Electromagnetic Field Intensity Research Articles

Free electron emission in vacuum assisted by photonic time crystals

The Cerenkov radiation and Smith–Purcell (SP) effect state that free electron emission occurs exclusively in dielectrics when the velocity of the particles exceeds the speed of light in the medium or in the vicinity of periodic gratings close to each other within a vacuum. We demonstrate that free electrons in a vacuum can also emit highly directional monochromatic waves when they are in close proximity to a medium that is periodically modulated temporally, suggesting the existence of the temporal SP effect. The momentum band gaps of time-varying media, such as photonic time crystals (PTCs), create new pathways for the injection of external energy, allowing the frequency, intensity, and spatial distribution of electromagnetic fields to be controlled. Moreover, the PTC substrate enables the conversion of localized evanescent fields into amplified, highly directional propagating plane waves that are only sensitive to the velocity of particles and the modulation frequency, which allows us to observe and utilize Cerenkov-like radiation in free space. Our work presents significant opportunities for the utilization of time-varying structures in various fields, including particle identification, ultraweak signal detection, and improved radiation source design.

Расчетная модель эффективности защиты электромагнитного поля (на примере рабочего места поездного диспетчера)

The article addresses the growing concern over the adverse health effects of electromagnetic radiation in workplaces, particularly in the context of train dispatchers who are exposed to various sources of electromagnetic fields. A computational model is developed to assess the effectiveness of shielding equipment in mitigating the impact of electromagnetic fields on train dispatchers. The study focuses on the design and evaluation of protective casings and shields to reduce electromagnetic field intensity, providing valuable insights for enhancing workplace safety.

Comparison of anomalies in the VLF spectrum of the natural electromagnetic field with data from the seismometer in a landslide-affected area

The data from a permanent monitoring station, based on a sound card as an AD/DA converter and a magnetic loop antenna for continuous recording of electromagnetic field intensities in the Very Low Frequency (VLF) range, were recorded and compared with data from a seismic station based on Raspberry Pi located in a landslide-affected area. The stations operated 24/7 and were placed in a room below ground level. Correlations were observed between seismic signals in the frequency spectrum from 0.1 Hz to 10 Hz (some extending beyond 20 Hz) and anomalies in the electromagnetic field in the VLF range. These anomalies are likely associated with micro-fracturing, piezo-electromagnetic, and triboelectric phenomena within the landslide body, producing relatively weak VLF emissions and a faint seismic signal. A single-component 4.5 Hz 395 Ohm vertical Racotech RGI-20DX geophone with electronic extension to lower frequencies (< 1 Hz) was used with a sampling rate of 100 sps (samples per second). VLF emissions cover almost the entire spectrum from 6 kHz with a peak at 14 kHz to 18 kHz. The received spectrum was divided into following sections: VLF band 4 kHz – 6 kHz; 6 kHz – 8 kHz; 8 kHz – 10 kHz; 10 kHz – 12 kHz; 12 kHz – 14 kHz; 14 kHz – 16 kHz; 16 kHz – 18 kHz. Simultaneously, there were changes in these sections analysed and compared with the seismic record within the same time interval.

Revolutionizing plasmonic platform via magnetic field-assisted confined ultrafast laser deposition of high-density, uniform, and ultrafine nanoparticle arrays

The remarkable capabilities of 2D plasmonic surfaces in controlling optical waves have garnered significant attention. However, the challenge of large-scale manufacturing of uniform, well-aligned, and tunable plasmonic surfaces has hindered their industrialization. To address this, we present a groundbreaking tunable plasmonic platform design achieved through magnetic field (MF) assisted ultrafast laser direct deposition in air. Through precise control of metal nanoparticles (NPs), with cobalt (Co) serving as the model material, employing an MF, and fine-tuning ultrafast laser parameters, we have effectively converted coarse and non-uniform NPs into densely packed, uniform, and ultrafine NPs (∼3 nm). This revolutionary advancement results in the creation of customizable plasmonic ‘hot spots,’ which play a pivotal role in surface-enhanced Raman spectroscopy (SERS) sensors. The profound impact of this designable plasmonic platform lies in its close association with plasmonic resonance and energy enhancement. When the plasmonic nanostructures resonate with incident light, they generate intense local electromagnetic fields, thus vastly increasing the Raman scattering signal. This enhancement leads to an outstanding 2–18 fold boost in SERS performance and unparalleled sensing sensitivity down to 10−10 M. Notably, the plasmonic platform also demonstrates robustness, retaining its sensing capability even after undergoing 50 cycles of rinsing and re-loading of chemicals. Moreover, this work adheres to green manufacturing standards, making it an efficient and environmentally friendly method for customizing plasmonic ‘hot spots’ in SERS devices. Our study not only achieves the formation of high-density, uniform, and ultrafine NP arrays on a tunable plasmonic platform but also showcases the profound relation between plasmonic resonance and energy enhancement. The outstanding results observed in SERS sensors further emphasize the immense potential of this technology for energy-related applications, including photocatalysis, photovoltaics, and clean water, propelling us closer to a sustainable and cleaner future.

Tecoma stans Floral Extract-Based Biosynthesis for Enhanced Surface Plasmon-Coupled Emission and a Preliminary Study on Fluoroimmunoassay.

We demonstrate the synthesis of biogenic supported silver spiked star architectures and their application to increase the electromagnetic field intensity at its tips that enhance plasmon-coupled emission. Tecoma stans floral extract has been used to synthesize silver nanocubes and spiked stars. We observe ∼445-fold and ∼680-fold enhancements in spacer and cavity configurations, respectively, in the SPCE platform. The hotspot intensity and Purcell factor are evaluated by carrying out finite-difference time-domain (FDTD) simulations. Time-based studies are presented to modulate the sharpness of the edges wherein an increase in the tip sharpness with the increase in reaction time up to 5 h is observed. The unique morphology of the silver architectures allowed us to utilize them in biosensing application. A SPCE-based fluoroimmunoassay was performed, achieving a 1.9 pg/mL limit of detection of TNF-α cytokine. This combination of anisotropic architectures, SPCE and immunoassay prove to be a powerful platform for the ultrasensitive detection of biomarkers in surface-bound assays.

Recent advance on fiber optic SPR/LSPR-based ultra-sensitive biosensors using novel structures and emerging signal amplification strategies

Biomarkers with ultralow concentration in the actual samples play a vital role in the clinical disease diagnosis, infectious disease screening, food security, and environmental monitoring. Fiber optic (FO)-based surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) biosensors attract immense attention for in situ, and rapid detection due to their merits of miniaturized devices, easy integration, and low cost, showing great promising for point of care point-of-caring test. In order to achieve ultrasensitive detection of biomarkers, great effort focused on design of a sensitive FO-based biosensor on the aspect of novel FO probes and signal amplification strategies. Firstly, novel FO probes, including gating and new structure-based, were develop to adjust the light propagation and allow intensely interaction between the light and metal film or nanoparticles, which excites strong SPR or LSPR for sensitive biosensor. Then, nanomaterials on FO surface improved the intensity of electromagnetic fields or provided a good scaffold to modify with more recognition element for signal amplification. Nucleic acid circuits get rid of the limitation of the signal-to-target ratio of 1:1 and exhibited high efficiency to amplify the signal. These efforts have also led to the application of FO-SPR and LSPR sensors for detection of various targets, such as cells, nucleic acids, proteins, and small molecules. In the review, we summarized the important progress of the ultrasensitive FO-based biosensor about emerging FO probes and signal amplification strategies, also discussed its opportunities and challenges for the point-of-caring test. The review aims to promote the application of the FO-SPR and LSPR from experiments to real samples.

Mapping of Electromagnetic Field Radiation Intensity in the JL Base Transceiver Station (BTS) Area. Kenangan 05 and the Impact of Health in Society


 
 
 
 Electromagnetic waves are a type of wave phenomenon. Electromagnetic waves are transverse waves that arise due to changes in electric fields and magnetic fields that oscillate with each other. Electromagnetic waves can be generated, one of the ways, from BTS towers so that they can produce intense electromagnetic field radiation. Health problems resulting from exposure to electromagnetic wave radiation cannot be felt directly. However, the longer you are exposed to electromagnetic wave radiation, the more dangerous it will be to your body's health. The aim of this research is to carry out mapping from measuring the intensity of electromagnetic field radiation in the BTS area and to determine the health impact of large electromagnetic field radiation on the surrounding community. Data processing in this research was carried out using quantitative techniques and qualitative techniques, namely by measuring the intensity of the electric field and magnetic field of electromagnetic waves and evaluating the results of the intensity of electromagnetic field radiation as well as conducting interviews as a public health survey. The data obtained in this research was processed using ArcGis and Surfer software for mapping results. Based on the evaluation and mapping results, it shows that the intensity of electromagnetic field radiation is still below the threshold value according to the 2020 ICNIRP standards. Based on the results of this research, there are no significant health effects occurring in the surrounding community.
 
 
 

Facilitating excited-state plasmonics and photochemical reaction dynamics

Continuously advancing technologies is crucial to tackling modern challenges such as efficient energy transfer, directing catalytic behavior, and better understanding of microscopic phenomena. At the heart of many of these problems is nanoscale chemistry. In previous decades, the scientific community has made significant progress in nanoscale structures and technologies, especially relating to their interactions with light. Plasmonic nanostructures have been extensively studied over the past decades because of their fascinating properties and vast technological applications. They can confine light into intense local electromagnetic fields, which has been exploited in the fields of spectroscopy, energy harvesting, optoelectronics, chemical sensing, and biomedicine. Recently, however, plasmonic nanostructures have shown great potential to trigger chemical transformations of proximal molecular species via hot carrier and thermally driven processes. In this review, we discuss the basic concepts governing nanoscale light–matter interactions, the immediate phenomena induced by them, and how we can use nanoscale light–matter interactions to our advantage with surface-enhanced spectroscopy techniques and chemical reactions in confined plasmonic environments.

Synergistic enhancement of ultrahigh SERS activity via Cu2O@Ag Core-Shell structure for accurate label-free identification of breast tumor subtypes

Conventional methodology for accurate identification of breast tumor subtypes is complex and time-consuming. Label-free SERS (surface-enhanced Raman scattering) enables rapid detection of biomolecules and provides intrinsic fingerprint information of analytes. Exploring reliable SERS bioprobes with high sensitivity and repeatability is essential for efficient typing of cancer cells. In this study, a novel core-shell noble metal-semiconductor Cu2O@Ag heterostructure with uniform morphology and outstanding SERS activity for label-free detection has been proposed. The Cu2O@Ag SERS substrates exhibit exceptional sensitivity to detect 4 nitrophenthiol (4NTP) at extreme low concentration (10−15 M), and the SERS spectra demonstrate excellent selectivity and repeatability (RSD ≈ 8.84%). The enhancement mechanism is attributed to the synergistic enhancement of photoinduced charge transfer and boosted surface plasmon resonance effect, confirmed by reduced fluorescence lifetime of methylene blue on SERS substrates and enhanced electromagnetic field intensity via finite-difference time-domain computational simulation. The ultrahigh sensitivity and good signal stability endow Cu2O@Ag SERS bioprobe potential for accurate detection of four breast cancer cells subtypes. The rich fingerprint information from SERS spectra is processed using linear differentiation analysis, revealing a high accuracy of 93.3% for subtypes classification. These results demonstrate an excellent SERS bioprobe with high sensitivity and repeatability for precision diagnosis has been developed.

Ultra‐Fast Pulsed Discharge Preparation of Coordinatively Unsaturated Asymmetric Copper Single‐Atom Catalysts for CO2 Reduction

AbstractSingle‐atom catalysts possess great potential for applications in electrochemical carbon dioxide reduction reactions. Recently, the fast and low‐cost preparation of highly efficient single‐atom catalysts remains a challenge. Herein, a high‐density current generated by pulsed discharge is employed for the formation of graphene aerogel anchored Cu single atom catalysts perfectly. The Cu atoms decomposed by Cu(NO3)2•xH2O are fixed on graphene under the local transient high temperature and intense electromagnetic field. The activity and selectivity of formic acid are correlated with the coordinatively unsaturated Cu─N1O1 moieties, reaching an optimal Faradaic efficiency (93.7%) at −0.9 V versus a reversible hydrogen electrode (RHE). In situ characterizations reveal that the asymmetric Cu─N/O structure in a pinched state displays better catalytic activity in CO2RR. Density functional theory results indicate that the Cu─N1O1 sites regulate the adsorption configuration of intermediates and lower the energy barrier for the hydrogenation of *OCHO species, thereby promoting CO2‐to‐HCOOH conversion.

Tunable acoustic graphene plasmon enhanced nano-infrared spectroscopy

Nano-infrared spectroscopy (nano-IR) technology can surpass the diffraction limit of light, achieving infrared spectroscopic detection with a spatial resolution of ~ 10 nm, which is an important technical means for studying the chemical composition and structure of molecules at the nanoscale. However, the weak infrared absorption signals of nanoscale materials pose a significant challenge due to the large mismatch between their dimensions and the wavelength of infrared light. The infrared absorption signals of molecular vibrational modes are proportional to the square of the electromagnetic field intensity at their location, meaning that higher electromagnetic field intensity can significantly enhance molecular detection sensitivity. Acoustic graphene plasmons (AGP), excited by the interaction between free charges in graphene and image charges in metals, exhibit strong optical field localization and electromagnetic field enhancement. These properties make AGP an effective platform for enhancing nano-IR detection sensitivity. However, the fabrication of graphene nanostructures often introduces numerous edge defects due to the limitations of nanofabrication techniques, significantly reducing the electromagnetic field enhancement observed in experiments. Here, using finite element simulation, we theoretically propose a tunable enhanced nano-IR detection platform based on nanocavity-acoustic graphene plasmon (n-AGP), utilizing a graphene/air gap/gold nanocavity structure. This platform avoids the need for nanofabrication of graphene, thereby preventing defects and contamination introduced by processes such as electron beam exposure and plasma etching. By plotting the dispersion of n-AGP, we found that n-AGP has a high wavelength compression capability comparable to AGP (<i>λ</i><sub>0</sub>/<i>λ</i><sub>AGP</sub> = 48). Additionally, due to the introduction of the gold nanocavity structure, n-AGP possess an extremely small mode volume (<i>V</i><sub>n-AGP</sub> ≈ 10<sup>-7</sup><i>λ</i><sub>0</sub><sup>3</sup>, <i>λ</i><sub>0</sub> = 6.25 μm). By calculating the electric field intensity distribution (|<i>E</i><sub>norm</sub>|) and the normalized electric field intensity spectrum (i.e., the relationship between frequency and (|<i>E</i><sub>z</sub>|/|<i>E</i><sub>0</sub>|) of the n-AGP structure, it is evident that due to the high electron density on the gold surface, electromagnetic waves can reflect at the boundaries of the gold nanocavity and be resonantly enhanced within the nanocavity. At the resonant frequency of n-AGP (1800 cm<sup>-1</sup>), the electric field enhancement within the cavity is about 50 times. In contrast, at similar resonant frequencies, the electric field enhancement factors of Graphene plasmon (resonant frequency 1770 cm<sup>-1</sup>) and AGP (resonant frequency 1843 cm<sup>-1</sup>) are approximately 3 and 2 times, respectively, significantly lower than that of n-AGP. Furthermore, by placing a protein film (60 nm wide and 10 nm high) under the graphene, we calculated the spectral dip depths caused by Fano resonance between n-AGP and AGP with the vibrational modes of protein molecules, thereby validating the enhancement factors of different modes for protein vibrational mode infrared absorption. For the amide I band of proteins, the detection sensitivity of n-AGP is about 60 times higher than that of AGP. Additionally, we discovered that by adjusting the structural parameters of the gold nanocavity, including cavity depth, width, and surface roughness, the response frequency band of n-AGP can be modulated (from 1290 to 2124 cm<sup>-1</sup>). Specifically, as the cavity depth increases, the electric field enhancement of n-AGP improves, and the wavelength compression capability of n-AGP decreases, causing the resonant frequency to blue-shift (from 1793 cm<sup>-1</sup> to 2124 cm<sup>-1</sup>). As the cavity width increases, the resonant frequency of n-AGP red-shift (from 1793 cm<sup>-1</sup> to 1290 cm<sup>-1</sup>), and the effectiveness of the gold nanocavity boundary in reflecting the resonant electric field within the cavity diminishes, resulting in a decrease in the electric field enhancement factor. With the gradual increase in the roughness of the gold nanocavity bottom, the effective depth of the gold nanocavity increases, causing a blue shift in the n-AGP resonant frequency (from 1793 cm-1 to 1861 cm<sup>-1</sup>) and an increase in the electric field enhancement factor. Moreover, by adjusting the Fermi level of graphene (from 0.3 eV to 0.6 eV), we achieved dynamic tuning of n-AGP (from 1355 to 1973 cm<sup>-1</sup>). As the Fermi level of graphene increases, the wavelength compression capability of n-AGP decreases, resulting in a blue-shift in the resonant frequency. Finally, by optimizing the structural parameters and Fermi level of n-AGP, and placing protein particles of different sizes (20 nm, 15 nm, and 10 nm wide, all 10 nm high) into the graphene/gold nanocavity structure, we verified the protein detection capability of n-AGP-enhanced nano-IR. We found that n-AGP can detect the vibrational fingerprint features of the amide I and amide II bands of a single protein particle (10×10 nm) with a 15-fold increase in sensitivity. This n-AGP-based enhanced structure holds promise for providing an important detection platform for nanoscale material characterization and single-molecule detection, with broad application potential in biomedicine, materials science, and geology.

Plasma amplifiers: multiscale light-enhanced uniform SERS composite substrates for breaking through resonance limitations.

A phenomenon known as plasmon resonance constitutes a unique optical effect that can induce an enhancement in localized electromagnetic fields, resulting in a substantial increase in the electromagnetic field intensity surrounding metallic nanostructures. In this work, the coupling effect of excitation of surface plasmon polaritons and local surface plasmons in nanoparticles is deeply studied under the background of nanoparticles/one-dimension grating composite structures through grating matching. By employing finite-difference time-domain simulations as our methodological approach, we discern gratings with a periodicity of 1.5 μm support surface plasmon bound states between the gratings. Furthermore, the modulation of SPs along the vertical sidewalls of the grating due to standing wave effects exhibits oscillatory behavior with varying grating heights. Experimental results obtained from the nanoparticle/grating composite SERS substrate validate theoretical predictions, demonstrating higher enhanced Raman signals at 633 nm compared to 532 nm. Remarkably, this structure exhibits good performance, with R6G detection sensitivity down to concentrations as low as 10-10 M and mapping achieving a relative standard deviation of 7.79%, underscoring its uniformity and capability of electromagnetic field enhancement.

Fabrication of multifunctional g-C3N4-modified Au/Ag NRs arrays for ultrasensitive and recyclable SERS detection of bisphenol A residues.

Monolayer g-C3N4-modified Au/Ag nanorods (g-C3N4/Au/Ag NRs) array is fabricated as a dual-function platform with high surface-enhanced Raman scattering (SERS) response and excellent photocatalytic degradation ability for bisphenol A (BPA) residues. FDTD simulation results of Au/Ag NRs proves that the electromagnetic field intensity is significantly enhanced at the gap of Ag NRs and Au NPs and the protrusion of Au NPs, which endows the arrays with excellent SERS activity. The arrays exhibit high sensitivity for rhodamine 6G (R6G) (LOD = 1.1 × 10-11 mol/L) and high SERS enhancement (EF = 9.2 × 107). In addition, the g-C3N4/Au/Ag NRs could degrade ˃90% of BPA adsorbed on the substrate surface within 140 min under visible light irradiation, and maintains its SERS activity after repeated use for 4 times. The dual-function platform with high SERS response and excellent recycling capability is proved to be reliable and is very promising for monitoring of BPA residues in food.

Rabi Waves for Excitation of Quantum Nanoantenna with Electrically Controlled Radiation Pattern and Its Application

Rabi waves for the excitation of quantum nanoantennas with electrically controlled radiation and frequency characteristics were studied. The operational frequency of the visible range was based on the high frequency component of the current. The low frequency component and its operational frequency was in the terahertz range. The feature of the Rabi wave antenna depends on the carrier frequency on the electromagnetic field intensity. The contribution of high order magnetic multipoles became essential. The radiation properties of an antenna were the same as the ideal magnetic dipole. The antenna frequency spectrum corresponded to the amplitude modulated Rabi oscillations. The high frequency current was in the optical range in the vicinity of the quantum transition frequency. The radiation field of the nano antenna was considered equivalent to the field of magnetic dipole placed in the centre of current ring and oriented orthogonal to the ring plane. The equivalence was consequence of the electrical smallness of the antenna over the working range of frequency. The results obtained were in good agreement with previous results.

Electromagnetic field-mediated chitosan/gelatin/nano-hydroxyapatite and bone-derived scaffolds regulate the osteoblastic and chondrogenic phenotypes of adipose-derived stem cells to construct osteochondral tissue engineering niche in vitro

It is critical to explore the effects of electromagnetic field (EMF) on the construction of functional osteochondral tissue, which has shown certain clinical significance for the treatment of osteochondral injury. At present, there are few studies on the effect of the direction of EMF on cells. This study aimed to investigate the effects of EMF coupling on different parameters to control adipose-derived stem cells (ADSCs) proliferation and specific chondrogenic and osteogenic differentiation at 2D level and 3D level. The proliferation and differentiation of EMF-induced ADSCs are jointly regulated by EMF and space structure. In this study, Cs7/Gel3/nHAP scaffolds were prepared with good degradation rate (86.75 ± 4.96 %) and absorb water (1100 %), and the pore size was 195.63 ± 54.72 μm. The bone-derived scaffold with a pore size of 267.17 ± 129.18 μm was obtained and its main component was hydroxyapatite. Cs7/Gel3/nHAP scaffolds and bone-derived scaffolds are suitable as 3D level materials. The optimal EMF intensity was 2 mT for chondrogenic differentiation and proliferation and 1 mT for osteogenic differentiation and proliferation. It is noteworthy that EMF has a negative correlation with ADSCs proliferation in the vertical direction at 2D level, while it has a positive correlation with ADSCs proliferation at 3D level. EMF mediated 3D osteochondral scaffold provide good strategy for osteochondral tissue engineering construction.

Chaotic dynamics of diatomic systems in an electromagnetic field: Dynamical and topological invariants

An advanced combined quantum-dynamic and chaos-geometric method for analysis, modelling, and forecasting of the chaotic dynamics of diatomic molecules in an intense electromagnetic field is presented. The method is based on the use of the non-stationary theory of the Schrödinger equation in the approximation of the density functional and the methods of the theory of chaos and dynamic systems for the analysis of time series of polarization and other characteristics of diatomic molecules in an intense electromagnetic field. In particular, the latter includes the Gottwald-Melbourne test, the correlation integral method , fractal and multifractal formalism, average mutual information, false nearest neighbours, surrogate data algorithms, analysis on the basis of the Lyapunov's exponents, Kolmogorov entropy, nonlinear forecast models based on algorithms of optimized predicted trajectories, B-spline approximations. As an illustration, the advanced data for the dynamical and topological invariants (correlation dimension, embedding dimension, Kaplan-York dimension, Lyapunov's exponents, Kolmogorov entropy, etc.) for the diatomic ZrO molecule in a linearly polarized electromagnetic field are listed.

THE RESONANT RESPONSE OF STRONGLY COUPLED NANORODS TO THE ELECTROMAGNETIC WAVE

The electromagnetic response of closely spaced nanorod dimers can be controlled via the modification of the nanoparticles interaction, caused by electron tunneling between them. The optical response to an intense external electromagnetic field of a system composed of two gold 230 nm long rods surrounded by air and separated by a gap of width 0.5 nm was analyzed. Using finite element method-based numerical simulations we show that the electron tunneling, taking place due to the extraordinary enhancement of the electromagnetic field inside the nanogap, results in the change of the nanoantenna coupling from the capacitive to the conductive one. As a result, the absorption-to-scattering ratio of the dimer significantly changes. Particularly, the scattering cross-section decreases by about three times, whereas the normalized absorption rises from about 12 to 18 with noticeably broadening of the spectral line.

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A novel core-shell heterostructure of zinc oxide/metal-organic frameworks anchored silver nanoparticles for enhanced SERS and photocatalytic performance

Here, a novel well-ordered ZnO rod-flower/zeolitic imidazolate framework-M (ZIF-M, using 5-mercapto-1-methyltetrazole as ligand) core-shell heterostructure (Al/ZnO/ZIF-M, AZZ*) is induced by aluminum (Al) sheet. Subsequently, Ag nanoparticles (AgNPs) are tightly attached to the ZIF-M layer in AZZ* through the strong Ag-N and Ag-S bonds, and a portable bifunctional substrate of Al/ZnO/ZIF-M/Ag (AZZ*Ag) is constructed. The finite difference time domain (FDTD) analysis shows that the AZZ*Ag substrate generates the stronger electromagnetic field intensity than the AZAg. Also, there is a strong synergistic effect among Al, ZnO, ZIF-M and Ag which can effectively facilitate the electron transfer. Importantly, the AZZ*Ag substrate exhibits outstanding SERS response with high sensitivity and selectivity for crystal violet (CV) molecules. The low detection limit (LOD) of CV molecule is 2.81 × 10−11 mol·L−1 with high analysis enhancement factor (AEF) of 1.93 × 106. In addition, AZZ*Ag substrate shows good photocatalytic performance for CV molecules with high degradation efficiency of 97.35% within 105 min, which is 4.72 times that of AZAg. Importantly, the SERS and photocatalytic performance of AZZ*Ag are 4.4 times and 3.09 times those of the Al/ZnO/ZIF-8/Ag (AZZ#Ag, using 2-methylimidazole as ligand), respectively. Moreover, the AZZ*Ag substrate displays excellent stability, good reproducibility, recyclability and uniformity. Thus, the designed portable bifunctional composite exhibits great potential for SERS detection and photocatalytic degradation of other pollutants in environmental wastewater.

Efficient vacuum pair production in frequency chirped electric fields with spatiotemporal inhomogeneity

Vacuum pair production under intense electromagnetic fields is an intriguing prediction in quantum electrodynamics (QED), and has become a topic of considerable interest with the rapid advancements in laser technologies. The pair production efficiency can be enhanced using chirped electric fields. In this study, the effects of electric field chirping on electron–positron pair production in different oscillating electric fields were investigated using the Dirac–Heisenberg–Wigner (DHW) formalism. We primarily considered quadratic and sinusoidal chirped electric fields. The results revealed that chirping significantly influences the momentum spectra of the generated particles in an electric field dominated by low-frequency tunneling effects, resulting in pronounced oscillations of the momentum spectrum, particularly in a sinusoidal chirped field. However, multiphoton processes gradually emerge as the chirp parameter increases. Consequently, in a high-frequency electric field dominated by multiphoton processes, the number density of the generated particles increases with the chirping parameter in a quadratic chirped field, whereas the momentum distribution remains relatively symmetric. However, in a sinusoidal chirped electric field, introducing a chirp parameter immediately alters the momentum distribution and enhances pair production rate. Moreover, there exists an optimal chirp parameter and the total particle number is enhanced approximately more than an order of magnitude with optimal chirping in a sinusoidal chirped electric field. These findings provide valuable insights into the intricate dynamics of pair production under the influence of chirping in different oscillating electric fields, and offer potential directions for future research in this domain.