CONCLUSIONS: The elongated needling at the points of hand and foot yang meridians and the Governor Vessel, combined with the routine acupuncture therapy alleviates CPSP, improves balance and muscle strength and promotes the recovery of neural function in the patients with post-stroke hemiplegia, the mechanism may be related to antioxidant damage.

Weak non-line-of-sight target echoes extraction without accumulation.

Non-line-of-sight (NLOS) technology has been rapidly developed in recent years, allowing us to visualize or localize hidden objects by analyzing the returned photons, which is expected to be applied to autonomous driving, field rescue, etc. Due to the laser attenuation and multiple reflections, it is inevitable for future applications to separate the returned extremely weak signal from noise. However, current methods find signals by direct accumulation, causing noise to be accumulated simultaneously and inability of extracting weak targets. Herein, we explore two denoising methods without accumulation to detect the weak target echoes, relying on the temporal correlation feature. In one aspect, we propose a dual-detector method based on software operations to improve the detection ability for weak signals. In the other aspect, we introduce the pipeline method for NLOS target tracking in sequential histograms. Ultimately, we experimentally demonstrated these two methods and extracted the motion trajectory of the hidden object. The results may be useful for practical applications in the future.

Color-Tunable Dual-Mode Organic Afterglow for White-Light Emission and Information Encryption Based on Carbazole Doping.

Dual-mode emission materials, combining phosphorescence and delayed fluorescence, offer promising opportunities for white-light afterglow. However, the delayed fluorescence lifetime is usually significantly shorter than that of phosphorescence, limiting the duration of white-light emission. In this study, a carbazole-based host-guest system that can be activated by both ultraviolet (UV) and visible light is reported to achieve balanced phosphorescence and delayed fluorescence, resulting in a long-lived white-light afterglow. Our study demonstrated the critical role of a charge transfer state in the afterglow mechanism, where the charge separation and recombination process directly determined the lifetime of afterglow. Simultaneously, an efficient reversed intersystem crossing process was obtained between the singlet and triplet charge transfer states, which facilitating the delayed fluorescence properties of host-guest system. As a result, delayed fluorescence lifetime was successfully prolonged to approach that of phosphorescence. This work presents a delayed fluorescence lifetime improvement strategy via doping method to realize durable white-light afterglow.

Analysis and Optimization of Dynamic and Static Characteristics of the Compliant-Amplifying Mechanisms.

Compliant amplifying mechanisms are used widely in high-precision instruments driven by piezoelectric actuators, and the dynamic and static characteristics of these mechanisms are closely related to instrument performance. Although the majority of existing research has focused on analysis of their static characteristics, the dynamic characteristics of the mechanisms affect their response speeds directly. Therefore, this paper proposes a comprehensive theoretical model of compliant-amplifying mechanisms based on the multi-body system transfer matrix method to analyze the dynamic and static characteristics of these mechanisms. The effects of the main amplifying mechanism parameters on the displacement amplification ratio and the resonance frequency are analyzed comprehensively using the control variable method. An iterative optimization algorithm is also used to obtain specific parameters that meet the design requirements. Finally, simulation analyses and experimental verification tests are performed. The results indicate the feasibility of using the proposed theoretical compliant-amplifying mechanism model to describe the mechanism's dynamic and static characteristics, which represents a significant contribution to the design and optimization of compliant-amplifying mechanisms.

High-performing polysulfate dielectrics for electrostatic energy storage under harsh conditions.

High capacity polymer dielectrics that operate with high efficiencies under harsh electrification conditions are essential components for advanced electronics and power systems. It is, however, fundamentally challenging to design polymer dielectrics that can reliably withstand demanding temperatures and electric fields, which necessitate the balance of key electronic, electrical and thermal parameters. Herein, we demonstrate that polysulfates, synthesized by sulfur(VI) fluoride exchange (SuFEx) catalysis, another near-perfect click chemistry reaction, serve as high-performing dielectric polymers that overcome such bottlenecks. Free-standing polysulfate thin films from convenient solution processes exhibit superior insulating properties and dielectric stability at elevated temperatures, which are further enhanced when ultrathin (~5 nm) oxide coatings are deposited by atomic layer deposition. The corresponding electrostatic film capacitors display high breakdown strength (>700 MV m-1) and discharged energy density of 8.64 J cm-3 at 150 °C, outperforming state-of-the-art free-standing capacitor films based on commercial and synthetic dielectric polymers and nanocomposites.

Realizing Photoswitchable Mechanoluminescence in Organic Crystals Based on Photochromism.

Organic mechanoluminescent (ML) materials possessing photophysical properties that are sensitive to multiple external stimuli have shown great potential in many fields, including optic and sensing. Particularly, the photoswitchable ML property for these materials is fundamental to their applications but remains a formidable challenge. Herein, photoswitchable ML is successfully realized by endowing reversible photochromic properties to an ML molecule, namely 2-(1,2,2-triphenylvinyl) fluoropyridine (o-TPF). o-TPF shows both high-contrast photochromism with a distinct color change from white to purplish red, as well as bright blue ML (λML  = 453 nm). The ML property can be repeatedly switched between ON and OFF states under alternate UV and visible light irradiation. Impressively, the photoswitchable ML is of high stability and repeatability. The ML can be reversibly switched on and off by conducting alternate UV and visible light irradiation in cycles under ambient conditions. Experimental results and theoretical calculations reveal that the change of dipole moment of o-TPF during the photochromic process is responsible for the photoswitchable ML. These results outline a fundamental strategy to achieve for the control of organic ML and pave the way to the development of expanded smart luminescent materials and their applications.

NIR TADF emitters and OLEDs: challenges, progress, and perspectives.

Near-infrared (NIR) light-emitting materials show excellent potential applications in the fields of military technology, bioimaging, optical communication, organic light-emitting diodes (OLEDs), etc. Recently, thermally activated delayed fluorescence (TADF) emitters have made historic developments in the field of OLEDs. These metal-free materials are more attractive because of efficient reverse intersystem crossing processes which result in promising high efficiencies in OLEDs. However, the development of NIR TADF emitters has progressed at a relatively slower pace which could be ascribed to the difficult promotion of external quantum efficiencies. Thus, increasing attention has been paid to NIR TADF emitters. In this review, the recent progress of NIR TADF emitters has been summarized along with their molecular design strategies and photophysical properties, as well as electroluminescence performance data of their OLEDs, respectively.

2-Hydroxybenzophenone Derivatives: ESIPT Fluorophores Based on Switchable Intramolecular Hydrogen Bonds and Excitation Energy-Dependent Emission.

In this work, a new series of 2-hydroxybenzophenone (BPOH) derivatives, BPOH-TPA, BPOH-PhCz, and BPOH-SF substituting with different electron-donating groups are designed and synthesized. Dual-emission spectra are observed in solutions indicating their excited-state intramolecular proton transfer (ESIPT) character. In solid states, all compounds exhibit a broad emission spectrum when excited at low excitation energy, deriving from the enol-type form stabilized by intramolecular hydrogen bonds. Compound BPOH-TPA shows a clear excitation wavelength dependence. However, such behavior is absent in BPOH-PhCz and BPOH-SF, as the rigid and weaker donor moieties may restrict this process. Furthermore, by increasing the excitation energy, dual emission with a high-energy band ranging from 550 to 582 nm and a low-energy band ranging from 625 to 638 nm is obtained in all three molecules. The photophysical studies and single-crystal analyses are performed to further illustrate the excitation-dependent emission. Higher excitation energies can promote more excitons to keto forms via ESIPT, giving a stronger redshifted emission. BPOH-TPA with a stronger donor strength exhibits an obvious color change gradually from yellow to orange-red with the increasing excitation power from 1 to 15 mW/cm2. This study provides a novel example of ESIPT materials with tunable emission colors.

Wide-range lifetime-tunable and responsive ultralong organic phosphorescent multi-host/guest system.

The rational lifetime-tuning strategy of ultralong organic phosphorescence is extraordinarily important but seldom reported. Herein, a series of multi-host/guest ultralong organic phosphorescence materials with dynamic lifetime-tuning properties were reported. By doping a non-room-temperature phosphorescence emitter into various solid host matrices with continuously reduced triplet energy levels, a wide-range lifetime (from 3.9 ms gradually to 376.9 ms) phosphorescence with unchangeable afterglow colors were realized. Further studies revealed that the host matrices were employed to afford rigid environment and proper energy levels to generate and stabilize the long-live triplet excitons. Meanwhile, these multi-host/guest ultralong organic phosphorescence materials also exhibited excitation-dependent phosphorescence and temperature-controlled afterglow on/off switching properties, according to the virtue of various photophysical and thermal properties of the host matrices. This work provides a guiding strategy to realize lifetime-tuning ultralong organic phosphorescence with lifetime-order encoding characteristic towards widespread applications in time-resolved information displaying, higher-level security protection, and dynamic multi-dimensional anti-counterfeiting.

Piston error correction of sparse aperture systems using the metaheuristic stochastic parallel gradient descent algorithm.

The next generation of optical telescopes will provide high-resolution imaging of celestial objects by using the aperture synthesis technique. To preserve the quality of the image, fast corrections of the pistons among subapertures have to be applied, namely, the co-phasing of the array. The image-based co-phasing method via an optimization procedure has been newly developed. Despite simplicity and strong commonality, when dealing with large piston errors, this correction method is also faced with a problem in which the metric function easily falls into the local convergence, especially in the case of broadband imaging with many subapertures. In this study, an improved stochastic parallel gradient descent (SPGD) algorithm based on heuristic search is proposed for co-phasing, termed the metaheuristic SPGD algorithm. The heuristic research scheme assists the original SPGD algorithm in getting rid of local extrema. By iterations of this algorithm, the synthetic system can be co-phased without any additional instruments and operations. The effectiveness of the proposed algorithm is verified by means of simulation. Given the efficiency and superiority, it is expected that the method proposed in this study may find wide applications in multi-aperture imaging.

Wide-band high-resolution synthetic imaging of a segmented large-scaled lightweight diffractive telescope.

In this Letter, we report a segmented large-scaled lightweight diffractive telescope testbed newly built in our laboratory. The telescope, consisting of one 710-mm-diameter element in the center surrounded by eight 352-mm-diameter elements and a smaller eyepiece of achromatic lenses, can realize wide-band high-resolution imaging of 0.55-0.65 µm. The stitching errors are coarsely corrected by adjusting the motion stage mounted on each element. In particular, an optical synthesis system inserted behind the eyepiece is designed to compensate the residual tip-tilt-piston errors. We present the experimental imaging result of two stitched elements, which is the first successful experimental verification obtained by a practical segmented diffractive telescope to enhance the resolution. Moreover, spatial modulation diversity technology is used to restore the synthetic image so as to improve its quality and contrast.

Hypertelescope with multiplexed fields of view.

Hypertelescope interferometers having many highly diluted sub-apertures are capable of directly imaging, within a narrow field of view, celestial objects at a high resolution thanks to pupil densification. This Letter verifies with OpticStudio modeling the possibility of simultaneously imaging multiple such fields. A strategy of multi-field sampling uses a microlens array to generate multiplexed field channels, where independent active corrections of the tip-tilt and piston are applied for compensating for the off-axis aberrations. Adopting this strategy, we have designed a model of a multi-field hypertelescope with OpticStudio. The reported design expands the observing performance of hypertelescopes for directly imaging multiple sources with very high angular resolution.

Two-photon-excited ultralong organic room temperature phosphorescence by dual-channel triplet harvesting.

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 Improved Method of Measuring Wavefront Aberration Based on Image with Machine Learning in Free Space Optical Communication.

In this paper, an improved method of measuring wavefront aberration based on image with machine learning is proposed. This method had better real-time performance and higher estimation accuracy in free space optical communication in cases of strong atmospheric turbulence. We demonstrated that the network we optimized could use the point spread functions (PSFs) at a defocused plane to calculate the corresponding Zernike coefficients accurately. The computation time of the network was about 6-7 ms and the root-mean-square (RMS) wavefront error (WFE) between reconstruction and input was, on average, within 0.1263 waves in the situation of D/r0 = 20 in simulation, where D was the telescope diameter and r0 was the atmospheric coherent length. Adequate simulations and experiments were carried out to indicate the effectiveness and accuracy of the proposed method.

Piston sensing of sparse aperture systems with a single broadband image via deep learning.

The pistons of sparse aperture systems need to be controlled within a fraction of a wavelength for the system's optimal imaging performance. In this paper, we demonstrate that deep learning is capable of performing piston sensing with a single wide-band image after appropriate training. Taking the sensing issue as a fitting task, the deep learning-based method utilizes a deep convolutional neural network to learn complex input-output mapping relations between the broadband intensity distributions and corresponding piston values. Given a trained network and one broadband focal intensity image as the input, the piston can be obtained directly and the capture range achieving the coherence length of the broadband light is available. Simulations and experiments demonstrate the validity of the proposed method. Using only in-focused broadband images as the inputs without defocus division and wavelength dispersion, obviously relaxes the optics complexity. In view of the efficiency and superiority, it's expected that the method proposed in this paper may be widely applied in multi-aperture imaging.

Research on high-resolution imaging technology based on light field manipulation for a lenslet-based plenoptic camera.

In this paper, an aberration correction method for an extended target is proposed to solve the problem of the lenslet-based plenoptic camera not imaging clearly under the influence of aberrations. We propose a light field manipulation method to improve performance of the light field imaging system. The principle of this method is that the sub-aperture images extracted from the raw light field image are offset when the light field imaging system is affected by aberrations, and the symmetrical arrangement of the sub-aperture image array is destroyed. By repairing the symmetrical arrangement of the sub-aperture image array, the influence of phase aberrations on the imaging system can be eliminated, and the resolution of the plenoptic camera can be improved. We use an image correlation algorithm to process the sub-aperture images of the plenoptic camera, calculate and compensate each sub-aperture image's displacement caused by aberrations, and restore the symmetrical arrangement of the sub-aperture image array; then, a corrected high-resolution refocused image can be generated. In particular, this method uses only the raw light field information obtained by the plenoptic camera in a single exposure, without adding other hardware devices. Furthermore, it takes the extended target itself as the reference image, so the ideal position need not be calibrated in advance. Also, the parallax information of the sub-aperture images is retained, and the method is simple and easy to use. Numerical simulation and experimental results show that the technology proposed in this paper can work well for high-resolution imaging of a plenoptic camera with phase aberrations. This method can be potentially applied to analyze lens aberration, media-induced image distortion such as water turbulence in underwater imaging, and atmospheric turbulence in remote imaging. It may have important application prospects in the fields of astronomical object detection, remote sensing, etc.

Alkyl Chain Introduction: In†Situ Solar-Renewable Colorful Organic Mechanoluminescence Materials.

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.