A memristor and artificial synapse based on a ZnO–phosphorene nano-heterojunction are demonstrated. The continuous internal resistance states and multi-wavelength response of the memristor are applied to emulate the functions of the artificial synapse including PPF, SRDP, STDP and STP to LTP transition.

High-performance photonic nonvolatile memory combining photosensing and data storage with low power consumption ensures the energy efficiency of computer systems. This study first reports in situ derived phosphorene/ZnO hybrid heterojunction nanoparticles and their application in broadband-response photonic nonvolatile memory. The photonic nonvolatile memory consistently exhibits broadband response from ultraviolet (380 nm) to near infrared (785 nm), with controllable shifts of the SET voltage. The broadband resistive switching is attributed to the enhanced photon harvesting, a fast exciton separation, as well as the formation of an oxygen vacancy filament in the nano-heterojunction. In addition, the device exhibits an excellent stability under air exposure compared with reported pristine phosphorene-based nonvolatile memory. The superior antioxidation capacity is believed to originate from the fast transfer of lone-pair electrons of phosphorene. The unique assembly of phosphorene/ZnO nano-heterojunctions paves the way toward multifunctional broadband-response data-storage techniques.

The flexible piezoresistive sensor has attracted more and more attention in health monitoring as a man−machine interface due to its simple structure and convenient signal reading. Herein, a highly sensitive flexible piezoresistive sensor with a 3D conductive sensing unit is presented. The 3D conductive sensing unit consists of a 3D network thermoplastic elastomer (TPE) substrate fabricated by fused deposition molding (FDM) 3D printing and carbon nanotubes (CNTs) conductive layer embedded into the surface of the TPE substrate. The finite element analysis (FEA) shows that the 3D network structure has excellent mechanical properties, which is basically consistent with the experimental results. Experimentally, based on the novel 3D conductive network, the flexible piezoresistive sensor exhibits superior comprehensive properties in the compressed or stretched state. The sensitivity of the sensor is as high as 136.8 kPa −1 at an applied pressure <200 Pa while compressing, and its gauge factor (GF) can reach 6.85 while stretching. Meanwhile, the sensor shows excellent stability and durability performance because CNTs embedded into the surface of the TPE substrate have little effect on the flexibility of the elastomeric composite of the sensor. Finally, the piezoresistive sensor is used for detecting subtle muscular movements (facial expressing and throat swallowing) and body movement like arm bending. These results indicate that the novel 3D conductive structure provides an alternative way to improve the performance of piezoresistive sensors and extend their potential applications in health monitoring.

Here, ultrahigh sensitivity flexible pressure sensors comprised of 3D‐printing flexible hollow microstructure substrates, gold film spray‐coated on the substrates, and Ag interdigital electrodes are reported. The finite element analysis (FEA) shows that the hollow microcylinder structure has better compression performance compared to solid microcylinder structure. Diverse solid and hollow microstructures, such as microcylinder, microsawtooth, and microrectangle structures are built to investigate the performance difference. The sensitivity of the sensor with hollow microcylinder structure is nearly 100% higher than that of the solid microcylinder structure sensor. By comparing the sensors with different spray‐coating time of Au nanoparticles, the influence of electrode microcrack on sensitivity is revealed. The flexible hollow microcylinder structure sensor with electrode microcrack effect shows ultrahigh sensitivity of 419.622 kPa−1 in the ultralow pressure range (< 100 Pa), rapid response time (30.76 ms), and recovery time (15.17 ms). To show the great performance of the sensor, it is used to detect human physiological signals such as cheek bulging, throat swallowing, and artery pulse. To realize the spatial sensing resolution, a 3 × 4 pressure sensor array is fabricated. The applications of the sensor may pave the way in human physiological signals monitoring and electronic skins in the future.

The coherent developments of high performance broadband photodetection and a discrimination technique are highly essential for multiscene imaging and optical communication applications. The integration of traditional bandpass filters or stacking other spectral absorber in photodetectors often complicates the device design and leads to asymmetric photogain for each waveband. Herein, we report on ultraviolet–visible (UV-vis) multispectral photodetection based on a single ZnO nanowire (NW) phototransistor, where defect reconstructions can be reliably induced by a two-step annealing that leads to the observed broadband photodetection. Electron paramagnetic resonance and photoluminescence spectra reveal the reconstructions of zinc-atom-related defects (i.e., zinc interstitials and vacancies). Combined microdifferential reflectance and multimode scanning probe microscope (SPM) technique confirm the presence of a unique visible-sensitive Zn-rich ZnO shell layer and a trap-free UV-sensitive ZnO core. We achieve not only an ultrahigh carrier mobility (212.4 cm2 V–1 s–1), but also a concurrent improvement for UV-vis photodetection with superior responsivities and detectivities on the orders of 105 AW–1 and 1015 Jones at 100 mV, respectively, and response speeds less than one second. Moreover, photocurrents under blue, green, and red stimuli can be selectively switched on/off by tuning the gate stress. These high performances in all figures of merit have opened new routes to tailor intrinsic properties of a single NW for optoelectronic applications.

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multiple capabilities in transistors, [2] biomedicine, [3] energy storage and conversion applications. [4] Thanks to its thicknessdependent band structure and anisotropic feature, explorations for basic optical properties of BP have recently been extensively performed, including layer-dependent optical absorption, [5] excitonic transition, [6] fluorescent engineering, [7] and polarized Raman behaviors, [8] which provide a lightmatter interaction platform to access novel electron-phonon phenomena. [9] Nevertheless, few methodologies have been developed to tune Raman scattering intensity of few-layer BP. In general, solvent exfoliated BP possess the damaged interlayer structure and abundant trap states, which suppress the extraction of Raman scattering signals as compared with mechanically cleaved ones. [10] Noble metal nanoparticles are often used to enhance Raman scattering of small molecules through a classic electromagnetic enhancement mechanism. Very recently, several attempts on noble metals loaded on few-layer BP have shown very limited effect, [11] indicating a strong near-field electron-phonon coupling is not so easy to obtain for BP. Inspired by charge transfer Black phosphorus (BP) has recently triggered an unprecedented interest in the 2D community. However, many of its unique properties are not exploited and the well-known environmental vulnerability is not conquered. Herein, a type-I mixed-dimensional (0D-1D) van der Waals heterojunction is developed, where three-atomic-layer BP quantum dots (QDs) are assembled on a single ZnO nanorod (NR). By adjusting the indium (In) content in ZnO NRs, the degree and even the direction of surface charge transfer doping within the heterojunction can be tuned, which result in selective Raman scattering enhancements between ZnO and BP. The maximal enhancement factor is determined as 4340 for BP QDs with sub-ppm level. Furthermore, an unexpected long-term ambient stability (more than six months) of BP QDs is revealed, which is ascribed to the electron doping from ZnO:In NRs. The first demonstration of selective Raman enhancements between two inorganic semiconductors as well as the improved stability of BP shed light on this emerging 2D material. Raman Modulation

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