Robust chelated lead octahedron surface for efficient and stable perovskite solar cells.

PbI octahedron as a fundamental framework endows the perovskite with excellent photoelectric properties, but also the defective and flimsy surface. Here, we report that the treatment of perovskite surface by bidentate ligands molecules N, N'-Dimethyl-1,2-ethanediamine can in-situ form a lead iodide chelates layer with excellently robust chelated lead octahedron, leading to effectively stabilize and passivate the underlying perovskite. The strong chelation with the lead enables the surface to largely inhibit the defects generation, iodide ion migration and skeleton collapse under external stimuli.

Optical engineering of infrared PbS CQD photovoltaic cells for wireless optical power transfer systems.

Infrared photovoltaic cells (IRPCs) have attracted considerable attention for potential applications in wireless optical power transfer (WOPT) systems. As an efficient fiber-integrated WOPT system typically uses a 1550 nm laser beam, it is essential to tune the peak conversion efficiency of IRPCs to this wavelength. However, IRPCs based on lead sulfide (PbS) colloidal quantum dots (CQDs) with an excitonic peak of 1550 nm exhibit low short circuit current (J) due to insufficient absorption under monochromatic light illumination.

Artificial Neural Pathway Based on a Memristor Synapse for Optically Mediated Motion Learning.

Animals execute intelligent and efficient interactions with their surroundings through neural pathways, exhibiting learning, memory, and cognition. Artificial autonomous devices that generate self-optimizing feedback mimicking biological systems are essential in pursuing future intelligent robots. Here, we report an artificial neural pathway (ANP) based on a memristor synapse to emulate neuromorphic learning behaviors.

Strain-Enabled Phase Transition of Periodic Metasurfaces.

Phase transitions are universal in solid-state matters, as well as in periodic electromagnetic metasurfaces-the photonic analogues of crystals. Although such transitions dictate the properties of active metasurfaces, universal ways to describe the structure transition of periodic metasurfaces have not yet been established. Here, the authors report the strain-enabled phase transition (or lattice deformation) of stretchable metasurfaces with the crystallographic description.

Ultra-narrowband perfect absorption of monolayer two-dimensional materials enabled by all-dielectric subwavelength gratings.

Monolayer two-dimensional materials (2DMs) have excellent optical and electrical properties and show great application potential in photodetectors. However, the thickness at the atomic scale leads to weak light absorption, which greatly limits the responsivity of corresponding photodetectors. Here we propose an all-dielectric sub-wavelength zero-contrast grating structure that enables a monolayer of MoS with ultra-narrow bandwidth perfect light absorption.

An Artificial Somatic Reflex Arc.

The emulation of human sensation, perception, and action processes has become a major challenge for bioinspired intelligent robotics, interactive human-machine interfacing, and advanced prosthetics. Reflex actions, enabled through reflex arcs, are important for human and higher animals to respond to stimuli from environment without the brain processing and survive the risks of nature. An artificial reflex arc system that emulates the functions of the reflex arc simplifies the complex circuit design needed for "central-control-only" processes and becomes a basic electronic component in an intelligent soft robotics system.

Broadband Extrinsic Self-Trapped Exciton Emission in Sn-Doped 2D Lead-Halide Perovskites.

As emerging efficient emitters, metal-halide perovskites offer the intriguing potential to the low-cost light emitting devices. However, semiconductors generally suffer from severe luminescence quenching due to insufficient confinement of excitons (bound electron-hole pairs). Here, Sn-triggered extrinsic self-trapping of excitons in bulk 2D perovskite crystal, PEA PbI (PEA = phenylethylammonium), is reported, where exciton self-trapping never occurs in its pure state.

Confinement of Perovskite-QDs within a Single MOF Crystal for Significantly Enhanced Multiphoton Excited Luminescence.

The development of the photostable higher-order multiphoton-excited (MPE) upconversion single microcrystalline material is fundamentally and technologically important, but very challenging. Here, up to five-photon excited luminescence in a host-guest metal-organic framework (MOF) and perovskite quantum dot (QD) hybrid single crystal ZJU-28⊃MAPbBr is shown via an in situ growth approach. Such a MOF strategy not only results in a high QD loading concentration, but also significantly diminishes the aggregation-caused quenching (ACQ) effect, provides effective surface passivation, and greatly reduces the contact of the QDs with the external bad atmosphere due to the confinement effect and protection of the framework.

Tactile Chemomechanical Transduction Based on an Elastic Microstructured Array to Enhance the Sensitivity of Portable Biosensors.

Tactile sensors capable of perceiving biophysical signals such as force, pressure, or strain have attracted extensive interest for versatile applications in electronic skin, noninvasive healthcare, and biomimetic prostheses. Despite these great achievements, they are still incapable of detecting bio/chemical signals that provide even more meaningful and precise health information due to the lack of efficient transduction principles. Herein, a tactile chemomechanical transduction strategy that enables the tactile sensor to perceive bio/chemical signals is proposed.

Enhancing the Matrix Addressing of Flexible Sensory Arrays by a Highly Nonlinear Threshold Switch.

The increasing need for smart systems in healthcare, wearable, and soft robotics is creating demand for low-power sensory circuits that can detect pressure, temperature, strain, and other local variables. Among the most critical requirements, the matrix circuitry to address the individual sensor device must be sensitive, immune to disturbances, and flexible within a high-density sensory array. Here, a strategy is reported to enhance the matrix addressing of a fully integrated flexible sensory array with an improvement of 10 fold in the maximum readout value of impedance by a bidirectional threshold switch.

Correlating the Surface Basicity of Metal Oxides with Photocatalytic Hydroxylation of Boronic Acids to Alcohols.

Photoredox catalysis provides opportunities in harnessing clean and green resources such as sunlight and O , while the acid and base surface sites of metal oxides are critical for industrial catalysis such as oil cracking. The contribution of metal oxide surfaces towards photocatalytic aerobic reactions was elucidated, as demonstrated through the hydroxylation of boronic acids to alcohols. The strength and proximity of the surface base sites appeared to be two key factors in driving the reaction; basic and amphoteric oxides such as MgO, TiO , ZnO, and Al O enabled high alcohol yields, while acidic oxides such as SiO and B O gave only low yields.

3D-Structured Stretchable Strain Sensors for Out-of-Plane Force Detection.

Stretchable strain sensors, as the soft mechanical interface, provide the key mechanical information of the systems for healthcare monitoring, rehabilitation assistance, soft exoskeletal devices, and soft robotics. Stretchable strain sensors based on 2D flat film have been widely developed to monitor the in-plane force applied within the plane where the sensor is placed. However, to comprehensively obtain the mechanical feedback, the capability to detect the out-of-plane force, caused by the interaction outside of the plane where the senor is located, is needed.

Mediating Short-Term Plasticity in an Artificial Memristive Synapse by the Orientation of Silica Mesopores.

Memristive synapses based on resistive switching are promising electronic devices that emulate the synaptic plasticity in neural systems. Short-term plasticity (STP), reflecting a temporal strengthening of the synaptic connection, allows artificial synapses to perform critical computational functions, such as fast response and information filtering. To mediate this fundamental property in memristive electronic devices, the regulation of the dynamic resistive change is necessary for an artificial synapse.

Auxetic Mechanical Metamaterials to Enhance Sensitivity of Stretchable Strain Sensors.

Stretchable strain sensors play a pivotal role in wearable devices, soft robotics, and Internet-of-Things, yet these viable applications, which require subtle strain detection under various strain, are often limited by low sensitivity. This inadequate sensitivity stems from the Poisson effect in conventional strain sensors, where stretched elastomer substrates expand in the longitudinal direction but compress transversely. In stretchable strain sensors, expansion separates the active materials and contributes to the sensitivity, while Poisson compression squeezes active materials together, and thus intrinsically limits the sensitivity.

Highly Stretchable, Compliant, Polymeric Microelectrode Arrays for In Vivo Electrophysiological Interfacing.

Polymeric microelectrode arrays (MEAs) are emerging as a new generation of biointegrated microelectrodes to transduce original electrochemical signals in living tissues to external electrical circuits, and vice versa. So far, the challenge of stretchable polymeric MEAs lies in the competition between high stretchability and good electrode-substrate adhesion. The larger the stretchability, the easier the delamination of electrodes from the substrate due to the mismatch in their Young's modulus.

A series of multifunctional coordination polymers based on terpyridine and zinc halide: second-harmonic generation and two-photon absorption properties and intracellular imaging.

How can imaging be improved? Coordination polymers (CPs) show fascinating potential in optoelectronic optics but limited potential in bioimaging. Without doubt, it was very meaningful when CPs were first used in second-harmonic generation (SHG) imaging. Herein, through reasonable design and synthesis, a series of nonlinear optical CPs bearing very good one-photon excited fluorescence (OPEF), two-photon excited fluorescence (TPEF) and very strong SHG properties has been presented.

Stretchable Motion Memory Devices Based on Mechanical Hybrid Materials.

Animals possess various functional systems such as sensory, nervous, and motor systems, which show effective cooperation in order to realize complicated and intelligent behaviors. This inspires rational designs for the integration of individual electronic devices to exhibit a series of functions, such as sensing, memory, and feedback. Inspired by the fact that humans can monitor and memorize various body motions, a motion memory device is developed to mimic this biological process.

3D Printed Photoresponsive Devices Based on Shape Memory Composites.

Compared with traditional stimuli-responsive devices with simple planar or tubular geometries, 3D printed stimuli-responsive devices not only intimately meet the requirement of complicated shapes at macrolevel but also satisfy various conformation changes triggered by external stimuli at the microscopic scale. However, their development is limited by the lack of 3D printing functional materials. This paper demonstrates the 3D printing of photoresponsive shape memory devices through combining fused deposition modeling printing technology and photoresponsive shape memory composites based on shape memory polymers and carbon black with high photothermal conversion efficiency.

High-Adhesion Stretchable Electrodes Based on Nanopile Interlocking.

High-adhesion stretchable electrodes are fabricated by utilizing a novel nanopile interlocking strategy. Nanopiles significantly enhance adhesion and redistribute the strain in the film, achieving high stretchability. The nanopile electrodes enable simultaneous monitoring of electromyography signals and mechanical deformations.

Soft Thermal Sensor with Mechanical Adaptability.

A soft thermal sensor with mechanical adaptability is fabricated by the combination of single-wall carbon nanotubes with carboxyl groups and self-healing polymers. This study demonstrates that this soft sensor has excellent thermal response and mechanical adaptability. It shows tremendous promise for improving the service life of soft artificial-intelligence robots and protecting thermally sensitive electronics from the risk of damage by high temperature.

Low Cytotoxic Metal-Organic Frameworks as Temperature-Responsive Drug Carriers.

Two zinc-based porous metal-organic frameworks, ZJU-64 and ZJU-64-CH , sharing the same crystal structure, have been synthesized from zinc ions, the biomolecular linker adenine, and carboxylate-based ligands, resulting in 3D frameworks with 1D channels (approximately 1.6 nm×1.9 nm).

Low Cytotoxic Metal-Organic Frameworks as Temperature-Responsive Drug Carriers.

Invited for this month's cover is the group of Prof. Guodong Qian from Zhejiang University, China. The cover picture shows low cytotoxic metal-organic frameworks (MOFs) used as drug carriers, whose drug release behavior can be tuned by controlling the temperature.

Alcohol-Mediated Resistance-Switching Behavior in Metal-Organic Framework-Based Electronic Devices.

Metal-organic frameworks (MOFs) have drawn increasing attentions as promising candidates for functional devices. Herein, we present MOF films in constructing memory devices with alcohol mediated resistance switching property, where the resistance state is controlled by applying alcohol vapors to achieve multilevel information storage. The ordered packing mode and the hydrogen bonding system of the guest molecules adsorbed in MOF crystals are shown to be the reason for the alcohol mediated electrical switching.

Polarized three-photon-pumped laser in a single MOF microcrystal.

Higher order multiphoton-pumped polarized lasers have fundamental technological importance. Although they can be used to in vivo imaging, their application has yet to be realized. Here we show the first polarized three-photon-pumped (3PP) microcavity laser in a single host-guest composite metal-organic framework (MOF) crystal, via a controllable in situ self-assembly strategy.