Optical anapole modes in hybrid metal–dielectric nanoantenna for near-field enhancement and optical sensing

Metal–dielectric nanostructures in the optical anapole modes are essential for light–matter interactions due to the low material loss and high near-field enhancement. Herein, a hybrid metal–dielectric nanoantenna composed of six wedgeshaped gold(Au) nanoblocks as well as silica(SiO2) and silicon(Si) nanodiscs is designed and analyzed by the finite element method(FEM). The nanoantenna exhibits flexibility in excitation and manipulation of the anapole mode through the strong coupling between the metal and dielectrics, consequently improving the near-field enhancement at the gap. By systematically optimizing the structural parameters, the electric field enhancement factors at wavelengths corresponding to the anapole modes(AM1 and AM2) can be increased to 518 and 1482, respectively. Moreover, the nanoantenna delivers great performance in optical sensing such as a sensitivity of 550 nm/RIU. The results provide guidance and insights into enhancing the coupling between metals and dielectrics for applications such as surface-enhanced Raman scattering and optical sensing.

Distribution of Electrical Field Energy for Conversion of Methane to C_2 Hydrocarbons via Dissymmetrical Electric Field Enhanced Plasma

Direct conversion of methane into C2 hydrocarbons through alternating current electric field enhanced plasma was studied under room temperature, atmospheric pressure and low power conditions. The distribution of electrical field intensity and distribution of energy were calculated with software that was developed by us according to the charge simulation method. The results indicated that the energy of tip of electrode was 0.36 J/mm^3 and it was higher than the methane dissociation energy （0.0553 J/mm^3）. The methane located at this area can be activated easily. The higher-energy particles produced by dissociation collided with molecules around them and initiated consecutive reactions between free radicals and molecules. The method was proved to be valided and could be taken as a basis for the electrical field study concerned.

Enormous enhancement of electric field in active gold nanoshells

The electric field enhancement properties of an active gold nanoshell with gain material inside have been investigated by using Mie theory. As the gain coefficient of the inner core increases to a critical value, a super-resonance appears in the active gold nanoshell, and enormous enhancements of the electric fields can be found near the surface of the particle. With increasing shell thickness, the critical value of the gain coefficient for the super-resonance of the active gold nanoshell first decreases and then increases, and the corresponding surface enhanced Raman scattering （SERS） enhancement factor （G factor） also first increases and then decreases. The optimized active gold nanoshell can be obtained with an extremely high SERS G factor of the order of 1019-1020. Such an optimized active gold nanoshell possesses a high-efficiency SERS effect and may be useful for single-molecule detection.

Engineering Geometric Electrodes for Electric Field-Enhanced High-Performance Flexible In-Plane Micro-Supercapacitors

In plane micro-supercapacitors that are miniaturized energy storage components have attracted significant attention due to their high power densities for various ubiquitous and sustainable device systems as well as their facile integration on various flexible/wearable platform.To implement the micro-supercapacitors in various practical applications that can accompany solid state or gel electrolyte and flexible substrates,ions must be readily transported to electrodes for achieving high power densities.Herein,we show large enhancement in electrochemical properties of flexible,inplane micro-supercapacitor using sharp-edged interdigitated electrode design,which was simply fabricated through direct laser scribing method.The sharp-edged electrodes allowed strong electric field to be induced at the corners of the electrode fingers which led to the greater accumulation of ions near the surface of electrode,significantly enhancing the energy storage performance of micro-supercapacitors.The electric field-enhanced in-plane micro-supercapacitor showed the volumetric energy density of 1.52 Wh L^(−1)and the excellent cyclability with capacitive retention of 95.4%after 20000 cycles.We further showed various practicability of our sharp-edged design in micro-supercapacitors by showing circuit applicability,mechanical stability,and air stability.These results present an important pathway for designing electrodes in various energy storage devices.

Intrinsic Mechanisms of Morphological Engineering and Carbon Doping for Improved Photocatalysis of 2D/2D Carbon Nitride Van Der Waals Heterojunction

Van der Waals(VDW)heterojunctions in a 2D/2D contact provide the highest area for the separation and transfer of charge carriers.In this work,a top-down strategy with a gas erosion process was employed to fabricate a 2D/2D carbon nitride VDW heterojunction in carbon nitride(g-C_(3)N_(4))with carbon-rich carbon nitride.The created 2D semiconducting channel in the VDW structure exhibits enhanced electric field exposure and radiation absorption,which facilitates the separation of the charge carriers and their mobility.Consequently,compared with bulk g-C_(3)N_(4)and its nanosheets,the photocatalytic performance of the fabricated carbon nitride VDW heterojunction in the water splitting reaction to hydrogen is improved by 8.6 and 3.3 times,respectively,while maintaining satisfactory photo-stability.Mechanistically,the finite element method(FEM)was employed to evaluate and clarify the contributions of the formation of VDW heterojunction to enhanced photocatalysis,in agreement quantitatively with experimental ones.This study provides a new and effective strategy for the modification and more insights to performance improvement on polymeric semiconductors in photocatalysis and energy conversion.

Catalysis Conversion Methane into C_(2) Hydrocarbons via Electric Field Enhanced Plasma

In this paper the effect of catalyst and carrier in electric field enhanced plasma on methane conversion into C2 hydrocarbons was investigated. Methane coupling reaction was studied in the system of continuous flow reactor on Ni, MoO3, MnO2 catalysts and different ZSM-5 carriers. The per pass conversion of methane can be as high as 22%, the selectivity of ethylene can be as high as 23.8%, of acetylene 60.8%, of ethane 5.4% and of total C2 hydrocarbons was more than 90%. ZSM-5-25 was the better carrier and MnO2 was the better active component. The efficiency of energy was as high as 7.81%.

Molybdenum Nanoscrews:A Novel Non-coinage-Metal Substrate for Surface-Enhanced Raman Scattering

For the first time, Mo nanoscrew was cultivated as a novel non-coinage-metal substrate for surface-enhanced Raman scattering(SERS). It was found that the nanoscrew is composed of many small screw threads stacking along its length direction with small separations. Under external light excitation, strong electromagnetic coupling was initiated within the gaps, and many hot-spots formed on the surface of the nanoscrew, which was confirmed by high-resolution scanning near-field optical microscope measurements and numerical simulations using finite element method. These hotspots are responsible for the observed SERS activity of the nanoscrews. Raman mapping characterizations further revealed the excellent reproducibility of the SERS activity. Our findings may pave the way for design of low-cost and stable SERS substrates.

Light focusing in linear arranged symmetric nanoparticle trimer on metal film system

Benefiting from the induced image charge on film surface,the nanoparticle aggregating on metal exhibits interesting optical properties.In this work,a linear metal nanoparticle trimer on metal film system has been investigated to explore the novel optical phenomenon.Both the electric field and surface charge distributions demonstrate the light is focused on film greatly by the nanoparticles at two sides,which could be strongly modulated by the wavelength of incident light.And the influence of nanoparticle in middle on this light focusing ability has also been studied here,which is explained by the plasmon hybridization theory.Our finding about light focusing in nanoparticle aggregating on metal film not only enlarges the novel phenomenon of surface plasmon but also has great application prospect in the field of surface-enhanced spectra,surface catalysis,solar cells,water splitting,etc.

Advancement in Science and Technology Enhanced the Growth of China's Electric Power Industry

Within the seven years’ period from 1987 to 1994. the total installed capacity of China’s electric power industry doubled from 100 GW to 200 GW. This high rate of growth has imposed new and more stringent requirements on all the branches in the

MXene based mechanically and electrically enhanced film for triboelectric nanogenerator

The development of triboelectric nanogenerator(TENG)technology which can directly convert ambient mechanical energy into electric energy may affect areas from green energy harvesting to emerging wearing electronics.And,the material of triboelectric layer is critical to the mechanical robustness and electrical output characteristics of the TENGs.Herein,a MXene enhanced electret polytetrafluoroethylene(PTFE)film with a high mechanical property and surface charge density is developed.The MXene/PTFE composite film was synthesized by spraying and annealing treatment.With the doping of MXene,the crystallinity of composite film could be tuned,leading to an enhancement in the tensile property of 450%and reducing the wear volume about 80%in the friction test.Furthermore,the as-fabricated TENG with this composite film outputs 397 V of open-circuit voltage,21µA of short-circuit current,and 232 nC of transfer charge quantity,which are 4,6,and 6 times higher than that of the TENG made by pure PTFE film,respectively.Therefore,this work provides a creative strategy to simultaneously improve the mechanical property and electrical performance of the TENGs,which have great potential in improving device stability under a complex mechanical environment.

Synthesis and Photoluminescence Enhancement of Silver Nanoparticles Decorated Porous Anodic Alumina

Silver nanoparticles（Ag NPs） were successfully assembled in porous anodic alumina（AAO） templates via a green silver mirror reaction.The Ag NPs/AAO composite templates then were characterized by field emission scanning electron microscopy（FESEM）,energy-dispersive X-ray microanalysis（EDX）,and X-ray diffraction（XRD）.Furthermore,the photoluminescence（PL） properties were also investigated.Compared with the blank AAO,the PL intensity of Ag NPs/AAO templates are enhanced and the maximum enhancement is 2.58 times.Based on the local electric field enhancement effect,the theoretical values were also deduced,which are basically coincident with the experimental.

A flat-based plasmonic fiber probe for nanoimaging

The difficulty of obtaining high-intensity localized light spots for optical probes leads to their lack of good applications in nanoimaging.Here we demonstrate a Fabry–Pérot resonance flat-based plasmonic fiber probe(FPFP).The simulation results show that the probe can obtain a nanofocusing spot at the tip with the radially polarized mode.The Fabry–Pérot interference structure is used to control the plasmon propagation on the surface of the probe,it effectively improves the local spot intensity at the tip.Furthermore,the experimental results verify that the FPFP(tip curvature radius is 20 nm)prepared by chemical etching method can obtain a nanofocusing spot at the tip.The nanoimaging of the gold slit structure demonstrates the nanoimaging capability of the FPFP,the 36.9 nm slit width is clearly identified by the FPFP.

High resolution and high signal-to-noise ratio imaging with nearfield high-order optical signals

The properties of near-field optics have always been the focus of nano-measurement technology.The 11th order effective nearfield optical signal with an incident laser wavelength of 1,550 nm is obtained using a platinum-coated optical probe(Pt–Si probe).The experimental results show that the local electric field intensity of the Pt–Si probe is nearly 30 times higher than that of silicon probe(Si probe).Therefore,the highest 7th order near-field optical imaging results are obtained with the Pt–Si probe.Further,near-field optical imaging is performed on samples such as gold grids and carbon nanotubes using the Pt–Si probe.The measurement results show that the high-order signal has the characteristics of less background,higher signal-to-noise ratio,and resolution up to 5.7 nm.

Multiple plasmon couplings in 3D hybrid Au-nanoparticles-decorated Ag nanocone arrays boosting highly sensitive surface enhanced Raman scattering

Plasmon coupling is an essential strategy to realize strong local electromagnetic(EM)field which is crucial for high-performance plasmonic devices.In this work,multiple plasmon couplings are demonstrated in three-dimensional(3D)hybrid plasmonic systems composed of polydimethylsiloxane-supported ordered silver nanocone(AgNC)arrays decorated with high-density gold nanoparticles(AuNPs)which are fabricated by a template-assisted physical vapor deposition process.Strong interparticle coupling,particle-film coupling,inter-cone coupling,and particle-cone coupling are revealed by numerical simulations in such composite nanostructures,which produce intense and high-density EM hot spots,boosting highly sensitive and reproducible surface enhanced Raman scattering(SERS)detection with an enhancement factor of-1.74×10^(8).Furthermore,a linear correlation between logarithmic Raman intensity and logarithmic concentration of probe molecules is observed in a large concentration range.These results offer new ideas to develop novel plasmonic devices,and provide alternative strategy to realize flexible and high-performance SERS sensors for trace molecule detection and quantitative analysis.

CMOS兼容的晶圆级硅锥阵列局域化细丝形成以实现极佳阻变存储器均一性

具有高密度三维集成特点的阻变存储器(RRAM)是下一代非易失性存储技术的有利竞争者之一.然而,导电细丝形成和断裂的随机性导致了RRAM均一性差的问题,这严重阻碍了RRAM芯片的大规模商用.目前,已有部分研究通过引入锥形结构,减少RRAM中导电细丝形成和断裂的随机性.但是,这些方法往往步骤繁琐、成本较高或分辨率有限,限制了这些技术的大规模推广.本研究提出了一种CMOS兼容的、可在纳米尺度调控的晶圆级硅锥阵列(SSA)制备方法.该方法可制备不同曲率半径的SSA,用于调控RRAM中的导电细丝.高分辨率透射电子显微镜和能量色散谱表征结果表明,SSA结构诱导器件在尖端区域形成准单根或少量的导电细丝,显著改善了器件转变参数的均一性.此外,减小尖端区域的曲率半径可显著提升器件转变电压和高/低阻态的分布均一性及器件阻态的保持特性等.器件转变参数均一性的改善归因于尖端区域内的局域电场增强效应.本研究所提出的SSA方法具备低成本、CMOS兼容且纳米尺度可控的特点,为高均一性RRAM器件的大规模集成提供了一种参考策略.

Selective deposition of a MOF at the spikes of Au nanostars for SERS detection

In the pursuit of advancing molecular sensing through surface-enhanced Raman spectroscopy(SERS),the combination of plasmonic nanoparticles and metal-organic frameworks(MOFs)has emerged as a highly effective approach to enhance the sensitivity and selectivity of SERS substrates.However,most prior investigations have predominantly focused on MOF-coated plasmonic nanoparticles in core@shell or layer-by-layer configurations,leaving a notable knowledge gap in exploring alternative configurations.Herein we present a facile method to construct a particle-on-mirror architecture by selectively coating a MOF,zeolitic imidazolate framework-8(ZIF-8),onto the tips of Au nanostars and subsequently depositing the resultant nanoparticles onto a Au film.This design integrates the electric field enhancement at the sharp tips and nanogaps,along with the molecular enrichment function within the porous MOF immobilized at the tips and nanogaps,leading to a substantial boost in the SERS signal intensity.Such a unique SERS platform enables consistent and outstanding SERS performance for analytes of different sizes.This work opens up a promising strategy for constructing multifunctional nanostructures for sensitive SERS detection in real-life scenarios.