The emulation of human multisensory functions to construct artificial perception systems is an intriguing challenge for developing humanoid robotics and cross‐modal human–machine interfaces. Inspired ...by human multisensory signal generation and neuroplasticity‐based signal processing, here, an artificial perceptual neuro array with visual‐tactile sensing, processing, learning, and memory is demonstrated. The neuromorphic bimodal perception array compactly combines an artificial photoelectric synapse network and an integrated mechanoluminescent layer, endowing individual and synergistic plastic modulation of optical and mechanical information, including short‐term memory, long‐term memory, paired pulse facilitation, and “learning‐experience” behavior. Sequential or superimposed visual and tactile stimuli inputs can efficiently simulate the associative learning process of “Pavlov's dog”. The fusion of visual and tactile modulation enables enhanced memory of the stimulation image during the learning process. A machine‐learning algorithm is coupled with an artificial neural network for pattern recognition, achieving a recognition accuracy of 70% for bimodal training, which is higher than that obtained by unimodal training. In addition, the artificial perceptual neuron has a low energy consumption of ∼20 pJ. With its mechanical compliance and simple architecture, the neuromorphic bimodal perception array has promising applications in large‐scale cross‐modal interactions and high‐throughput intelligent perceptions.
Artificial visual‐tactile perceptual arrays for enhanced memory and neuromorphic computations have promising applications in the field of human‐computer interaction. This work combines mechanoluminescence materials with optoelectronic synapses, which enable tactile and visual perception, learning and memory individually and in concert. With its mechanical compliance and simple structure, this array holds promise for large‐scale cross‐modal interaction and high‐throughput intelligent perception.
Nanoscale phosphorene quantum dots (PQDs) with few-layer structures were fabricated by pulsed laser ablation of a bulk black phosphorus target in diethyl ether. An intense and stable ...photoluminescence (PL) emission of the PQDs in the blue-violet wavelength region is clearly observed for the first time, which is attributed to electronic transitions from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) and occupied molecular orbitals below the HOMO (H-1, H-2), respectively. Surprisingly, the PL emission peak positions of the PQDs are not red-shifted with progressively longer excitation wavelengths, which is in contrast to the cases of graphene and molybdenum disulphide quantum dots. This excitation wavelength-independence is derived from the saturated passivation on the periphery and surfaces of the PQDs by large numbers of electron-donating functional groups which cause the electron density on the PQDs to be dramatically increased and the band gap to be insensitive to the quantum size effect in the PQDs. This work suggests that PQDs with intense, stable and excitation wavelength-independent PL emission in the blue-violet region have a potential application as semiconductor-based blue-violet light irradiation sources.
Tactile sensors with multimode sensing ability are cornerstones of artificial skin for applications in humanoid robotics and smart prosthetics. However, the intuitive and interference-free reading of ...multiple tactile signals without involving complex algorithms and calculations remains a challenge. Herein a pressure–temperature bimodal tactile sensor without any interference is demonstrated by combining the fundamentally different sensing mechanisms of optics and electronics, enabling the simultaneous and independent sensing of pressure and temperature with the elimination of signal separation algorithms and calculations. The bimodal sensor comprises a mechanoluminescent hybrid of ZnS–CaZnOS and a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) thermoresistant material, endowing the unambiguous transduction of pressure and temperature into optical and electrical signals, respectively. This device exhibits the highest temperature sensitivity of −0.6% °C–1 in the range of 21–60 °C and visual sensing of the applied forces at a low limitation of 2 N. The interference-free and light-emitting characteristics of this device permit user-interactive applications in robotics for encrypted communication as well as temperature and pressure monitoring, along with wireless signal transmission. This work provides an unexplored solution to signal interference of multimodal tactile sensors, which can be extended to other multifunctional sensing devices.
All-inorganic CsPb1- xBi xI3 perovskite film was successfully fabricated by incorporating Bi3+ in CsPbI3 to stabilize the cubic lattice. Furthermore, the perovskite film was applied to manufacture a ...simple Ag/CsPb1- xBi xI3/indium tin oxide (ITO) memory device with a bipolar resistive switching behavior. Nonvolatile, reliable, and reproducible switching properties are demonstrated through retention and endurance test under fully open-air conditions. The memory device also presents highly uniform and long-term stable characteristics. Importantly, by modulating the reset stop voltages, multilevel high-resistance states are observed for the first time in lead halide perovskite memory device. The resistive switching behavior is proposed to explain the formation and partial rupture of conductive multifilament that are dominated by the migration of iodine ions and their corresponding vacancies in perovskite film. This study suggests Ag/CsPb1- xBi xI3/ITO device potential application for multilevel data storage in a nonvolatile memory device.
Designing high-efficiency and low-cost bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great significance to produce hydrogen by ...water electrolysis. Herein, a hierarchical FeCo2S4@CoFe layered double hydroxide (LDH) core–shell structure catalyst was successfully fabricated via a hydrothermal–sulfuration–electrodeposition three-step method. The unique structure can provide more abundant catalytically active sites for the electrochemical reaction. The resulting FeCo2S4@CoFe LDH electrode only requires overpotentials of 115 and 247 mV to reach a current density of 10 mA cm−2 for the HER and OER in 1 M KOH electrolyte, respectively. The electrode also exhibits a low Tafel slope and excellent stability. Furthermore, the bifunctional catalyst for overall water splitting can exhibit a cell voltage of 1.6 V at 10 mA cm−2, along with outstanding durability for 24 h testing. This work provides a new strategy to design effective bifunctional catalysts for overall water splitting.
3D organic–inorganic and all‐inorganic lead halide perovskites have been intensively pursued for resistive switching memories in recent years. Unfortunately, instability and lead toxicity are two ...foremost challenges for their large‐scale commercial applications. Dimensional reduction and composition engineering are effective means to overcome these challenges. Herein, low‐dimensional inorganic lead‐free Cs3Bi2I9 and CsBi3I10 perovskite‐like films are exploited for resistive switching memory applications. Both devices demonstrate stable switching with ultrahigh on/off ratios (≈106), ultralow operation voltages (as low as 0.12 V), and self‐compliance characteristics. 0D Cs3Bi2I9‐based device shows better retention time and larger reset voltage than the 2D CsBi3I10‐based device. Multilevel resistive switching behavior is also observed by modulating the current compliance, contributing to the device tunability. The resistive switching mechanism is hinged on the formation and rupture of conductive filaments of halide vacancies in the perovskite films, which is correlated with the formation of AgIx layers at the electrode/perovskite interface. This study enriches the library of switching materials with all‐inorganic lead‐free halide perovskites and offers new insights on tuning the operation of solution‐processed memory devices.
Instability and lead toxicity are two important challenges for the application of 3D lead halide perovskites in resistive switching memories. Dimensional reduction and composition engineering are effective means to overcome these challenges. Herein, low‐dimensional lead‐free inorganic Cs3Bi2I9 and CsBi3I10‐based devices exhibit stable switching with ultrahigh On/Off ratios (≈106) and ultralow operation voltages (as low as 0.12 V).
The design of electrode materials with rational core/shell structures is promising for improving the electrochemical properties of supercapacitors. Hence, hierarchical FeCo2S4@FeNi2S4 core/shell ...nanostructures on Ni foam were fabricated by a simple hydrothermal method. Owing to their structure and synergistic effect, they deliver an excellent specific capacitance of 2393 F g−1 at 1 A g−1 and long cycle lifespan as positive electrode materials. An asymmetric supercapacitor device with FeCo2S4@FeNi2S4 as positive electrode and graphene as negative electrode exhibited a specific capacitance of 133.2 F g−1 at 1 A g−1 and a high energy density of 47.37 W h kg−1 at a power density of 800 W kg−1. Moreover, the device showed remarkable cycling stability with 87.0 % specific‐capacitance retention after 5000 cycles at 2 A g−1. These results demonstrate that the hierarchical FeCo2S4@FeNi2S4 core/shell structures have great potential in the field of electrochemical energy storage.
Nanocomposite electrode: An FeCo2S4@FeNi2S4 composite nanostructure in which FeNi2S4 nanowires evenly coat FeCo2S4 nanoneedles and connect adjacent FeCo2S4 nanoneedles was grown on Ni foam by a mild hydrothermal process. Owing to this structure and the synergistic effect, an FeCo2S4@FeNi2S4 supercapacitor electrode showed excellent specific capacitance and good cycling stability (see figure).
Lead halide perovskites‐based memory devices have attracted considerable interest due to their unique current–voltage (I–V) hysteresis. Herein, all‐inorganic CsPbI3 perovskite film surviving 30 d of ...air storage is prepared by using a poly‐vinylpyrrolidone‐assisted passivation method under fully open‐air condition. Afterwards, a memory device with a sandwich structure of Ag/CsPbI3/indium tin oxide is manufactured. From I–V characteristics of pristine device, a spontaneous reaction between the active Ag electrode and I− ions under air exposure is suggested. Furthermore, complete degradation of Ag electrode and formation of AgIx are verified, which also accompanies with generation of more iodine vacancies (VI) in perovskite film. The memory device with AgIx layer shows a bipolar resistive switching behavior, ultrahigh ON/OFF ratio (above 106), nonvolatile, reliable, and reproducible switching performance. Cell area and temperature dependent characteristics propose that the resistive switching is dominated by VI filament in low‐resistance state and thermally assisted hopping in high‐resistance state. This study provides a new insight to understand switching behavior from the way of electrode degradation and metal iodide formation in lead iodide perovskites‐based memory devices and also suggests a potential application for AgIx‐induced resistive switching in CsPbI3‐based memory device.
All‐inorganic CsPbI3 perovskite film is prepared by using a poly‐vinylpyrrolidone‐assisted passivation method. Complete degradation of Ag electrode and formation of AgIx in memory device of Ag/CsPbI3/indium tin oxide are verified which also accompanies with generation of more iodine vacancies. The memory device with AgIx layer shows a bipolar resistive switching behavior, ultrahigh ON/OFF ratio, nonvolatile, reliable, and reproducible switching performance.
Halide perovskites featuring remarkable optoelectronic properties hold great potential for threshold switching devices (TSDs) that are of primary importance to next-generation memristors and ...neuromorphic computers. However, such devices are still in their infancy due to the unsolved challenges of high threshold voltage, poor stability, and lead-containing features. Herein, a unipolar TSD based on an all-inorganic halide perovskite of CsCu2I3 is demonstrated, exhibiting the fascinating attributes of a low threshold voltage of 0.54 V, a high ON/OFF ratio of 104, robust air stability over 70 days, a steep switching slope of 6.2 mV·decade–1, and lead-free composition. Moreover, the threshold voltage can be further reduced to 0.23 V using UV illumination to reduce the barrier of iodide ion migration. The multilevel threshold switching behavior can be realized through the modulation of either the compliance current or the scan rate. The TSD with mechanical compliance and transparency is also demonstrated. This work enriches TSDs with expanded perovskite materials, boosting the related applications of this emerging class of device families.
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