Droplet-Pen Writing of Ultra-Uniform Graphene Pattern for Multi-Spectral Applications.

Artificial optical patterns bring wide benefits in applications like structural color display, photonic camouflage, and electromagnetic cloak. Their scalable coating on large-scale objects will greatly enrich the multimodal-interactive society. Here, a droplet-pen writing (DPW) method to directly write multi-spectral patterns of thin-film graphene is reported. By amphiphilicity regulations of 2D graphene nanosheets, ultra-uniform and ultrathin films can spontaneously form on droplet caps and pave to the substrate, thus inducing optical interference. This allows the on-surface patterning by pen writing of droplets. Specifically, drop-on-demand thin films are achieved with millimeter lateral size and uniformity up to 97% in subwavelength thickness (<100 nm), corresponding to an aspect ratio of over 30 000. The pixelated thin-film patterns of disks and lines in an 8-inch wafer scale are demonstrated, which enable low-emittance structural color paintings. Furthermore, the applications of these patterns for dual-band camouflage and infrared-to-visible encryption are investigated. This study highlights the potential of 2D material self-assembly in the large-scale preparation and multi-spectral application of thin film-based optical patterns.

Robustly and Intrinsically Stretchable Ionic Gel-Based Moisture-Enabled Power Generator with High Human Body Conformality.

Direct harvesting of energy from moist air will be a promising route to supply electricity for booming wearable and distributed electronics, with the recent rapid development of the moisture-enabled electricity generator (MEG). However, the easy spatial distortion of rigid MEG materials under severe deformation extremely inconveniences the human body with intense physical activity, seriously hindering the desirable applications. Here, an intrinsically stretchable moisture-enabled electricity generator (s-MEG) is developed based on a well-fabricated stretchable functional ionic gel (SIG) with a flexible double-network structure and reversible cross-linking interactions, demonstrating stable electricity output performance even when stretched up to 150% strain and high human body conformality. This SIG exhibits ultrahigh tensile strain (∼600%), and a 1 cm × 1 cm SIG film-based s-MEG can generate a voltage of ∼0.4 V and a current of ∼5.7 µA when absorbing water from humidity air. Based on the strong adhesion and the excellent interface combination of SIG and rough fabric electrodes induced by the fabrication process, s-MEG is able to realize bending or twisting deformation and shows outstanding electricity output stability with ∼90% performance retention after 5000 cycles of bending tests. By connecting s-MEG units in series or parallel, an integrated device of "moisture-powered wristband" is developed to wear on the wrist of humans and drive a flexible sensor for tracking finger motions. Additionally, a comfortable "moisture-powered sheath" based on s-MEGs is created, which can be worn like clothing on human arms to generate energy while walking and flexing the elbow, which is promising in the field of wearable electronics.

Weak-Field Electro-Flash Induced Asymmetric Catalytic Sites toward Efficient Solar Hydrogen Peroxide Production.

Borocarbonitride (BCN), in a mesoscopic asymmetric state, is regarded as a promising photocatalyst for artificial photosynthesis. However, BCN materials reported in the literature primarily consist of symmetric N-[B]3 units, which generate highly spatial coupled electron-hole pairs upon irradiation, thus kinetically suppressing the solar-to-chemical conversion efficiency. Here, we propose a facile and fast weak-field electro-flash strategy, with which structural symmetry breaking is introduced on key nitrogen sites. As-obtained double-substituted BCN (ds-BCN) possesses high-concentration asymmetric [B]2-N-C coordination, which displays a highly separated electron-hole state and broad visible-light harvesting, as well as provides electron-rich N sites for O2 affinity. Thereby, ds-BCN delivers an apparent quantum yield of 7.6% at 400 nm and a solar-to-chemical conversion efficiency of 0.3% for selective 2e-reduction of O2 to H2O2, over 4-fold higher than that of the traditional calcined BCN analogue and superior to the metal-free C3N4-based photocatalysts reported so far. The weak-field electro-flash method and as-induced catalytic site symmetry-breaking methodologically provide a new method for the fast and low-cost fabrication of efficient nonmetallic catalysts toward solar-to-chemical conversions.

Bio-Inspired Ultrathin Perfect Absorber for High-Performance Photothermal Conversion.

Ultrathin perfect absorber (UPA) enables efficient photothermal conversion (PC) in renewable chemical and energy systems. However, it is challenging so far to obtain efficient absorption with thickness significantly less than the wavelength, especially considering the common view that an ultrathin film can absorb at most 50% of incident light. Here, a highly light-absorbing and mechanically stable UPA is reported by learning from the honeycomb mirror design of the crab compound eyes. With the hollow apertures enclosed by the self-supporting ultrathin film of reduced graphene oxide and gold nanoparticles, the absorber achieves spoof-plasmon enhanced broadband absorption in solar spectrum and low radiative decay in infrared. Specifically, a strong absorption (87%) is realized by the apertures with cross-section thickness of 1/20 of the wavelength, which is 7.3 times stronger than a planar counterpart with the identical material. Its high PC efficiency up to 64%, with hot-electron temperature as high as 2344 K, is also experimentally demonstrated. Utilizing its low thermal mass nature, a high-speed visible-to-infrared converter is constructed. The absorber can enable high-performance PC processes for future interfacial catalysis and photon-detection.

Inorganic Hydrogel Based on Low-Dimensional Nanomaterials.

Composed of three-dimensional (3D) nanoscale inorganic bones and up to 99% water, inorganic hydrogels have attracted much attention and undergone significant growth in recent years. The basic units of inorganic hydrogels could be metal nanoparticles, metal nanowires, SiO2 nanowires, graphene nanosheets, and MXene nanosheets, which are then assembled into the special porous structures by the sol-gel process or gelation via either covalent or noncovalent interactions. The high electrical and thermal conductivity, resistance to corrosion, stability across various temperatures, and high surface area make them promising candidates for diverse applications, such as energy storage, catalysis, adsorption, sensing, and solar steam generation. Besides, some interesting derivatives, such as inorganic aerogels and xerogels, can be produced through further processing, diversifying their functionalities and application domains greatly. In this context, we primarily provide a comprehensive overview of the current status of inorganic hydrogels and their derivatives, including the structures of inorganic hydrogels with various compositions, their gelation mechanisms, and their exceptional practical performance in fields related to energy and environmental applications.

Moisture-Enabled Electricity from Hygroscopic Materials: A New Type of Clean Energy.

Water utilization is accompanied with the development of human beings, whereas gaseous moisture is usually regarded as an underexploited resource. The advances of highly efficient hygroscopic materials endow atmospheric water harvesting as an intriguing solution to convert moisture into clean water. The discovery of hygroelectricity, which refers to the charge buildup at a material surface dependent on humidity, and the following moisture-enabled electric generation (MEG) realizes energy conversion and directly outputs electricity. Much progress has been made since then to optimize MEG performance, pushing forward the applications of MEG into a practical level. Herein, the evolvement and development of MEG are systematically summarized in a chronological order. The optimization strategies of MEG are discussed and comprehensively evaluated. Then, the latest applications of MEG are presented, including high-performance powering units and self-powered devices. In the end, a perspective on the future development of MEG is given for inspiring more researchers into this promising area.

Boosting the Viable Water Harvesting in Solar Vapor Generation: From Interfacial Engineering to Devices Design.

Continuously increasing demand for the life-critical water resource induces severe global water shortages. It is imperative to advance effective, economic, and environmentally sustainable strategies to augment clean water supply. The present work reviews recent reports on the interfacial engineering to devices design of solar vapor generation (SVG) system for boosting the viability of drinkable water harvesting. Particular emphasis is placed on the basic principles associated with the interfacial engineering of solar evaporators capable of efficient solar-to-thermal conversion and resulting freshwater vapor via eliminating pollutants from quality-impaired water sources. The critical configurations manufacturing of the devices for fast condensation is then highlighted to harvest potable liquid water. Fundamental and practical challenges, along with prospects for the targeted materials architecture and devices modifications of SVG system are also outlined, aiming to provide future directions and inspiring critical research efforts in this emerging and exciting field.

Laser-Induced Electron Synchronization Excitation for Photochemical Synthesis and Patterning Graphene-Based Electrode.

Micro-supercapacitors (MSCs) represent a pressing requirement for powering the forthcoming generation of micro-electronic devices. The simultaneous realization of high-efficiency synthesis of electrode materials and precision patterning for MSCs in a single step presents an ardent need, yet it poses a formidable challenge. Herein, a unique shaped laser-induced patterned electron synchronization excitation strategy has been put forward to photochemical synthesis RuO2 /reduced graphene oxide (rGO) electrode and simultaneously manufacture the micron-scale high-performance MSCs with ultra-high resolution. Significantly, the technique represents a noteworthy advancement over traditional laser direct writing (LDW) patterning and photoinduced synthetic electrode methods. It not only improves the processing efficiency for MSCs and the controllability of laser-induced electrode material but also enhances electric fields and potentials at the interface for better electrochemical performance. The resultant MSCs exhibit excellent area and volumetric capacitance (516 mF cm-2 and 1720 F cm-3 ), and ultrahigh energy density (0.41 Wh cm-3 ) and well-cycle stability (retaining 95% capacitance after 12000 cycles). This investigation establishes a novel avenue for electrode design and underscores substantial potential in the fabrication of diverse microelectronic devices.

All Plant-Based Compact Supercapacitor in Living Plants.

Biomass-based energy storage devices (BESDs) have drawn much attention to substitute traditional electronic devices based on petroleum or synthetic chemical materials for the advantages of biodegradability, biocompatibility, and low cost. However, most of the BESDs are almost made of reconstructed plant materials and exogenous chemical additives which constrain the autonomous and widespread advantages of living plants. Herein, an all-plant-based compact supercapacitor (APCSC) without any nonhomologous additives is reported. This type of supercapacitor formed within living plants acts as a form of electronic plant (e-plant) by using its tissue fluid electrolyte, which surprisingly presents a satisfying electrical capacitance of 182.5 mF cm-2 , higher than those of biomass-based micro-supercapacitors reported previously. In addition, all constituents of the device come from the same plant, effectively avoid biologically incompatible with other extraneous substances, and almost do no harm to the growth of plant. This e-plant can not only be constructed in aloe, but also be built in most of succulents, such as cactus in desert, offering timely electricity supply to people in extreme conditions. It is believed that this work will enrich the applications of electronic plants, and shed light on smart botany, forestry, and agriculture.

Moisture-Electric-Moisture-Sensitive Heterostructure Triggered Proton Hopping for Quality-Enhancing Moist-Electric Generator.

Moisture-enabled electricity (ME) is a method of converting the potential energy of water in the external environment into electrical energy through the interaction of functional materials with water molecules and can be directly applied to energy harvesting and signal expression. However, ME can be unreliable in numerous applications due to its sluggish response to moisture, thus sacrificing the value of fast energy harvesting and highly accurate information representation. Here, by constructing a moisture-electric-moisture-sensitive (ME-MS) heterostructure, we develop an efficient ME generator with ultra-fast electric response to moisture achieved by triggering Grotthuss protons hopping in the sensitized ZnO, which modulates the heterostructure built-in interfacial potential, enables quick response (0.435 s), an unprecedented ultra-fast response rate of 972.4 mV s-1, and a durable electrical signal output for 8 h without any attenuation. Our research provides an efficient way to generate electricity and important insight for a deeper understanding of the mechanisms of moisture-generated carrier migration in ME generator, which has a more comprehensive working scene and can serve as a typical model for human health monitoring and smart medical electronics design.

Ultralow-resistance electrochemical capacitor for integrable line filtering.

Electrochemical capacitors are expected to replace conventional electrolytic capacitors in line filtering for integrated circuits and portable electronics1-8. However, practical implementation of electrochemical capacitors into line-filtering circuits has not yet been achieved owing to the difficulty in synergistic accomplishment of fast responses, high specific capacitance, miniaturization and circuit-compatible integration1,4,5,9-12. Here we propose an electric-field enhancement strategy to promote frequency characteristics and capacitance simultaneously. By downscaling the channel width with femtosecond-laser scribing, a miniaturized narrow-channel in-plane electrochemical capacitor shows drastically reduced ionic resistances within both the electrode material and the electrolyte, leading to an ultralow series resistance of 39 mΩ cm2 at 120 Hz. As a consequence, an ultrahigh areal capacitance of up to 5.2 mF cm-2 is achieved with a phase angle of -80° at 120 Hz, twice as large as one of the highest reported previously4,13,14, and little degradation is observed over 1,000,000 cycles. Scalable integration of this electrochemical capacitor into microcircuitry shows a high integration density of 80 cells cm-2 and on-demand customization of capacitance and voltage. In light of excellent filtering performances and circuit compatibility, this work presents an important step of line-filtering electrochemical capacitors towards practical applications in integrated circuits and flexible electronics.

A universal approach to dual-metal-atom catalytic sites confined in carbon dots for various target reactions.

Here, a molecular-design and carbon dot-confinement coupling strategy through the pyrolysis of bimetallic complex of diethylenetriamine pentaacetic acid under low-temperature is proposed as a universal approach to dual-metal-atom sites in carbon dots (DMASs-CDs). CDs as the "carbon islands" could block the migration of DMASs across "islands" to achieve dynamic stability. More than twenty DMASs-CDs with specific compositions of DMASs (pairwise combinations among Fe, Co, Ni, Mn, Zn, Cu, and Mo) have been synthesized successfully. Thereafter, high intrinsic activity is observed for the probe reaction of urea oxidation on NiMn-CDs. In situ and ex situ spectroscopic characterization and first-principle calculations unveil that the synergistic effect in NiMn-DMASs could stretch the urea molecule and weaken the N-H bond, endowing NiMn-CDs with a low energy barrier for urea dehydrogenation. Moreover, DMASs-CDs for various target electrochemical reactions, including but not limited to urea oxidation, are realized by optimizing the specific DMAS combination in CDs.

Multistage coupling water-enabled electric generator with customizable energy output.

Constant water circulation between land, ocean and atmosphere contains great and sustainable energy, which has been successfully employed to generate electricity by the burgeoning water-enabled electric generator. However, water in various forms (e.g. liquid, moisture) is inevitably discharged after one-time use in current single-stage water-enabled electric generators, resulting in the huge waste of inherent energy within water circulation. Herein, a multistage coupling water-enabled electric generator is proposed, which utilizes the internal liquid flow and subsequently generated moisture to produce electricity synchronously, achieving a maximum output power density of ~92 mW m-2 (~11 W m-3). Furthermore, a distributary design for internal water in different forms enables the integration of water-flow-enabled and moisture-diffusion-enabled electricity generation layers into mc-WEG by a "flexible building blocks" strategy. Through a three-stage adjustment process encompassing size control, space optimization, and large-scale integration, the multistage coupling water-enabled electric generator realizes the customized electricity output for diverse electronics. Twenty-two units connected in series can deliver ~10 V and ~280 µA, which can directly lighten a table lamp for 30 min without aforehand capacitor charging. In addition, multistage coupling water-enabled electric generators exhibit excellent flexibility and environmental adaptability, providing a way for the development of water-enabled electric generators.

Nanoscale multi-beam lithography of photonic crystals with ultrafast laser.

Photonic crystals are utilized in many noteworthy applications like optical communications, light flow control, and quantum optics. Photonic crystal with nanoscale structure is important for the manipulation of light propagation in visible and near-infrared range. Herein, we propose a novel multi beam lithography method to fabricate photonic crystal with nanoscale structure without cracking. Using multi-beam ultrafast laser processing and etching, parallel channels with subwavelength gap are obtained in yttrium aluminum garnet crystal. Combining optical simulation based on Debye diffraction, we experimentally show the gap width of parallel channels can be controlled at nanoscale by changing phase holograms. With the superimposed phase hologram designing, functional structures of complicated channel arrays distribution can be created in crystal. Optical gratings of different periods are fabricated, which can diffract incident light in particular ways. This approach can efficiently manufacture nanostructures with controllable gap, and offer an alternative to the fabrication of complex photonic crystal for integrated photonics applications.

Laser maskless fast patterning for multitype microsupercapacitors.

Downsizing electrode architectures have significant potential for microscale energy storage devices. Asymmetric micro-supercapacitors play an essential role in various applications due to their high voltage window and energy density. However, efficient production and sophisticated miniaturization of asymmetric micro-supercapacitors remains challenging. Here, we develop a maskless ultrafast fabrication of multitype micron-sized (10 × 10 µm2) micro-supercapacitors via temporally and spatially shaped femtosecond laser. MXene/1T-MoS2 can be integrated with laser-induced MXene-derived TiO2 and 1T-MoS2-derived MoO3 to generate over 6,000 symmetric micro-supercapacitors or 3,000 asymmetric micro-supercapacitors with high-resolution (200 nm) per minute. The asymmetric micro-supercapacitors can be integrated with other micro devices, thanks to the ultrahigh specific capacitance (220 mF cm-2 and 1101 F cm-3), voltage windows in series (52 V), energy density (0.495 Wh cm-3) and power density (28 kW cm-3). Our approach enables the industrial manufacturing of multitype micro-supercapacitors and improves the feasibility and flexibility of micro-supercapacitors in practical applications.

Low-Grade Waste Heat Enables Over 80 L m- 2 h-1 Interfacial Steam Generation Based on 3D Superhydrophilic Foam.

Clean water scarcity and energy shortage have become urgent global problems due to population growth and human industrial development. Low-grade waste heat (LGWH) is a widely available and ubiquitous byproduct of human activities worldwide, which can provide effective power to address the fresh water crisis without additional energy consumption and carbon emissions. In this regard, 3D superhydrophilic polyurethane/sodium alginate (PU/SA) foam and LGWH-driven interfacial water evaporation systems are developed, which can precipitate over 80 L m-2  h-1 steam generation from seawater and has favorable durability for purification of high salinity wastewater. The excellent water absorption ability, unobstructed water transport, and uniform thin water layer formed on 3D skeletons of PU/SA foam ensure the strong heat exchange between LGWH and fluidic water. As a result, the heat-localized PU/SA foam enables the efficient energy utilization and ultrafast water evaporation once LGWH is introduced into PU/SA foam as heat flow. In addition, the precipitated salt on PU/SA foam can be easily removed by mechanical compression, and almost no decrease in water evaporation rate after salt precipitation and removal for many times. Meanwhile, the collected clean water has high rejection of ions of 99.6%, which meets the World Health Organization (WHO) standard of drinking water. Above all, this LGWH-driven interfacial water evaporation system presents a promising and easily accessible solution for clean water production and water-salt separation without additional energy burden for the society.

Fluorescence enhancement of organic dyes by femtosecond laser-induced cavitation bubbles for crystal imaging.

Fluorescence from organic dyes can be applied in many research fields such as imaging, bio-sensing and diagnosis. One shortcoming of fluorescence imaging is the limitation in emission intensity. Amplification of fluorescence signals can be achieved by the enhancement of localized electromagnetic fields. Metallic nanoparticles are widely applied to produce plasmon resonance, but they cause thermal damage to fragile bio-materials. In this study, we propose a method for nanoparticle-free fluorescence enhancement by ultrafast laser-induced cavitation bubbles in organic dye solutions. Fluorescence enhancement without the use of nanoparticles prevents potential hazards including thermal effects and biotoxicity. In order to achieve fluorescence enhancement in neat dye solution, cavitation bubbles were induced by focusing an 800 nm ultrafast laser beam. Another 400 nm laser beam was used to pump the gain medium. Fluorescence enhancement was observed in various dye solutions. The intensity and spectra of the fluorescence emission can be controlled by changing the power and focus of the excitation laser. According to time-resolved microscopy and simulation results, the cavity formed by the laser-induced bubbles results in the enhancement of the localized electromagnetic field and induces the amplification of the fluorescence signal. The bubble-enhanced fluorescence emission was used for imaging of protein crystals without causing thermal damage to the samples. This study provides an effective method for bio-compatible fluorescence enhancement and has application prospects in fields such as bio-imaging.

The role of oxygen-vacancy in bifunctional indium oxyhydroxide catalysts for electrochemical coupling of biomass valorization with CO2 conversion.

Electrochemical coupling of biomass valorization with carbon dioxide (CO2) conversion provides a promising approach to generate value-added chemicals on both sides of the electrolyzer. Herein, oxygen-vacancy-rich indium oxyhydroxide (InOOH-OV) is developed as a bifunctional catalyst for CO2 reduction to formate and 5-hydroxymethylfurfural electrooxidation to 2,5-furandicarboxylic acid with faradaic efficiencies for both over 90.0% at optimized potentials. Atomic-scale electron microscopy images and density functional theory calculations reveal that the introduction of oxygen vacancy sites causes lattice distortion and charge redistribution. Operando Raman spectra indicate oxygen vacancies could protect the InOOH-OV from being further reduced during CO2 conversion and increase the adsorption competitiveness for 5-hydroxymethylfurfural over hydroxide ions in alkaline electrolytes, making InOOH-OV a main-group p-block metal oxide electrocatalyst with bifunctional activities. Based on the catalytic performance of InOOH-OV, a pH-asymmetric integrated cell is fabricated by combining the CO2 reduction and 5-hydroxymethylfurfural oxidation together in a single electrochemical cell to produce 2,5-furandicarboxylic acid and formate with high yields (both around 90.0%), providing a promising approach to generate valuable commodity chemicals simultaneously on both electrodes.

Electrically Modulated Nanofiltration Membrane Based on an Arch-Bridged Graphene Structure for Multicomponent Molecular Separation.

Tunable regulation of molecular penetration through porous membranes is highly desirable for membrane applications in the pharmaceutical and medical fields. However, in most previous reports additional reagents or components are usually needed to provide the graphene-based membranes with responsiveness. Herein, we report tunable arch-bridged reduced graphene oxide (rGO) nanofiltration membranes modulated by the applied voltage. Under a finite voltage of 5 V, the rGO membrane could completely reject organic/anionic molecules. With assistance of the voltage, the positive-charge-modified rGO membrane realized the universal rejection of both cationic and anionic dyes, also showing the valid modulation in harsh organic solvents. The efficient electrical modulation depended on the synergetic effects of Donnan repulsion and size exclusion, benefiting from the electric field enhancement in arch-bridged rGO structures. Furthermore, multicomponent separation was achieved by our electrically modulated rGO-based membranes, demonstrating their potential in practical applications such as pharmaceutical industries.

Tailor-Made White Photothermal Fabrics: A Bridge between Pragmatism and Aesthetic.

Maintaining human thermal comfort in the cold outdoors is crucial for diverse outdoor activities, e.g., sports and recreation, healthcare, and special occupations. To date, advanced clothes are employed to collect solar energy as a heat source to stand cold climates, while their dull dark photothermal coating may hinder pragmatism in outdoor environments and visual sense considering fashion. Herein, tailor-made white webs with strong photothermal effect are proposed. With the embedding of cesium-tungsten bronze (Csx WO3 ) nanoparticles (NPs) as additive inside nylon nanofibers, these webs are capable of drawing both near-infrared (NIR) and ultraviolet (UV) light in sunlight for heating. Their exceptional photothermal conversion capability enables 2.5-10.5 °C greater warmth than that of a commercial sweatshirt of six times greater thickness under different climates. Remarkably, this smart fabric can increase its photothermal conversion efficiency in a wet state. It is optimal for fast sweat or water evaporation at human comfort temperature (38.5 °C) under sunlight, and its role in thermoregulation is equally important to avoid excess heat loss in wilderness survival. Obviously, this smart web with considerable merits of shape retention, softness, safety, breathability, washability, and on-demand coloration provides a revolutionary solution to realize energy-saving outdoor thermoregulation and simultaneously satisfy the needs of fashion and aesthetics.