Dissipative solitons are self-localized coherent structures arising from the balance between energy supply and dissipation. Besides stationary dissipative solitons, there are dynamical ones exhibiting oscillatory behavior, known as breathing dissipative solitons. Substantial interest in breathing dissipative solitons is driven by both their fundamental importance in nonlinear science and their practical applications, such as in spectroscopy. Yet, the observation of breathers has been mainly restricted to microresonator platforms. Here, we generate breathers in a mode-locked fiber laser. They exist in the laser cavity under the pump threshold of stationary mode locking. Using fast detection, we are able to observe the temporal and spectral evolutions of the breathers in real time. Breathing soliton molecules are also observed. Breathers introduce a new regime of mode locking into ultrafast lasers. Our findings may contribute to the design of advanced laser sources and open up new possibilities of generating breathers in various dissipative systems.

Cobalt carbide (Co2C) has recently been reported to be efficient for the conversion of syngas (CO+H2) to lower olefins (C2–C4) and higher alcohols (C2+ alcohols); however, its properties and formation conditions remain ambiguous. On the basis of our previous investigations concerning the formation of Co2C, the work herein was aimed at defining the mechanism by which the manganese promoter functions in the Co-based catalysts supported on activated carbon (CoxMn/AC). Experimental studies validated that Mn facilitates the dissociation and disproportionation of CO on the surface of catalyst and prohibits H2 adsorption to some extent, creating a relative C-rich and H-lean surface chemical environment. We advocate that the surface conditions result in the transformation from metallic Co to Co2C phase under realistic reaction conditions to form Co@Co2C nanoparticles, in which residual small Co0 ensembles (<6 nm) distribute on the surface of Co2C nanoparticles (∼20 nm). Compared with the Co/AC catalyst, where the active site is composed of Co2C phase on the surface of Co0 nanoparticles (Co2C@Co), the Mn-promoted catalysts (Co@Co2C) displayed much higher olefin selectivity (10% versus 40%), while the selectivity to alcohols over the two catalysts are similar (∼20%). The rationale behind the strong structure–performance relationship is twofold. On the one hand, Co–Co2C interfaces exist universally in the catalysts, where synergistic effects between metallic Co and Co2C phase occur and are responsible for the formation of alcohols. On the other hand, the relative C-rich and H-lean surface chemical environment created by Mn on the Co@Co2C catalysts facilitates the formation of olefins.

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Graphene, with its properties of intrinsic flexibility, reliable electrical performance, and high chemical stability, is highly desirable as bioelectrodes for detecting electrophysiological signals. However, its mechanical properties limit its application to a great extentenergy dissipation mechanisms are not provided by the carbon network for external strain and it easily cracks. Herein, inspired by the very structure of the avian nest, we report a durable and nondisposable transparent graphene skin electrode for detecting electrophysiological signals, which was fabricated by semi-embedding highly graphitized electrospun fiber/monolayer graphene (GFG) into soft elastomer. Because of the semi-embedded structure and strong interaction between annealed electrospun fiber and graphene through graphitization, as-fabricated conductive film demonstrated high conductivity and transparency (∼150 Ω/□ at 83% transmittance), as well as a stable electrical performance under mechanical vibrations (strain, peel-off, stir, etc.). It can be used to reliably collect vital biometric signals, such as electrocardiogram (ECG), surface electromyogram (sEMG), and electroencephalogram (EEG). Furthermore, the semi-embedded GFG in the elastomer demonstrated excellent washability (rinsing/stirring in water) and repeatability (∼10 repeats) with high signal-to-noise ratio (up to 30 dB) while detecting sEMG. This is the first report of durable and transparent graphene skin electrode for biometric signals detection, revealing potential opportunities in wearable healthcare applications.

Boron‐based adhesives have attracted considerable attention in recent years due to their strong adhesive behavior and reversible capacities. However, limited by the humidity sensitivity and poor dynamicity, it remains challenging for the boron‐based adhesive materials to realize strong and long‐term adhesion underwater. In this study, a novel boronic ester (BN‐6) with changeable ring strain induced by the heat‐responsive BN coordination bond is designed and synthesized. Due to the low strain of the six‐membered ring at ambient conditions and the high strain of the ten‐membered ring at elevated temperature, BN‐6 exhibits enhanced hydrolytic/thermal stabilities as well as dynamicity. The model dynamic crosslinking polymers containing BN‐6 linkages present significantly improved water‐resistance and recyclability. Specifically, based on the hydrolytically stable whilst kinetically active boronic ester linkage, a strong and recyclable adhesive material is successfully prepared. Long‐term adhesion performance under water and harsh conditions is realized on different substrates, with the maximum adhesion strength of 4.21 MPa. The report provides a novel chemical strategy for designing stable and dynamic boronic ester linkages and the synthesized adhesive has pioneered in the field of long‐term underwater application of boron‐based adhesives.

B–O bonds are effective for constructing self-healing polymers, because of their unique combination of high thermodynamic stability and kinetic tunability. However, it is still challenging to develop boron-containing polymers that show simultaneously high mechanical strength, good hydrolytic stability, and autonomous self-healing ability. Herein, we designed and synthesized a phenol compound with three hydroxyls, two of which form boronic ester with boronic acid while the other one can promote the dynamic exchange of B–O bonds. Taking advantage of the new boronic esters as the cross-linking sites, a series of strong and tough elastomers with outstanding self-healing capacities at room temperature were successfully fabricated. The new design concept provides a novel type of dynamic covalent boronic esters as the platform for synthesizing durable and functional self-healing materials. Moreover, phenol compounds with three hydroxyl groups are abundant in the natural product, tannic acid (TA), which can also form dynamic boronic esters with boronic acid and be used to derive polymers with excellent recyclability. Therefore, this new system might facilitate the commercialization of boron-based dynamic covalent polymers as viable alternatives to contemporary commodity thermosets.

Introduction of defects in a controllable way is important to modulate the electronic structure of catalysts towards enhancement of electrocatalytic activity. Herein, we report that fluorine incorporation into cobalt phosphide alloy has a unique effect -it creates both F-anion doping and P vacancy, which results in nearly 15-fold enhancement in catalytic activity for hydrogen evolution reaction (HER) in neutral solution. The existence of dual defects in CoP is confirmed by extended X-ray absorption fine structure (EXAFS) curve fitting results and density functional theory calculation. We show that the dual-defect feature is beneficial to increasing the Page 2 of 27 ACS Paragon Plus Environment ACS Materials Letters 3 active site exposure, tuning the surface wettability and optimizing the electronic configuration of CoP for HER. Our fluorine-based modulation protocol may be applicable to other metal alloy electrocatalysts towards more efficient energy conversion reactions. TOC GRAPHICSAmong the various new and sustainable energy systems, electrolysis of water is considered as a promising technology to generate hydrogen which is regarded as a potential alternative to fossil fuels. [1][2][3]

Breathing solitons are nonlinear waves in which the energy concentrates in a localized and oscillatory fashion. Similarly to stationary solitons, breathers in dissipative systems can form stable bound states displaying molecule-like dynamics, which are frequently called breather molecules. So far, the experimental observation of optical breather molecules and the real-time detection of their dynamics are limited to diatomic molecules, that is, bound states of only two breathers. In this work, the observation of different types of breather complexes in a mode-locked fiber laser: multibreather molecules, and molecular complexes originating from the binding of two breather-pair molecules or a breather pair molecule and a single breather is reported. The intermolecular temporal separation of the molecular complexes attains several hundreds of picoseconds, which is more than an order of magnitude larger than that of their stationary soliton counterparts and is a signature of long-range interactions. Numerical simulations of the laser model support the experimental findings. Moreover, nonequilibrium dynamics of breathing solitons are also observed, including breather collisions and annihilation. This work opens the possibility of studying the dynamics of many-body systems in which breathers are the elementary constituents.