Local Electric Field Research Articles

Research on Typical Decay-like Fracture Defects of Composite Insulators Based on Electro-Thermal Coupling

In response to the typical decay and fracture defects of composite insulators, a three-dimensional electrically and thermally coupled simulation physical model was constructed based on the finite element method, and the local electric field distortion and temperature rise were analyzed. The study confirms that the insulator interface’s axial electric and thermal fields show a U-shaped curve; the interface field strength is the largest. There is an electric field gradient difference between the mandrel and the sheath, and the thermal field is concentrated at the mandrel and the interface. The field strength at the edge of the defect is the largest, the aberrant electric field at the defect shows a sawtooth shape, and the temperature rise is concentrated in the defect area. The degradation is fast in the air gap, the etching hole diameter direction, and the carbonation channel axial direction. The larger the defect volume, the larger the aberration in the electric field and temperature rise. Water vapor air gaps, breakdown holes, and carbonized channels have the most pronounced electric field and temperature changes. The functional relationship between electric field aberration, temperature rise, and defect volume is established. The results provide a basis for the protection of insulator decay-like fracture.

Enhanced Control of Single-Molecule Emission Frequency and Spectral Diffusion.

The Stark effect provides a powerful method to shift the spectra of molecules, atoms, and electronic transitions in general, becoming one of the simplest and most straightforward ways to tune the frequency of quantum emitters by means of a static electric field. At the same time, in order to reduce the emitter sensitivity to charge noise, inversion symmetric systems are typically designed, providing a stable emission frequency with a quadratic-only dependence on the applied field. However, such nonlinear behavior might be reflected in correlations between the tuning ability and unwanted spectral fluctuations. Here, we provide experimental evidence of this trend using molecular quantum emitters in the solid state cooled down to liquid helium temperatures. We finally combine the electric field generated by electrodes, which is parallel to the molecule's induced dipole, with optically excite long-lived charge states acting in the perpendicular direction. Based on the anisotropy of the molecule's polarizability, our two-dimensional control of the local electric field allows us not only to tune the emitter's frequency but also to sensibly suppress the spectral instabilities associated with field fluctuations.

Prolonged Phase Segregation of Mixed-Halide Perovskite Nanocrystals in the Dark.

A critical issue hindering the potential applications of semiconductor mixed-halide perovskites is the phase segregation effect, wherein localized regions enriched with one type of halide anions would be formed upon continuous photogeneration of the excited-state charge carriers. These unexpected phases are capable of remixing again in the dark under the entropic driving force, the process of which is now being exclusively studied after the mixed-halide perovskites have arrived at the final stage of complete phase segregation. Here, we show that after the removal of laser excitation from a solid film of the mixed-halide perovskite nanocrystals (NCs) with partial phase segregation, the iodide- and bromide-rich regions can continuously grow in the dark for a prolonged time period of several minutes. We propose that this dark phase segregation is sustained by the local electric fields from the surface-trapped charge carriers, whose slow dissipation out of the mixed-halide perovskite NCs causes a delayed occurrence of the reversal phase remixing process.

ICRF resonance cones in the low-density scrape-off-layer of ASDEX Upgrade

Abstract The ICRF slow wave is a potential carrier for parallel RF electric fields known to cause unwanted plasma-wall interactions in magnetic confinement fusion experiments.
In nowadays machines the slow wave is usually confined to the far scrape-off layer or the limiter shadow, but conditions in future experiments and reactors may allow the slow wave to be propagative in a larger region.

Simulations with RAPLICASOL for various geometries show that the ICRF slow waves appear as the so-called resonance cones characterized by large localized electric fields.
The resonance cones emerge from the points along the plasma-antenna interface where (in the cold plasma approximation) the radio frequency electric field diverges.
We demonstrate that in the parameter range of interest, the propagation of the resonance cones in a plasma with a density gradient is defined by a simple geometric model, using the local plasma density and the frequency as input parameters.
In the context of experiments at ASDEX Upgrade, simulations illustrate that the resonance cones can emerge from a single tile of the ICRF antenna limiter.
Experiments at the Ion-cyclotron System Hardware Test ARrangement (ISHTAR) were conducted to test the detection principle in a simple environment.
In agreement with simulations and with predicted characteristics which depend on operation parameters, the resonance cones are excited by an RF antenna and propagate through the relatively homogeneous plasma in ISHTAR. 
The cones are detected at a distance from the antenna using two probes scanning through the plasma.
In ASDEX Upgrade, a single tile of an antenna limiter was modified to launch RF power into a specially tailored low-density scrape-off layer.
Probes at the midplane manipulator were then used to detect the wave electric fields at a distance from the RF source.
The detected RF signals show that the signal maxima are located close to the lower hybrid resonance density and are highest when the source and the probes are connected along magnetic field lines.
These observations agrees with the model for resonance cones from the simulations.

Narrow‐Gap‐Integrated Ring Arrays (GRA) as Ultrahigh Field‐Enhancement Optical Resonators

AbstractGold nanoring nanoantenna are increasingly being utilized in biological and chemical sensing owing to their favorable spatially expanded hotspot distribution and distinctive field focusing capabilities. However, it is extremely challenging to further elevate the local electric field of nanorings for higher sensitivity without trading off the two aforementioned features. Here, a new nanoantenna design integrates conventional nanorings with nanogaps is introduced: in conjunction with metal sputtering and ion milling on a nanopillar template, narrow‐gap‐integrated ring arrays (GRA) are successfully nanofabricated featuring monolithic integration of nanoring arrays with sub‐5 nm nanogaps on‐chip. This new GRA nanophotonic structure simultaneously preserves the intrinsic benefits of the nanoring and amplifies the local electric field, achieving a field enhancement factor of up to 104 magnitudes. Using both top‐down and bottom‐up thin‐film processes, the GRA shows high degree‐of‐freedom in nanoantenna geometry, leading to tunable resonances throughout visible and near‐infrared wavelengths. These results combined showcased the potential of using GRA's tunable resonance, high e‐field enhancement, and wide hotspot‐distribution features in the creation of a universal molecular sensing platform for enhanced fluorescence.

Modeling Infrared Spectroscopy of Nucleic Acids: Integrating Vibrational Non-Condon Effects with Machine Learning Schemes.

Vibrational non-Condon effects, which describe how molecular vibrational transitions are influenced by a system's rotational and translational degrees of freedom, are often overlooked in spectroscopy studies of biological macromolecules. In this work, we explore these effects in the modeling of infrared (IR) spectra for nucleic acids in the 1600-1800 cm-1 region. Through electronic structure calculations, we reveal that the transition dipole moments of the C═O and C═C stretching modes in nucleobases are highly sensitive to solvation, hydrogen bonding, and base stacking conditions. To incorporate vibrational non-Condon effects into spectroscopy modeling, we use local electric fields on chromophore atoms as collective coordinates and leverage experimental IR spectra of oligonucleotides to develop deep neural network-based transition dipole strength (TDS) maps for the C═O and C═C chromophores. By integrating molecular dynamics simulations with a mixed quantum/classical treatment of the line shape theory, we apply the TDS maps to calculate the IR spectra of nucleoside 5'-monophosphates, DNA double helices and yeast phenylalanine tRNA. The resulting theoretical spectra show quantitative agreement with experimental measurements. While the predictions for nucleoside 5'-monophosphates are comparable to baseline performance, the TDS maps yield significantly improved IR peak intensities across all oligonucleotides. This theoretical framework effectively bridges atomistic simulations and IR spectroscopy experiments, offering molecular insights into how vibrational non-Condon effects impact the observed spectral features.

Plasmon-enhanced NIR-II photoluminescence of rare-earth oxide nanoprobes for high-sensitivity optical temperature sensing.

With ongoing advancements in photothermal therapy, achieving efficient tumor cell eradication while minimizing damage to healthy tissues necessitates a highly effective and non-invasive real-time temperature monitoring technique for human tissues. Herein, we report a near-infrared (NIR)-II optical temperature sensing nanoprobe featuring rare-earth-doped gadolinium oxide nanocrystals (RENCs) attached to the dumbbell mesoporous silica-coated gold nanorods (AuNRs). The composite nanoprobe presents an intense absorption in the NIR region, and NIR-II photoluminescence (PL) increases by 97.2 to 102-fold compared to pure RENCs upon 980 nm irradiation. The localized electric field generated through surface plasmon resonance effects of AuNRs demonstrated a dumbbell-shaped distribution that aligns with the structure of nanoprobes, maximizing the PL enhancement of RENCs. Moreover, the NIR-II emissions are changed with the rising temperature, with an exceptional relative sensitivity of 7.25% K-1 at 338 K based on PL lifetime, indicating the nanoprobe is highly potential for optical temperature sensing.

Bipolar Membranes With Controlled, Microscale 3D Junctions Enhance the Rates of Water Dissociation and Formation

AbstractA soft lithographic method is developed for making bipolar membranes (BPMs) with catalytic junctions formed from arrays of vertically oriented microscale cylinders. The membranes are cast from reusable polydimethylsiloxane (PDMS) molds made from silicon masters, which are fabricated on 2″ to 4″ wafer scales by nanosphere lithography. High‐aspect‐ratio junctions are made on a length scale similar to the thickness of optimized catalyst layers for water dissociation, creating a platform for probing the dual effects of catalysis and local electric field at the microscale BPM junction. Optimized polymer materials and nanoscale metal oxide catalysts are used in this study. 3D BPMs are tested under reverse and forward bias conditions, exhibiting superior performance relative to their 2D counterparts. Under forward bias in H2‐O2 fuel cells, 3D BPMs achieve a current density of 1500 mA cm−2, ≈7 times higher than 2D membranes made from the same materials.

Understanding melting behavior of aluminum clusters using machine learned deep neural network potential energy surfaces.

Deep neural network-based deep potentials (DP), developed by Tuo et al., have been used to compute the thermodynamic properties of free aluminum clusters with accuracy close to that of density functional theory. Although Jarrold and collaborators have reported extensive experimental measurements on the melting temperatures and heat capacities of free aluminum clusters, no reports exist for finite-temperature abinitio simulations on larger clusters (N > 55 atoms). We report the heat capacities and melting temperatures for 32 clusters in the size range of 48-342 atoms, computed using the multiple histogram technique. Extensive molecular dynamics (MD) simulations at twenty four temperatures have been performed for all the clusters. Our results are in very good agreement with the experimental melting temperatures for 19 clusters. Except for a few sizes, the interesting features in the heat capacities have been reproduced. To gain insight into the striking features reported in the experiments, we used structural and dynamical descriptors such as temperature-dependent mean squared displacements and the Lindemann index. Bimodal features observed in Al116 and the weak shoulder seen in Al52 are attributed to solid-solid structural transitions. In confirmation of the earlier reports, we observe that the behavior of the heat capacities is significantly influenced by the nature of the ground state geometries. Our findings show that the sharp drop in the melting temperature of the 56-atom cluster is a consequence of the change in the geometry of Al55. Mulliken population analysis of Al55 reveals that the charge-induced local electric field is responsible for the strong bonding between core and surface atoms, leading to the higher melting temperature. Our calculations do not support the lower melting temperature observed in experimental studies of Al69. Our results indicate that Al48 is in a liquid state above 600K and does not support the high melting temperature reported in the experiment. It turns out that the accuracy of the DP model by Tuo et al. is not reliable for MD simulations beyond 750K. We also report low-lying equilibrium geometries and thermodynamics of 11 larger clusters (N = 147-342) that have not been previously reported, and the melting temperatures of these clusters are in good agreement with the experimental ones.

Extraordinary terahertz transmission and field enhancement via hybrid surface plasmon coupling in rhombic and bow-tie composite aperture metasurface

Metasurface that achieves extraordinary terahertz transmission (ETT) and local electric field enhancement (FE) holds significant potential for terahertz studies involving extremely low concentrations of target materials. In this study, we explore a composite aperture metasurface capable of both ETT and local FE. By inserting bow-tie apertures in the “minimum-resonance” zone between four adjacent rhombic lattices, a local FE factor is achieved. Notably, adjusting the configuration of the bow-tie aperture enhances the coupling between surface plasmons, thereby expanding the transmission bandwidth. Through parameter optimization, the metasurface achieves a peak transmission exceeding 95% and a transmittance above 80% in the frequency range of 2.44–3.65 THz, while simultaneously exhibiting a maximum local FE factor of 1005 at 3.45 THz. This approach offers a promising avenue for the design of metasurfaces for spectroscopy and biosensor applications.

Elucidating the Interplay between Symmetry Distortions in Passivated MAPbI3 and the Rashba Splitting Effect.

Hybrid organic-inorganic perovskites play a critical role in modern optoelectronic applications, particularly as single photon sources due to their unusual bright ground state. However, the presence of trap states resulting from surface dangling bonds hinders their widespread commercial application. This work uses density functional theory (DFT) to study the effects of various passivating ligands and their binding sites on Rashba splitting, a phenomenon directly linked to the bright ground state. Our results predict that X2- and X4-type ligands that adsorb at acidic oxygen binding sites and zwitterionic binding sites efficiently eliminate trap states introduced by surface iodine vacancies. Furthermore, our results show that distortions from the nominally symmetric cubic structure of the perovskite predominantly determine the presence and magnitude of the Rashba splitting. Specifically, the loss of more symmetry elements consistently leads to Rashba splitting in both the valence band (VB) and the conduction band (CB) with small Rashba splitting coefficients. Conversely, although inversion symmetry breaking alone fails to guarantee the presence of pure Rashba splitting in both the VB and the CB, it significantly increases the degree of splitting. The adsorption of ligands not only mitigates trap states but also plays a critical role in altering the local symmetry, thus influencing Rashba splitting. DFT predicts a distinct Rashba-Dresselhaus splitting in the CB with X2 ligands, causing the largest splitting. The presence of local electric fields causes consistent Rashba splitting of the VB across all studied systems except for the X4 zwitterionic passivated systems (sulfobetaine and lecithin). Electric fields are predicted to cause significant splitting of the CB, particularly for MAPbI3 and SH passivated MAPbI3 surfaces that possess freely rotating ligand binding sites. This study reveals that the wavelength, tunability of Rashba splitting through an applied electric field, and nature of Rashba-Dresselhaus splitting are influenced by the characteristics of the ligand binding site. On the other hand, pure Rashba splitting is predicted to exhibit a greater susceptibility to symmetry distortion than to specific ligand binding sites. These findings elucidate how surface passivating ligands and symmetry distortions influence Rashba splitting, shaping the optoelectronic properties of perovskite nanocrystals.

Exploring the potential of induced dipole-dominated electrorheological effect: advancing ER elastomers

Abstract Prior research has predominantly focused on traditional electrorheological (ER) effects while overlooking the transformative potential of induced dipoles in enhancing the overall performance of ER materials. In this study, we introduced a novel type of ER elastomer called induced dipole-dominated ER elastomer (ID-ERE). Through high-energy ball milling (HEBM) of the filler particles, the oxygen vacancies were produced within the particles that acted as local charge centers. In the presence of an external electric field (E), these oxygen vacancies induced the dipoles with significant dipole moments, thus amplifying the local electric field EL within the particle gaps. The powerful interactions of these dipoles significantly improved the overall performance of elastomer; the phenomenon referred to as the ID-ER effect. The viscoelastic results showed that ID-EREs have high field-induced storage modulus (G’ = 395.7 kPa), a significant increment in storage modulus (ΔG’ = 270.5 kPa) and high relative ER effect (ΔG’/G0 = 217.2%) at 3 kV mm−1. Additionally, after testing ID-EREs viscoelastic properties, it was discovered that excessive powder content leads to a decline in the elastomer’s performance. The results showed that ID-ERE’s viscoelastic, mechanical, dielectric, and overall efficiency is finer than the control ER elastomer (C-ERE) having unmilled TiO2 particles. Besides, the preparation method is straightforward, easily replicated, scalable, and cost effective. Thus, these ID-EREs should be a new generation of elastomer with the potential to be used in various automotive, robotics, construction, and electroactive actuators industries.

Improved piezoelectric properties and thermal stability in ZnO-modified 0.39BiScO3-0.61PbTiO3 ceramics by structure regulation

In this work, ZnO was introduced into 0.39BiScO3-0.61PbTiO3 (xZn-BS-61PT), and the phase structure and local structure of ceramics were controlled by a combination of cation substitution and ceramic/semiconductor composite, so as to improve the piezoelectric properties and temperature stability of ceramics. Zn2+ substitute B-site Ti4+ of BS-61PT, resulting in a stable coexistence of rhombohedral (R)-tetragonal (T)-monoclinic (M) phases dominated by T phase. Excessive Zn ions displace the Sc ions, making Sc ions spontaneously crystallize at grain boundaries in the form of an oxide at x ≥ 0.015. The piezoelectric coefficient and Curie temperature (d33, Tc) are increased from (326 pC/N, 416 °C) for x = 0 to (431 pC/N, 433 °C) for x= 0.015. After annealing at 200 °C, the ZnO-modified samples still retrain high d33 value (d33 > 330 pC/N). For x=0.015 sample, after aged 12 months, the retrained d33 is 395 pC/N, only down 8%. The improved properties are attributed to the synergistic effects of phase structure, point defects and local electric fields. Our results provide a design strategy to simultaneously improve the piezoelectric properties and temperature stability. Meanwhile, it is beneficial to broaden the phase.boundary (MPB) composition range of BS-xPT ceramics, and reduce the dependence of performance on components.

Discharge modes evolution characteristics of metal particle on the spacer surface in AC gas insulated switchgear

Abstract Flashover faults on gas insulated switchgear (GIS) insulators induced by metal particles occur frequently. Previous studies have obtained the characteristics of partial discharges (PDs) induced by metal particles on spacer surfaces, but these characteristics cannot explain the detection failure of ultra-high frequency (UHF) online monitoring. To enable further study of the PD characteristics induced by surface metal particles, the space electric field and a very-high-sensitivity pulse current (PC) measurement system were established. The electric field and PC characteristics of a PD induced by metal particle on the spacer surface of a 126 kV GIS were obtained. Two PD modes were found to be induced by surface metal particles. In addition to the typical pulse discharge (TP), there is a micro-discharge group (MG) mode with low apparent charge and long duration. The average apparent charge of the MG mode is approximately one-tenth of that of the TP at 0.4 pC. Its duration may extend to the millisecond level, causing significant distortion of the spatial electric field while hardly producing UHF signals. Moreover, increasing the applied voltage will increase the proportion of the MG within the total discharge, where this proportion can reach more than 90% before flashover, and the proportion of the discharge pulses that generates UHF signals is as low as 1%. The MG generation mechanism is analysed, the ion group stranded on the spacer surface by the TP changes the local electric field at the tip of the metal particle, which reduces the development length and apparent charge of the MG. Low apparent charge is cleared easily by the background electric field and thus the discharge interval is very short. This paper can provide an important basis for revealing the mechanism of GIS spacer surface discharge induced by metal particles and solving the effectiveness of PD monitoring devices.

TM@MoSSe (TM = Ni, Fe) as novel electrocatalysts for reduction of CO2 to CO: A DFT study

It is crucial to develop highly efficient, selective and low-overpotential electrocatalysts for CO2 reduction. This paper proposes an efficient iron and nickel single-atom catalyst using Janus MoSSe as the substrate to reduce CO2 to CO by using DFT calculations. The adsorption of a single TM atom like Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt on Janus MoSSe monolayer results in a decrease in band gap, which may accelerate the catalytic CO2 reduction. The excellent catalytic activity of Fe@MoSSe and Ni@MoSSe is owing to the high d-band center and hence the strong TM-CO2 bonding. The asymmetric structure of Janus MoSSe creates the local built-in electric field, which further increases by about 8% or 0.8% after the adsorption of single Ni or Fe atom so as to afford the better electrocatalytic performances for reduction of CO2 to CO in both TM modified systems. So, this work proposes the catalysts Fe@MoSSe and Ni@MoSSe with good selectivity and activity for CO2 reduction by revealing their underlying mechanisms, and Janus MoSSe may be used as a potential substrate material for CO2 reduction catalysts.

Low-voltage and high-contrast polymer dispersed liquid crystals enabled by ferroelectric fluoro-copolymer doped polyimide film

Smart windows incorporating polymer dispersed liquid crystal (PDLC) technology provide user-friendly operation and play a significant role in intelligent buildings and building energy conservation. Long standing issues of the PDLCs such as high driving voltage, low contrast ratio, and narrow viewing angle hinder their applications. Here PDLCs are sandwiched between the hybrid substrates composed of the ferroelectric polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) copolymer and the homogeneous polyimide. The high dielectric constant and ion-trapping ability of ferroelectric copolymers increase the effective voltage drop in the PDLCs. Concurrently, the local electric field created by large dipole moment of ferroelectric copolymers triggers the alignment of liquid crystals (LCs) along the applied field. These synergistic effects contribute to a substantial decrease in the driving voltage of PDLCs. In the opaque state, the random dipole moments in ferroelectric copolymers disrupt the LC orientations near hybrid substrates, thereby increasing the light scattering and reducing the transmission of PDLCs. Consequently, the proposed PDLCs exhibit a contrast ratio ∼2× higher compared to the conventional PDLCs at normal incident. Moreover, the proposed PDLCs demonstrate a wider viewing angle in the transparent state compared to conventional PDLCs. This development promises energy-efficient, eco-friendly, and cost-effective smart windows.

Effects of translation misalignment on ion optics with slit apertures

For ion thrusters, the deflection of the ion beam caused by the relative translation of the grids is one of the primary factors limiting the erosion lifetime of the ion optical system. A two-dimensional (2D) simulation package of the ion optic system is developed to investigate the ion sputtering corrosion due to grid translation misalignment. For benchmark cases, the 2D simulation package shows a reasonable consistency compared to the experimental method in ion beam deflection angle and drain-to-beam current ratio, indicating the effectiveness of the simulation package. The deviation between the simulated deflection angle and the experimental value is within 8.86%. Furthermore, this 2D package is employed to analyze the variation patterns of ion beam, ion collection, and the distribution of ion sputtering rates caused by grid translation. The simulation results indicate that the ion beam deflection occurs in the direction opposite to grid translation. The number of ions collected at different positions on the acceleration grid shows different tendencies. Only the upstream surface Sy− and the aperture surface Sx+ will be subjected to energetic ion impingement. The sputtering of energetic ions on these two surfaces becomes the dominant factor limiting the grid’s ion corrosion lifetime when the grid translation is significant. The sputtering rate of energetic ions can exceed that of charge exchange (CEX) ions by more than 10 times. The proportion of the region where energetic ions contribute to sputtering expands with increasing grid misalignment, reaching up to 52.5% on surface Sx+. Additionally, the downstream surface Sy+ and the aperture surface Sx− are only subjected to CEX ion sputtering regardless of grid translation. Moreover, the CEX ion sputtering regions on surfaces Sx− and Sx+ expand as the grid misalignment distance increases. The peak in the ion sputtering rate distribution profile on surface Sy+ becomes more prominent due to grid translation, with the sputtering rate at the peak position reaching approximately 1.65 times that of the surrounding lower-rate regions. The analysis of the electric field indicates that local electric field variations caused by grid misalignment are the underlying reason for the ion erosion characteristics.

Linear dielectric ceramics for near-zero loss high-capacitance energy storage

High energy-density (Wrec) dielectric capacitors have gained a focal point in the field of power electronic systems. In this study, high energy storage density materials with near-zero loss were obtained by constructing different types of defect dipoles in linear dielectric ceramics. Mg2+and Nb5+ are strategically chosen as acceptor/donor ions, effectively replacing Ti4+ within Ca0.5Sr0.5TiO3-based ceramics. The results indicate that under an applied electric field, specific defects such as [MgTi″−VO··] and [NbTi·−Ti3+], can effectively regulate VO·· and electron movement, significantly reducing losses. Furthermore, high-density insulating grain boundaries, reduced VO·· concentrations and diminished carrier mobility contribute to enhanced resistivity, resulting in high Wrec ∼7.62 J/cm3 and η ∼92 % at 640 kV/cm, making it one of the most promising linear dielectrics to date. Notably, Wrec and η remain remarkably stable across a broad range of frequencies (1–500 Hz), temperatures (25–175 °C) and numerous cycles (up to 106). Additionally, finite element software was used to simulate the distribution of dielectric constant, electric potential, and local electric field, further verifying the correlation between microstructure and breakdown resistance. This innovative work provides a sustainable strategy to optimize the energy storage capacity of lead-free ceramics over a wide temperature range through strategic manipulation of defects.

High Q transparency, strong third harmonic generation, and giant nonlinear chirality driven by toroidal dipole-quasi-BIC

Electromagnetically induced transparency (EIT), nonlinearity, and optical chirality hold significant applications in many areas such as optical switches, slow-light devices, chiral harmonic conversion, and optical storage. In this work, we theoretically propose an asymmetric all-dielectric metasurface supporting toroidal dipole-quasi-bound states in the continuum (TD-q-BICs). High quality (Q) EIT, strong third harmonic generation (THG), and giant nonlinear chirality are achieved via the extremely enhanced electric field energy localized in the Si plate by the TD-q-BIC. A huge transition from high Q EIT with transmission of ∼0.99 to strong chirality with circular dichroism (CD) of ∼0.9 is realized by tuning the angle and polarization state of incident light. Strong THG with efficiency of 4.5 × 10−3 under linear polarization light is due to the highly localized electric field supported by the TD-q-BIC and perfect nonlinear CD chirality with theoretically value of ∼1 originates from the large discrepancy in electric field distributions under different circularly polarized light. Our work provides an innovative paradigm to construct TD-q-BICs-governed EIT analogs, THG, and nonlinear chirality for the development of multifunction nanophotonic meta-devices.

Piezoelectric Heterojunctions as Bacteria-Killing Bone-Regenerative Implants.

Heterojunctions are widely used in energy conversion, environmental remediation, and photodetection, but have not been fully explored in regenerative medicine. In particular, piezoelectric heterojunctions have never been examined in tissue regeneration. Here the development of piezoelectric heterojunctions is shown to promote bone regeneration while eradicating pathogenic bacteria through light-cellular force-electric coupling. Specifically, an array of heterojunctions (TiO2/Bi2WO6), made of piezoelectric nanocrystals (Bi2WO6) decorating TiO2 nanowires, is fabricated as a biocompatible implant. Upon exposure to near-infrared light, the piezoelectric heterojunctions generate reactive oxygen species and heat to kill bacteria through photodynamic and photothermal therapy, respectively. Meanwhile, the mechanical forces of the stem cells grown on the implant trigger the heterojunctions to produce electric fields that further promote osteogenesis to achieve osteointegration. The heterojunctions effectively suppress postoperative recurrent infections while promoting osseointegration through the local electric fields induced by cells. Therefore, the piezoelectric heterojunctions represent a promising antibacterial tissue-regenerative implant.