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Organic-inorganic hybrid halide perovskites (OIHPs) with inherent mixed ionic-electronic conduction ability have been proposed as promising candidates for memristors with unique optoelectronic characteristics. Despite the great achievements toward understanding the working mechanism and exploring their functionality as water-sensitive materials, the humidity effect on the resistive switching (RS) characteristics still remains to be studied. This study investigates the humidity effect on the RS characteristics of Au/CH3NH3PbI3/FTO memristor. The memristor works well at moderate relative humidity (RH

In this letter, the dual buffer layers of AgInSbTe (AIST) and monolayer defective graphene (DG) are introduced into amorphous carbon (a-C)-based electrochemical metallization (ECM) type memristor. The advantages of promoting Ag dissolution and localizing cation diffusion region of AIST and DG layers can effectively suppress the well-known current overshoot issue and break the current-retention dilemma. Compared with its counterpart without buffer layer (Ag/a-C/Pt), the device with dual buffer layers (Ag/AIST/DG/a-C/Pt) presents excellent resistive switching (RS) performance, such as lower forming voltage with reduced overshoot current, smaller parameter fluctuations, and better cycling endurance. More importantly, the nonvolatile RS with low operation current of 10 $\mu \text{A}$ and remarkable endurance ( $> {3.1}\times {10}^{{7}}$ cycles) is realized, which is among the best of reported a-C-based ECM memories. Benefit from the low operation current, the device also shows the capacity of multilevel memory with six nonvolatile resistance states through regulating the compliance current.

Memristive devices are widely recognized as promising hardware implementations of neuromorphic computing. Herein, a flexible and transparent memristive synapse based on polyvinylpyrrolidone (PVP)/N-doped carbon quantum dot (NCQD) nanocomposites through regulating the NCQD doping concentration is reported. In situ Kelvin probe force microscopy showed that the trapping/detrapping of space charge can account for the memristive mechanism of the device. Diverse synaptic functions, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), spike-timing-dependent plasticity (STDP), and the transition from short-term plasticity (STP) to long-term plasticity (LTP), are emulated, enabling the PVP–NCQD hybrid system to be a valuable candidate for the design of novel artificial neural architectures. In addition, the synaptic device showed excellent flexibility against mechanical strain after repeated bending tests. This work provides a new approach to develop flexible and transparent organic artificial synapses for future wearable neuromorphic computing systems.

Optoelectronic resistive switching (RS) devices are attracting attention due to their promising potential in optical communication technology. In this study, a photo-tunable organic memory device based on poly(4-vinylphenol) (PVP) and N-doped carbon quantum dot nanocomposites is presented. After UV light irradiation, the set voltage of the device can be gradually reduced by adjusting the irradiation time. This memory device presents excellent memory performance after large-angle bending or repetitive bending tests. More importantly, the controlled switching voltage characteristic enabled the realization of encrypted image storage. Raman spectra evidence that a local conductive sp2-hybridized carbon region was generated through UV light reduction, which can effectively enhance the internal electrical field and shorten the tunneling distance between the carbon dots, thus decreasing the set voltage. Our work provides a new approach towards the development of photo-tunable organic memory for future wearable optoelectronic neuromorphic computing systems.

Electromagnetic interference (EMI) shielding materials with lightweight and tunability are highly desirable for practical applications in complex environments. Carbon-based materials as EMI materials are lightweight and highly environment-friendly, but generally rigid. Herein, we demonstrate novel nitrogenous carbon foams (NCFs) with the hollow framework, possessing multiple merits of ultralight, ultraelasticity and proper electrical conductivity. Such a significant architecture thus results in an excellent EMI shielding performance. Experimental characterizations combining with the first principle calculations indicate that the origins of microwave absorption and shielding characteristics are ascribed to the atomic-scale nitrogen substitutions in carbon matrix, which induce the structural symmetry breaking and the re-distribution of localized charge, forming a high density of electric dipoles. By compressing/releasing the NCFs, the electromagnetic (EM) performance can be arbitrarily tuned due to the phase cancellation within the three-dimensional foam structure and the tunable conductivity. The present work has important implications in understanding the intrinsic origin of strengthening EM radiation, and meanwhile provides a strategy for the design of “dynamic” EM functional materials.

Organic‐inorganic halide perovskites (OHPs) have been intensively studied for application in solar cells with high conversion efficiency exceeding 22%. The unique electrical and optical properties of OHPs have led to their use in optoelectronic device applications beyond photovoltaics, such as light‐emitting diodes, photodetectors, transistors. New information storage technologies and computing architectures are being researched extensively with the aim of addressing the growing challenge of approaching end of Moore's law and von Neumann bottleneck. As the fourth basic circuit element, memristor is a leading candidate with powerful capabilities in information storage and neuromorphic computing applications. Recently, OHPs have received growing attention as promising materials for memristors. In particular, their mixed ionic‐electronic conduction ability paired with light sensitivity provide OHPs with the opportunity to display novel functions such as optical‐erase memory, optogenetics‐inspired synaptic functions, and light‐accelerated learning capability. This review covers recent advances in OHP‐based memristors development including memristive mechanism and analytical models, universal memristive characteristics for memory and neuromorphic computing applications, and novel multi‐functionalization. Challenges and future prospects of OHP‐based memristors are also discussed.

Chemiluminescence (CL) functionalized materials have found tremendous value in developing CL assays for clinical assays and point-of-care tests. To date, the design and optimization of these materials have mainly relied on conventional trial-and-error procedures in which the ensemble performance is evaluated using conditional experiments. Here we have built an optical microscope to acquire the CL emission from single magnetic-polymer hybrid microbeads functionalized with luminol analogues, and to access the CL kinetics of each individual particle. It was incidentally found that a minor subpopulation of microbeads exhibited intense and delayed CL emission while the majority showed transient and weak emission. Structural characterization of the very same individual particles uncovered that the amorphous multi-core microstructures were responsible for the enhanced encapsulation efficiency and optimized CL reaction kinetics. Guided by this knowledge stemming from single particle CL imaging, the synthesis procedure was rationally optimized to enrich the portion of microbeads with better CL performance, which was validated by both single particle imaging and the significantly improved analytical performance at the ensemble level. The present work not only demonstrates the CL imaging and CL kinetics curve of single microbeads for the first time, but also sets a clear example showing the capability of single particle studies to investigate the structure–activity relationship in a bottom-up manner and to help the rational design of ensemble materials with improved performance.

Hybrid organic–inorganic perovskite, CH3NH3PbI3 (MAPbI3), has attracted great attention as promising building blocks for resistive switching memory. However, the reproductive switching uniformity a...

We demonstrated an effective method of Ar surface plasma treatment (SPT) to improve the resistive switching (RS) uniformity of HfO2−x based resistive random access memory (RRAM) device. More importantly, the operation of multilevel RRAM and low power consumption can be further achieved by reliable RS, which enabled to obtain five distinguishable low resistance states and can be operated with a low power consumption of ∼30 pJ. The results of atomic force microscope and X-ray photoelectron spectroscopy analysis confirmed that the Ar SPT induced more oxygen defects and higher roughness on the surface, which decreased the migration barrier of oxygen migration and some tips below the electrode. Eventually, a moderate forming process and local electric-field enhancement around these tips were obtained, accounting for the improvement of RS uniformity. This method could be promising to develop RRAM with high uniformity for the low-power multilevel memory applications.

An all-carbon memristive synapse is highly desirable for hardware implementation in future wearable neuromorphic computing systems. Graphene oxide (GO) can exhibit resistive switching (RS) and may be a feasible candidate to achieve this objective. However, the digital-type RS often occurring in GO-based memristors restricts the biorealistic emulation of synaptic functions. Here, an all-carbon memristive synapse with analog-type RS behavior was demonstrated through photoreduction of GO and N-doped carbon quantum dot (NCQD) nanocomposites. Ultraviolet light irradiation induced the local reduction of GO near the NCQDs, therefore forming multiple weak conductive filaments and demonstrating analog RS with a continuous conductance change. This analog RS enabled the close emulation of several essential synaptic plasticity behaviors; more importantly, the high linearity of the conductance change also facilitated the implementation of pattern recognition with high accuracy. Furthermore, the all-carbon memristive synapse can be transferred onto diverse substrates, showing good flexibility and 3D conformality. Memristive potentiation/depression was stably performed at 450 K, indicating the resistance of the synapse to high temperature. The photoreduction method provides a new path for the fabrication of all-carbon memristive synapses, which supports the development of wearable neuromorphic electronics. A graphene-based device can help computer chips behave more like human brains by transmitting current across thread-like wires. Neural synapses store memories by accessing different types of conductive states. Chinese researchers led by Haiyang Xu at Northeast Normal University in Changchun and Zhenhui Kang at Soochow University in Suzhou now demonstrate that graphene sheets with different conductivity levels—caused by adding or removing oxygen atoms—can also exhibit synapse-like behavior. The team developed a carbon-nitrogen composite to sandwich between two graphene electrodes with high and low levels of conductivity. Exposing the composite to ultraviolet light created numerous tiny filaments between the electrodes that physically restrict electron flow and provide gradual smooth transitions between the graphene electrodes’ two conductive states. The organic framework of this device also provides inherent flexibility for wearable devices. All-carbon memristive synapse is built through photo-reduction of a nanocomposite comprised of graphene oxide and N-doped carbon quantum dots. The analog-type resistive switching was demonstrated, which enabled the emulation of synaptic learning and pattern recognition with high accuracy. The all-carbon devices possess excellent transferability, flexibility and resistance to high temperature, showing the potential for the development of wearable neuromorphic computing system.

Metal nanowire networks (MNNs) are promising as transparent electrode materials for a diverse range of optoelectronic devices and also work as active materials for electrical heating and electromagnetic interference (EMI) shielding applications. However, the relatively low performance and poor durability of MNNs are limiting the practical application of the resulting devices. Here, we report a controllable approach to enhance the conductivity and the stability of MNNs with their transmittance remaining unchanged, in which reduced graphene oxide conformally wrapped silver nanowire networks (AgNW@rGO networks) are synthesized by selective electrodeposition of GO nanosheets on AgNWs followed by a pulsed laser irradiation treatment. Experimental characterizations and finite-difference time-domain simulations indicate that pulsed laser irradiation at a specific wavelength not only reduces the GO but also welds the AgNWs together through a surface plasmon resonance process. As a result, the AgNW@rGO networks exhibit low sheet resistance of 3.3 Ω/□, average transmittance of 91.1%, and good flexibility. Wrapping with rGO improves the maximum electrical heating temperature of the AgNW network transparent heaters due to the effective suppression of the oxidation and the migration of surface silver atoms. In addition, excellent EMI shielding effectiveness of up to 35.5 dB in the 8.2-12.4 GHz frequency range is obtained as a consequence of the combined effects of dual reflection, conduction loss, and multiple dielectric polarization relaxation processes.

An analytical model was proposed to simulate the resistive switching (RS) process of electrochemical metallization memory (ECM) device with a dual-layer structure, in which the AgInSbTe (AIST) buffer layer was introduced to combine with the amorphous carbon (a-C) dielectric layer. This dual-layer ECM device presented good memory performance, such as high switching uniformity, however, a suitable model was absent to understand its RS mechanism. The analytical model of Ag/AIST/a-C/Pt device was developed based on the formation and dissolution of the Ag-ion-based CF. Comparing to the common RS model considering one-step set/reset process, the multi-step of set/reset was utilized to fit with the dual-layer structure. The set/reset always occurs in the AIST layer at first step and in the a-C layer subsequently due to the lower active energy and thermal conductivity of AIST layer. Random disturbances were also introduced to simulate the device variation during the cycling process. Eventually, this model can well fit with the experimental data, providing an analytical tool for describing the RS process of ECM device.

We investigated microwave absorption properties of the close-packed Fe at C nanocapsules under an external electric-field stimulus. The results indicate that the reflection parameter ( $S_{11}$ ) linearly increases as the applied voltage ranging from 0 to 12 V at 18 to 26.5 GHz ( $K$ -band) frequencies, while the transmission parameter ( $S_{21}$ ) remains constant. Such tunability is a consequence of the energy transfer between the permeability and the permittivity, physically originating from the multiple dielectric polarizations at the core at shell interfaces, ascribed to the electric-field induced asymmetric distribution of localized charge. The present finding might open up a new avenue for designing smart microwave absorbers targeted to complex serving environments.

In this article, a porous flexible membrane electrode of nickel oxide is developed by a facile method based on liquid-liquid phase-separation. The effects of the membrane components on structures and electrochemical behaviors of membrane electrode are investigated. The results reveal that nano NiO and conducting graphite are imbedded into the polymer membrane of polyethersulfone to form a flexible hybrid membrane (M-NiO-G), which shows the highest specific capacitance of 794.0 F/g at a current density of 1.0 A/g. The asymmetrical supercapacitor device based on the as-synthesized of M-NiO-G (positive electrode) and activated carbon membrane (negative electrode) exhibits a high specific capacitance of 154.0 F/g at a current density of 0.2 A/g. The coulombic efficiency remains about 95.0%, and the capacitance retention is 84.8% after 5000 charging-discharging cycles at 1.0 A/g. The energy density of the asymmetrical supercapacitor device reaches 39.6 Wh/kg at a power density of 516.9 W/kg, still remains 20.0 Wh/kg at a high power density of 2567.4 W/kg in the potential window from 0 to 1.36 V in 6 M KOH aqueous solution.

Transition-metal nitrides exhibit wide potential windows and good electrochemical performance, but usually experience imbalanced practical applications in the energy storage field due to aggregation, poor circulation stability, and complicated syntheses. In this study, a novel and simple multi-phase polymeric strategy was developed to fabricate hybrid vanadium nitride/carbon (VN/C) membranes for supercapacitor negative electrodes, in which VN nanoparticles were uniformly distributed in the hierarchical porous carbon 3D networks. The supercapacitor negative electrode based on VN/C membranes exhibited a high specific capacitance of 392.0 F g−1 at 0.5 A g−1 and an excellent rate capability with capacitance retention of 50.5% at 30 A g−1. For the asymmetric device fabricated using Ni(OH)2//VN/C membranes, a high energy density of 43.0 Wh kg−1 at a power density of 800 W kg−1 was observed. Moreover, the device also showed good cycling stability of 82.9% at a current density of 1.0 A g−1 after 8000 cycles. This work may throw a light on simply the fabrication of other high-performance transition-metal nitride-based supercapacitor or other energy storage devices. Electronic supplementary material The online version of this article (10.1007/s40820-018-0217-1) contains supplementary material, which is available to authorized users.

In this work, we demonstrated an effective method to improve the switching reliability of HfOx based RRAM device by inserting mountain-like surface-graphited carbon (MSGC) layer. The MSGC layer was fabricated through thermal annealing of amorphous carbon (a-C) film with high sp2 proportion (49.7%) under 500 °C on Pt substrate, whose characteristics were validated by XPS and Raman spectrums. The local electric-field (LEF) was enhanced around the nanoscale tips of MSGC layer due to large surface curvature, which leads to simplified CFs and localization of resistive switching region. It takes responsibility to the reduction of high/low resistance states (HRS/LRS) fluctuation from 173.8%/64.9% to 23.6%/6.5%, respectively. In addition, the resulting RRAM devices exhibited fast switching speed ( 104 s at 85 °C) and low cycling degradation. This method could be promising to develop reliable and repeatable high-performance RRAM for practical applications.

In this letter, complementary resistive switching (CRS) was demonstrated in a single-stack graphene oxide (GO) memory cell for the first time, where the high resistance state can be distinguished into ”0” and ”1” states by different bias polarities. The high switching uniformity ensures reliable reading/writing operations. By changing the compliance currents in the forming and switching processes, the quantity of oxygen defects required for the conducting-filament (CF) formation and supplied by the GO layer ( ${Q} _{R}$ and ${Q} _{S}$ ) was adjusted to determine their influence on the CRS. It was found that the CRS only occurred at the condition of ${Q} _{R} > {Q}_{S}$ and its mechanism is due to the inversion of CF geometry.

In this work, biomass pomelo peel is used to fabricate the porous activated carbon microsheets, and diammonium hydrogen phosphate (DHP) is employed to dual-dope carbon with nitrogen and phosphorus elements. With the benefit of DHP inducement and dual-doping of nitrogen and phosphorus, the prepared carbon material has a higher carbon yield, and exhibits higher specific surface area (about 807.7 m2/g), and larger pore volume (about 0.4378 cm3/g) with hierarchically structure of interconnected thin microsheets compared to the pristine carbon. The material exhibits not only high specific capacitance (240 F/g at 0.5 A/g), but also superior cycling performance (approximately 100% of capacitance retention after 10,000 cycles at 2 A/g) in 2 M KOH aqueous electrolyte. Furthermore, the assembled symmetric electrochemical capacitor in 1 M Na2SO4 aqueous electrolyte exhibits a high energy density of 11.7 Wh/kg at a power density of 160 W/kg.

Microwave absorption materials are usually designed to integrate multiple heterogeneous components containing magnetic and dielectric loss abilities, solving the electromagnetic impedance matching. We herein report a simple strategy to further improve the dielectric loss capacity of magnetic/dielectric-composed Fe@C nanocapsules absorbents by incorporating substitutional sulfur atoms into highly defective graphitic shells. Moreover, by optimizing the sulfur contents, the microwave absorption efficiency could be effectively adjusted. Experimental results coupled with the theoretical calculations evidence that the dielectric enhancement is originated from the atomic-scale symmetry breaking at the sulfur-substituted sites, resulting in the charge separation of localized microstructures. The present work has important implications in understanding the structural origin of electromagnetic phenomena, and meanwhile could be widely extended to exploit high-performance carbon-based microwave absorbents.

We fabricate a porous and flexible membrane electrode composed of nano-nickel hydroxide as an electrochemically active material, a polymer as a substrate material, and a copolymer as a modification additive. A series of amphiphilic block copolymers of PAA-b-PAN-b-PAA, F127, PDMC-b-PAN-b-PDMC, and PVP-b-PAN-b-PVP are prepared, and their effects on the thickness, surface structure, and electrochemical performance of the electrode materials are investigated. It is discovered that the hydrophilic chains of the amphiphilic block copolymer contribute a lot to improving the surface properties of electrolyte-affinity. The results indicate that the electrode membrane with a membrane thickness of 60 μm modified by PAA-b-PAN-b-PAA demonstrates the highest specific capacitance of 3090.0 F g−1 at a current density of 0.5 A g−1. An asymmetric supercapacitor based on the fabricated electrode membrane using Ni(OH)2 as the positive active material and activated carbon as the negative electrode obtains a capacitance of 114.1 F g−1 at 0.5 A g−1. The device shows good cycling stability with a capacitance retention of up to 90.7% after 5000 cycles at 1.0 A g−1. The maximum energy density of the asymmetrical supercapacitor reached 40.6 W h kg−1 at a power density of 400.0 W kg−1, and a high power density of 4000.0 W kg−1 was obtained at 23.5 W h kg−1 in 6 M KOH aqueous electrolyte.

Reversible alternation between bipolar and unipolar resistive switching (RS) modes was observed by controlling voltage-polarity in Ag/MoS2/Au memory on polyethylene terephthalate (PET) substrate. The temperature-dependent low-resistance-state and Raman measurement indicated that Ag and sulphur vacancy (Vs)-based conductive filaments (CFs) were responsible for these two RS modes. The two kinds of CFs had different responses under positive read voltages. Thus, a new operation scheme of multilevel memory was demonstrated in which multiple states were distinguished by CF composition rather than resistance values. The memory capacity of the cell could be further extended by adjustments in CFs’ size in each mode. The RS performance of the device did not degrade under bending conditions even over 104 bending cycles, which indicated good mechanical flexibility. The present Ag/MoS2/Au memory has promise for future high-density flexible information storage.

Data retention of nano-sized conducting filaments is a critical reliability issue in the pursuit of low-power graphene oxide-based resistive switching (RS) memory devices. Herein, an improvement in the low resistance state retention is demonstrated in fabricated oxidized carbon quantum dot (OCQD)–graphene oxide nanocomposites. Reliable RS characteristics with good retention properties were achieved instead of volatile switching, even with a relatively low compliance current of 100 μA. More epoxy groups were introduced as the concentration of embedded OCQDs was increased, resulting in a larger high resistance state, a higher set voltage, and deeper trapping levels. The dependence of the set switching time on the temperature acts as experimental verification that the oxygen migration energy barrier Ea was improved from 0.37 to 0.78 eV after embedding the OCQDs, which explains the enhancement of the low resistance state retention based on a filamentary model.

A thermal-assisted electroforming (TAE) method is proposed to address the current overshoot issue and improve the resistive switching (RS) performance of electrochemical metallization (ECM) memory with a Cu/amorphous carbon (a-C)/Pt structure. In the initial electroforming process, thermal treatment can promote the electrochemical formation of metallic conductive filament (CF). The required electroforming voltage is reduced, and the undesirable overshoot current is suppressed. As a result, the RS performance of the cell is improved, including reduced RS parameter fluctuations, enlarged off/on ratio, and enhanced cycling endurance. The cell can be operated with a low compliance current (ICC) of 50 μA, which is among the lowest value of reported a-C-based ECM memories. Benefit from the low ICC, multilevel memory with five nonvolatile resistance states in a single cell is obtained. The main role of the TAE method is interpreted as to avoid the extreme high-temperature caused by the overshoot current. Conductive-atomic force microscopy mapping implies that the suppression of overshoot current can avoid over-injection of Cu cations into the a-C layer, facilitating CF with a simple structure and low randomness. The present work offers a feasible approach for addressing the current overshoot issue and improving the performance of ECM memory.

We report on the microwave absorption properties of Fe@ZnO nanocapsules composed of a ferromagnetic Fe core and a dielectric ZnO shell. By integrating such heterogeneous components in each particle, it results in reciprocal resonances for the relatively complex permeability and permittivity at ∼15 GHz, contributing to efficient complementarities between the dielectric and magnetic losses. Therefore, more than 90% microwave power can be attenuated at 8.2–18 GHz. X-ray photoelectron spectra reveals that the origin of reciprocal resonances is induced by the electronic interactions at Fe and ZnO interfaces. The present work has important implications in the understanding the physical mechanism of dielectric behaviors at heterogeneous interfaces.

The development of high-efficient catalyst simultaneously possessing both the high activity and the remarkable stability is a major focus in fuel cell applications. Herein we utilized an arc-discharge approach with an ultrafast cooling system to synthesize the core@shell structural Au@C nanocomposite, comprising 3~5 nm gold clusters confined within high-defective graphitic layers. Such a construction not only improves the conductivity for accelerating the penetration of ions and electrons during the electro-catalytic process of methanol molecules, but also suppresses the chemical/thermal coarsening of gold clusters. More importantly, the atomic-scale Au/C interfaces contribute to a synergistic effect for enhancing the activity over other gold-based catalysts in the electro-oxidation methanol reaction. This work highlights the role of heterogeneous interfaces on the catalytic efficiency of precious metal catalysts and rationalizes optimization in catalyst engineering.

In this work, we demonstrated the high switching uniformity and 50 fJ/bit energy consumption in an amorphous silicon-based resistive switching (RS) device by inserting the AgInSbTe (AIST) layer between the silicon insulating layer and Ag top electrodes. The improved RS performance is attributed to the introduction of an Ag ion reservoir layer, which helps to suppress conducting filament overgrowth. After insertion of the AIST layer, the cumulative probability of low/high resistance states decreased from 176.8%/46.2% to 3.1%/11.9%, respectively. The advantages of promoting Ag dissolution enable the realization of fast switching speed (

Superparamagnetic core/shell nanoparticles, composed of Fe3O4 cores and biocompatible slica shells, have been utilized as a nano-vehicle for the delivery of peptides. The silica shells with amine groups were functionalized with 1,2-cyclohexanedicarboxylic anhydride as click linkers, forming pH-sensitive amides and terminal carboxylic groups for the conjugation and release of bradykinin B1 receptor antagonist (R-954) peptides. The results show that the loading capacity of R-954 can reach up to 19.8 wt.% of the total mass of Fe3O4/silica/R-954 nanoparticles, which is far higher than non-chemical binding adsorption (1.2 wt.%). In this case, ∼92.3% peptides could be released at pH 5.0 for about 5 h, while only 10.2% occured at pH 7.4. Meanwhile such nanovehicles present a monodispersibility in aqueous solution and thus have a great potential for their use as delivery systems.

We studied the influence of sp2 clustering on resistive switching uniformity in Cu/amorphous carbon/Pt electrochemical metallization memory. Herein, a simple method was utilized to adjust the degree of sp2 clustering by changing compliance currents (CCs). The small sp2 clusters within the a-C layer were found to condense into larger clusters with increasing CCs because of the CC-dependent Joule heating effect. Raman spectra experimentally verified the increase of sp2 cluster diameter with increasing CCs. Importantly, a switching uniformity improvement can be obtained by increasing the degree of sp2 clustering. The enhanced local electric field around sp2 clusters can account for the reduction of the Cu conductive filament randomness and corresponding improvement of memory performance.

In this study, a super-high flexible membrane electrode (FME) was developed via a facile method based on liquid–liquid phase separation involving the migration and self-assembly of the components. Note that the surface segregation and chain orientation of the amphiphilic block copolymer PAA-b-PAN-b-PAA on the membrane surface during the phase separation process provide the hierarchical porous structure and electrolyte-affinity electrode surface; this hierarchical porous structure provides pathways for the electrolyte ions into and from the electrolyte/solution interface for further contact and reaction of the electrochemically active materials with the electrolyte ions. In a three-electrode system, the specific capacitance of FME-Ni(OH)2 can reach up to 2198.6 F g−1 (769.5 C g−1) at the current density of 0.5 A g−1 from 0 to 0.35 V as compared to that for non-flexible Ni(OH)2 (1588.6 F g−1; 556.0 C g−1). Moreover, a flexible asymmetric supercapacitor with FME-Ni(OH)2 as the positive electrode and FME-AC (commercial activated carbon) as the negative electrode showed the high specific capacitance of 102.2 F g−1 (163.5 C g−1) and the maximum energy density of 36.3 W h kg−1 at the power density of 400 W kg−1; moreover, it retained the energy density of 20.6 W h kg−1 at the high power density of 4000 W kg−1 in the potential window ranging from 0 to 1.6 V in a 6 M KOH aqueous solution.

Ultra-small vanadium nitride quantum dots embedded in porous carbon (VNQDs/PC) were fabricated by a thermal treatment process of NH 4 VO 3 /C 3 H 6 N 6 under nitrogen atmosphere. The specific capacitance of VNQDs/PC was 1008 mF cm −2 at a current density of 0.004 A cm −2 , whereas the VN/carbon hybrid material obtained by a solid-state blending of NH 4 VO 3 and C 3 H 6 N 6 just exhibited a capacitance of 432 mF cm −2 at the same current density. By mediating the ratio of NH 4 VO 3 and C 3 H 6 N 6 , a maximum specific capacitance of 1124 mF cm −2 was achieved at a current density of 0.002 A cm −2 in aqueous 6 mol/L KOH electrolyte with the potential range from 0 to −1.15 V when it reached 1: 7 (wt./wt.). Additionally, symmetrical supercapacitor fabricated with synthesized VNQDs/PC presented a high specific capacitance of 215 mF cm −2 at 0.002 A cm −2 based on the entire cell, and exhibited a high capacitance retention of 86.6% with current density increased to 5 A g −1 . The VNQDs/PC negative electrodes were combined with Ni(OH) 2 positive electrodes for the fabrication of hybrid supercapacitors. Remarkably, at a power density of 828.7 W kg −1 , the device delivered an ultrahigh energy density of 47.2 Wh kg −1 .

In this letter, we demonstrated a novel approach to effectively improve the reliability of amorphous carbon (a-C) memory via the insertion of a thin nanoporous TiOxNy layer between the top electrode and the a-C. Owing to the nanoporous structure of TiOxNy, Ag atoms could migrate into the film during the Ag electrode evaporation process, resulting in a pre-formed Ag tip inside the TiOxNy layer. The Ag tip provides an enhancement of the local electric field, and a confinement of the Ag conductive filament (CF) location and Ag atom distribution is therefore created using this method. Compared with its counterpart without a nanoporous layer, the growth of CF into a-C started preferentially from this tip with its simple structure, leading to good switching reliability.

In this article, a facile method based on in-situ phase-separation was developed for the fabrication of ultrathin hybrid membranes for highly flexible supercapacitors. The structures and morphologies of the prepared electrodes were characterized by scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) measurements; and the electrochemical behaviors were examined in 2 M KOH solution. SEM and FTIR characterizations reveal that activated carbon was imbedded into the polymer membrane of polyethersulfone to form a uniform and flexible hybrid membrane. When the thin polymer-carbon membrane (PCM) was used as an electrode material for supercapacitor, a high specific capacitance of 169.4 Fg −1 was obtained at a current density of 0.5 Ag −1 along with good long-term cycle life of 94.6% capacity retention after 2000 charging-discharging cycles. Benefiting from these merits, the as-fabricated PCM//PCM cell shows an excellent electrochemical property. These results suggest a promising route towards the fabrication of highly flexible electrodes for high-performance supercapacitors.

The development of neuromorphic computation faces the appreciable challenge of implementing hardware with energy consumption on the level of a femtojoule per synaptic event to be comparable with the energy consumption of human brain. Controllable ultrathin conductive filaments are needed to achieve such extremely low energy consumption in memristive synapses but their formation is difficult to control owing to their stochastic morphology and unexpected overgrowth. Herein, a zeolite-based memristive synapse is demonstrated for the first time, in which Ag exchange in the sub-nanometer pore closely resembles synaptic Ca2+ dynamics across biomembrane channel. Particularly, the confined ultrasmall pore and low Ag ion migration barrier give the zeolite-based memristive synapse ultralow energy consumption below 10 fJ per synaptic spike, on par with the biological counterpart. Experimental results reveal that the gradual memristive effect is attributed to the dimension modulation of Ag clusters. In addition to emulating inherent cognitive functions through electrical stimulations, the experience-dependent transition of short-term plasticity to long-term plasticity using a chemical modulation method is achieved by treating the initial Ag quantity as a learning experience. The proposed memristors can be used to develop highly efficient memristive neural networks and are considered as a candidate for application in neuromorphic computation.

An energy-efficient memristive synapse is highly desired for the development of brain-like neurosynaptic chips. In this work, a ZnO-based memristive synapse with ultralow-power consumption was achieved by simple N-doping. The introduction of N atoms, as the acceptor, reduces the carrier concentration and greatly increases the resistance of the ZnO film. The low energy consumption, which is as low as 60 fJ per synaptic event, can be achieved in our device. Essential synaptic learning functions have been demonstrated, including excitatory postsynaptic current, paired-pulse facilitation, and experience-dependent learning behaviors. Furthermore, the device can still exhibit the synaptic performance in the bent state or even after 100 bending cycles. Our memristive synapse is not only promising for energy-efficient neuromorphic computing systems but also suitable for the development of wearable neuromorphic electronics.

We demonstrate a forming-free electrochemical metallization resistive memory device (Ag/TiOxNy/Pt) based on the nanoporous titanium oxynitride (TiOxNy) thin film. Due to the nanoporous structure of TiOxNy, Ag atoms can migrate into the film during the Ag electrode evaporation process, resulting in a pre-formed Ag conductive filament inside the switching layer. This is responsible for the forming-free resistive switching behavior. Subsequently, resistive switching with attractive performance is achieved after a reset process, including good endurance, low operation voltages, and fast switching speed. The forming-free and reliable switching characteristics suggest that nanoporous TiOxNy thin film is one of the promising material candidates for future nonvolatile memory applications.

Different metal-oxide films were fabricated by radio frequency magnetron sputtering. Further, a layer of silver nanoparticles (NPs) was deposited on the surface of the substrate by physical sputtering. Photochromism of the silver/metal-oxide nanocomposite films were investigated in situ under the irradiation of a linearly-polarized green laser beam (532 nm). Silver NPs were found to be easily photo-dissolved on the n-type metal-oxide films. By changing experimental conditions, it was also verified that both oxygen and humidity accelerate the photochromism of silver NPs. The corresponding micro-mechanism on charge separation and Ag+-ions mobility was also discussed. These results provided theoretical basis for the application of silver NPs in biological, chemical and medical areas.

The electrochemical hydrogen evolution reaction (HER) is a promising strategy for production of hydrogen; however, it is still restricted by appropriate efficient and low-cost electrocatalysts. Herein, for the first time, the n-octylammonium hypophosphite, a kind of protic ionic liquid (IL), was used as a new phosphorus source for the manufacture of nickel metaphosphate (Ni2P4O12) electrocatalysts. In contrast to traditional multi-step fabrication processes, the n-octylammonium hypophosphite acted as both reactant and solvent to synthesize Ni2P4O12 by a one-step calcination approach. The obtained Ni2P4O12 as an alkaline HER catalyst required a low overpotential of 116 mV at −10 mA cm−2 and a small Tafel slope of 97 mV dec−1, comparable to the majority of reported Ni-based materials and other phosphate catalysts. Furthermore, this catalyst exhibited robust stability with no distinct attenuation of current density after a long-term durability test in 1 M KOH. Therefore, this task-specific IL strategy with a simple reaction system, reducing the occurrence of side reactions, provided a new perspective on design of high-efficiency metaphosphate electrocatalysts.

Emulation of biological synapses by electronic devices will form a foundation for realizing brain‐inspired computational systems. In addition to mimicking functional synapses, it is also important to demonstrate activation functionality of silent synapses in memristors, to emulate the evolutionary processes of human brain development. Here, a silent synapse without synaptic plasticity is achieved in a single‐crystalline TiO2 nanowire‐based memristor. Importantly, the short‐term plasticity transforms to long‐term plasticity in plasma (O2, Ar, and Ar‐H2) treated devices, representing activation of a silent synapse to a functional synapse. The memristive mechanism is attributed to the accumulation and diffusion of oxygen vacancies at the Pt/TiO2 interface, which adjusts the Schottky barrier and conductance. The use of various plasma treatments also enables synaptic function modulation by changing the density of oxygen vacancies. The results provide a feasible method for activating silent synapses and modulating synaptic learning functions in a memristor‐based artificial synapse.

Self-powered memristors have the potential capability to promote highly efficient memory and neuromorphic computing, allowing the exploration of power-free electronics for future. The present study developed a novel moisture-powered memristor, having a multi-layer structure of W/WOx/oxygen-plasma-treated amorphous-carbon (OAC)/Pt. The reversible oxygen migration across the WOx/OAC interface formed between the memristor layer and the nanogenerator layer occurs in this integrated device, which allows simultaneous modulation of resistance state and open circuit voltage (Voc). This device not only presented the reversible characteristics of resistive switching and moisture-powered reading through human breath, but also further demonstrated the capability of the selective reading of multiple memory states for the first time. Cross-sectional transmission electron microscopy observations provided solid evidence of the important role of interfacial oxygen migration, accounting for the mechanism of Voc modulation and resistive switching. This work provides a feasible strategy to build up the self-powered memristor for constructing highly efficient memristive neural networks.

Bipolar resistive-switching (RS) memories were demonstrated based on an Ag/amorphous-carbon (a-C)/Pt sandwich structure. Here, the Ag-nanoclusters (NCs) were embedded into the a-C film via the sputtering deposition and thermal agglomeration. Versus the device without Ag-NCs, the embedding of the Ag-NCs in the a-C film favors the formation of incomplete Ag conducting filaments (CFs). This can act as tip electrodes for the RS. Therein, the local electric field can be enhanced and concentrated and lead to a simplified CF structure. Therefore, embedding Ag-NCs with a proper concentration into the electrolyte layer can effectively decrease the forming/switching voltages and improve the RS uniformity.

In this study, investigation of the unipolar resistive switching (RS) of InGaZnO film indicates that the reset voltage polarity can strongly affect the RS region. The dependence of the RS characteristics on the top electrode (Pt, Al, or Cu) was investigated. Asymmetrical electrodes (Cu/InGaZnO/Al) were chosen and the dependence of the RS parameters (e.g., high and low resistance states, set and reset voltages) on these two diverse electrodes can provide two indicators to trace the location of the RS region. The RS region is usually located near the anode when the applied set and reset voltages have the same polarity. In comparison, when the reset voltage has the opposite polarity to the set voltage, the RS region prefers to be located near the anode of the reset process rather than the cathode (which is used as the anode in the set process), indicating the movement of the RS region during the reset process. With the aid of joule heating, oxygen ions can overcome the energy barrier during the reset process under small voltage, resulting in the CFs restructuring and having the inverse shape, which is responsible for the drift mechanism of the RS region.

A facile method was reported for preparing self-assembly Pt nanochains (PtNCs) by using octreotide acetate (AOC) as template in aqueous environment at room temperature. The influence of pH values on the reaction system was examined, and other synthesis parameters were optimized in order to prepare AOC-templated Pt nanoparticle arrays with high electrocatalytic activities. AOC was found with diameters in the range of 50±5 nm at pH 2.0/9.0, while the diameter of AOC was in the range of 20±5 nm under the condition of pH 4.0. Catalytic activities of the PtNCs prepared with different conditions were investigated, and the results demonstrated that the PtNCs catalyst prepared at pH 4 had higher catalytic activities in relative to those prepared at other conditions. Hence, the PtNCs will be a good anode catalyst candidate for direct methanol fuel cells.

The circular shaped ZnS nanowires were synthesized using genome DNA of Escherichia coli as templates for the first time. The morphology and structure of the products have been characterized by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Cubic sphalerite structure of ZnS nanowires was established by X-ray diffraction (XRD) characterization. The optical properties of the obtained ZnS nanocircles were investigated by Ultraviolet–visible (UV–vis) absorption and photoluminescence (PL) spectra.The possible growth mechanism of the nano-ZnS is briefly discussed.

Current stressing treatment on amorphous carbon (a-C)-based electrochemical metallization (ECM) memory cells before the electroforming process is proposed. The resistive switching (RS) performance of a Cu/a-C/Pt ECM cell after low current (10 μA) stressing treatment is improved, including reduced forming voltages, improved switching uniformity, enhanced cycling endurance, and enhanced switching speed. MicroRaman mapping and conductive-atomic force microscopy measurements reveal that current stressing can cause clustering of sp2 sites in a-C and the conductive filament (CF) randomness is reduced. The reduction of CF nucleation site randomness and enhancement of the local electric field through sp2-clustering are assumed to be responsible for the observed RS performance improvement. The results demonstrate that current stressing is a feasible approach for optimizing the RS performance of a-C-based ECM memory, and it can also be extended to the development of carbon-based electronic devices.