Swift Electrons Research Articles

Solvothermal synthesis of Zr-metal-organic framework/V2C MXene based composite on nickel foam for highly selective detection of epinephrine in simulated blood serum

Metal-organic frameworks (MOFs) combined with MXene materials have recently gained considerable attention for their unique properties, including exceptional structural characteristics and electrical conductivity. These attributes enable them to maintain a high concentration of electroactive sites, making them particularly suitable for electrochemical applications. Here, we demonstrate solvothermal synthesis of Zr-metal–organic framework(Zr-MOF)/V2C MXene composite decorated nickel foam (NF) for electrochemical detection of Epinephrine (EP) in simulated blood serum samples. X-ray diffraction analysis confirms the formation of the cubic structured Zr-MOF/V2C MXene composite. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) reveal the existence of numerous rectangular sheets and nanospheres of the composite. Utilizing the differential pulse voltammetry (DPV) technique, the sensor demonstrates a remarkable sensitivity of 19 µA/µM.cm−2 to EP within a wide linear detection range from 1 µM to 1 mM with a lower limit of detection of 0.86 µM (=3 S/m). The fabricated sensor exhibits high selectivity against interfering species like uric acid (UA), ascorbic acid (AA), glucose (GLU), urea, etc. Real-sample analysis conducted in simulated blood samples using the standard addition method showcases an outstanding recovery percentage of approximately 100 %. Zr-MOF/V2C MXene composite, with its conductive nature and high surface area, forms a robust interaction with EP, leading to a significant alteration in the sensor’s electrical properties. Meanwhile, the porous NF substrate is crucial in maintaining stability, boosting catalytic activity by offering numerous active sites, and enabling swift electron transfer. Affirming the efficacy of the Zr-MOF/V2C MXene composite, herein, as an exceptional electrode with high performance. The composite shows significant promise in detecting various biomolecules essential for biomedical research applications.

Graphitic carbon nitride nanosheets decorated with HAp@Bi2S3 core–shell nanorods: Dual S-scheme 1D/2D heterojunction for environmental and hydrogen production solutions

By combining different semiconductors, scientists have developed innovative materials capable of converting solar energy into useful forms of energy or driving chemical reactions that clean up pollutants. These materials offer a promising path to combat global environmental and energy challenges. In this study, HAp@Bi2S3 core–shell structures were synthesized using a facile microemulsion technique, and then loaded onto graphitic carbon nitride via a hydrothermal method to create an advanced HAp@Bi2S3/g-C3N4 dual S-scheme heterojunction. The engineered heterojunction exhibited enhanced hydrogen production and visible light photocatalytic oxidation of metronidazole. The improved photocatalytic efficiency was attributed to the core–shell structure of HAp@Bi2S3 along with the formation of a dual S-scheme heterojunction in HAp@Bi2S3/g-C3N4. As a result, the novel dual S-scheme HAp@Bi2S3/g-C3N4 heterojunction demonstrated a significantly higher hydrogen production rate, ca. 20 times higher than that of hydroxyapatite (HAp), 11 times higher than Bi2S3, and 5 times higher than the HAp@Bi2S3. This research introduces a novel approach to crafting dual S-scheme heterojunctions based on Bi2S3, which enables swift electron transfer across heterojunction interfaces, thereby enlarged possibility windows to sustainable hydrogen production and wastewater remediation technologies.

Enhanced Cherenkov radiation in twisted hyperbolic Van der Waals crystals

AbstractCherenkov radiation in artificial structures experiencing strong radiation enhancements promises important applications in free‐electron quantum emitters, broadband light sources, miniaturized particle detectors, etc. However, the momentum matching condition between swift electrons and emitted photons generally restricts the radiation enhancement to a particular momentum. Efficient Cherenkov radiation over a wide range of momenta is highly demanded for many applications but still remains a challenging task. To this end, we explored the interaction between swift electrons and twisted hyperbolic Van der Waals crystals and observed enhanced Cherenkov radiation at the flatband resonance frequency. We show that, at the photonic magic angle of the twisted crystals, the electron momentum, once matching with that of the flatband photon, gives rise to a maximum energy loss (corresponding to the surface phonon generation), one‐order of magnitude higher than that in conventional hyperbolic materials. Such a significant enhancement is attributed to the excitation of flatband surface phonon polaritons over a broad momentum range. Our findings provide a feasible route for highly directional free‐electron radiation and radiation shaping.

In situ decoration of 0D-nickel boride on 2D-vanadium MXene composites: An advanced electrode material for high energy density supercapacitors

Vanadium carbide-MXene (V2CTx) is considered a rising star among 2D materials and is an ideal electrode material for energy storage due to its unique features. However, oxidation and layer restacking can impair specific capacity (Cs) and cycling performance. Considering this challenge, we have developed a composite material consisting of amorphous nickel boride (NixB NPs) and V2CTx. To prevent oxidation and restacking of the layers and to improve the performance of the supercapacitor, NixB was decorated between the gaps and the surface. The V2CTx and its composites were prepared by simple etching and direct liquid-phase methods. Under the optimized conditions, the NixB/V2CTx modified nickel foam exhibited an improved Cs value of 705.9 C g−1 and a rate capability of 53.8 % at a current density of 10 A g−1; the excellent cycling stability was 120.5 % after 10,000 cycles at 10 A g−1 in 3 M KOH. The improved Cs values, shortened ion diffusion paths, swift electron transfer, and excellent cycling stability of the composites are due to the V2CTx layers surface entrapped/gaps filled by the NixB NPs. For practical application, an asymmetric device with NixB/V2CTx and reduced graphene oxide (rGO) as positive and negative electrodes was fabricated. The NixB/V2CTx//rGO device achieved a maximum energy density of 50.22 Wh kg−1 at 800 W kg−1 and 26 Wh kg−1 at 16000 W kg−1. The capacity retention was 89.98 % and the Coulombic efficiency was 99.9 % after 20,000 continuous cycles at 8 A g−1. These results emphasized that the developed 0D/2D NixB/V2CTx electrode materials with novel composite architecture are suitable for advanced energy storage applications.

Modeling Electron Energy Loss and Momentum Transfer in a Swift Electron Interaction with Small Polyhedral Nanoparticles

Modeling Electron Energy Loss and Momentum Transfer in a Swift Electron Interaction with Small Polyhedral Nanoparticles

Angular momentum transfer from swift electrons to non-spherical nanoparticles within the dipolar approximation

In this work, we study the angular momentum transfer from a single swift electron to non-spherical metallic nanoparticles, specifically investigating spheroidal and polyhedral (Platonic Solids) shapes. While previous research has predominantly focused on spherical nanoparticles, our work expands the knowledge by exploring various geometries. Employing classical electrodynamics and the small particle limit, we calculate the angular momentum transfer by integrating the spectral density, ensuring causality through Fourier-transform analysis. Our findings demonstrate that prolate spheroidal nanoparticles exhibit a single blueshifted plasmonic resonance, compared to spherical nanoparticles of equivalent volume, resulting in lower angular momentum transfer. Conversely, oblate nanoparticles display two resonances — one blueshifted and one redshifted — resulting in a higher angular momentum transfer than their spherical counterparts. Additionally, Platonic Solids with fewer faces exhibit significant redshifts in plasmonic resonances, leading to higher angular momentum transfer due to edge effects. We also observe resonances and angular momentum transfers with similar characteristics in specific pairs of Platonic Solids, known as duals. These results highlight promising applications, particularly in electron tweezers technology.

Free Electron-Plasmon Coupling Strength and Near-Field Retrieval through Electron Energy-Dependent Cathodoluminescence Spectroscopy.

Tightly confined optical near fields in plasmonic nanostructures play a pivotal role in important applications ranging from optical sensing to light harvesting. Energetic electrons are ideally suited to probing optical near fields by collecting the resulting cathodoluminescence (CL) light emission. Intriguingly, the CL intensity is determined by the near-field profile along the electron propagation direction, but the retrieval of such field from measurements has remained elusive. Furthermore, the conditions for optimum electron near-field coupling in plasmonic systems are critically dependent on such field and remain experimentally unexplored. In this work, we use electron energy-dependent CL spectroscopy to study the tightly confined dipolar mode in plasmonic gold nanoparticles. By systematically studying gold nanoparticles with diameters in the range of 20-100 nm and electron energies from 4 to 30 keV, we determine how the coupling between swift electrons and the optical near fields depends on the energy of the incoming electron. The strongest coupling is achieved when the electron speed equals the mode phase velocity, meeting the so-called phase-matching condition. In aloof experiments, the measured data are well reproduced by electromagnetic simulations, which explain that larger particles and faster electrons favor a stronger electron near-field coupling. For penetrating electron trajectories, scattering at the particle produces severe corrections of the trajectory that defy existing theories based on the assumption of nonrecoil condition. Therefore, we develop a first-order recoil correction model that allows us to account for inelastic electron scattering, rendering better agreement with measured data. Finally, we consider the albedo of the particles and find that, to approach unity coupling, a highly confined electric field and very slow electrons are needed, both representing experimental challenges. Our findings explain how to reach unity-order coupling between free electrons and confined excitations, helping us understand fundamental aspects of light-matter interaction at the nanoscale.

POMs-based metal-organic frameworks with interpenetrating structures and their carbon nanotube-coated materials for lithium-ion anode applications

The inherent characteristics of abundant, stable, and swift electron transfer make polyoxometalates (POMs) exceptionally suitable for utilization in energy storage applications, particularly in Lithium-ion batteries (LIBs). By immobilizing POMs within metal-organic frameworks, Ag-BTBA-POM was synthesized to address the challenges associated with the low electronic conductivity and solubility of POMs. To enhance the electronic conductivity of POMOFs crystals further, CNT@Ag-BTBA-POM was developed. This carbon composite material exhibits exceptional cyclic stability and electrochemical characteristics, with the discharge specific capacity stabilizing at around 730 mA h g−1 over 100 cycles.

Coherent radiation at visible wavelengths from sub-keV electron beams.

The Smith-Purcell effect allows for coherent free-electron-driven compact light sources over the entire electromagnetic spectrum. Intriguing interaction regimes, with prospects for quantum optical applications, are expected when the driving free electron enters the sub-keV range, though this has until now remained an experimental challenge. Here, we demonstrate the Smith-Purcell light emission from UV to visible using engineerable, fabricated gratings with periodicities as low as 19 nm and with electron energies as low as 300 eV. Our findings constitute a major step toward broadband, highly tunable, on-chip light sources, observation of quantum recoil effects, and tunable EUV and x ray sources from swift electrons.

The High Stability and Selectivity of Electrochemical Sensor Using Low-Cost Diamond Nanoparticles for the Detection of Anti-Cancer Drug Flutamide in Environmental Samples.

In this study, a novel electrochemical sensor was created by fabricating a screen-printed carbon electrode with diamond nanoparticles (DNPs/SPCE). The successful development of the sensor enabled the specific detection of the anti-cancer drug flutamide (FLT). The DNPs/SPCE demonstrated excellent conductivity, remarkable electrocatalytic activity, and swift electron transfer, all of which contribute to the advantageous monitoring of FLT. These qualities are critical for monitoring FLT levels in environmental samples. Various structural and morphological characterization techniques were employed to validate the formation of the DNPs. Remarkably, the electrochemical sensor demonstrated a wide linear response range (0.025 to 606.65 μM). Additionally, it showed a low limit of detection (0.023 μM) and high sensitivity (0.403 μA μM-1 cm-2). Furthermore, the practicability of DNPs/SPCE can be successfully employed in FLT monitoring in water bodies (pond water and river water samples) with satisfactory recoveries.

Efficient Electrochemical Lead Detection by a Histidine-Grafted Metal-Organic Framework MOF-808 Electrode Material.

As the excessive presence of heavy metals in the environment significantly affects human health, it becomes necessary to develop efficient, selective, and sensitive methods for their detection. In this study, a novel electrochemical sensor for the detection of Pb2+ ions is described. The proposed sensor is based on a glassy carbon electrode (GCE) modified by a thin film of histidine-grafted metal-organic framework (MOF-808-His). The MOF-808 was obtained solvothermally, and then postsynthetically modified by substituting the coordinated acetate with histidinate. By electrochemistry, the MOF-808-His-modified GCE demonstrated high charge selectivity, while electrochemical impedance spectroscopy (EIS) and kinetic studies gave a lower charge transfer resistance (4196 Ω) and a better standard heterogeneous electron transfer rate constant (1.80 × 10-5 cm s-1) on MOF-808-modified GCE. These results indicated a swift and direct electron transfer rate from [Fe(CN)6]3-/4- to the electrode surface. Using square wave anodic stripping voltammetry (SWASV), the rapid and highly sensitive determination of Pb2+ was achieved on MOF-808-His-modified GCE. By optimizing the accumulation-detection parameters including pH of the detection medium, deposition time and potential, and concentration, a remarkable limit of detection (LoD, based on a signal-to-noise ratio of 3) of (1.12 × 10-10 ± 0.10 × 10-10) mol L-1 was obtained, with a sensitivity of (9.6 ± 0.1) μA L μmol-1. After interference and stability studies, the MOF-808-His-modified GCE was applied to the detection of Pb2+ in a tap water sample with a concentration of 10 μmol L-1 Pb2+.

Electronic cross section, stopping power and energy-loss straggling of metals for swift protons, alpha particles and electrons

Understanding and quantifying the electronic inelastic interactions of swift ions and electrons in metals is fundamental for many applications of charged particle beams. A common theoretical approach is moreover desirable for the case of both types of projectiles, as large numbers of secondary electrons arise as the result of ion interaction with metals. The electronic cross section, stopping power and energy-loss straggling resulting from the interaction of swift protons, alpha particles and electrons when moving through the metals aluminum, iron, copper, molybdenum, platinum and gold, are calculated theoretically for a wide energy range of the projectiles. The model is based on the dielectric formalism, which realistically accounts for the excitation spectrum of each metal through the Mermin Energy-Loss Function–Generalized Oscillator Strength (MELF-GOS) methodology. The impact of the complexity of the excitation spectrum of each metal (encompassing interband transitions and collective excitations), as well as the different sources of (sometimes conflicting) optical data is analysed in detail. Specific interactions are considered for each projectile, such as electron capture/loss and electron cloud polarisation for ions, and indistinguishability, exchange and low-energy corrections for electrons. An estimate of possible contributions of surface excitations to the interaction probabilities of low energy electrons is given. Comparison of our results with a large collection of available experimental data shows good agreement. As a practical and useful outcome of the work, we provide analytical expressions fitting all our calculated quantities, which can be applied for simulation or comparison purposes.

Insight into What Is inside Swift Heavy Ion Latent Tracks in PET Film.

We present here a novel experimental study of changes after contact electrification in the optical transmission spectra of samples of both pristine and irradiated PET film treated with Kr+15 ions of energy of 1.75 MeV and a fluence of 3 × 1010 cm2. We used a non-standard electrification scheme for injecting electrons into the film by applying negative electrodes to both its surfaces and using the positively charged inner regions of the film itself as the positive electrode. Electrification led to a decrease in the intensity of the internal electric fields for both samples and a hypsochromic (blue) shift in their spectra. For the irradiated PET sample, electrification resulted in a Gaussian modulation of its optical properties in the photon energy range 2.3-3.6 eV. We associate this Gaussian modulation with the partial decay of non-covalent extended conjugated systems that were formed under the influence of the residual radial electric field of the SHI latent tracks. Our studies lead us to suggest the latent track in the PET film can be considered as a variband material in the radial direction. Consideration of our results along with other published experimental results leads us to conclude that these can all be consistently understood by taking into account both the swift and slow electrons produced by SHI irradiation, and that it appears that the core of a latent track is negatively charged, and the periphery is positively charged.

Biomimetic anode with atomically dispersed iron sites to enhance biotic-abiotic interfacial interaction towards efficient wastewater energy recovery in bioelectrochemical systems

Bioelectrochemical systems (BESs) are promising for future wastewater treatment towards carbon neutrality. Hemes, as the active centers of outer-membrane c-type cytochromes, play an important role in anodic electron transfer. In this work, a biomimetic Fe–Nx incorporated carbon membrane (Fe-NCM) mimicking the heme active center was proposed based on a nanocage confinement-electrospinning strategy and applied as the anode in BESs. The aligned carbon fibers with high electrical conductivity could serve as the electron “expressway” for swift electron transfer while the Fe–Nx nexus served as the “gas station” and endowed the membrane anode with boosted redox activity. The Fe-NCM anode featuring great biocompatibility and electrochemical activity was conducive to microbe adhesion and biotic-abiotic interfacial interaction. The power output and chemical oxygen demand (COD) removal rate constant in the BES with this Fe-NCM anode reached 1406 ± 44 mW m−2 and 0.42 ± 0.01 h−1 under filtration operation mode, which were 156% and 191% as high as those of the pristine carbon membrane. The introduction of Fe–Nx species exerted a significant influence on the anodic biofilm property, composition and function, which were of importance to bolstering wastewater energy conversion. Metagenomics unveiled that simultaneous intensification of intracellular electron production and extracellular electron transfer processes was achieved in the Fe-NCM BES. The Fe-NCM anode with electroactive Fe–Nx sites facilitated the biotic-abiotic interfacial interaction in BESs and highlighted the rational design of anodes for efficient wastewater treatment and energy conversion.

Bidirectional host-guest interactions promote selective photocatalytic CO2 reduction coupled with alcohol oxidation in aqueous solution

Existing artificial photosynthesis systems often underperform due to challenges in water oxidation and extensive photogenerated carrier transfer. Herein, we demonstrate that β-cyclodextrin-decorated CdS nanocrystals (CdS-CD) can simultaneously anchor cobalt tetraphenyl porphyrin (CoTPP) catalysts and alcohol reductants onto CdS surfaces through bidirectional host-guest interactions between β-CD and CoTPP/alcohol. This configuration ensures swift electron transfer from CdS to β-CD bonded CoTPP, facilitating CO2 reduction to HCOOH. Results showcase a remarkable yield of 1610 μmol g−1 h−1 and a 96.5% selectivity. Meanwhile, photogenerated holes in CdS are efficiently neutralized by β-CD bonded furfuryl alcohol, achieving a furfural yield of 1567 μmol g−1 h−1 and > 99% selectivity. In contrast, the discrete CoTPP-CdS system achieved a HCOOH yield of only 306 μmol g−1 h−1 and a poor HCOOH selectivity of 46.4%. It was also observed that the CoTPP@CdS-CD system maintained high CO2-to-HCOOH conversion rates when using other alcohols as reductants.

Angular Momentum Transfer from Swift Electrons to Small Spheroidal Nanoparticles in the Dipole Approximation.

Angular Momentum Transfer from Swift Electrons to Small Spheroidal Nanoparticles in the Dipole Approximation.

Enhanced dye degradation performance enabled by swift electron mediator decorated WO3/g-C3N4/V2O5 hybrid nanomaterials.

Organic pollutants such as dyes and pharmaceutical drugs have become a significant environmental problem due to their unrestricted discharge, especially in water bodies. As a result, an economically viable and environmentally friendly approach to their degradation in water bodies is required and the incorporation of metal tungstate with single metal oxide has attracted attention due to its potential ability towards the photocatalytic degradation of pollutants. The work demonstrates a WO3/g-C3N4/V2O5 nanocomposite synthesized using a facile routewet impregnation method. The results revealed that WO3/g-C3N4/V2O5 nanocomposites are suitable, mainly for their better surface properties, enhanced visible-light absorption, and preferred band positions. Besides that, the degradation of methylene blue (MB) dye is carried out and demonstrated that the complete degradation occurs over 120min using 10mg L-1 of WO3/g-C3N4/V2O5 nanocomposite under UV-visible-light irradiation. The scavenger experimental result implies that the photogenerated free electrons and superoxide radials are important role in MB dye degradation. In addition, a possible mechanism is proposed for the photocatalytic activity of WO3/g-C3N4/V2O5 nanocomposite. Moreover, the stability analysis demonstrated that the WO3/g-C3N4/V2O5 nanocomposite can be recycled multiple times.

Free‐Electron‐Driven Frequency Comb

AbstractFree‐electron radiations prompt numerous advanced applications such as particle detectors, biological imaging, and light sources from microwave to X‐ray. While their polarization, directionality, and phase could be shaped with prosperous metamaterials, their natural broad spectra have not been tailored to yield frequency combs, which are state‐of‐the‐art technology in metrology, spectroscopy, and precision frequency synthesis. Here, the frequency comb directly emitted from the free‐electron radiation is demonstrated by simultaneously exciting a series of modes with equidistant spectral lines. Both the offset and repetition frequencies are readily adapted by structural parameters, and relative spectrum intensities between the comb teeth are customizable based on selective coupling, thus permitting flexible tunability over broadband. Moreover, the repetition rate is experimentally verified at the microwave regime. The proposed methodology implies that swift electrons present a natural and versatile platform for generating frequency combs, facilitating the development of metrology and spectroscopy in the terahertz band.

Phase-locked photon–electron interaction without a laser

Ultrafast photon–electron spectroscopy in electron microscopes commonly requires ultrafast laser setups. Photoemission from an engineered electron source is used to generate pulsed electrons, interacting with a sample excited by the laser pulse at a known time delay. Thus, developing an ultrafast electron microscope demands the exploitation of extrinsic laser excitations and complex synchronization schemes. Here we present an inverse approach to introduce internal radiation sources in an electron microscope based on cathodoluminescence spectroscopy. Our compact method is based on a sequential interaction of the electron beam with an electron-driven photon source and the investigated sample. Such a source in an electron microscope generates phase-locked photons that are mutually coherent with the near-field distribution of the swift electron. We confirm the mutual frequency and momentum-dependent correlation of the electron-driven photon source and sample radiation and determine a degree of mutual coherence of up to 27%. With this level of mutual coherence, we were able to perform spectral interferometry with an electron microscope. Our method has the advantage of being simple, compact and operating with continuous electron beams. It will open the door to local photon–electron correlation spectroscopy of quantum materials, single-photon systems and coherent exciton–polaritonic samples with nanometre resolution.

Analysis and design of transition radiation in layered uniaxial crystals using tandem neural networks

With the flourishing development of nanophotonics, a Cherenkov radiation pattern can be designed to achieve superior performance in particle detection by fine-tuning the properties of metamaterials such as photonic crystals (PCs) surrounding the swift particle. However, the radiation pattern can be sensitive to the geometry and material properties of PCs, such as periodicity, unit thickness, and dielectric fraction, making direct analysis and inverse design difficult. In this paper, we propose a systematic method to analyze and design PC-based transition radiation, which is assisted by deep learning neural networks. By matching boundary conditions at the interfaces, effective Cherenkov radiation of multilayered structures can be resolved analytically using the cascading scattering matrix method, despite the optical axes not being aligned with the swift electron trajectory. Once properly trained, forward deep learning neural networks can be utilized to predict the radiation pattern without further direct electromagnetic simulations. In addition, tandem neural networks have been proposed to inversely design the geometry and/or material properties for the desired effective Cherenkov radiation pattern. Our proposal demonstrates a promising strategy for dealing with layered-medium-based effective Cherenkov radiation detectors, and it can be extended to other emerging metamaterials, such as photonic time crystals.