A ratiometric fluorescent probe for imaging the fluctuation of HOBr during endoplasmic reticulum stress.

Endoplasmic reticulum (ER) stress is closely associated with cell apoptosis, autophagy, DNA damage, metabolism, and migration. When ER stress occurs, a large number of reactive oxygen species, including hypobromous acid (HOBr), are generated. The degree of ER stress can be understood by accurately detecting the HOBr concentration in the ER. Unfortunately, no ER-targetable probes for detecting HOBr have been reported to date. To solve this problem, we developed a naphthalimide-based fluorescent probe (ER-NABr) for imaging HOBr in the ER. Upon reaction with HOBr, a red shift in the fluorescence spectrum occurs due to the difference in the molecular conjugation between the original ER-NABr and the reaction product. ER-NABr showed a fast response (within 30 s) and high selectivity towards HOBr, with a ratiometric quantitative response (5-40 µM) and high sensitivity (138 nM). With its excellent biocompatibility and remarkable ER-targetable ability, ER-NABr was successfully utilized to ratiometrically image intracellular HOBr, particularly during ER stress, which is beneficial for revealing the role of HOBr in ER-associated diseases.

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.

PDI-Based Organic Small Molecule Regulated by Inter/Intramolecular Interactions for Efficient Solar Vapor Generation.

Organic small molecules with processing feasibility, structural diversity, and fine-tuned properties have the potential applications in solar vapor generation. However, the common defects of narrow solar absorption, low photothermal conversion efficiency, and photobleaching result in limited materials available and unsatisfactory evaporation performance. Herein, the perylene diimide (PDI) derivatives are exploited as stable sunlight absorbers for solar vapor generation. Particularly, the N,N'-bis(3,4,5-trimethoxyphenyl)-3,4,9,10-perylenetetracarboxylic diimide (PDI-DTMA) is well-designed with donor-acceptor-donor configuration based on plane rigid PDI core. The efficient photothermal conversion is enabled through strong intermolecular π-π stacking and intramolecular charge transfer, as revealed by experimental demonstration and theoretical calculation. The PDI-DTMA with a narrow band gap of 1.17 eV exhibits expanded absorption spectrum and enhanced nonradiative transition capability. The 3D hybrid hydrogels (PPHs) combining PDI-DTMA and polyvinyl alcohol are constructed. With the synergistic effect of solar-to-heat conversion, thermal localization management, water activation, and unobstructed water transmission of PPHs, the high water evaporation rates can reach 3.61-10.07 kg m-2 h-1 under one sun. The hydrogels also possess great potential in seawater desalination and sewage treatment. Overall, this work provides valuable insights into the design of photothermal organic small molecules and demonstrates their potentials in solar water evaporation.

An endoplasmic reticulum-specific ratiometric fluorescent probe for imaging esterase in living cells.

Esterase is primarily distributed in the endoplasmic reticulum (ER) and often overexpressed in cancer cells. Therefore, the detection of esterase in ER is significant for monitoring the metabolic process of various esters and evaluating the efficacy of chemotherapeutic prodrugs. However, only few fluorescent probes can detect esterase in the ER due to the lack of ER-specificity. More seriously, these probes are often limited by low pearson's colocalization coefficient and one single wavelength emission. To solve those problems, an ER-specific ratiometric fluorescent probe (ER-EST) is designed for detecting esterase in living cells. The ER-EST shows a ratiometric and red-shifted emission (125 nm) from 435 to 560 nm after hydrolysis by esterase. The fluorescence intensity ratio of ER-EST displays quantitative response to the esterase activity (0-0.5 U/mL) with low detection limit of 1.8 × 10-4 U/mL. Importantly, the ER-EST with good biocompatibility and excellent ER-targeted ability was successfully employed to ratiometric image the endogenous endoplasmic reticulum esterase in living cells.

Superelastic 3D Assembled Clay/Graphene Aerogels for Continuous Solar Desalination and Oil/Organic Solvent Absorption.

Superelastic, arbitrary-shaped, and 3D assembled clay/graphene aerogels (CGAs) are fabricated using commercial foam as sacrificial skeleton. The CGAs possess superelasticity under compressive strain of 95% and compressive stress of 0.09-0.23 MPa. The use of clay as skeletal support significantly reduces the use of graphene by 50%. The hydrophobic CGAs show high solvent absorption capacity of 186-519 times its own weight. Moreover, both the compression and combustion methods can be adopted for reusing the CGAs. In particular, it is demonstrated a design of 3D assembled hydrophilic CGA equipped with salt collection system for continuous solar desalination. Due to energy recovery and brine transport management promoted by this design, the 3D assembled CGA system exhibits an extremely high evaporation rate of 4.11 kg m-2  h-1 and excellent salt-resistant property without salt precipitation even in 20 wt% brine for continuous 36 h illumination (1 kW m-2 ), which is the best reported result from the solar desalination devices. More importantly, salts can be collected conveniently by squeezing and drying the solution out of the salt collection system. The work provides new insights into the design of 3D assembled CGAs and advances their applications in continuous solar desalination and efficient oil/organic solvent adsorption.

Fixture-free omnidirectional prestretching fabrication and integration of crumpled in-plane micro-supercapacitors.

Multidimensional folded structures with elasticity could provide spatial charge storage capability and shape adaptability for micro-supercapacitors (MSCs). Here, highly crumpled in-plane MSCs with superior conformality are fabricated in situ and integrated by a fixture-free omnidirectional elastic contraction strategy. Using carbon nanotube microelectrodes, a single crumpled MSC holds an ultrahigh volumetric capacitance of 9.3 F cm-3, and its total areal capacitance is 45 times greater than the initial state. Experimental and theoretical simulation methods indicate that strain-induced improvements of adsorption energy and conductance for crumpled microelectrodes are responsible for the prominent enhancement of electrochemical performance. With outstanding morphological randomicity, the integrated devices can serve as smart coatings in moving robots, withstanding extreme mechanical deformations. Notably, integration on a spherical surface is possible by using a spherical mask, in which a small area of the microdevice array (3.9 cm2) can produce a high output voltage of 100 V.

Grain Boundary Design of Solid Electrolyte Actualizing Stable All-Solid-State Sodium Batteries.

Advanced inorganic solid electrolytes (SEs) are critical for all-solid-state alkaline metal batteries with high safety and high energy densities. A new interphase design to address the urgent interfacial stability issues against all-solid-state sodium metal batteries (ASSMBs) is proposed. The grain boundary phase of a Mg2+ -doped Na3 Zr2 Si2 PO12 conductor (denoted as NZSP-xMg) is manipulated to introduce a favorable Na3-2 δ Mgδ PO4 -dominant interphase which facilitates its intimate contact with Na metal and works as an electron barrier to suppress Na metal dendrite penetration into the electrolyte bulk. The optimal NZSP-0.2Mg electrolyte endows a low interfacial resistance of 93 Ω cm2 at room temperature, over 16 times smaller than that of Na3 Zr2 Si2 PO12 . The Na plating/stripping with small polarization is retained under 0.3 mA cm-2 for more than 290 days (7000 h), representing a record high cycling stability of SEs for ASSMBs. An all-solid-state NaCrO2 //Na battery is accordingly assembled manifesting a high capacity of 110 mA h g-1 at 1 C for 1755 cycles with almost no capacity decay. Excellent rate capability at 5 C is realized with a high Coulombic efficiency of 99.8%, signifying promising application in solid-state electrochemical energy storage systems.

Laser photonic-reduction stamping for graphene-based micro-supercapacitors ultrafast fabrication.

Micro-supercapacitors are promising miniaturized energy storage devices that have attracted considerable research interest. However, their widespread use is limited by inefficient microfabrication technologies and their low energy density. Here, a flexible, designable micro-supercapacitor can be fabricated by a single pulse laser photonic-reduction stamping. A thousand spatially shaped laser pulses can be generated in one second, and over 30,000 micro-supercapacitors are produced within 10 minutes. The micro-supercapacitor and narrow gaps were dozens of microns and 500 nm, respectively. With the unique three-dimensional structure of laser-induced graphene based electrode, a single micro-supercapacitor exhibits an ultra-high energy density (0.23 Wh cm-3), an ultra-small time constant (0.01 ms), outstanding specific capacitance (128 mF cm-2 and 426.7 F cm-3) and a long-term cyclability. The unique technique is desirable for a broad range of applications, which surmounts current limitations of high-throughput fabrication and low energy density of micro-supercapacitors.

Retarding Ostwald Ripening to Directly Cast 3D Porous Graphene Oxide Bulks at Open Ambient Conditions.

Graphene aerogels (GAs) with attractive properties have shown tremendous potentials in energy- and environment-related applications. Unfortunately, current assembly methods for GAs such as sol-gel and freeze-casting processes must be conducted in enclosed spaces with unconventional conditions, thus being literally inoperative for in situ and continuous productions. Herein, a direct slurry-casting method at open ambient conditions is established to arbitrarily prepare three-dimensional (3D) porous graphene oxide (GO) bulks without macroscopic dimension limits on a wide range of solid surfaces by retarding Ostwald ripening of 3D liquid GO foams when being dried in air. A subsequent fast thermal reduction (FTR) of GO foams leads to the formation of graphene aerogels (denoted as FTR-GAs) with hierarchical closed-cellular graphene structures. The FTR-GAs show outstanding high-temperature thermal insulation (70% decrease for 400 °C), as well as superelasticity (>1000 compression-recovery cycles at 50% strain), ultralow density (10-28 mg cm-3), large specific surface area (BET, 206.8 m2 g-1), and high conductivity (ca. 100 S m-1). This work provides a viable method to achieve in situ preparations of high-performance GAs as multifunctional structural materials in aircrafts, high-speed trains, or even buildings for the targets of energy efficiency, comfort, and safety.

Compact Assembly and Programmable Integration of Supercapacitors.

Microsized supercapacitors (mSCs) with small volume, rapid charge-discharge rate, and ultralong cyclic lifetime are urgently needed to meet the demand of miniaturized portable electronic devices. A versatile self-shrinkage assembling (SSA) strategy to directly construct the compact mSCs (CmSCs) from hydrogels of reduced graphene oxide is reported. A single CmSC is only 0.0023 cm3 in volume, which is significantly smaller than most reported mSCs in fiber/yarn and planar interdigital forms. It exhibits a high capacitance of up to 68.3 F cm-3 and a superior cycling stability with 98% capacitance retention after 25 000 cycles. Most importantly, the SSA technique enables the CmSC as the building block to realize arbitrary, programmable, and multi-dimensional integration for adaptable and complicated power systems. By design on mortise and tenon joint connection, autologous integrated 3D interdigital CmSCs are fabricated in a self-holding-on manner, which thus dramatically reduces the whole device volume to achieve the high-performance capacitive behavior. Consequently, the SSA technique offers a universal and versatile approach for large-scale on-demand integration of mSCs as flexible and transformable power sources.

Tunable-Deformed Graphene Layers for Actuation.

Benefiting from unique planar structure, high flexibility, splendid thermal, and electric properties; graphene as a crucial component has been widely applied into smart materials and multi-stimulus responsive actuators. Moreover, graphene with easy processing and modification features can be decorated with various functional groups through covalent or non-covalent bonds, which is promising in the conversion of environmental energy from single and/or multi-stimuli, to mechanical energy. In this review, we present the actuating behaviors of graphene, regulated by chemical bonds or intermolecular forces under multi-stimuli and summarize the recent advances on account of the unique nanostructures in various actuation circumstances such as thermal, humidity, electrochemical, electro-/photo-thermal, and other stimuli.

Large-Scale Production of Flexible, High-Voltage Hydroelectric Films Based on Solid Oxides.

Spontaneous electricity generation through water evaporation is becoming a hot research area. However, low power output, limited material availability, and unscalable fabrication largely hinder its wide applications. Here, we report scalable painting and blade coating approaches for the mass production of flexible hydroelectric films (HEFs) based on solid oxides (e.g., Al2O3), which are of tolerance to mechanical deformation and are compatible with three-dimensional diverse configuration. The electricity power is generated continuously and can last for more than 10 days in ambient conditions. A single HEF unit is capable of supplying an output voltage of more than 2.5 V and even up to 4.5 V at specific conditions. The accumulative energy output can be tuned conveniently by means of series/parallel connections or size control to meet the practical needs of commercial electronics. A family of solid oxides has been verified to have the ability for water evaporation-induced electricity generation, which offers considerable room for the development of high-performance energy-supplying devices.

Laser-Assisted Multiscale Fabrication of Configuration-Editable Supercapacitors with High Energy Density.

The construction of multidimensional, diversified microsupercapacitors (MSC) is urgently needed for fast-changing flexible and wearable microelectronics, which still meets the challenges of tedious construction and difficult integration. Herein, a laser direct writing strategy has been developed for the one-step preparation of multiscale MSCs from editable macro-supercapacitors. The microstructured supercapacitors with predefined multiscale shapes not only maintain the high capacitance performance and stability but also display the tensile properties in arbitrary direction. The heat-treated ion liquid-modified reduced graphene oxide guarantees the thermal stability of an electrode material during laser cutting, and its high ion-accessible surface area improves the capacitance performance of the supercapacitor. The as-fabricated MSC demonstrates a wide voltage window (0-3 V), high areal specific capacitance (27.4 mF cm-2), and high energy density (32.1 µW h cm-2), which are far higher than those of most reported articles. Notably, the editable supercapacitors can imitate the stereo paper cutting to achieve an arbitrary one-dimensional to three-dimensional configuration, promising for various portable, stretchable, and wearable devices.

Laser-Assisted Large-Scale Fabrication of All-Solid-State Asymmetrical Micro-Supercapacitor Array.

The micro-supercapacitors are of great value for portable, flexible, and integrated electronic equipments. Here, the large-scale and integrated asymmetrical micro-supercapacitor (AMSC) array is fabricated in virtue of the laser direct writing and electrodeposition technology. The AMSC shows the ideal flexibility, high areal specific capacitance (21.8 mF cm-2 ), and good rate capability. Moreover, its energy density reaches 12.16 µW h cm-2 , outperforming most micro-supercapacitors reported previously. Meanwhile, large-scale series-connected AMSCs are integrated on the flexible substrates (e.g., indium tin oxide-polyethylene terephthalate film), which can power a veriety of the commercial electronics. The combination of AMSCs array, solar cell, and electronic device proves the feasibility for practical application in the portable, flexible, and integrated electronic equipments.

Electric Power Generation through the Direct Interaction of Pristine Graphene-Oxide with Water Molecules.

Converting ubiquitous environmental energy into electric power holds tremendous social and financial interests. Traditional energy harvesters and converters are limited by the specific materials and complex configuration of devices. Herein, it is presented that electric power can be directly produced from pristine graphene oxide (GO) without any pretreatment or additives once encountering the water vapor, which will generate an open-circuit-voltage of up to 0.4-0.7 V and a short-circuit-current-density of 2-25 µA cm-2 on a single piece of GO film. This phenomenon results from the directional movement of charged hydrogen ions through the GO film. The present work demonstrates and provides an extremely simple method for electric energy generation, which offers more applications of graphene-based materials in green energy converting field.

Flexible and integrated supercapacitor with tunable energy storage.

A flexible integrated supercapacitor based on three dimensional reduced graphene oxide/graphene oxide/reduced graphene oxide (RGO-GO-RGO) foam has been fabricated via a laser direct writing strategy. The supercapacitor with outstanding mechanical properties shows a high capacitance performance which can be easily regulated by controlling the compressive state of the electrodes. This work provides a new platform for potential applications in the next-generation intelligent power supply of electronics.

Unusual Assembly and Conversion of Graphene Quantum Dots into Crystalline Graphite Nanocapsules.

The development of a facile strategy for conversion of graphene quantum dots (GQDs) into crystalline graphite is of great practical significance and still remains challenging. Herein, rationally assembled crystalline-intercrossed graphite nanocapsules (CI-GNCs) have been realized by a one-step electrochemically induced strategy with the assistance of a soft template, in which the GQDs act as the initial building blocks. The as-prepared CI-GNCs exhibit highly crystalline graphitic nanostructures. Moreover, they possess promising electrocatalytic activity for the oxygen reaction reduction (ORR) in alkaline medium. This simple fabrication technology presents a great advance for synthesizing CI-GNCs composite catalysts, which have potential as new metal-free catalysts for efficient ORR applications.

A fast-response, highly sensitive and selective fluorescent probe for the ratiometric imaging of nitroxyl in living cells.

A fast-response, highly sensitive and selective fluorescent probe with the 2-(diphenylphosphino)benzoate moiety as a recognition receptor for the ratiometric imaging of nitroxyl in living cells was first developed.