Highly sensitive and stable SERS probes of alternately deposited Ag and Au layers on 3D SiO2 nanogrids for detection of trace mercury ions

The hazard of Hg ion pollution triggers the motivation to explore a fast, sensitive, and reliable detection method. Here, we design and fabricate novel 36-nm-thick Ag-Au composite layers alternately deposited on three-dimensional （3D） periodic SiO2 nanogrids as surface-enhanced Raman scattering （SERS） probes. The SERS effects of the probes depend mainly on the positions and intensities of their localized surface plasmon resonance （LSPR） peaks, which is confirmed by the absorption spectra from finite-difference time-domain （FDTD） calculations. By optimizing the structure and material to maximize the intrinsic electric field enhancement based on the design method of 3D periodic SERS probes proposed, high performance of the Ag-Au/SiO2 nanogrid probes is achieved with the stability further enhanced by annealing. The optimized probes show the outstanding stability with only 4.0% SERS intensity change during 10-day storage, the excellent detection uniformity of 5.78% （RSD）, the detection limit of 5.0 × 10-12 M （1 ppt）, and superior selectivity for Hg ions. The present study renders it possible to realize the rapid and reliable detection of trace heavy metal ions by developing high- performance 3D periodic structure SERS probes by designing novel 3D structure and optimizing plasmonic material.

Electron Beam Lithographic Pixelated Micropolarizer Array for Real-Time Phase Measurement

Pixelated micropolarizer arrays （PMAs） have recently been used as key components to achieve real-time phase measurement. PMA fabrication by electron beam lithography and inductively coupled plasma-reactive ion etching is proposed in this work. A 320 × 240 aluminum PMA with 7.4 μm pitch is successfully fabricated by the proposed technique. The period of the grating is 140nm, and the polarization directions of each of the 2 × 2 units are 0°, 45°, 90°, and 135°. The scanning electron microscopy and optical microscopy results show that the PMA has a good surface characteristic and polarization performances. When the PMA is applied to phase-shifting interferometry, four fringe patterns of different polarization directions are obtained from only one single frame image, and then the object wave phase is calculated in real time.

Temperature dependence of positive and negative magnetoresistances of tantalum-covered multiwalled carbon nanotubes

Carbon nanotubes(CNTs)have garnered significant attention due to their remarkable electronic and magnetic properties.In this research,we intro-duced multiwalled carbon nanotubes covered with tantalum(MWNTs/Ta)to systematically modulate the magnetoresistive properties of the MWNTs/Ta hybrid nanostructures.We observed distinct changes in both positive and negative magnetoresistances of MWNTs/Ta across a broad temperature range using a physical property measurement system and a four-terminal method.This study on temperature-dependent magnetore-sistive behavior of the MWNTs/Ta sheds light on the fundamental proper-ties of carbon-based materials and holds promise for practical applications inthefieldofspintronicdevices.

Broadband achromatic polarization insensitive metalens over 950 nm bandwidth in the visible and near-infrared

Metalenses are expected to play an increasingly important role in miniaturized and integrated optical imaging components/systems.However,devising broadband achromatic metalenses with high focusing efficiencies is still quite challenging.In this work,we proposed an aperture-shared partition phase cooperative manipulation approach for designing a highefficiency broadband achromatic metalens composed of two concentric sub-metalenses.As a proof-of-concept,an achromatic polarization-independent metalens is successfully designed for the visible and near-infrared range from450 nm to 1400 nm with the focusing efficiency over 70% for the wavelength range of 600 nm to 1400 nm.The approach reported here provides a possibility for designing a high-performance metalens,which has great potential applications in integrated optics.

Ultra-low-loss on-chip zero-index materials

Light travels in a zero-index medium without accumulating a spatial phase,resulting in perfect spatial coherence.Such coherence brings several potential applications,including arbitrarily shaped waveguides,phase-mismatch-free nonlinear propagation,large-area single-mode lasers,and extended superradiance.A promising platform to achieve these applications is an integrated Dirac-cone material that features an impedance-matched zero index.Although an integrated Dirac-cone material eliminates ohmic losses via its purely dielectric structure,it still entails out-of-plane radiation loss,limiting its applications to a small scale.We design an ultra-low-loss integrated Dirac cone material by achieving destructive interference above and below the material.The material consists of a square array of low-aspectratio silicon pillars embedded in silicon dioxide,featuring easy fabrication using a standard planar process.This design paves the way for leveraging the perfect spatial coherence of large-area zero-index materials in linear,nonlinear,and quantum optics.

Topological Landau–Zener nanophotonic circuits

Topological edge states(TESs),arising from topologically nontrivial phases,provide a powerful toolkit for the architecture design of photonic integrated circuits,since they are highly robust and strongly localized at the boundaries of topological insulators.It is highly desirable to be able to control TES transport in photonic implementations.Enhancing the coupling between the TESs in a finite-size optical lattice is capable of exchanging light energy between the boundaries of a topological lattice,hence facilitating the flexible control of TES transport.However,existing strategies have paid little attention to enhancing the coupling effects between the TESs through the finite-size effect.Here,we establish a bridge linking the interaction between the TESs in a finite-size optical lattice using the Landau–Zener model so as to provide an alternative way to modulate/control the transport of topological modes.We experimentally demonstrate an edge-to-edge topological transport with high efficiency at telecommunication wavelengths in silicon waveguide lattices.Our results may power up various potential applications for integrated topological photonics.

Electrodes for Li-ion batteries: From high-voltage LiCoO_(2) to Coreduced /Co-free layered oxides with potential anodes

Li-ion batteries(LIBs)are one type of more and more widely used devices for energy storage and power supply in which cathode materials are playing a relatively more decisive role at current stage.In this review,we start with pioneeringly commercialized R¯3mLiCoO_(2)(LCO)with a layered rhombohedral structure(space group)to discuss novel sequentially emerging LCO-derived layered oxides from the perspectives of both cobalt content reduction and performance improvement.Emphasis is placed on the improvement of high-voltage performance of LCO and Co-reduced/free layered oxides,including Co-reduced high-nickel layered oxides,Co-free Li-rich layered oxides,and Ni-based layered oxides cathodes,and their underlying mechanisms via different strategies.Also,possibly matched carbon and silicon-based anode materials are briefly discussed.The common issues and prospects of the layered oxides cathodes and their potential anodes are summarized and commented on.This review can help understand the emergence logics of novel layered oxides with gradually vanishing cobalt involved,provide insights about the underlying mechanisms of performance enhancement pertaining to particular strategies,and even inspire the discovery of novel cathode materials with high performance and low cost.

Ferromagnetism in sp^(2) carbon

The bulk,pristine sp^(2) carbons,such as graphite,carbon nanotubes,and graphene,are usually assumed to be typical diamagnetic materials.However,over the past two decades,there have been many reports about the ferromagnetism in these sp^(2) carbon materials,which have attracted intense interest for basic research and potential applications.In this review,we focus on the evidence and developments of the emergent ferromagnetism in sp^(2) carbon revealed by nine kinds of experimental methods:magnetic force microscopy(MFM),magnetization measurements with physical property measurement system(PPMS),X-ray magnetic circular dichroism(XMCD),scanning tunneling microscopy(STM),miniaturized magnetic particle inspection(MPI),anomalous Hall effect(AHE),mechanical deflection of carbon nanotube cantilevers,magnetoresistance,and spin-related devices(spin field effect transistor and spin memory).The advantages,conclusions,challenges,and future of these methods are discussed.The ferromagnetism in sp^(2) carbon will open a door to explore exotic physical phenomena and lay the basis for the development of integrated circuit of spintronics,which is fundamentally different from charge-based conventional electronics.

4^(th) generation synchrotron source boosts crystalline imaging at the nanoscale

New 4^(th)-generation synchrotron sources,with their increased bilince,promise to greatly improve the performances of coherent X-ray microscopy.This perspective is of major interest for crystal microscopy,which aims at revealing the 3D crystalline structure of matter at the nanoscale,an approach strongly limited by the available coherent flux.Our results,based on Bragg ptychography experiments performed at the frst 4-generation synchrotron source,demonstrate the possibility of retrieving a high-quality image of the crystalline sample,with unprecedented quality.Importantly,the larger available coherent flux produces datasets with enough information to overcome experimental limitations,such as strongly deteriorated scanning conditions.We show this achievement would not be posible with 30-generation sources,a limit that has inhibited the development of this otherwise powerful microscopy method,so far.Hence,the advent of next-generation synchrotron sources not only makes Bragg ptychography suitable for high throughput studies but also strongly relaxes the associated experimental constraints,making it compatible with a wider range of experimental set-ups at the new synchrotrons.