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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. [ABSTRACT FROM AUTHOR]

Nonlinear nanophotonic devices have shown great potential for on‐chip information processing, quantum source, 3D microfabrication, greatly promoting the developments of integrated optics, quantum science, nanoscience and technologies, etc. To promote the applications of nonlinear nanodevices, improving the nonlinear efficiency, expanding the spectra region of nonlinear response and reducing device thickness are three key issues. Herein, this study focuses on the nonlinear effect of third‐harmonic generation (THG), and present a thin Si meta‐sructure to improve the THG efficiency in the ultraviolet (UV) region. The measured THG efficiency is up to 10−5 at an emission wavelength of 309 nm. Also, the THG nanosystem is only 100 nm in thickness, which is two–five times thinner than previous all‐dielectric nanosystems applied in THG studies. These findings not only present a powerful thin meta‐structure with highly efficient THG emission in UV region, but also provide a constructive avenue for further understanding the light–matter interactions at subwavelength scales, guiding the design and fabricating of advanced photonic devices in future. [ABSTRACT FROM AUTHOR]

Nanoporous metallic films have attracted great attention as surface-enhanced Raman scattering (SERS) substrates. The presence of nanosized protrusions in such nanoporous metallic films gives rise to remarkably improved SERS enhancement due to an additional lightning rod effect of protrusions. However, the positive contribution of protrusions was only preliminarily demonstrated by SERS measurements so far, and several important questions remain unaddressedfundamental understanding into the near-field enhancement of protrusions, qualitative link between the measured SERS enhancement and properties of protrusions, and facile strategy for nanoporous metallic films with protrusions. In this paper, plasma oxidation-reduction of Ag nanofilms was used to fabricate various nanoporous Ag films with nanosized protrusions. The fundamental protrusion size dependence of near-field enhancement was elucidated from both the electrodynamic model and FDTD simulation, with the protrusion approximately treated as a hemiprolate spheroid positioned on a semi-infinite metallic base. With the as-fabricated nanoporous Ag films as the SERS substrates, the qualitative link between the measured SERS enhancement and density/size distribution of protrusions was established. The findings reported here contribute significantly to gaining deeper insight into the SERS enhancement of nanoporous metallic films and guiding future SERS substrate design. [ABSTRACT FROM AUTHOR]

A promising design combining low loss, high refractive index dielectric materials with metal nanoparticles, and local plasma resonance is described for ring-disk nanoantenna. A hybrid Au ring Si disk structure with chain gaps is constructed and the distributions of the electric field and near-field enhancement of the electric fields are analyzed by numerical simulation utilizing the multipole decomposition method. The electric field strength can be enhanced efficiently using metals to improve the anapole mode response of dielectric materials with large refractive indexes. Additional enhancement of the electric field is achieved by opening the chain gap to create high-intensity hot spots inside the disk. The chain comprises 14 normal octahedrons and a few tips are created by intersecting octahedrons. The electric field is greatly enhanced at the tips where there are high-intensity hot spots. The effectiveness of this structure as a refractive index sensor is assessed. The scattering cross-section (SCS) and wavelength shifts result in a maximum sensitivity of 210 nm/RIU. The results validate the design concept and the hybrid structure boasting large electric field enhancement and excellent optical sensing properties have large potential in nonlinear photonics. In the hybrid ring-disk structure, the construction of a chain gap made of 14 intersecting hexagonal prisms can produce strong electric field enhancement at various locations. The electric field enhancement contour around the hybrid structure under illumination was analyzed at the plasmon resonance wavelength. And the scattering characteristics of the hybrid ring-disk antenna were calculated by the multipole decomposition approach. [ABSTRACT FROM AUTHOR]

Abstract Nonlinear nanophotonic devices have shown great potential for on‐chip information processing, quantum source, 3D microfabrication, greatly promoting the developments of integrated optics, quantum science, nanoscience and technologies, etc. To promote the applications of nonlinear nanodevices, improving the nonlinear efficiency, expanding the spectra region of nonlinear response and reducing device thickness are three key issues. Herein, this study focuses on the nonlinear effect of third‐harmonic generation (THG), and present a thin Si meta‐sructure to improve the THG efficiency in the ultraviolet (UV) region. The measured THG efficiency is up to 10−5 at an emission wavelength of 309 nm. Also, the THG nanosystem is only 100 nm in thickness, which is two–five times thinner than previous all‐dielectric nanosystems applied in THG studies. These findings not only present a powerful thin meta‐structure with highly efficient THG emission in UV region, but also provide a constructive avenue for further understanding the light–matter interactions at subwavelength scales, guiding the design and fabricating of advanced photonic devices in future.

The increasing demand for miniature, flexible electronic devices have fueled the need for compact and high‐performing energy storage solutions. Microsupercapacitors (mSCs) with reduced dimension and novel electrode design have gained prominence. This concept paper summarizes and views the recent advancements in mSCs with a focus on 3D graphene electrodes and their novel electrode design to increase energy performance of the devices. Especially, we focus on these 3D graphene structures fabricated using a laser‐scribing method which offer an efficient, cost‐effective approach for enhanced mSC performance. Further, this work delves into the vital link between the electrical field effect and geometrically engineered interdigitated electrodes, which is pivotal for maximizing the ion transport and mSC energy storage performance. The insights presented here are promising for meeting the power requirements of future miniature electronics. [ABSTRACT FROM AUTHOR]

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We present an analytical theory of plasmons excited in spherical metal resonators filled with the molecules under study. A simple L‒C model of plasmons generated in a metal nanoshell is developed. The electromagnetic mechanism of surface-enhanced (giant) Raman scattering (SERS) can be investigated qualitatively and quantitatively. The theoretical results are in qualitative agreement with computer simulations. The results of the SERS experiment in polystyrene spheres coated with a silver nanolayer are presented. [ABSTRACT FROM AUTHOR]

Lubricating oil is easily polluted by solid particles, causing it to deteriorate; therefore, solid particles must be separated from the oil. Furthermore, as conventional filtration devices cannot meet both filtration accuracy and service life requirements, an oil and solid separation method for multi-gradient filtration enhanced by an electric field is proposed. A numerical model for multi-gradient separation was established by coupling the governing equations of electric and flow fields, the particle-wall collision equation, and the discrete phase-tracking equation. Enhanced by an electric field, the characteristics of the multi-gradient filtration of solid particles in oil were investigated using finite element method. The effects of the main control parameters on the filtration performance were analyzed. The results indicate that using the electric field-enhanced multi-gradient filtration method can achieve highly efficient separation of solid particles from the oil. When the electric field strength was increased from 0 kV/mm to 2 kV/mm, the deposition concentration of particles was 2.5 times higher and filtration efficiency of the system increased to 97.46%. Additionally, the deposition concentration and filtration efficiency decreased from 0.15 m/s to 0.3 m/s, while gradually increased from 0.3 m/s to 0.5 m/s, for a particle size range of 10–40 µm. [Display omitted] • An oil and solid separation method for multi-gradient filtration enhanced by an electric field was proposed. • A numerical model for multi-gradient separation enhanced by an electric field was established. • Characteristics of electric field-enhanced multi-gradient of solid particles in oil were investigated. • The effects of the main control parameters on the filter efficiency were analyzed. [ABSTRACT FROM AUTHOR]

Generic, analytical equations are suggested for the localized plasmon excited in a narrow gap formed between a metal/dielectric cylinder and a metal surface. The local distribution of the electric field was found by employing the quasi-static approximation. A strong electric field can be achieved in the nanogap in the optical and infrared frequency regimes. The maximum electric field was reached when the incident light was in resonance with the mode of the plasmon gap and can be expressed in terms of the incident field E 0 as E m a x / E 0 ∝ ε m δ − 2 with δ = ℑ ε m / ℜ ε m . This aspect of the maximum field achievable in the nanogap can be enhanced by many orders of magnitude. The results of the analytical model were in relatively good agreement with a known theoretical model and the experimental results of surface-enhanced Raman scattering (SERS). The narrow gap resonator seems to be a powerful and flexible tool for different spectroscopies such as SERS and infrared absorption. [ABSTRACT FROM AUTHOR]

Abstract The increasing demand for miniature, flexible electronic devices have fueled the need for compact and high‐performing energy storage solutions. Microsupercapacitors (mSCs) with reduced dimension and novel electrode design have gained prominence. This concept paper summarizes and views the recent advancements in mSCs with a focus on 3D graphene electrodes and their novel electrode design to increase energy performance of the devices. Especially, we focus on these 3D graphene structures fabricated using a laser‐scribing method which offer an efficient, cost‐effective approach for enhanced mSC performance. Further, this work delves into the vital link between the electrical field effect and geometrically engineered interdigitated electrodes, which is pivotal for maximizing the ion transport and mSC energy storage performance. The insights presented here are promising for meeting the power requirements of future miniature electronics.

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 wedge-shaped 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. [ABSTRACT FROM AUTHOR]

Plasmonic molecules, which are geometrically well-defined plasmonic metal nanoparticle clusters, have attracted significant attention due to their enhancement of light–matter interactions owing to a stronger electric field enhancement than that by single particles. High-resolution lithography techniques provide precise positioning of plasmonic nanoparticles, but their fabrication costs are excessively high. In this study, we propose a lithography-free, self-assembly fabrication method, termed the dual-dewetting process, which allows the control of the size and density of gold nanoparticles. This process involves depositing a gold thin film on a substrate and inducing dewetting through thermal annealing, followed by a second deposition and annealing. The method achieves a uniform distribution of particle size and density, along with increased particle density, across a 6-inch wafer. The superiority of the method is confirmed by a 30-fold increase in the signal intensity of surface-enhanced Raman scattering following the additional dewetting with an 8 nm film, compared to single dewetting alone. Our findings indicate that the dual-dewetting method provides a simple and efficient approach to enable a variety of plasmonic applications through efficient plasmonic molecule large-area fabrication. [ABSTRACT FROM AUTHOR]

Results of a deep‐level transient spectroscopy (DLTS) study of trapping states in Ni/Au Schottky diodes made on Si‐doped GaN layers grown by metal–organic vapor‐phase epitaxy (MOVPE) on highly conductive n‐type Ammono‐GaN substrates are reported. In all as‐grown samples, the DLTS signals due to traps with the activation energies for electron emission (Eem) of about 0.26 and 0.60 eV (referred to as E1 and E3 traps, respectively) have been detected. It is found that the electric field (E) significantly enhances the electron emission rate (eem) for the E1 trap, while for the E3 trap the eem(E) dependence is not very strong. The eem(E) dependence for the E1 trap is found to be characteristic of attractive traps with spherically symmetric square well potential with a radius of about 2.9 ± 0.25 nm. The eem(E) dependence for the E3 trap is accounted for by a phonon‐assisted tunneling mechanism. The zero‐EEem values for both traps are determined. Correlations between the concentrations of the E1 and E3 traps and concentrations of impurities (H, C, Si, O, Mg, and Fe) determined by secondary ion mass spectrometry in the samples are investigated. Charge states and origins of the E1 and E3 traps are discussed. [ABSTRACT FROM AUTHOR]

A silicon-nanostructured array coating on silicon film (SAS film) is designed based on the plasmonic optical tweezer and demonstrated for optical trapping and manipulation of nanospheres with negligible impact on the local thermal conditions. The electric field enhancement, optical force, and trapping potential of the SAS film are investigated by the finite element method. The trapping position is affected by the incident light wavelength, structure of the nanoarray, and refractive index of the nanospheres. The presence of four energy wells around the nanoarray suggests that it is possible to trap multiple nanoparticles. Moreover, the circularly polarized light, Gaussian beam, and silicon nanoarray facilitate the trapping of nanoparticles. This study showcases the potential of SAS film as optical tweezers to capture nanoparticles for the development of nanophotonic devices. [ABSTRACT FROM AUTHOR]

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, in‐plane 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 20 000 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. [ABSTRACT FROM AUTHOR]

Herein, we report the theoretical investigation to understand the role of size-dependent damping (SDD) due to electron–surface scattering on the Al nanoparticle-based deep ultraviolet surface-enhanced fluorescence. First, the absorption spectra and electric field enhancement (EFE) inside and outside Al nanoparticles of different sizes are plotted without and with considering SDD. Later, the role of SDD on the near- and far-field plasmonic properties of Au and Ag nanoparticles of different sizes is investigated for comparison. Finally, Al nanoparticle-based SEF enhancement is estimated for different nanoparticle sizes, emission wavelengths, and separations between nanoparticle and fluorophore without and with considering the SDD. [ABSTRACT FROM AUTHOR]

As a semimetal, tellurium (Te) shows metallic and dielectric properties in the UV and visible ranges, respectively, and has potential as a broad-band light absorber. In this paper, plasmonic–semiconductor hybrid nanoscale films consisting of Fe2O3 thin films and Te nanospheres are designed and demonstrated. Te clusters are proved to have an enhancement of the electric near-field in a broad UV–vis–NIR spectrum, which facilitates light absorption and charge separation in photoelectrocatalysis. The thickness of Fe2O3 films is adjusted from 22 to 137 nm. The photocurrent density enhancement factor of Te-modified films is 13 times higher than that of 22 nm Fe2O3 films. Particularly, a Te-decorated Fe2O3 ultrathin film exhibits photoelectrochemical activity comparable to that of bulk Fe2O3, suggesting significant near-field enhancement from plasmon modes of the Te clusters. It is found that the Te cluster decoration led to a significant decrease of the charge transfer resistance, demonstrating that the Te clusters could boost the formation rate and suppress the recombination rate of electron–hole pairs. The hybridization of Te nanoparticles with nanoscale semiconductor films represents an efficient way to enhance the solar energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Surface charge accumulation on an insulating spacer is a critical issue that causes electric field distortion and flashover voltage reduction in DC-GIS. In the operating environment, high-voltage electrode is heated by Joule heat, and the surface charge accumulation is strongly affected by the temperature. This study reports the temperature dependence of surface charge accumulation on DC-GIS insulating spacer and its impact on electric field distortion. Surface charge density distribution is measured on a downsized epoxy spacer under isothermal conditions at room temperature, 40 °C, and 70 °C. Special care is taken to realize a low-moisture and low-dust environment. We obtain the saturation tendency of homo-charge accumulation with less random charges and its temperature dependence. Homo-charge accumulation develops more rapidly and more extensively on the spacer at the higher temperatures. Our results indicate that the surface charge accumulation cannot be explained by a conventional resistive field calculation, and that an explanation based on charge trapping is reasonable. They also show that the homo-charge accumulation significantly contributes to the electric field enhancement after the polarity reversal in our experimental system, especially at high temperatures. [ABSTRACT FROM AUTHOR]

Using N,N-bis(1-methylheptyl)acetamide (N503) synergized with TBP-NaFeCl 4 (T Fe), a ternary composite extraction membrane known as T Fe N-PIM was created. Under optimum membrane phase conditions, the mass transfer properties of T Fe N-PIM-Li(Ⅰ) and its Li/Mg selective separation performance by electric field augmentation were examined, and confirmed the mechanism of T Fe N-PIM-Li(Ⅰ) electric field enhanced mass transfer. The findings demonstrate a homogeneous distribution of [FeCl 4 -] in the T Fe N-PIM membrane phase and a decrease in the water contact angle as the T Fe content increases. In the T Fe N-PIM membrane, the cation binding order of the composite carrier was H+>Li+>Na+>Mg2+, and the mass transfer was carried out at the interface of the two phases of the membrane through the mechanism of "cation exchange-neutralization", in which Li(Ⅰ) was bonded with the carrier in the form of 2N503-LiFeCl 4 -2TBP, and showed a fixed-site "hopping" mass transfer characteristics under the reinforcement of electric field. The mass transfer process of the T Fe N-PIM- Li(Ⅰ) system under electric field enhancement conforms to the first-order kinetic rate equation, and the voltage (5–45 V) is positively correlated with the permeability coefficient P Li(Ⅰ) but decreases the Li/Mg selectivity of T Fe N-PIM. The S Li(Ⅰ)/Mg(Ⅱ) of T Fe N-PIM was 9.18 at 3 V. After three cycles of 72 h cycling at 40 V, the decrease rate of P Li(Ⅰ) was <7.42 %, which showed good stability. [Display omitted] • A ternary composite extraction membrane (T Fe N-PIM) of N503 synergy with TBP-NaFeCl 4 (T Fe) was prepared. • The increase in permeability coefficient stabilization after T Fe /N503 > 2/1 (w/w) in T Fe N-PIM. • Voltage accelerates the "ion hopping" rate of Li(Ⅰ) in T Fe N-PIM. • Voltage positively correlates with permeability coefficient but reduces Li/Mg selectivity of T Fe N-PIM. • The separation factor of T Fe N-PIM for Li/Mg at 3 V was 9.18. [ABSTRACT FROM AUTHOR]

Generic, analytical equations are suggested for the localized plasmon excited in a narrow gap formed between a metal/dielectric cylinder and a metal surface. The local distribution of the electric field was found by employing the quasi-static approximation. A strong electric field can be achieved in the nanogap in the optical and infrared frequency regimes. The maximum electric field was reached when the incident light was in resonance with the mode of the plasmon gap and can be expressed in terms of the incident field E0 as Emax/E0∝εmδ−2 with δ=ℑεm/ℜεm. This aspect of the maximum field achievable in the nanogap can be enhanced by many orders of magnitude. The results of the analytical model were in relatively good agreement with a known theoretical model and the experimental results of surface-enhanced Raman scattering (SERS). The narrow gap resonator seems to be a powerful and flexible tool for different spectroscopies such as SERS and infrared absorption.

A grating-assisted hybrid plasmonic slot resonator is proposed and theoretically investigated as an on-chip surface-enhanced Raman scattering (SERS) sensor. A dielectric Bragg grating and a gold baffle are introduced into the hybrid plasmonic slot waveguide as two mirrors to form a plasmonic–dielectric cavity, in which the constructive interference of the input pump light greatly enhances the electric field. The grating reflects the wasted pump light for reverse secondary coupling and acts as a built-in notch filter for filtering out pump light from Raman scattered light simultaneously, improving the coupling efficiency and realizing a compact and miniaturized on-chip SERS sensor. Both the volumetric electric field enhancement and Raman collection efficiency are taken into account. The proposed scheme provides a simple, effective and universal method for improving the performance of the plasmonic-antennas-type waveguide-based SERS sensors.

Dielectric materials exhibit negligible dissipative losses and strong electromagnetic multipolar optical responses at operating wavelengths compared to metallic materials. In a high-refractive-index dielectric, the destructive interference of the radiation fields from electric and toroidal dipole moments results in the anapole, which has the optical properties of a dark state and cannot emit energy in the far-field region. This study uses periodic Si nanocubes (SN) to support anapole excitation with lattice resonance based on numerical simulation and manipulates the anapole by tailoring structures according to the electromagnetic field distribution characteristics of the anapole. Long slits are introduced in the center to regulate the electric dipole moments, and elliptical holes are opened on both sides to adjust the current distribution and thus influence the toroidal dipole moments. The reflection resonance peak of tailored Si nanocubes shows a narrow bandwidth of 0.11 nm and a large Q-factor of 8053. Also, their reflection resonance peak shows more than 237 times the electric field enhancement in the dielectric. The tailored Si nanocubes provide an alternative to plasmonic metal to support hot spots and achieve near-field enhancement, which can be applied to enhance photon emission, surface-enhanced Raman scattering (SERS), and photocatalysis. [ABSTRACT FROM AUTHOR]

The synergistic effect of electrostatically enhanced fibrous filtration originates from the charging characteristics of aerosol particles and electret fibers in an electric field. Two electrostatically enhanced fibrous filter systems are designed in this study to investigate the mechanism of the effects of the charging characteristics of oily aerosol on the filtration efficiency. We investigate the charging characteristics and their effects on the filtration efficiency of dioctyl-phthalate (DOP) aerosol particles of various sizes by setting different filter systems and electric field intensities. The experimental results show that the charge of DOP particles increases with the strength of the electric field, and the average charge increases with the particle size. The maximum charge of DOP particles reaches 4760 eC/P, and the filtration efficiency of the coupled system improves when DOP particles are amply charged. For 0.25 μm DOP particles as the most penetrating particle size, the system had good long-term stability, and the filtration efficiency is approximately 72% higher than that of the fiber acting alone. Meanwhile, the problem of oily aerosol deposition reducing the electret filtration efficiency is solved, providing a basis for long-term filtration and oily aerosol purification by electret fiber. [ABSTRACT FROM AUTHOR]

Plasmonic metal nanoparticles due to their characteristic localized surface plasmon resonance (LSPR) in the optical region of the electromagnetic wave are of much interest right from the medieval ages. Herein, we present a robust single-step synthetic protocol for the synthesis of Au and Cu alloy nanoparticles, which are typically used in various catalytic and sensing applications. For alloy formation, co-reduction of Au and Cu salts was used in four different Au/Cu mass ratios (1:1, 1:2, 1:3, and 1:4) yielding "marigold" like nanostructures. The formation of the desired alloy composition was confirmed from their optical spectra giving an LSPR peak among the specific peak nature of Au and Cu and also, from the XRD pattern, displaying diffraction peaks corresponding to Au and Cu only, but not the copper oxides. Additionally, the effect of plasmonic damping due to inter-band transition and polydispersity in the formed alloys was also discussed. Moreover, their optical spectra confirm a broadband bathochromic shifted LSPR peak alongside a lowering intensity with the surge in Cu concentration. For the respective compositions of the alloy nanoparticles, optical spectra (compared with experimental data) and the electric field enhancement data were also simulated using the MATLAB-based boundary element method to investigate their application in antennas for SERS, SEIRA, etc. Furthermore, these AuCu nanoalloys were utilized in crystal violet dye degradation, which provides an enhanced catalytic character in comparison with that of pure Au nanoparticles. Subsequently, the turnover frequency of the degradation process provides the superlative AuCu composition. A similar enhanced nature was likewise obtained for simulated refractive index sensitivity for n = 1−1.5, establishing not only the inherent cost-effectiveness and single-step procedure of our versatile synthetic protocol, but also the formation of robust alloy with different combinations of nanoparticles. [ABSTRACT FROM AUTHOR]

Metal-dielectric-graphene hybrid heterostructures based on oxides Al2O3, HfO2, and ZrO2 as well as on complementary metal–oxide–semiconductor compatible dielectric Si3N4 covering plasmonic metals Cu and Ag have been fabricated and studied. We show that the characteristics of these heterostructures are important for surface plasmon resonance biosensing (such as minimum reflectivity, sharp phase changes, resonance full width at half minimum and resonance sensitivity to refractive index unit (RIU) changes) can be significantly improved by adding dielectric/graphene layers. We demonstrate maximum plasmon resonance spectral sensitivity of more than 30,000 nm/RIU for Cu/Al2O3 (ZrO2, Si3N4), Ag/Si3N4 bilayers and Cu/dielectric/graphene three-layers for near-infrared wavelengths. The sensitivities of the fabricated heterostructures were ~ 5–8 times higher than those of bare Cu or Ag thin films. We also found that the width of the plasmon resonance reflectivity curves can be reduced by adding dielectric/graphene layers. An unexpected blueshift of the plasmon resonance spectral position was observed after covering noble metals with high-index dielectric/graphene heterostructures. We suggest that the observed blueshift and a large enhancement of surface plasmon resonance sensitivity in metal-dielectric-graphene hybrid heterostructures are produced by stationary surface dipoles which generate a strong electric field concentrated at the very thin top dielectric/graphene layer. [ABSTRACT FROM AUTHOR]

Frequent failures of transition joints were reported mainly near to the crutch area of the paper insulated cable side of the joints. In this paper, the authors present an estimation of the electric field and temperature distribution in the paper insulated cable side of a transition joint using simulations based on finite element method for 3-D geometry, which, apparently did not get much attention until now. It is found that non-linearities in material properties result in drastic changes in the distribution of electric field. The results indicate electric field enhancement near crutch area. The effect of varying load current, and ambient temperature on the peak electric field has been investigated. The simulations are validated analytically. The results are considered important for utilities and manufacturers. [ABSTRACT FROM AUTHOR]

As a waste product of phosphorus production, phosphorus electrostatic precipitator (ESP) dust contains approximately 14% potassium and is a potential resource for potassium recovery. In this study, we aimed to extract potassium from phosphorus ESP dust using a novel approach based on ionic liquid. To achieve this goal, we constructed the leaching-extraction-electrodeposition process based ionic liquid, which allowed for the efficient extraction of potassium. We determined the occurrence of potassium in ESP dust and found that under optimal conditions with electro-field enhancement, the recovery rate of potassium was 95.37%, the leaching process was found to fit the mixed control model well. We obtained a maximum extraction amount of 452.256 mg/L in the extraction section. Importantly, both the leaching and extraction processes exhibited high selectivity for potassium, indicating their potential for targeted potassium recovery from ESP dust. To verify the feasibility of the electrodeposition of potassium, we conducted additional experiments and found that our method was capable of recovering potassium via electrodeposition, further highlighting the potential of this approach. Overall, our study demonstrates a novel and environmentally friendly method for potassium recovery from phosphorus ESP dust, with high efficiency and selectivity, and contributes to the growing body of research on sustainable resource utilization. • New process for leaching-extraction-electrodeposition of potassium by ionic liquids. • An electric field to enhance leaching and selective while reducing leaching time. • The feasibility of electrodeposition of potassium in ionic liquids was verified. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mie resonant silicon nanoparticles were separated by size to manage the scattering light at certain frequencies. • Direct comparison of 5 solutions with different size distribution of Si nanoparticles on optical properties of a perovskite layer. • Generation of electric and magnetic dipoles and quadrupoles by Si nanoparticles placed in a perovskite solar cell allows the maximum of light harvesting by a semiconductor layer. • Light harvesting by inclusion of Mie resonant nanoparticles is a universal tool to improve PV characteristics with any APbX3 composition. Optically resonant Mie-resonant nanoparticles are powerful tools for light control at the nanoscale, which have been employed for such applications as coloration, and metaoptics, where the size and shape of nanoparticle play a critical role in the device performance. Moreover, such nanoparticles are successfully used for the improvement of perovskite solar cells. However, there is a lack of experimental knowledge on how the size of Mie-resonant nanoparticles affects the improvement of parameters in the photovoltaic devices. Here we apply monodisperse silicon nanoparticles to investigate optical effects responsible for the improvement of perovskite solar cells. The experimental analysis shows that the most optimal sizes of silicon nanoparticles for the perovskite with bandgap 1.53 eV are in the range 140–160 nm. The main reason for such improvement is the optimization of absorption in the perovskite layer around wavelength 500–800 nm, where the Mie resonances in nanoparticles are not completely damped but contribute to additional light trapping and scattering. Our results can be useful not only for further optimization of perovskite solar cells, but also pave the way for improvement of a broader range of photovoltaic devices with integrated Mie-resonant nanoparticles. [ABSTRACT FROM AUTHOR]

Photonic crystals (PhC) can be elaborately tailored to enhance the electromagnetic properties of materials and are drawing increasing attention in recent years. However, there is no sufficient theoretical framework to optimize photonic crystal designs for electric enhancement. A comprehensive theoretical model is presented to illustrate Au/Ag photonic crystal enhancement on electric fields and obtain a group of optimal photonic crystal parameters after large number of statistics and parameter scans. The second and deeper layers of PhC only contribute to both 5% extinction and absorption in the far‐field, and there is almost no difference in |E|max among different layers with the coefficient variation at ≈1%. Furthermore, increment of both lattice constants and NP diameters can trigger dramatic changes in |E|max, and the maximal |E|max derived from 190 nm AuNP (nanoparticle)‐Au PhC with the lattice constant of 560 nm. This structure is 47.7, 7.39, 4.63, and 2.69 times that of AuNP incorporated silica wafer, silicon wafer, Ag wafer, and Au wafer, respectively. The strong electric field enhancement attributes to not only the plasmonic effect but also the photonic crystal enhancement effect. The simulation procedures open the possibility of precise photonic crystal structure design and pave the way for various electric field enhancement applications. [ABSTRACT FROM AUTHOR]

In this work, we present a plasmonic platform capable of the enhanced electric field (E-field) intensity, tunable LSPR effect, and trapping nanoparticles in different configurations of Ag triangular nanoplates. Our nanostructures equip the higher structural anisotropy (larger aspect ratio, 10:1), which localize surface plasmons in the gap region and possess the great factor of E-field enhancement (~850). Tunable near-field enhanced hotspots of Ag nanoplates support different resonant modes from 350 to 1200 nm, and the distribution of electric field and trapping potential well can also be manipulated. The hotspots for dimer enhance the optical force (~3.2 nN) on 30-nm polystyrene nanoparticles with a power density as low as 1 mW/μm2, which shows brilliant trapping characteristics. The tetramer with higher periodic symmetry provides a deep potential well (~ 1.3 × 10 3 kBT). It offers opportunities for the trapping and manipulating particles of nanoscale. And the nanogap structures pave a way for applications in surface-enhanced Raman scattering, surface-enhanced infrared absorption tunable biosensors. [ABSTRACT FROM AUTHOR]

A novel approach to the design and fabrication of field-emission tips with self-aligned gates intended for electric propulsion micro-thruster applications is presented. Their micro-electromechanical systems fabrication process is derived from the recent proliferation of research toward developing field emitter arrays, which are used primarily for field-emission flat-panel display applications. An array of micronsized tips for electric field enhancement via wet isotropic etching of silicon, using silicon nitride as a hard mask is fabricated. The wet etching is accomplished using a combination of hydrofluoric, nitric, and acetic acids. The tips were then coated with a metal layer to enhance wetting by indium, the proposed propellant. Next, a layer of SU-8 photoresist was applied by spin coating and patterned to serve as a dielectric spacer. A second layer of metal was then applied to serve as a gate electrode. In addition, the results of electrostatic simulations of the prototype is described.

Gold nanoparticle assemblies show a strong plasmonic response due to the combined effects of the individual nanoparticles' plasmon modes. Increasing the number of nanoparticles in structured assemblies leads to significant shifts in the optical and physical properties. We use finite-difference time-domain (FDTD) simulations to analyze the electromagnetic response of structurally ordered gold nanorods in monomer and dimer configurations. The plasmonic coupling between nanorods in monomers or dimers configurations provides a unique technique for tuning the spectrum intensity, spatial distribution and polarization of local electric fields within and surrounding nanostructures. This study shows an exponential coupling behavior when two gold nanorods are assembled in end-to-end and side-by-side dimer configurations with a small separation distance. The maximum electric field in the gaps between adjacent nanorods in end-to-end dimer configuration describes a more significant enhancement factor than the individual gold nanorod. Our FDTD simulation on dimer in end-to-end assembly for small separation distance up to ∼ 4 0 nm can well explain the observed experimental growth dynamics of gold nanorods. [ABSTRACT FROM AUTHOR]

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 × 108. 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. [ABSTRACT FROM AUTHOR]

Aligned electrospun fibers have always been obtained through various physical methods such as collector replacement or collecting acceleration. However, that faces a huge challenge for experimental complexity and risk. Here, adding a small amount of silver nitrate into electrospun solutions was confirmed as an effective approach that could change the final morphology of electrospun fibers to be aligned. Experiments had proved that electrospun fibers which were usually chaotic and disorderly at 500 rpm tend to form extremely aligned fibers after adding 0.1 wt% of silver nitrate. This conversion was considered that caused by the addition of silver nitrate which increases the conductivity of the electrospun solution and causes the mutual electric field to change during the spinning process. It turned the behavior of electrospinning in a twisting angle, which was originally disordered, into the result of cluster electrospinning. This method was expected to generate far-reaching significance for the development of aligned electrospun fibers. [ABSTRACT FROM AUTHOR]

Using state-of-the-art quantum mechanical calculations, we investigate the spatial profile of the electric field enhancements induced within an optical cavity embedded with a variety of organic molecules. We observed marked differences in the spectral positions, spectral intensities, maximum achievable electric field, and spatial profile of the electric field with a remarkable sensitivity to the embedded molecular type. In a broader perspective, our quantum mechanical calculations provide quantitative access to the molecule-dependent electric field distributions and unveil intricate and rich optical features. [ABSTRACT FROM AUTHOR]

The synergistic effect of electrostatically enhanced fibrous filtration originates from the charging characteristics of aerosol particles and electret fibers in an electric field. Two electrostatically enhanced fibrous filter systems are designed in this study to investigate the mechanism of the effects of the charging characteristics of oily aerosol on the filtration efficiency. We investigate the charging characteristics and their effects on the filtration efficiency of dioctyl-phthalate (DOP) aerosol particles of various sizes by setting different filter systems and electric field intensities. The experimental results show that the charge of DOP particles increases with the strength of the electric field, and the average charge increases with the particle size. The maximum charge of DOP particles reaches 4760 eC/P, and the filtration efficiency of the coupled system improves when DOP particles are amply charged. For 0.25 μm DOP particles as the most penetrating particle size, the system had good long-term stability, and the filtration efficiency is approximately 72% higher than that of the fiber acting alone. Meanwhile, the problem of oily aerosol deposition reducing the electret filtration efficiency is solved, providing a basis for long-term filtration and oily aerosol purification by electret fiber.

We propose a new theoretical method of producing a single attosecond pulse by high-order harmonic generation in hydrogen gaseous atoms above the conical plasmonic nanostructure (CPN) with a radially polarized laser field. The results show that the maximum amplification of the laser field above the structure apex about 4879 times can be provided by adjusting several physical characteristics of the structure and the incident light. Numerical studies show that the distribution of the amplification field above the CPN apex satisfies high-order harmonics generation (HHG) and attosecond pulse generation (APG) conditions by various incident laser beam intensities. Spectral analysis shows that this scheme can modulate the electron quantum paths. Selecting one quantum path, a broadband supercontinuum spectrum can be produced, which without phase compensation, directly generates a sharp isolated sub-20-attosecond pulse with a high signal-to-noise ratio. • High-order harmonic generation in gaseous atoms above the conical plasmonic nanostructure (CPN) with a radially polarized laser field. • Huge amplification of the laser field above the structure apex about 4879 times. • Generation of short sub-20as pulse without phase compensation at 10 10 W/cm 2 incident pulse. • Generation of intense high-order harmonics and attosecond pulses. [ABSTRACT FROM AUTHOR]

Anisotropic metal nanoparticles (NPs), such as high-aspect-ratio Au nanorods (NRs), play an important role for applications in photocatalysis, sensing, and drug delivery because of their adjustable plasmon resonances. Their performance for these applications can be further improved by fine-tuning their morphologies. Achieving desired NP architectures requires insight into their formation mechanisms. Here, liquid-phase transmission electron microscopy is used to directly follow the overgrowth of Au NR seeds into nanoarrows (NAs) with fourfold symmetric wings along the sides. Adding thiol molecules like L-cysteine to the growth solution can lead to the formation of NAs with periodic prismatic teeth instead of the straight side wings. These observations suggest that this transition is controlled by binding of L-cysteine to the NR surface, which in turn, slows down the metal deposition rate, switching the overgrowth from the kinetically to thermodynamically controlled process. Furthermore, simulations demonstrate that these prismatic teeth enhance the NPs' plasmonic properties. The study describes how thiol additives control the morphological evolution of metal NPs, which is important for the fabrication of NPs with tailored shapes for a broad range of applications. [ABSTRACT FROM AUTHOR]

A simplified and obvious electrotechnique model of the electric field enhancement in front of the propagating gas-discharge plasma channel is presented. A theory, developed some time ago by Yakovlenko, is criticized proving that a displacement of the electric field due to the plasma polarization behind the flat channel front is sufficient for the field enhancement ahead of the front. Arguing with this opinion, it is shown, in terms of the developed electrotechnique model, that for a significant field enhancement, as is known long ago, the cross-sectional area of the channel should be much less than that of the gas-discharge gap. The polarization self-acceleration of electrons is discussed. [ABSTRACT FROM AUTHOR]

We propose an approach for designing binary nanoslit structures (BNSs) in the case of back-side illumination to simultaneously control the propagation direction of surface plasmon polaritons (SPPs) and enhance their electric field intensities. In this approach, the geometrical parameters of two unit nanoslits of BNSs are first designed with the proposed SPP interference models, and then the number and the spatial arrangement of designed nanoslits are optimized to increase the electric field intensity and the unidirectivity of the SPPs produced by BNSs. We numerically demonstrate that under the back-side illumination condition, a BNS designed by the proposed approach can produce the SPPs whose extinction ratio is about 2420 and electric field intensity is enhanced by a factor of about 7.3, which is significantly larger than the electric field intensities of the SPPs produced by reference grating couplers under the same illumination condition.

This paper reviewed the research status of biodiesel catalytic hydrogenation and electric field enhanced treatment of biofuels in recent years. The industrialization process, progress of biodiesel catalytic hydrogenation, and electric field enhanced treatment of biofuel in recent years are reviewed in the investigation. The future research direction of biodiesel hydrogenation development is dug out according to the strengthening effect of the electric field on a chemical reaction. Researches have shown that the charged multiphase reaction system under electric field has significant advantages in enhancing mass transfer and phase interaction. Selective catalytic hydrogenation in an electric field environment, using electric field enhancement combined with catalytic process for hydrogenation upgrading, can enhance the activity and stability of the catalyst, greatly improve the catalytic chemical reaction rate, and significantly improve its oxidation stability and cetane number. This is an active technical method for modifying and upgrading biodiesel as a high-quality automotive biofuel. [ABSTRACT FROM AUTHOR]

The electric field distribution of Ag nanoparticles under femtosecond laser is simulated by solving Maxwell equations in this article. The results show that with the same laser energy, the coupling electric field between adjacent nanoparticles becomes stronger and stronger as the spacing between nanoparticles decreases, while the enhancement factor decreases rapidly when the spacing between nanoparticles is less than 1 nm, because under this condition, its mechanism includes not only the coupling of two dipoles, but also the electron tunneling between two surfaces. Besides laser energy, the electric field of Ag nanoparticles is greatly affected by the nanoparticles size and their spatial distribution. With the same laser energy and spacing, the smaller the particle size, the higher the peak value of electric field intensity, but the faster the attenuation with distance. In the polarization direction of the laser, the enhancement factor of the electric field is more obvious. When the laser acts on several Ag nanoparticles, the electric field of nanoparticles in the range of spot size is quite different from that of the nanoparticles outside the spot. [ABSTRACT FROM AUTHOR]

Strong electric field enhancement in the interparticle gap of resonators formed by two spherical Au nanoparticles occurs for polarization of the incoming light parallel to the dimer axis. This enhancement exhibits a strong dependence on gap width and is the basis of surface‐enhanced Raman scattering or tip‐enhanced Raman scattering. The enhancement factor as a function of gap width can be readily calculated solving Maxwellapos;s equations. However, the derived dependence is difficult to verify experimentally, in particular, because of the large uncertainty in determining the interparticle gap value, which is typically one or two orders of magnitude smaller than the diameters of the Au spherical nanoparticles forming the resonator. We demonstrate that a much more reliable verification of the predicted interparticle gap dependence of the electric field enhancement is possible using an approach analogous to triangulation in surveying and mapping. [ABSTRACT FROM AUTHOR]

We theoretically present the nanofocusing of the metal-coated fiber tip under internal excitation of the radial vector beam within visible band based on the finite difference time domain (FDTD) analysis. The electric field intensity enhancement factor of the localized surface plasmons (LSP) mode at the tip apex is quantitatively shown in relation with incident wavelength, coating material, conical angle of tip, and coating film thickness/length. Specially, the evolution of fiber radial vector mode to surface mode with respect to the radius of metal-coated fiber tip is calculated under typical excitation wavelengths of 633 nm and 785 nm. Furthermore, the reason of the tip eliminating far-field background signal is explained, and the transverse electric field distributions of LSP mode and the tip-substrate coupling are also given at the optimal excitation wavelength. These calculation results will be a good reference for the fabrication of metal-coated fiber tips and for the experimental design of the tip-enhanced spectroscopy (TES) system. [ABSTRACT FROM AUTHOR]