Ultrathin In2O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In₂O₃) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In₂O₃ NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36 mA W⁻¹ and a high specific detectivity of 4.43 × 10¹¹ Jones under 254 nm irradiation, which originates from the smaller charge transfer resistance (R_ct) at the In₂O₃ NSs/electrolyte interface. The light absorption of In₂O₃ NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In₂O₃ NSs PEC PDs is 1567, which is 30 times higher than that of In₂O₃ nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In₂O₃ NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In₂O₃ NSs have potential in underwater optoelectronic devices.     

An Electrically Modulated Single-Color/Dual-Color Imaging Photodetector

An electrically modulated single-/dual-color imaging photodetector with fast response speed is developed based on a small molecule (CO_i8DFIC)/perovskite (CH₃NH₃PbBr₃) hybrid film. Owing to the type-I heterojunction, the device can facilely transform dual-color images to single-color images by applying a small bias voltage. The photodetector exhibits two distinct cut-off wavelengths at ≈544 nm (visible region) and ≈920 nm (near-infrared region), respectively, without any power supply. Its two peak responsivities are 0.16 A W⁻¹ at ≈525 nm and 0.041 A W⁻¹ at ≈860 nm with a fast response speed (≈10² ns). Under 0.6 V bias, the photodetector can operate in a single-color mode with a peak responsivity of 0.09 A W⁻¹ at ≈475 nm, showing a fast response speed (≈10² ns). A physical model based on band energy theory is developed to illustrate the origin of the tunable single-/dual-color photodetection. This work will stimulate new approaches for developing solution-processed multifunctional photodetectors for imaging photodetection in complex circumstances.     

Single Atom Array Mimic on Ultrathin MOF Nanosheets Boosts the Safety and Life of Lithium–Sulfur Batteries

The development of Li–S batteries is largely impeded by the growth of Li dendrites and polysulfide shuttling. To solve these two problems simultaneously, herein the study reports a “single atom array mimic” on ultrathin metal organic framework (MOF) nanosheet-based bifunctional separator for achieving the highly safe and long life Li–S batteries. In the designed separator, the periodically arranged cobalt atoms coordinated with oxygen atoms (Co O₄ moieties) exposed on the surface of ultrathin MOF nanosheets, “single atom array mimic”, can greatly homogenize Li ion flux through the strong Li ion adsorption with O atoms at the interface between anode and separator, leading to stable Li striping/plating. Meantime, at the cathode side, the Co single atom array mimic serves as “traps” to suppress polysulfide shuttling by Lewis acid-base interaction. As a result, the Li–S coin cells with the bifunctional separator exhibit a long cycle life with an ultralow capacity decay of 0.07% per cycle over 600 cycles. Even with a high sulfur loading of 7.8 mg cm⁻², an areal capacity of 5.0 mAh cm⁻² can be remained after 200 cycles. Moreover, the assembled Li–S pouch cell displays stable cycling performance under various bending angles, demonstrating the potential for practical applications.     

Novel SnO2@open microcell-liked graphene network as efficient detection for NO2

Abstract

The design of reduced graphene oxide (RGO) with novel porous structure has attracted tremendous attention owing to their larger specific surface area. Herein, three-dimensional open microcells, bowl-shaped RGO were fabricated through spray drying method which employed polystyrene spheres as a sacrificial template. The bowl-shaped, open microcell-liked pores observed in the RGO network had an average diameter of ≈1?μm. Subsequently, the catalytic SnO₂ nanoparticles were loaded on RGO network via a simple solvothermal method (SnO₂@RGO), and their gas sensing properties were investigated at room temperature (RT). In a comparison with pristine RGO network, the SnO₂@RGO composite exhibited almost 4 times higher response to 400?ppm NO₂ at RT and rapid recovery time. The extraordinary sensing performance can be attributed to the novel open microcell-liked porous microstructure with the SnO₂ catalyst nanoparticles.     

Ultra-High bit rate all-optical AND/OR logic gates based on photonic crystal with multi-wavelength simultaneous operation

In this paper, a novel two-dimensional photonic crystal based all-optical AND/OR logic gates are designed, simulated and optimized. The structure is built on a linear square lattice photonic crystal platform. A multi-wavelength operation, together with a simultaneous operation, is achieved at ultra-high bit rates. The concurrent operation is attained without altering the proposed design continuously, as stated in the literature. It provides simplicity because there is no auxiliary input required along with the absence of externally attached phase shift units. The enhancement process has been done to the rod radius. A magnificent representation tool is developed. The benefit of the mentioned tool lies in the data combination of different operating wavelengths, contrast ratio, and bit rate; which will establish an efficient optimization process. Each gate is enhanced independently, then an overall improvement has been done. As a result, the operation at 1.52?µm will provide a successful multi logic gate operation with ultra-high bit rates of 6.76 and 4.74 Tbit/s for AND and OR logic gates, respectively. The design has an acceptable size of (19.8?×?12.6 µm) and a contrast ratio of 9.74?dB and 17.95?dB for the designed AND and OR gate, respectively. The design is highly sensitive to the waveguide length to verify the gates on demand.     

TiO2 ALD decorated CuO/BiVO4 p-n heterojunction for improved photoelectrochemical water splitting

Bismuth vanadate (BiVO₄) is a promising photoanode material owing to the narrow bandgap, appropriate band position, and excellent resistance against photocorrosion, however, the performance of photoelectrochemical (PEC) water splitting is largely limited by the poor carrier separation and transport ability. To address these issues, for the first time, we fabricate BiVO₄ film/CuO nanocone p-n junctions as photoanodes by combing a facile spin-coating process and water bath reaction. This structure strengthens the light harvesting and promotes the charge separation and transport ability. The surface defects states are passivated by coating conformally ultrathin TiO₂ onto CuO surface through atomic layer deposition (ALD) technique. Benefiting from the favorable morphology, energy band, and surface treatment, the BiVO₄/CuO/TiO₂ heterojunction generates an improved photocurrent that is much higher than pure BiVO₄. The detailed mechanism investigations indicate that the synergetic optimization of charge separation and injection efficiency in the bulk and surface of photoelectrodes can significantly improve the performance of PEC cells.     

Nonlinear THz-Nano Metasurfaces

Extreme terahertz (THz) science and technologies, the next disruptive frontier in nonlinear optics, provide multifaceted capabilities for exploring strong light-matter interactions in a variety of physical systems. However, current techniques involve the need for an extremely high-field free space THz source that is difficult to generate and has limited investigations to a rather weak and linear regime of light-matter interactions. Therefore, new approaches are being sought for the tight confinement of THz waves that can induce nonlinear effects. Here, a nonlinear “tera-nano” metasurface is demonstrated exhibiting extremely large THz nonlinearity and sensitive self-modulation of resonances at moderate incident THz field strengths. A record deep-subwavelength (≈λ/33 000) confinement of strongly enhanced (^≈3200) THz field in a nano-gap (15 nm) exhibits remarkable THz field-tailored nonlinearity. Further, ultrafast injection of photocarriers reveals a competition between nonlinear THz field-induced intervalley scattering and optically driven interband excitations. The results on “tera-nano” metasurfaces enable a novel platform to realize enhanced nonlinear nano/micro composites for field-sensitive extreme THz nonlinear applications without the need for intense THz light sources.     

MEMS四元数卡尔曼滤波算法的电梯姿态估计

将多维MEMS传感器应用于电梯监测,根据电梯的工作特点,优化四元数互补滤波方法修正陀螺仪数据求解电梯的实时姿态,然后应用卡尔曼滤波方法进一步提高姿态监测精度.实际验证表明,该方法可以提高电梯姿态监测数据的准确性,利用运行的姿态角和加速度峰度进行分析、比对可为电梯安全舒适度评估提供关键的数据依据.     

基于深度学习的齿轮视觉微小缺陷检测

针对齿轮视觉微小缺陷,采用一种基于深度学习算法的Mask R-CNN网络进行检测,并对网络进行相应地优化调整.首先,通过比较5种残差神经网络检测效果,选择resnet-101作为图像共享特征提取网络.然后,剔除特征金子塔网络中对特征图P₅进行的不合理的3×3卷积,缺齿检出率指标相应得到提升.最后,为了对候选区域网络进行有效的训练,根据设计的样本标注方案中小范围波动的标注尺寸,设置合适的anchors大小以及宽高比.最终,经过优化的Mask R-CNN网络达到了98.2%缺齿检出率.     

C-V2X边缘缓存中文件请求预测机制

在基于蜂窝通信演进形成的车用无线通信技术(Cellular-Vehicle to everything, C-V2X)场景下, 基站作为多接入边缘计算(Multi-access Edge Computing, MEC)边缘缓存节点可提高用户获取数据的效率, 但其缓存容量有限. 因此, C-V2X中如何准确预测缓存请求内容成为待解决的重要问题. 本文从文件请求的时变性出发, 针对实际的城市场景, 采用Simulation of Urban MObility (SUMO)对交通流进行建模; 其次, 通过采集实际网站分时分类的点击量数据, 并根据各路段交通流规律进行预处理, 构建用户请求模型; 最后, 利用Long Short-Term Memory (LSTM)深度学习模型进行训练, 预测各基站的文件请求. 仿真结果表明, 在网易新闻流行度分布和请求间隔分布形成的文件请求下, vanillaLSTM模型对娱乐类型数据集预测时的均方根误差在1.3左右.