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The application of solar steam generation in seawater desalination is an effective way to solve the shortage of fresh water resources. At present, many kinds of photothermal conversion materials have been developed and used as evaporators in seawater desalination. However, some evaporators need additional thermal insulation or water supply devices to achieve efficient photothermal conversion. In addition, their complex, time consuming and no scalable preparation process, high cost of raw materials and poor salt resistance hinder the practical application of these evaporator. Owing to its distinctive nanoporous structure, diatomite as fossilized single-cells algae diatoms is a promising natural silica-based material for seawater desalination. They are taken from sea and that makes true sense to use them in the sea. Herein, we report the first example of synthesis robust three-dimensional (3D) natural-diatomite composite by assembling polyaniline nanoparticles covered diatomite into the polyvinyl alcohol pre-treated melamine foam frameworks and demonstrate its application as new evaporator for seawater desalination. The porous framework does not only improve the sunlight scattering efficiency, but also offer large network of channels for water transportation. The inherent mechanism behind salt desalination process involves the absorption of water molecules on the surface of the internal silica micro-nano pores, and evaporation under the heat induced by the polyaniline absorbed sunlight. Meanwhile, the metal ions are segregated by many available pores and channels to achieve the self-desalting effect. The developed evaporator possesses the superiority of multi-stage pore structure, strong hydrophilicity, low thermal conductivity, excellent light absorption, fast water transportation and salt-resistant crystallization as well as good durability. The evaporation rate without an additional device is found to be 1.689 kg m−2 h−1under 1-Sun irradiation, and the energy conversion efficiency is as high as 95%. This work creates a platform and develops the prospect of employing green and sustainable natural-diatomite composite evaporator for practical applications of seawater desalination.

The HfxZr1−xO2 (HZO) based ferroelectric field-effect transistors (FeFETs) with oxide semiconductor channel have been proposed to have the potential of interface layer (IL) free, but the FeFET properties with real IL-free structure has rarely been demonstrated. In this work, we experimentally and theoretically clarified that real IL-free FeFET with ferroelectric (FE) HZO as gate oxide is difficult to get memory window (MW) because the polarization switching is difficult to occur due to insufficient positive charge compensation from oxide channel. In addition, we demonstrate that IL-free FeFETs with antiferroelectric (AFE) HZO provides a solution to get MW through positive subloop which does not require positive charge compensation in polarization changing. And an endurance performance up to $10^{{9}}$ cycles is achieved in this FeFET structure. Our results provide new insights into engineering of HZO-based FeFET with oxide channel.

Abstract: In this report, a novel chemical synthesis of polyaniline/gold nanocomposite is explored using ionic liquid (IL) 1-Butyl-3-methylimidazolium hexafluorophosphate. The direct chemical synthesis of polyaniline/gold nanocomposite was initiated via the spontaneous oxidation of aniline by AuCl4− in IL. A nearly uniform dispersion of polyaniline/Au particles with a diameter of 450 ± 80 nm was produced by this method, which indicates that this method is more suitable for controlling particle dimensions. It was also found that the electrical conductivity of the polyaniline/gold nanocomposite was more than 100 times higher than that of the pure polyaniline nanoparticles. The polyaniline/gold nanocomposite displays superior function in the biocatalytic activation of microperoxidase-11 because of the high surface area of the assembly and the enhanced charge transport properties of the composite material. We also report the possible application of polyaniline/gold nanocomposite as a H2O2 biosensor.

Clinically, an excellent electrode is of great significance for obtaining high-fidelity electroencephalogram (EEG) signals, which is a valuable tool for diagnosing brain-related diseases and exploring human brain activity. However, traditional wet electrode encounters a natural drawback in moisturizing ability due to the lack of water-locking ability to the electrolyte, unsuitable for long-term EEG acquisition. Hence, we propose a gelatin-based ionic conductive hydrogel electrode with a high moisturizing ability for wearable EEG acquisition. The gelatin material, derived mainly from animal collagen, is highly biocompatible and user-friendly. The gelatin-based hydrogel electrode is easy to prepare, possesses strong moisturizing ability, and performs relatively stable interfacial contact impedance. Remarkably, the gelatin-based hydrogel electrode modified by glycerol can still work normally even after 60 days. Additionally, the gelatin-based hydrogel electrode exhibits a low potential drift ( $1.863 \mu $ Vmin $^{-{1}}$ ) and a low short-circuit noise level. This work can lead to a new era of wearable EEG acquisition and provide an effective strategy for the convenient preparation of highly moisturizing hydrogel electrodes.

The measurement of ferroelectric (FE) polarization switching time was known to be strongly related with RC delay, but this phenomenon has not been fully understood, as several kinds of RC effects may be involved extrinsically and/or intrinsically. In this work, by carefully excluding the extrinsic RC charging effects before and in polarization switching, we experimentally and theoretically demonstrate an intrinsic RC effect coupled in polarization switching dynamics of Hf0.5Zr0.5O2 (HZO) FE capacitor. We found that such an intrinsic RC effect not only dominantly determine the switching time under high electric field but also significantly affect it under low field. And, a mechanism is proposed that a RC re-charging is coupled with each domain flipping in multiple domain FE system, so that the switching time is unavoidably and intrinsically affected by this coupling effect. Thus, our results provide critical messages to the speed evaluation and integrated circuit design of FE devices.

Indoor gaseous formaldehyde is the main environmental pollutant that can cause fatal threats to human health. A number of physical and chemical methods have been developed to tackle this issue. However, the existing methods are still unsatisfactory to meet the requirement of sustainable development owing to the flaws of low efficiency and reversible or second pollution. Herein, a chemical method based on a nucleophilic reaction between hydrazine and aldehyde that generates the only by-product of H2O is designed for the removal of formaldehyde. 1-Pyrenebutyric hydrazide was synthesized by a simple esterification reaction and then self-assembled on reduced graphene oxide (rGO) with a large surface area by forming π–π stacking to obtain a composite for chemical removal of gaseous formaldehyde under ambient conditions. In a practical test, the formaldehyde removal rate could reach 91% of the theoretical value, which meets the requirement for commercial formaldehyde removal applications. After 10 times recycling, the formaldehyde removal rate still remains as high as 85%. Moreover, the composite could be regenerated in weak acidic media, which greatly reduce the manufacturing cost in practical applications.

The artificial nitrogen (N2) reduction reaction (NRR) viaelectrocatalysis is a newly developed methodology to produce ammonia (NH3) at ambient conditions, but faces the challenges in N2activation and poor reaction selectivity. Herein, Nb-based MXenes are developed to remarkably enhance the NRR activity through the engineering of the stretched 3D structure and oxygen vacancies (VO). The theoretical studies indicate that N2could be initially adsorbed on VOwith an end-on configuration, and the potential determining step might be the first hydrogenation step. The catalysts achieve an NH3production rate of 29.1 μg h−1mgcat−1and excellent Faradic efficiency of 11.5%, surpassing other Nb-based catalysts. The selectivity of NRR is assigned to the unique structure of the catalysts, including (1) the layered graphitic structure for fast electron transfer and active site distribution, (2) the reactive VOfor N2adsorption and activation, and (3) the expanded interlayer space for mass transfer.

Transition-metal selenides (TMSs) have great potential in the synthesis of supercapacitor electrode materials due to their rich content and high specific capacity. However, the aggregation phenomenon of TMS materials in the process of charging and discharging will cause capacity attenuation, which seriously affects the service life and practical applications. Therefore, it is of great practical significance to design simple and efficient synthesis strategies to overcome these shortcomings. Hence, P-doped Cu3Se2nanosheets are loaded on vertically aligned Cu2S nanorod arrays to synthesize CF/Cu2S@Cu3Se2/P nanocomposites with a unique core–shell heterostructure. Notably, the Cu2S precursors can be rapidly converted into Cu3Se2nanorod arrays in situ in just 30 min at room temperature. The unique core–shell heterostructure effectively avoids the aggregation phenomenon, and the doped P elements further enhance the electrochemical properties of the electrode materials. Therefore, the as-prepared CF/Cu2S@Cu3Se2/P electrode exhibits a high areal capacitance of 5054 mF cm–2(1099 C g–1) at 3 mA cm–2and still retains 90.2% capacitance after 10 000 galvanostatic charge–discharge (GCD) cycles. The asymmetric supercapacitor (ASC) device assembled from synthetic CF/Cu2S@Cu3Se2/P and activated carbon (AC) possesses an energy density of 41.1 Wh kg–1at a power density of 480.4 W kg–1. This work shows that the designed CF/Cu2S@Cu3Se2/P electrode has broad application prospects in the field of electrochemical energy storage.

In recent years, optogenetic-based neural regulation technologies have attracted extensive attention. Among them, the active neural optrode integrated with optical stimulating micro-laser diode (LD)/light-emitting diode (LED) and electrical recording microelectrodes presents significant advantages. However, the performance of the neural optrode is still hindered by high amplitude noises generated by micro-LD/LED and silicon substrate. A silicon optrode with heavy-doped probes, LD-coupled optical fiber, and electrochemical modified microelectrodes is here developed for low-noise and high-fidelity optical modulation. First, the electromagnetic interference (EMI) free and high-efficiency optical stimulation is realized by adopting an optical coupling module with microfabricated locating slot. Second, the photovoltaic (PV) noise and the photoelectrochemical (PEC) noise are significantly decreased by an order of magnitude through combination of heavy doping and electrochemical modification of the optrode. More importantly, it is confirmed for the first time that the PV and PEC noise can be further reduced by an order of magnitude through LD driving pulse shaping. Finally, the in vivo acute recording experiments show that the light-induced photoelectric noise ( $< 50 \mu \text{V}$ ) has little influence on the firing rate (1.2 spikes/s) and signal-to-noise ratio (SNR = 4.9) of the recorded signals accompanied by optical stimulation. The results indicate that the developed noise mitigation strategies are promising for optogenetics-based neural circuit research.

Flexible and self-powered sensing device has aroused considerable interest in the field of the Internet of Things (IoT) and artificial intelligence (AI) in recent years. For more detailed and sensitive perception of the surroundings and external stimuli, sensors with high density and sensitivity are highly desirable. Here, this article reported a simple and low-cost strategy to realize a high-performance flexible piezoelectric sensor array composed of 30 sensing points with a high density of 11.11 cm $^{-{2}}$ . The piezoelectric sensor array was analyzed by a finite-element model and characterized through sound pressure measurement and wrist bending for motion monitoring under ${d}_{{33}}$ and ${d}_{{31}}$ modes, respectively. The flexible sensor array with the total thickness of 125 $\mu \text{m}$ exhibits a high sensitivity of 447.82 mV $\cdot $ kPa $^{-{1}}$ with an ultralow detection limit of $\sim 3.60$ Pa. Our work provides a simple strategy for the application potential in smart wearable electronics and human–machine interaction (HMI) areas.

Cryogenic temperature measurement in strong magnetic field is indispensable for researches based on cryogenic and strong magnetic field composite environment. In this work, oxygen is added into CrNx film to form CrOxNy for the development of resistive cryogenic temperature sensor with high sensitivity, high stability and low magnetoresistance. CrOxNy thin films with different electric properties were deposited under variant N2/O2 gas flow rates by DC magnetron reactive sputtering, and micro sensors were fabricated. The sensors’ performances were systematically analyzed in 4.2K~300K. They show super-high sensitivities, the absolute sensitivity is between 2.61 and 4.26 when the N2/O2 flow rate is 17.8sccm. The temperature measurement shift after 10 and 15 thermal cycles between 4.2K ~ 300K is in the range of −8.26mK ~ 11.79mK. The temperature measurement shift in magnetic field of 9T is in the range of −30.2mK~178mK, and the relative deviation is in the range of ±0.164%, with an absolute value of less than 0.086% at most of the measured points, indicating strong performance of against the influence of magnetic field.

Negative capacitance (NC) effects in ferroelectric (FE) films have attracted intensive attention recently in terms of both polarization kinetics modeling and low-power CMOS applications. Its physical origin, however, is controversial because the experimentally observed NC effects are different from the initial concept, particularly on the frequency/voltage dependence and hysteresis. Recently, we have proposed an electrostatic model, with which the NC effect with hysteresis and voltage dependence in FE/paraelectric (PE) stacks in dc mode is explained from a viewpoint of polarization switching. Based on this, in this work, the NC effect in the dimension of time in both FE/PE and FE capacitor–resistor (FE-R) circuit is analytically formulated and experimentally studied by comprehensively considering the dynamics of polarization switching, charge communication with power supply, and charge leaking through the capacitor. Our results suggest that such NC effects only occur in a time window in both systems and a competition between FE switching and charge compensation is the key to determine the time window. Thus, a systematic understanding is accomplished to explain most of the phenomenon associated with NC effects in FEs.

High-performance wearable sensors are required for applications in medical health and human–machine interaction, but their application has limited owing to the trade-off between sensitivity, pressure range, and durability. Herein, we propose the combined spraying and self-diffusion process of carbon nanotubes (CNTs) to balance and improve these parameters with the CNTs spontaneously diffusing into the film surface before the film curing. The obtained sensor not only achieves high sensitivity (155.54 kPa–1) and ultrawide pressure detection range (0.1–500 kPa) but also exhibits exceptional durability (over 12,000 pressure cycles at a high pressure of 300 kPa). In addition, the sensor exhibits a fast response (25 ms), good stability, and full flexibility. This process is a general approach that may improve the performance of various types of thin film piezoresistive sensors. Besides, the fabricated sensors can be flexibly scaled into sensor arrays and communicate with smart devices to achieve wireless smart monitoring. At present, the sensor shows broad application prospects in the fields of intelligent medical health and motion sensing.

Reasonable design of materials with complex nanostructures and diverse chemical compositions is of great significance in the field of energy storage. Cu7KS4(CKS) is considered a potential electrode material for supercapacitors due to its superior electrical conductivity. Transition metal hydroxides are widely used as electrode materials for supercapacitors due to their high theoretical specific capacitance (Cs); however, single metal species with limited active sites restrict their further applications for energy storage. Herein, through a hydrothermal reaction, CKS nanorods were prepared, and then binary metal hydroxide NixCo1–x(OH)2nanosheets were generated directly on CKS nanorods through a one-step hydrothermal reaction to form a nano-core–shell structure (NCSS). By regulating the mole ratio of nickel nitrate to cobalt nitrate, the resulting Ni0.75Co0.25(OH)2nanosheets with the best electrochemical activity were prepared and supported on CKS nanorods to form a CKS@N0.75C0.25OH NCSS. The as-prepared CKS@N0.75C0.25OH NCSS has a larger specific surface area, which can provide more active sites, while the abundant metal species composition can generate abundant redox reactions to boost the pseudocapacitance. The prepared CKS@N0.75C0.25OH/NF electrode exhibits outstanding specific capacitance and cycle life. The assembled CKS@N0.75C0.25OH/NF//AC all-solid-state asymmetric supercapacitor achieves a high energy density of 88.7 Wh kg–1at a power density of 849.9 W kg–1with superior cycle life. Therefore, the use of polymetallic hydroxides to construct NCSS electrodes has great research significance and broad application prospects.

Ternary layered double-hydroxide-based active compounds are regarded as ideal electrode materials for supercapacitors because of their unique structural characteristics and excellent electrochemical properties. Herein, an NiCeCo-layered double hydroxide with a core–shell structure grown on copper bromide nanowire arrays (CuBr2@NCC-LDH/CF) has been synthesized through a hydrothermal strategy and calcination process and utilized to fabricate a binder-free electrode. Due to the unique top-tangled structure and the complex assembly of different active components, the prepared hierarchical CuBr2@NCC-LDH/CF binder-free electrode exhibits an outstanding electrochemical performance, including a remarkable areal capacitance of 5460 mF cm–2at 2 mA cm–2and a capacitance retention of 88% at 50 mA cm–2as well as a low internal resistance of 0.163 Ω. Moreover, an all-solid-state asymmetric supercapacitor (ASC) installed with CuBr2@NCC-LDH/CF and activated carbon electrodes shows a high energy density of 118 Wh kg–1at a power density of 1013 W kg–1. Three assembled ASCs connected in series can operate a multifunctional display for over three and a half hours. Therefore, this innovative work provides new inspiration for the preparation of electrode materials for supercapacitors.

Aqueous batteries are well-suited for extensive energy storage because of their cost-effectiveness and safety benefits. The zinc electrode, owing to its lower equilibrium potential and higher exchange current density, makes aqueous zinc-ion batteries (ZIBs) a highly promising energy storage device. The advancement of ZIBs hinges on the development and production of sophisticated positive electrode materials that align with the zinc anode and demonstrate outstanding electrochemical performance. Herein the synthesis of MnO/C@rGO composites is achieved by directly anchoring Mn-MOFs on reduced graphene oxide (rGO) sheets, followed by heat treatment in argon and hydrogen atmosphere. As the cathode for ZIBs, in which the graphene oxide promotes the generation of nanoparticles with smaller sizes instead of larger ones and MnO wrapped in a carbon layer are fixed on rGO sheets can not only slow down the manganese dissolution rate but also increase electrical conductivity. These features endow MnO/C@rGO cathode with good cycling stability (85.1 % capacity retention after 1200 cycles at 2 A g−1) and rate performance (318.7 mAh g−1at 0.2 A g−1). This research achievement will provide new directions for the design and preparation of the anode of ZIBs based on MOFs.

As the core component of supercapacitors, the choice of electrode material is critical in determining the energy and power density of the supercapacitors. To date, transition metal materials have been widely employed as electrodes in supercapacitors. In this study, we successfully designed and fabricated nanoflower-like Ag-NiMo(OH)xcomposite materials on a nickel foam base using a combination of hydrothermal and calcination techniques. NiMoOxflower-like nanosheets grown on NF increase the overall specific surface area of the electrode material and improve charge transport, provide mechanical stability, and supporting template for Ag nanoparticles attachment in the next step. With the solvothermal method, we are able to generate Ag nanoparticles onto NiMoOxnanosheets to obtain Ag-NiMo(OH)x. Utilizing the Ag-NiMo(OH)xcomposite as the cathode which displayed distinguished electrochemical performance with a specific capacity of 3548 mF cm−2at 2 mA cm−2. We also construct solid-state asymmetric supercapacitors (ASCs) with Ag-NiMo(OH)x/NF electrode as the cathode and activated carbon electrode as the anode. The two-electrode system was analyzed, and the energy density achieved is 80.21 Wh kg−1under 717.98 W kg−1. Furthermore, 84.66 % of the original capacity is left over after 10,000 charge-discharge cycles, indicating good cycling stability of the material.

The real-time observation of chemical bond formation at the single-molecule level is one of the great challenges in the fields of organic and biomolecular chemistry. Valuable information can be gleaned that is not accessible using ensemble-average measurements. Although remarkably sophisticated techniques for monitoring chemical reactions have been developed, the ability to detect the specific formation of a chemical bond in situat the single-molecule level has remained an elusive goal. Amide bonds are routinely formed from the aminolysis of N-hydroxysuccinimide (NHS) esters by primary amines, and the protocol is widely used for the synthesis, cross-linking, and labeling of peptides and proteins. Herein, a plasmonic nanocavity was applied to study aminolysis reaction for amide bond formation, which was initiated by single nanoparticle collision events between suitably functionalized free-moving gold nanoparticles and a gold nanoelectrode in an aqueous buffer. By means of simultaneous surface enhanced Raman spectroscopy (SERS) and single-entity electrochemistry (EC) measurements, we have probed the dynamic evolution of amide bond formation in the aminolysis reaction with 10 s of millisecond time resolution. Hence, we demonstrate that single-entity EC-SERS is a valuable and sensitive technique by which chemical reactions can be studied at the single-molecule level.

Excessive application of nitrogen (N) fertilizer is common in Chinese apple production. High N reduced the contents of soluble sugar and total flavonoids by 16.05 and 19.01%, respectively, resulting in poor fruit quality. Moreover, high N increased the total N and decreased the total C and C/N ratio of apple fruits. On the basis of the transcriptomic, proteomic, and metabolomic analyses, the global network was revealed. High N inhibited the accumulation of carbohydrates (sucrose, glucose, and trehalose) and flavonoids (rhamnetin-3-O-rutinoside, rutin, and trihydroxyisoflavone-7-O-galactoside) in fruits, and more C skeletons were used to synthesize amino acids and their derivatives (especially low C/N ratio, e.g., arginine) to be transferred to N metabolism. This study revealed new insights into the decline in soluble sugar and flavonoids caused by high N, and hub genes (MD07G1172700, MD05G1222800, MD16G1227200, MD01G1174400, and MD02G1207200) and hub proteins (PFK, gapN, and HK) were obtained.

Superelastic aerogels with excellent electrical conductivity, reversible compressibility, and high durability hold great potential for varied emerging applications, ranging from wearable electronics to multifunctional scaffolds. In the present work, superelastic MXene/reduced graphene oxide (rGO) aerogels are fabricated by mixing MXene and GO flakes, followed by a multistep reduction of GO, freeze-casting, and finally an annealing process. By optimizing both the composition and reducing conditions, the resultant aerogel shows a reversible compressive strain of 95%, surpassing all current reported values. The conducting MXene/rGO network provides fast electron transfer and stable structural integrity under compression/release cycles. When assembled into compressible supercapacitors, 97.2% of the capacitance was retained after 1000 compression/release cycles. Moreover, the high conductivity and porous structure also enabled the fabrication of a piezoresistive sensor with high sensitivity (0.28 kPa–1), wide detection range (up to 66.98 kPa), and ultralow detection limit (∼60 Pa). It is envisaged that the superelasticity of MXene/rGO aerogels offers a versatile platform for utilizing MXene-based materials in a wide array of applications including wearable electronics, electromagnetic interference shielding, and flexible energy storage devices.

Opto-electrophysiology neural probes targeting single-cell levels offer an important avenue for elucidating the intrinsic mechanisms of the nervous system using different physical quantities, representing a significant future direction for brain–computer interface (BCI) devices. However, the highly integrated structure poses significant challenges to fabrication processes and the presence of photoelectric artifacts complicates the extraction and analysis of target signals. Here, we propose a highly miniaturized and integrated opto-electrophysiology neural probe for electrical recording and optical stimulation at the single-cell/subcellular level. The design of a total internal reflection layer addresses the photoelectric artifacts that are more pronounced in single-cell devices compared to conventional implantable BCI devices. Finite element simulations and electrical signal tests demonstrate that the opto-electrophysiology neural probe eliminates the photoelectric artifacts in the time domain, which represents a significant breakthrough for optoelectrical integrated BCI devices. Our proposed opto-electrophysiology neural probe holds substantial potential for promoting the development of in vivoBCI devices and developing advanced therapeutic strategies for neurological disorders.

Nitrogen (N) and potassium (K) are two important mineral nutrients in regulating leaf photosynthesis. However, the influence of N and K interaction on photosynthesis is still not fully understood. Using a hydroponics approach, we studied the effects of different N and K conditions on the physiological characteristics, N allocation and photosynthetic capacity of apple rootstock M9T337. The results showed that high N and low K conditions significantly reduced K content in roots and leaves, resulting in N/K imbalance, and allocated more N in leaves to non-photosynthetic N. Low K conditions increased biochemical limitation (BL), mesophyll limitation (MCL), and stomatal limitation (SL). By setting different N supplies, lowering N levels under low K conditions increased the proportion of water-soluble protein N (Nw) and sodium dodecyl sulfate-soluble proteins (Ns) by balancing N/K and increased the proportion of carboxylation N and electron transfer N. This increased the maximum carboxylation rate and mesophyll conductance, which reduced MCLand BLand alleviated the low K limitation of photosynthesis in apple rootstocks. In general, our results provide new insights into the regulation of photosynthetic capacity by N/K balance, which is conducive to the coordinated supply of N and K nutrients.

Solvent plays an important role in the surface interaction of molecules. In this study, we use “chlorophyll a”, an archetypical molecule, to investigate its supramolecular self-assembly with chemically reduced graphene oxide in three different types of solvents: polar protic, polar aprotic, and non-polar. It was observed that only a polar protic solvent that can donate protons facilitates the hydrogen bonding between chlorophyll a and chemically reduced graphene oxide nanosheets in a hybrid system. The formation of hydrogen bonds further initiates the other non-covalent interactions such as π–π stacking and hydrophobic interaction, which altogether play a key driving force for supramolecular self-assembly of chlorophylls on chemically reduced graphene oxides. The experimental results are strongly supported by density functional theory calculations, which show robust electron coupling between chlorophylls and chemically reduced graphene oxide.

NiCo-layered double hydroxide (LDH) has attracted increasing attention in recent years for application in supercapacitors (SCs) owing to its high redox activity and intercalating capability. However, the pristine NiCo-LDH is unable to reach theoretical specific capacitance and satisfying rate capability due to the limited electroactive species and a low ion diffusion rate. Here, we demonstrate novel vertically aligned nanosheet arrays of cobalt metal–organic framework (Co-MOF)@CoNiO2core–shell composites constructed by the in situ grown Co-MOF shell with a uniform and controlled thickness on the CoNiO2core via a vapor-phase approach. Owing to the intimate contact and synergistic effect between the Co-MOF shell and the CoNiO2core, the as-synthesized Co-MOF@CoNiO2displays a high specific capacitance of about 571 F g–1, which is significantly higher than the pristine NiCo-LDH electrode (380 F g–1). Moreover, the capacitive properties of Co-MOF@CoNiO2can be further boosted to 757.2 F g–1after cyclic voltammetry oxidation. The easy preparation and high electrochemical performance of the Co-MOF@CoNiO2composite make it a potential material for SC application. These findings may inspire the exploration and construction of other MOF shell coating metal oxide from various nanostructured LDHs for varied applications. In addition, the as-assembled EO-Co-MOF@CoNiO2/carbon cloth (CC)//activated carbon (AC) device can achieve a high capacitance of 87.67 F g–1. Meanwhile, the asymmetric supercapacitor (ASC) device exhibits a high energy density of 27.4 Wh kg–1at a power density of 750 W kg–1.

Water splitting by electrolysis is an appealing pathway for sustainable hydrogen production. The practical performance of water splitting is highly dependent on the efficiency of electrocatalysts, which can promote the anodic oxygen evolution reaction (OER) or cathodic hydrogen evolution reaction (HER). Downsizing the metal nanostructures to atomic level to construct single-atom catalysts (SACs) has attracted enormous attention due to its distinct advantages in maximizing the efficiency of metal atom utilization and enhancing activity over corresponding metal nanoparticles. Research on SACs towards electrochemical water splitting application is an emerging field and intensive investigations have been focused on their rational syntheses and applications in HER/OER. In this review, we focus on the wet chemical method developed to prepare non-noble metal based SACs with an emphasis on the synthetic strategies and structure-activity relationship between single metal atoms and catalytic activity. Finally, the challenges and future opportunities for application of single-atom catalysts in water splitting are briefly addressed.

The delicate serpentine structures are widely used in high-performance stretchable electronics over the past decade. The metal interconnects encapsulated in biocompatible polymer Parylene-C film is a superior choice for long-term implantation in vivo, especially as neural interface to acquire electrophysiological signals or apply electrical stimulation. To avoid the physical contact damages from the neural tissues such as the brain or peripheral nerves, serpentine interconnects are utilized as stretchable electrodes and usually bonded to the soft elastomer substrate. The adhesion strength between the serpentine interconnects and the elastomer substrate becomes a considerable issue to ensure reliability and structural integrity. In this paper, the stretchable Parylene-C electrodes can be transfer printed onto arbitrary elastomer substrates by a thin layer of silicone rubber adhesive with low modulus for electrocorticogram (ECoG) recording. Mechanical simulation of serpentine structures consisting of same periodic arcs and different straight segments is investigated by uniaxial stretching. Then, the elastic stretchability of serpentine electrodes is further studied by simulation and experiments. After 5000 repetitive stretching cycles, the electrochemical impedance of microelectrodes remains in steady states. These results prove that the silicone rubber adhesive facilitates the interfacial bonding in the structure of stretchable electrodes as the compliant and reliable neural interface.

The development for environmentally friendly energy conversion and storage equipment has given rise to tremendous research efforts as a result of the growing requirements for environmental friendly resources and the rapid consumption of traditional fossil fuel. Herein, a novel hierarchical CoO/NiO–Cu@CuO heterostructure is successfully devised and synthesized. Cobalt/nickel ions are used to generate novel CoO/NiO-doped laminated CuO nanospheres through the facile in situ wet oxidation combined with cation exchange and calcination strategies. As a result, the electrochemical supercapacitance of the as-prepared CoO/NiO–Cu@CuO electrode can reach 875 C cm–2(2035 mF cm–2), which exhibits much better electrochemical performance compared to other precursor electrodes at a same current density of 2 mA cm–2. Moreover, an excellent rate capacity of 1395 mF cm–2(50 mA cm–2) can be achieved when measured at a relative high current density; 90.3% of the initial supercapacitance remains even after 5000 cycles. Furthermore, the as-prepared hierarchical hybrid of laminated CoO/NiO–CuO nanospheres in situ generated on three-dimensional (3D) porous Cu foam is applied to prepare a solid-state asymmetric supercapacitor equipment unit. The fabricated equipment unit shows an energy density of 69.3 W h kg–1at a power density of 1080 W kg–1. Additionally, the commercially applied 2.5 V light-emitting-diode indicator with blue light can be energized for 4 min when two as-fabricated supercapacitor devices are in series connection. The unique hierarchical heterostructure of the novel laminated nanospheres combined with the 3D grid structure brings about the outstanding electrochemical capacitor performances. This strategy for the fabrication of hierarchical heterostructure electrodes could have an enormous potential for high-performance electrochemical equipment.

In this Letter, a novel humidity sensor based on a chip-scale silicon nanobeam cavity with polymethyl methacrylate (PMMA) cladding is demonstrated. This sensor is easy to fabricate and compatible with CMOS technology. It shows a humidity sensing with a linear wavelength dependence of 22.9 pm/% relative humidity (RH) in a wide range of RH from 10% to 85%, an ultra-fast response time of 540 ms, and high stability. After annealing, the sensor exhibits high reversibility, repeatability, and temperature insensitivity at the range of 25°C–40°C. To the best of our knowledge, this is the first application of integrated photonics in high performance humidity detection. It provides a new way for the chip-scale sensor to integrate with photonic devices and optical systems.

The bimetallic oxide CuCo2O4(CCO) is highly promising for supercapacitors owing to the character of high theoretical capacitance, high electrical conductivity and rich redox reactions. However, pure CuCo2O4components do not provide sufficient capacitance and operating voltage in the application. The appropriate collocation as well as design is one of the keys means to improve the performance of the material. Herein, we brilliantly construct hierarchical CuCo2O4@NiMn-layered double hydroxides (CCO@NM-LDH) core-shell heterostructures, which exhibit impressive capacitive performance (2955.2 F g−1) compared to individual CCO materials (750.2 F g−1). The foremost reason is ultrathin NiMn-LDH nanosheets anchored evenly on the surface of CCO nanoneedles and this structure provide a large specific surface area, numerous active sites, and accelerate the efficiency of ion transport. Also, by modulating the reaction time of NiMn-LDH, several different samples are prepared, among which, the CCO@NM-LDH-2 electrode is found to be the one that can display the best-performance capacitance and retention of capacitance can maintain 86.6 % during 10,000 cycles. In addition, the assembled CCO@NM-LDH-2//AC asymmetric supercapacitor (ASC) with CCO@NM-LDH-2 as the positive electrode can exhibit an energy density of 62.93 Wh kg−1at 799.96 W kg−1power density. Therefore, we believe that the construction and utilization of CuCo2O4composites as electrodes should have a powerful enlightenment on the exploration of energy storage devices.