The performance of lithium and sodium‐ion batteries is partly determined by the microstructures of the active materials and anodes. Much attention has been paid to the construction of various nanostructured active materials, with emphasis on optimizing the electronic and ionic transport kinetics, and structural stability. However, less attention has been given to the functionalization of electrode microstructure to enhance performance. Therefore, it is significant to study the effect of optimized microstructures of both active materials and electrodes on the performance of batteries. In this work, porous MoS2/carbon spheres anchored on 3D interconnected multiwall carbon nanotube networks (MoS2/C‐MWCNT) are built as sodium‐ion battery anodes to synergistically facilitate the sodium‐ion storage process. The optimized MoS2/C‐MWCNT possesses favorable features, namely few‐layered, defect‐rich, and interlayer‐expanded MoS2 with abundant mesopores/macropores and carbon incorporation. Notably, the presence of 3D MWCNT network plays a critical role to further improve interparticle and intraparticle conductivity, sodium‐ion diffusion, and structural stability on the electrode level. As a result, the electrochemical performance of optimized MoS2/C‐MWCNT is significantly improved. This study suggests that rational design of microstructures on both active material and electrode levels simultaneously might be a useful strategy for designing high performance sodium‐ion batteries.

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Light polarization control is a key factor in modern photonics. Recent advances in surface plasmon manipulation have introduced the prospect of more compact and more efficient devices for this purpose. However, the current plasmonic-based polarization optics remain much larger than the wavelength of light, which limits the design degrees of freedom. Here, we present a plasmonic traveling-wave nanoantenna using a gold-coated helical carbon nanowire end-fired with a dipolar aperture nanoantenna. Our nonresonant helical nanoantenna enables tunable polarization control by swirling surface plasmons on the subwavelength scale and taking advantage of the optical spin–orbit interaction. Four closely packed helical traveling-wave nanoantennas (HTNs) are demonstrated to locally convert an incoming light beam into four beams of tunable polarizations and intensities, with the ability to impart different polarization states to the output beams in a controllable way. Moreover, by near-field coupling four HTNs of opposite handedness, we demonstrate a subwavelength waveplate-like structure providing a degree of freedom in polarization control that is unachievable with ordinary polarization optics and current metamaterials.

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AbstractSecond harmonic generation (SHG) with a material of large transparency is an attractive way of generating coherent light sources at exotic wavelength range such as VUV, UV and visible light. It is of critical importance to improve nonlinear conversion efficiency in order to find practical applications in quantum light source and high resolution nonlinear microscopy, etc. Here an enhanced SHG with conversion efficiency up to 10−2% at SH wavelength of 282.7 nm under 11 GW/cm2 pump intensity via the excitation of anapole in lithium niobite (LiNbO3, or LN) nanodisk through the dominating d33 nonlinear coefficient is investigated. The anapole has advantages of strongly suppressing far-field scattering and well-confined internal field which helps to boost the nonlinear conversion. Anapoles in LN nanodisk is facilitated by high index contrast between LN and substrate with properties of near-zero-index via hyperbolic metamaterial structure design. By tailoring the multi-layers structure of hyperbolic metamaterials, the anapole excitation wavelength can be tuned at different wavelengths. It indicates that an enhanced SHG can be achieved at a wide range of pump light wavelengths via different design of the epsilon-near-zero (ENZ) hyperbolic metamaterials substrates. The proposed nanostructure in this work might hold significances for the enhanced light–matter interactions at the nanoscale such as integrated optics.

Graphene-based electrical chemical vapor sensors can achieve extremely high sensitivity, whereas the comparatively slow sensing response and recovery, the research focused on only low concentration detection, have been known as drawbacks for many applications requiring rapid and high concentration detection. Here we report a novel graphene-based fiber-optic relative humidity (RH) sensor relying on fundamentally different sensing mechanism. The sensor can achieve power variation of up to 6.9 dB in high relative humidity range (70-95%), and display linear response with correlation coefficient of 98.2%, sensitivity of 0.31 dB/%RH, response speed of faster than 0.13%RH/s, and good repeatability in 75-95%RH. Theoretical analysis of sensing mechanism can explain the experimental result, and reveal the broad applying prospect of the sensor for other kinds of chemical vapor detection. This novel graphene-based optical sensor provides a beneficial complement to the existing electrical ones, and will promote the employment of graphene in chemical sensing techniques.

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The fabrication of circularly polarized luminescence (CPL) active materials by self‐assembly is still in its challenge. In this work, a family of homochiral metal–organic frameworks (MOFs) and metal–organic cages (MOCs) are constructed by solvothermal subcomponent self‐assembly. These MOFs feature an eta topology with trifold helical chains, while the MOCs adopt a cubic cage structure. The chiral ligands show two distinct types of conformations: “opened” and “closed” in MOFs and MOCs, respectively. Although homochiral MOFs and MOCs show similar spectra of circular dichroism and photoluminescence with similar quantum yields and lifetimes, the MOFs yield clear CPL signals and the CPL of MOCs are silent. The turn‐on CPL in MOFs achieved by tuning the conformation of ligands and controlling self‐assembly provides a new approach for development of CPL‐active MOF materials.