Direct Polarimetric Image Sensor and Wide Spectral Response Based on Quasi-1D Sb2S3 Nanowire

Polarized photodetectors with wide spectral detection and ultra-fast photoresponses based on anisotropic semiconductors have potential applications in military and civilian fields and have been widely studied in recent years. The dual advantages of low-symmetry crystal structure and special electronic band-structure make Sb₂S₃ the perfect choice for polarized photodetection. In this work, the optical, vibrational, and optoelectronic anisotropy of the high-quality orthorhombic Sb₂S₃ nanowires are systematically investigated by experimental and theoretical studies. The metal-semiconductor-metal photodetectors based on a single Sb₂S₃ nanowire exhibit good polarization sensitivity in a broadband range from ultraviolet to near-infrared (360 to 1550 nm) and the obtained maximum dichroic ratio is 2.54 at 638 nm. The polarization-sensitive photocurrent mapping results show that the photocurrent is mainly derived from the Schottky junction at the interface between Au and Sb₂S₃. The effective separation of the photo-generated carriers near the Schottky junction gives a photodetector response time of 470 µs. The direct polarimetric imaging demonstrates that the gray value of the image obtained by the imaging system is sensitive to the object's polarized direction. This natural sensitivity of the Sb₂S₃-based photodetector to polarized objects makes it possible to image polarized objects directly as an image sensor.     

改进混合积累的单通道机载SAR高径向速度目标检测方法

高径向速度目标会产生严重的距离走动并伴随方位失配,方位压缩会使其散焦并弥散在SAR图像中,不易被检测。该文针对高径向速度目标的检测问题,提出一种基于单通道机载SAR的检测方法。该方法通过抽取等效双通道,利用相干对消抑制杂波,并去除动目标的频谱分裂,再运用Dechirp处理和Hough变换积累目标在距离单元内和距离单元间的能量,以获得更大的积累增益。与传统的混合积累方法相比,该方法在抑制杂波的基础上,更好地积累高径向速度目标的能量,从而有效提高该类目标的检测性能。仿真数据和实测数据均验证了该方法的有效性和优越性。     

交替收发模式下SAR-GMTI沿航迹基线形式及其影响分析

采用子孔径交替收发的工作模式,可以增加沿航迹基线长度和相位中心个数,是提升单平台多通道SAR系统地面动目标检测(GMTI)性能的有效途径。该文在建立交替收发模式下多通道动目标信号模型的基础上,通过分析推导明确了形成GMTI基线的必备条件。以建立的模型和推导为依据,给出了交替收发工作模式的设计考虑,通过对同一系统采用不同天线孔径划分和交替方式下的GMTI性能的比较,说明了合理选择天线孔径划分和交替方式对提升GMTI性能的重要性。仿真和实测数据处理结果验证了结论的正确性。     

A Fluorophore‐Doped Polymer Nanomaterial for Referenced Imaging of pH and Temperature with Sub‐Micrometer Resolution

A new kind of pH and temperature sensitive material is reported. It is composed of dye‐doped polymer nanoparticles incorporated into a thin film of a polyurethane hydrogel. The new pH/temperature‐sensitive nanoparticles are obtained by post‐staining oxygen‐impermeable amino‐functionalized polyacrylonitrile nanoparticles with a long‐lifetime reference dye. Staining is followed by covalently linking fluorescein isothiocyanate onto the surface of the nanoparticle. The new sensor material has several distinct features: a) it enables imaging of pH via time domain dual‐lifetime referencing; b) effects of temperature on pH sensing may be compensated for; and c) temperature can simultaneously be visualized via rapid lifetime imaging. The new material enables referenced and temperature‐compensated pH imaging with superior spatial resolution due to the use of nanosized sensor nanoparticles.     

Self‐Assembled Sugar‐Substituted Perylene Diimide Nanostructures with Homochirality and High Gas Sensitivity

A new symmetrical sugar‐based perylenediimide derivative PTCDI‐BAG is synthesized and its aggregate morphologies and formation mechanisms are studied in detail in the mixed solvent system water/N,N‐dimethylformamide (H₂O/DMF) with changing volume ratios. PTCDI‐BAG molecules self‐assemble into planar ribbons in 20/80 and 40/60 H₂O/DMF (v/v), but their chiralities are opposite according to recorded circular dichroism (CD) spectra. With a further increase of the water content, only left‐handed helical nanowires are obtained in 60/40 and 80/20 H₂O/DMF (v/v) mixtures. By combining density functional theory (DFT) calculations with the experimental investigations, it is proposed that kinetic and thermodynamic factors play key roles in tuning PTCDI‐BAG structures and helicity. The formation of the ribbon is thermodynamically controlled in the 20/80 H₂O/DMF system, but kinetically controlled nucleation followed by thermodynamically controlled self‐assembly plays the governing roles for the formation of nanoribbons in 40/60 H₂O/DMF. Devices based on single nanoribbons for hydrazine sensing exhibit better performance than nanofiber bundles obtained in this study and achiral nanostructures reported in previous study. This study not only provides an elaborated route to tuning the structures and helicity of PTCDI molecules, but also provides new possibilities for the construction of high‐performance nanodevices.     

Robust H ∞ Control for a Class of Uncertain Neutral Stochastic Systems with Mixed Delays: a CCL Approach

In this paper, the problem of robust H _∞ control for a class of uncertain neutral stochastic systems with mixed delays is investigated. The parameter uncertainties are assumed to be norm-bounded. A delay-dependent sufficient condition is derived in terms of the nonlinear matrix inequality by constructing proper Lyapunov–Krasovskii functional, using matrix inequality techniques and introducing free weighting matrices. The new result obtained in this paper can be tested numerically by using the so-called cone complementarity linearization (CCL) algorithm. Two examples provided in the literature show the effectiveness of the proposed approach.     

Precisely Controlled Microsphere Design via Visible‐Light Cross‐Linking of Functional Prepolymers

A new strategy for particle synthesis is enabled by utilizing modern synthetic, polymer, and photochemical techniques to facilitate the synthesis of highly narrow–disperse multifunctional microspheres from visible‐light induced crosslinking of prepolymers in both a single and dual polymer system. The approach requires no stabilizers, bases, or initiators, and proceeds at ambient temperature to yield microspheres with a tunable size range (0.25–5 µm) in less than 4 h, depending largely on solvent composition, but also polymer concentration (2–10 mg mL^?1), ratio, and irradiation intensity (3–20 W). Critically, the visible‐light induced dimerization reaction exploited herein enables simple functional particle syntheses via a single polymer system. Underpinned by an in‐depth kinetic analysis of the particle formation as well as a detailed small molecule study, the mechanism for particle formation is also elucidated. Importantly, inherent advantages of the system are exploited for surface functionalization of residual acrylate and hydroxyl groups (generating inherently fluorescent particles).     

Green Biocomposites for Thermoelectric Wearable Applications

The materials commonly used to fabricate thermoelectric devices are tellurium, lead, and germanium. These materials ensure the best thermoelectric performance, but exhibit drawbacks in terms of availability, sustainability, cost, and manufacturing complexity. Moreover, they do not guarantee a safe and cheap implementation in wearable thermoelectric applications. Here, p‐Type and n‐type flexible thermoelectric textiles are produced with sustainable and low‐cost materials through green and scalable processes. Cotton is functionalized with inks made with biopolyester and carbon nanomaterials. Depending on the nanofiller, i.e., graphene nanoplatelets, carbon nanotubes, or carbon nanofibers, positive or negative Seebeck coefficient values are obtained, resulting in a remarkable electrical conductivity value of 55 S cm^?1 using carbon nanotubes. The best bending and washing stability are registered for the carbon nanofiber‐based biocomposites, which increase their electrical resistance by 5 times after repeated bending cycles and only by 30% after washing. Finally, in‐plane flexible thermoelectric generators coupling the best p‐ and n‐type materials are fabricated and analysed, resulting in an output voltage of ≈1.65 mV and a maximum output power of ≈1.0 nW by connecting only 2 p/n thermocouples at a temperature difference of 70 °C.     

Functionality of Dual‐Phase Lithium Storage in a Porous Carbon Host for Lithium‐Metal Anode

Lithium (Li) metal is regarded as the most attractive anode material for high‐energy Li batteries, but it faces unavoidable challenges—uncontrollable dendritic growth of Li and severe volume changes during Li plating and stripping. Herein, a porous carbon framework (PCF) derived from a metal–organic framework (MOF) is proposed as a dual‐phase Li storage material that enables efficient and reversible Li storage via lithiation and metallization processes. Li is electrochemically stored in the PCF upon charging to 0 V versus Li/Li⁺ (lithiation), making the PCF surface more lithiophilic, and then the formation of metallic Li phase can be induced spontaneously in the internal nanopores during further charging below 0 V versus Li/Li⁺ (metallization). Based on thermodynamic calculations and experimental studies, it is shown that atomically dispersed zinc plays an important role in facilitating Li plating and that the reversibility of Li storage is significantly improved by controlled nanostructural engineering of 3D porous nanoarchitectures to promote the uniform formation of Li. Moreover, the MOF‐derived PCF does not suffer from macroscopic volume changes during cycling. This work demonstrates that the nanostructural engineering of porous carbon structures combined with lithiophilic element coordination would be an effective approach for realizing high‐capacity, reversible Li‐metal anodes.