Spectrum Reconstruction Model Based on Multispectral Electrochromic Devices.

Reconstructing the visible spectra of real objects is critical to the spectral camouflage from emerging spectral imaging. Electrochromic materials exhibit unique superiority for this goal due to their subtractive color-mixing model and structural diversity. Herein, a simulation model is proposed and a method is developed to fabricate electrochromic devices for dynamically reproducing the visible spectrum of the natural leaf. Over 20 kinds of pH-dependent leuco dyes have been synthesized/prepared through molecular engineering and offered available spectra/bands to reconstruct the spectrum of the natural leaf. More importantly, the spectral variance between the device and leaf is optimized from an initial 98.9 to an ideal 10.3 through the simulation model, which means, the similarity increased nearly nine-fold. As a promising spectrum reconstruction approach, it will promote the development of smart photoelectric materials in adaptive camouflage, spectral display, high-end encryption, and anti-counterfeiting.

An electrochemically responsive B-O dynamic bond to switch photoluminescence of boron-nitrogen-doped polyaromatics.

Boron-doped polycyclic aromatic hydrocarbons exhibit excellent optical properties, and regulating their photophysical processes is a powerful strategy to understand the luminescence mechanism and develop new materials and applications. Herein, an electrochemically responsive B-O dynamic coordination bond is proposed, and used to regulate the photophysical processes of boron-nitrogen-doped polyaromatic hydrocarbons. The formation of the B-O coordination bond under a suitable voltage is confirmed by experiments and theoretical calculations, and B-O coordination bond can be broken back to the initial state under opposite voltage. The whole process is accompanied by reversible changes in photophysical properties. Further, electrofluorochromic devices are successfully prepared based on the above electrochemically responsive coordination bond. The success and harvest of this exploration are beneficial to understand the luminescence mechanism of boron-nitrogen-doped polyaromatic hydrocarbons, and provide ideas for design of dynamic covalent bonds and broaden material types and applications.

Anion receptor and heavy metal-free redox mediator decorated separator for lithium-sulfur batteries.

The adsorption-catalysis synergy for accelerated conversion of polysulfides is critical toward the electrochemical stability of lithium-sulfur battery (LSB). Herein, a non-metallic polymer network with anion receptor units, trifluoromethanesulfonyl (CF3SO2-) substituted aza-ether, was in-situ integrated on PE separator, working as an efficient host for anchoring lithium thiophosphates (LPS) as redox mediators and polysulfides through Lewis acid-base interaction. The anchored LPS on the modified PE separator displayed a robust chemical adsorption ability towards polysulfides through the formation of SS bond. Meanwhile, LPS decreased the energy barrier of Li2S nucleation and promoted redox reaction kinetics. The battery with LPS decorated separator revealed a long cycling lifespan with a per cycle decay of 0.056 % after 600 cycles, and a competitive initial capacity of 889.1 mAh/g when the of sulfur cathode increased to 3 mg cm-2. This work developed a new design strategy to promote the utilization of lithium phosphorus sulfide compounds in LSB.

Emerging Electrochromic Materials and Devices for Future Displays.

With the rapid development of optoelectronic fields, electrochromic (EC) materials and devices have received remarkable attention and have shown attractive potential for use in emerging wearable and portable electronics, electronic papers/billboards, see-through displays, and other new-generation displays, due to the advantages of low power consumption, easy viewing, flexibility, stretchability, etc. Despite continuous progress in related fields, determining how to make electrochromics truly meet the requirements of mature displays (e.g., ideal overall performance) has been a long-term problem. Therefore, the commercialization of relevant high-quality products is still in its infancy. In this review, we will focus on the progress in emerging EC materials and devices for potential displays, including two mainstream EC display prototypes (segmented displays and pixel displays) and their commercial applications. Among these topics, the related materials/devices, EC performance, construction approaches, and processing techniques are comprehensively disscussed and reviewed. We also outline the current barriers with possible solutions and discuss the future of this field.

A Flexible Circularly Polarized Luminescence Switching Device Based on Proton-Coupled Electron Transfer.

Flexible circularly polarized luminescence (CPL) switching devices have been long-awaited due to their promising potential application in wearable optoelectronic devices. However, on account of the few materials and complicated design of manufacturing systems, how to fabricate a flexible electric-field-driven CPL-switching device is still a serious challenge. Herein, a flexible device with multiple optical switching properties (CPL, circular dichroism (CD), fluorescence, color) is designed and prepared efficiently based on proton-coupled electron transfer (PCET) mechanism by optimizing the chiral structure of switching molecule. More importantly, this device can maintain the switching performance even after 300 bending-unbending cycles. It has a remarkable comprehensive performance containing bistable property, low open voltage, and good cycling stability. Then, prototype devices with designed patterns have been fabricated, which opens a new application pattern of CPL-switching materials.

Multi-Component Collaborative Step-by-Step Coloring Strategy to Achieve High-Performance Light-Responsive Color-Switching.

Light-responsive color-switching materials (LCMs) are long-lasting hot fields. However, non-ideal comprehensive performance (such as color contrast and retention time cannot be combined, unsatisfactory repeatability, and non-automated coloring mode) significantly hinder their development toward high-end products. Herein, the development of LCMs that exhibit long retention time, good color contrast, repeatability, and the property of automatic coloring is reported. The realization of this goal stems from the adoption of a bio-inspired multi-component collaborative step-by-step coloring strategy. Under this strategy, a conventional one-step photochromic process is divided into a "light+heat" controlled multi-step process for the fabrication of the desired LCMs. The obtained LCMs can effectively resist the long-troubled ambient-light interference and avoid its inherent yellow background, thereby achieving the longest retention time and good repeatability. Multiple colors are generated and ultra-fast imaging compatible with the laser-printing technology is also realized. The application potential of the materials in short-term reusable identity cards, absorptive readers, billboards, and shelf labels is demonstrated. The results reported herein can potentially help in developing and designing various high-performance, switchable materials that can be used for the production of high-end products.

Dynamic Metal-Ligand Interaction of Synergistic Polymers for Bistable See-Through Electrochromic Devices.

Bistable electrochromic materials are a promising alternative solution to reduce energy consumption in displays. Limited by the mechanism and lack of a design strategy, only a few electrochromic materials have truly been able achieve bistability. Herein, a novel strategy is proposed to design bistable electrochromic materials based on polymer-assisted dynamic metal-ligand coordination. The mechanism and materials of such unconventional electrochromic systems are proved by sufficient characterization. Synergistic stabilization of polymerized switchable dyes and the ionic ligand polymer are attracted to each other by supramolecular forces. The color states of the dye molecules are controlled and stabilized by valence changes of the metal ions. Meanwhile, through the polymerization of the electrochromic material and the nearby metal-ligand material, the metal ions of the electroinduced valence change are tightly fixed, and the related diffusion problem of the active EC component is also almost completely suppressed. This strategy successfully enables preparation of the corresponding transparent electrochromic displays with good performances, such as, the display information is clearly visible for more than 1.5 h without consuming energy. Furthermore, the new way of dynamic coordination or dissociation bistable displays could likely prosper the development of the electrochromic area and inspire other fields.

Stimuli-Induced Reversible Proton Transfer for Stimuli-Responsive Materials and Devices.

ConspectusStimuli-responsive materials have a great potential in various novel photoelectric devices, such as self-adaptive adjustment devices, intelligent detection, molecular computers with information storage capability, camouflage and anticounterfeiting display, various energy-saving displays, and others. However, progress in related areas has been relatively slow because of the lack of high-performance smart materials and the limitations of available reaction mechanisms currently. To address these problems fundamentally, new mechanisms need to be designed and developed, and learning from nature is an effective and intelligent method to achieve this long-awaited target, such as mimicking of proton transfer processes in nature at the molecular/supramolecular level. The stimuli-induced reversible proton transfer system is composed of materials that release or capture protons in response to stimuli and switch molecules that control color and/or fluorescence modulation by protons, and it is applied in stimuli-responsive materials and devices, including bistable electronic/electrochromic devices, electrofluorochromic devices, water-jet rewritable paper, visible-light-responsive rewritable paper, and mechanochromic materials.To help researchers gain deep insight into stimuli-induced reversible proton transfer, we attempted to summarize its reaction mechanism and design principle, and discuss strategies to design and prepare various related stimuli-responsive materials and devices. This Account discusses the different systems in which a color/fluorescence change is induced by the proton transfer process under various stimuli, including electric field, water, light, heat, and stress. Relative very promising applications as well as their performance especially for energy-saving and environmentally friendly devices are then summarized, such as energy-saving bistable electrochromic devices, water-jet rewritable paper, and visible-light-responsive rewritable paper. Meanwhile, we focus on the key influence factors and useful additives for improving the device's performance. At last, challenges and bottlenecks faced by stimuli-responsive materials and devices based on the mechanism of reversible proton transfer are proposed. Moreover, we put forward some suggestions on solving these limitations.These exciting results reveal that smart materials based on the mechanism of proton transfer are extremely attractive and possess great potential in the next generation of energy and resource saving and environmental protection display. We hope that this Account further prospers the field of intelligent stimuli-responsive discoloration materials and next-generation green displays.

Green revolution in electronic displays expected to ease energy and health crises.

The technological revolution of long-awaited energy-saving and vision-friendly displays represented by bistable display technology is coming. Here we discuss methods, challenges, and opportunities for implementing bistable displays in terms of molecular design, device structure, further expansion, and required criteria, hopefully benefiting the light-related community.

A Multiple Chirality Switching Device for Spatial Light Modulators.

A new and simple strategy towards electric-field-driven multiple chirality switching device has been designed and fabricated by combining a newly synthesized base-responsive chiroptical polymer switch (R-FLMA) and p-benzoquinone (p-BQ) via proton-coupled electron transfer (PCET) mechanism. Clear and stable triple chirality states (silence, positive, negative) of this device in visible band can be regulated reversibly (>1000 cycles) by adjusting voltage programs. Furthermore, such chiral switching phenomena are also accompanied by apparent changes of color and fluorescence. More importantly, the potential application of this device for a spatial light modulator has also been demonstrated.

Advances in nanomaterials for electrochromic devices.

Electrochromic devices (ECDs) have been regarded as promising candidates for energy-saving smart windows, next-generation displays and wearable electronics due to their significant benefits of simple and adjustable structures, low power consumption, flexible and stretchable features, and eye-friendly modes for displays. However, there are many existing issues waiting to be solved such as durability, reversibility and inadequate switching performances. These insurmountable technical bottlenecks significantly slow down the commercialization of next-generation ECDs. Nanomaterials with superior active reaction surface area have played indispensable roles in optimizing heterogeneous electron transfer and homogeneous ion transfer for ECDs and other optoelectronic devices. In recent years, with the joint efforts of various outstanding research teams, new kinds and methods for nanomaterials to fabricate ECDs with excellent performances have been rapidly developing. This review highlights the latest exciting results regarding the design and application of new and unique nanomaterials for each layer of ECDs. Meanwhile, the structures, mechanisms, features and preparation of the reported nanomaterials to improve the electrochromic properties have been discussed in detail. In addition, the remaining challenges and corresponding strategies of this field are also proposed. Hopefully, this review can inspire more and more researchers to enrich the nanomaterials for ECDs and other related fields to overcome faced technical barriers by innovative means and promote industrialization of ECDs and other optoelectronic technologies.

A Single-Pixel RGB Device in a Colorful Alphanumeric Electrofluorochromic Display.

With the rapid development of human society, consumer electronics have brought marvelous changes to human daily life, but they are accompanied by the much higher demand of display quality and visual experience. Therefore, ideal conversion among the three primary colors-red (R), green (G), and blue (B)-in a single pixel has been a better way to avoid the insurmountable technical barrier of subpixel technology of modern displays. Electrofluorochromic (EFC) materials capable of a novel luminescent switching, open a powerful way to design optoelectronic devices for displays and information storage etc. Colorful EFC devices, especially emitting the ideal three primary colors without subpixel technology, have been a challenge for years. Herein, a long-awaited single-pixel device with RGB color is fabricated successfully based on proton-coupled electron transfer. The RGB EFC device exhibits outstanding EFC properties, such as low turn-on voltage (+1.0 and -1.0 V), large color gamut, and good stability (500 cycles for each color). Prototypes of colorful alphanumeric displays are well demonstrated in a facile way. The success of this new exploration of single-pixel RGB EFC device not only provides the possibility of full-color emission in EFC devices, but also will widely broaden the EFC system and their applications.

Using RNA-Seq to Explore the Repair Mechanism of the Three Methods and Three-Acupoint Technique on DRGs in Sciatic Nerve Injured Rats.

Objective: To study the effects of the three methods and three-acupoint technique on DRG gene expression in SNI model rats and to elucidate the molecular mechanism of the three methods and three-acupoint technique on promoting recovery in peripheral nerve injury. Methods: 27 male SD rats were randomly divided into three groups: a Sham group, the SNI group, and the Tuina group. The Tuina group was treated with a tuina manipulation simulator to simulate massage on points, controlling for both quality and quantity. Point-pressing, plucking, and kneading methods were administered quantitatively at Yinmen (BL37), Chengshan (BL57), and Yanglingquan (GB34) points on the affected side once a day, beginning 7 days after modeling. Intervention was applied once a day for 10 days, then 1 day of rest, followed by 10 more days of intervention, totally equaling 20 times of intervention. The effect of the three methods and three-point technique on the recovery of injured rats was evaluated using behavior analysis. RNA sequencing (RNA-Seq) analysis of differentially expressed genes in DRGs of the three groups of rats was also performed. GO and KEGG enrichment was analyzed and verified using real-time PCR. Results: RNA-Seq combined with database information showed that the number of differentially expressed genes in DRG was the largest in the Tuina group compared with the SNI group, totaling 226. GO function is enriched in the positive regulation of cell processes, ion binding, protein binding, neuron, response to pressure, response to metal ions, neuron projection, and other biological processes. GO function is also enriched in the Wnt, IL-17, and MAPK signaling pathways in the KEGG database. PCR results were consistent with those of RNA sequencing, suggesting that the results of transcriptome sequencing were reliable. Conclusion: The three methods and three-acupoint technique can promote the recovery of SNI model rats by altering the gene sequence in DRGs.

A Transparent Multidimensional Electrode with Indium Tin Oxide Nanofibers and Gold Nanoparticles for Bistable Electrochromic Devices.

Due to the high energy efficiency and a wide range of potential applications in daily life, bistable electrochromic devices (BECDs) have gained extensive attention in recent years. However, poor bistability and slow response rate are the main barriers, which restrict the development of BECDs. Herein, a transparent multidimensional electrode with indium tin oxide (ITO) nanofibers and gold nanoparticles was fabricated to improve both the bistability and responsiveness of devices. Its criss-crossed ITO nanofibers with high length-to-diameter ratios to reduce the distance of heterogeneous electron transfer and its gold nanoparticles to form a stable Au-S bond to avoid self-erasing of electrochromic materials have been demonstrated and discussed systematically. This device based on the transparent multidimensional working electrode had a shorter response time (1/5) and a longer bistability (12/1) compared with the prototype devices based on common fluorine-doped tin oxide electrodes. Besides, this device had a promising electrochromic performance with a high coloration efficiency of 448.27 cm2/C and a switching stability with no significant attenuation after 1200 cycles.

A multicolour bistable electronic shelf label based on intramolecular proton-coupled electron transfer.

Bistable electrochromic materials have been explored as a viable alternative to reduce energy consumption in display applications. However, the development of ideal bistable electrochromic displays (especially multicolour displays) remains challenging due to the intrinsic limitations associated with existing electrochromic processes. Here, a bistable electrochromic device with good overall performance-including bistability (>52 h), reversibility (>12,000 cycles), colouration efficiency (≥1,240 cm2 C-1) and transmittance change (70%) with fast switching (≤1.5 s)-was designed and developed based on concerted intramolecular proton-coupled electron transfer. This approach was used to develop black, magenta, yellow and blue displays as well as a multicolour bistable electrochromic shelf label. The design principles derived from this unconventional exploration of concerted intramolecular proton-coupled electron transfer may also be useful in different optoelectronic applications.

Spontaneous proton transfer in a series of amphoteric molecules under hydrostatic pressure.

Herein, high-pressure behaviour of a series of amphoteric molecules in the crystal form was investigated, and the detailed experimental and calculated data revealed that hydrostatic pressure could result in intermolecular proton transfer in addition to the previously reported changes in molecular conformations and enhancement of intermolecular forces. Furthermore, by comparing (2-(3,3-dimethyl-3H-indol-2-yl)vinyl)-4-nitrophenol (AM-N) with the control molecules de-nitrated AM, nitro-mismatched OM-N and methylated AM-N-C, it was found that the pressure-triggered proton transfer in the crystal was not a simple loss or gain of protons as that in solution; instead, it involved the sharing of protons by their gradual deviation from a proton donor to a proton acceptor. The proton deviation degree strongly depends on the distance between the proton donor and acceptor in the crystal, rather than molecular acidity and basicity in solution. Moreover, regarding its potential applications, the acid-base conjugated amphoteric molecule AM-N could be applied in accurate colorimetric pressure sensing, and its accuracy was close to that of the widely used high-pressure indicator ruby pressure marker.

Photo-/Baso-Chromisms and the Application of a Dual-Addressable Molecular Switch.

Two typical molecular switches of spiropyran (SP) and benzoxazine (OX) were fused by sharing an indole to achieve a new dual-addressable molecular switch (SP-OX-NO2 ). Through proper molecular modification with NO2 , the transformation from merocyanine (MC) to ring-closed SP or ring-closed OX can be controlled separately with visible light or base stimuli in solution, respectively, and these processes are verified by UV-vis and NMR spectroscopy as well as control experiments. The cis-merocyanine (cis-MC) form is involved in the basochromic process in solution. DFT calculation suggests that the bidirectional switching property of the fused SP-OX molecular switch can be controlled separately, when the OX isomer is more stable than the deprotonated SP isomer. Because of the significant color variations in solution, the simple dual-addressable switch has been further successfully applied to construct a multicolor reversible display on paper.

Bio-inspired ultra-high energy efficiency bistable electronic billboard and reader.

Bistable display has been a long-awaited goal due to its zero energy cost when maintaining colored or colorless state and electrochromic material has been highly considered as a potential way to achieve bistable display due to its simple structure and possible manipulation. However, it is extremely challenging with insurmountable technical barriers related to traditional electrochromic mechanisms. Herein a prototype for bistable electronic billboard and reader with high energy efficiency is demonstrated with excellent bistability (decay 7% in an hour), reversibility (104 cycles), coloration efficiency (430 cm2 C-1) and very short voltage stimulation time (2 ms) for color switching, which greatly outperforms current products. This is achieved by stabilization of redox molecule via intermolecular ion transfer to the supramolecular bonded colorant and further stabilization of the electrochromic molecules in semi-solid media. This promising approach for ultra-energy-efficient display will promote the development of switching molecules, devices and applications in various fields of driving/navigation/industry as display to save energy.

Firefly-Inspired Approach to Develop New Chemiluminescence Materials.

Bioluminescence, wherein marine and terrestrial organisms chemically produce light for communication, is a burgeoning area of research. Herein, we demonstrate a new series of artificial chemiluminescent compounds inspired by the enol-degradation reaction of natural bioluminescent molecules, luciferins. Based on systematic optical experiments, isotope labeling, and theoretical calculations, the chemiluminescent mechanism of these new materials and the relationship of enol-degradation reaction and chemiluminescence are fully discussed. The color and efficiency of the artificial chemiluminescent materials can be easily adjusted, and blue (486 nm), yellow (565 nm), and near-infrared (756 nm) luminescence can thus be obtained. The findings and in-depth understanding herein may accelerate the development of bio/chemiluminescent materials for analytical applications and non-invasive bioluminescence imaging.