Dispersion-Enabled Symmetry Switching of Photonic Angular-Momentum Coupling

Photonic spin-orbit interactions describe the interactions between spin angular momentum and orbital angular momentum of photons, which play essential roles in subwavelength optics. However, the influence of frequency dispersion on photonic angular-momentum coupling is rarely studied. Here, by elaborately designing the contribution of the geometric phase and waveguide propagation phase, the dispersion-enabled symmetry switching of photonic angular-momentum coupling is experimentally demonstrated. This notion may induce many exotic phenomena and be found in enormous applications, such as the spin-Hall effect, optical calculation, and wavelength division multiplexing systems. As a proof-of-concept demonstration, two metadevices, a multi-channel vectorial vortex beam generator and a phase-only hologram, are applied to experimentally display optical double convolution, which may offer additional degrees of freedom to accelerate computing and a miniaturization configuration for optical convolution without collimation operation. These results may provide a new opportunity for complex vector optical field manipulation and calculation, optical information coding, light-matter interaction manipulation, and optical communication.     

A Low-Hysteresis and Highly Stretchable Ionogel Enabled by Well Dispersed Slidable Cross-Linker for Rapid Human-Machine Interaction

Ionic conductive soft materials for mimicking human skin are a promising topic since they can be thought of as a possible basis for biomimetic sensing. In pursuit of devices with a long working range and low signal delay, conductive materials with low hysteresis and good stretchability are highly demanded. To overcome the challenges of highly stretchable conductive materials with good resilience, herein a chemical design is proposed where polyrotaxanes act as topological cross-linkers to enhance the stretchability by sliding-induced reduced stress concentration while the compatible ionic liquid is introduced as a dispersant for low hysteresis. The obtained ionogels exhibit versatile properties more than low hysteresis (residual strain = 7%) and good stretchability (550%), and also anti-fatigue, biocompatibility, and good adhesion. The low hysteresis is attributed to lower energy dissipation from the well-dispersed polyrotaxanes by compatible ionic liquids. The mechanism provides a new insight in fabricating highly stretchable and low-hysteresis slide-ring materials. Furthermore, the conductivity of the ionogels and their responses to strains and temperatures are measured. Benefiting from the good conductivity and low hysteresis, the ionogel is applied to develop a wireless communication system to realize rapid human-machine interactions.     

Adhesion and Surface Interactions of a Self‐Healing Polymer with Multiple Hydrogen‐Bonding Groups

The surface properties and self‐adhesion mechanism of self‐healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2‐ureido‐4[1H]‐pyrimidinone quadruple hydrogen bonding groups (UPy) are investigated using a surface forces apparatus (SFA) coupled with a top‐view optical microscope. The surface energies of PBA–UPy4.0 and PBA–UPy7.2 (with mole percentages of UPy 4.0% and 7.2%, respectively) are estimated to be 45–56 mJ m^?2 under dry condition by contact angle measurements using a three probe liquid method and also by contact and adhesion mechanics tests, as compared to the reported literature value of 31–34 mJ m^?2 for PBA, an increase that is attributed to the strong UPy–UPy H‐bonding interactions. The adhesion strengths of PBA–UPy polymers depend on the UPy content, contact time, temperature and humidity level. Fractured PBA–UPy films can fully recover their self‐adhesion strength to 40, 81, and 100% in 10 s, 3 h, and 50 h, respectively, under almost zero external load. The fracture patterns (i.e., viscous fingers and highly “self‐organized” parallel stripe patterns) have implications for fabricating patterned surfaces in materials science and nanotechnology. These results provide new insights into the fundamental understanding of adhesive mechanisms of multiple hydrogen‐bonding polymers and development of novel self‐healing and stimuli‐responsive materials.     

沥青质分子聚集体的聚集内因

运用量子力学、分子动力学等方法,研究沥青质分子聚集体形成过程的分子构型变化、能量变化以及电子分布情况。结果表明：沥青质分子形成聚集体过程中形变能很小,沥青质分子发生形变不是沥青质聚集体形成的决定因素,但为沥青质分子聚集进而形成聚集体提供基础,沥青质分子具有很强的本征聚集活性;沥青质分子间相互作用能很大,是沥青质分子聚集体形成的决定因素,其中,属于分子间固有属性的范德华力及泡利排斥作用之和相对较小,与沥青质分子结构特征相关的π π相互作用及氢键作用之和很大,表明由沥青质分子的大芳环体系和多杂原子的结构特征引起的π π相互作用及氢键作用是导致形成沥青质分子聚集体的主要原因;在所研究体系中,金属卟啉分子与含吡啶氮的沥青质分子通过π π相互作用而非轴向配位作用形成聚集体。     

Modulating Blue Phosphorene by Synergetic Codoping: Indirect to Direct Gap Transition and Strong Bandgap Bowing

The structural and electronic properties of synergistically modified blue phosphorene (BP) is investigated. The inversion and threefold rotational symmetries of BP are broken. The codoping of group IV and VI impurities can turn monolayer BP into direct bandgap semiconductors. The underlying physical mechanism is that group IV and VI impurities tailor the valence band maximum and conduction band minimum, respectively, and move them to Γ. All the bandgaps of monolayer, nanoribbons, and quantum dots of BP can be modulated in a wide range, and the strong bandgap bowing is found. In addition, the Coulomb interactions between the screened impurities are revealed. Lower formation energies indicate the fabricating practicability of synergeticly modified BP. Spin–orbit coupling (SOC) can also be tuned by the introduction of impurities.     

Heterojunction Architecture of N‐Doped WO3 Nanobundles with Ce2S3 Nanodots Hybridized on a Carbon Textile Enables a Highly Efficient Flexible Photocatalyst

The availability of robust, versatile, and efficient photocatalysts is the main bottleneck in practical applications of photocatalytic degradation of organic pollutants. Herein, N‐WO₃/Ce₂S₃ nanotube bundles (NBs) are synthesized and successfully immobilized on a carbon textile, resulting in a flexible and conducting photocatalyst. Due to the large interfacial area between N‐WO₃ and Ce₂S₃, the interwoven 3D carbon architecture and, more importantly, the establishment of a heterojunction between N‐WO₃ and Ce₂S₃, the resultant photocatalyst exhibits excellent light absorption capacity and superior ability to separate photoinduced electron–hole pairs for the photocatalytic degradation of organic compounds in air and water media. Theoretical calculations confirm that the strong electronic interaction between N‐WO₃ and Ce₂S₃ can be beneficial to the enhancement of the charge carrier transfer dynamics of the as‐prepared photocatalyst. This work provides a new protocol for constructing efficient flexible photocatalysts for application in environmental remediation.