Electron Emission Research Articles

Bleaching effect of radiation-induced darkening in Yb3+-doped large mode area photonic crystal fiber based on deuterium and hydrogen loading.

We report the radiation-induced darkening (RD) effect caused by X-ray radiation and the bleaching effect caused by D2/H2/N2 loading in self-developed Yb3+-doped large mode-area photonic crystal fibers (LMA PCFs). The decrease in the slope efficiency caused by irradiation decays exponentially with an increase in the X-ray radiation doses, and the radiation-induced gain variation (RIGV) showed a linear decay trend with increasing irradiation doses. The slope efficiency of Yb3+-doped LMA PCF, which significantly degraded from 71.00% to 50.42% after 50 Gy irradiation, can be significantly restored after D2 loading to 97.21% of the slope efficiency of pristine fiber. However, the slope efficiency of the PCF loaded by H2 can be recovered to 88.54% that of the pristine. These results suggest that D2 loading has a more pronounced bleaching ability than H2, while N2 does not exhibit any bleaching effect. Based on the all-fiber modular amplification experiment, an average amplified output power of 41.4 W at the pump power of 62.3 W was achieved from Yb3+-doped LMA PCFs irradiated with 50 Gy followed by D2 loading. The slope efficiency (with respect to the pump power) was 69.05%, with the laser beam quality factor M2 of 1.2. No obvious power decaying of the laser output was observed for about 10 h. RD and bleaching effects of the Yb3+-doped LMA PCF core glass have been thoroughly investigated using the absorption, radiation-induced attenuation (RIA), continuous wave electron paramagnetic resonance (CW-EPR), emission, Raman, and Fourier transform infrared (FTIR) spectra.

Electron Emission Efficiency of Graphene/h-BN/2D-Semiconductor Heterostructure: Thermotical Analysis and Experimental Verification

Abstract Metal-insulator-semiconductor (MIS) heterostructures have important applications in vacuum microelectronic devices. Among these, graphene-insulator-semiconductor (GIS) heterostructure field electron emitters are among the most widely utilized. Improving the electron emission performance is a major challenge for GIS heterostructure field emitters. A comprehensive theoretical model is needed to predict the electron emission process from such a structure. In this work, a theoretical calculation was carried out on the electron emission current from an GIS heterostructure structure based on a tunneling model that considers the density of states of the semiconductor, scattering of the insulation layer, and hot-hole-induced Auger emission process. Using graphene/h-BN/MoS2 as an example, we obtain the band structure of the MoS2 using first principle calculation, simulate the scattering in h-BN with the Monte Carlo method, and calculate the emission current density using the modified Fowler-Nordheim equation. The results indicate that h-BN thickness and Auger coefficient are key factor affecting emission current density and emission efficiency. To validate our model, a few-layer graphene/h-BN/MoS2 heterostructure device was prepared and the field emission results validate the calculation results. The theoretical model can be expanded to other GIS heterostructures and is useful for designing a high-performance electron source using a GIS tunneling junction.

Field emission study on atomically heterogeneous micro-metallic emitters produced by ion beam from inert gas plasmas

Abstract High doses of irradiation in extreme environments, such as space or fusion reactors, cause significant substrate modifications, requiring systematic experimental data to understand the underlying processes. This study explores the effects of ion irradiation on aluminum and titanium sheets used in spacecraft, with fluence levels ranging from 3.8 to 4.0 × 1018 cm-2, employing 2 keV ions of argon and krypton generated by 2.45 GHz microwave plasma to investigate surface modifications and atomic heterogeneity induced by ion implantation, while minimizing complications from chemical bond formation. This experimental investigation is further extended to understand the impact of implanted ions and surface modifications on electron emission properties in high electric fields. Notable field emission improvements are observed: for Kr-irradiated Al, turn-on potential is 2.3 ± 0.6 kV, a maximum current is 3.4 ± 0.3 nA, and enhancement factor is 1059, with Kr incorporation at 76.9 %; for Ar-irradiated Ti, turn-on potential is 1.6 ± 0.2 kV, a maximum current is 9.8 ± 0.8 nA, and enhancement factor is 2540, with Ar content at 88.5 %. This study thus systematically discusses the discernible variations in field emission properties with the morphological changes, ion implantation percentages, and local work function measurements, providing valuable insights into the effects of inert gas ion irradiation on metallic substrates.

Superior charge storage performance of optimized nickel cobalt carbonate hydroxide hydrate nanostructures for supercapacitor application

In our work, we report superior electrochemical performance of optimized 3D nanostructured, nickel-cobalt carbonate hydroxide hydrate (Ni3 − xCox-CHH (1 ≤ x ≤ 2)) materials with flower like morphology synthesised via one-step hydrothermal methods. A Ni rich sample (x = 1) demonstrate better specific capacitance and the improvement is attributed to more oxygen deficient neighbourhood of Ni compared to that of Co. The structural, morphological and electronic properties of the samples were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM), field emission electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). A comprehensive characterization was used for physicochemical properties-electrochemical performance correlation. Cyclic voltammetry (CV), Galvanostatic charging and discharging (GCD) shows the supercapacitor feature of the samples for the composition containing the highest nickel concentration achieving a specific capacitance of 1649.51 F g− 1 at a current density of 1 A g− 1 and excellent rate capability of 1610.30 F g− 1 at a high current density of 5 A g− 1. The sample shows high cyclic stability of 80.86% after 3000 cycles. Improved specific capacitance is attributed to the synergy effect of bimetallic transition metals as well as improved surface area of flower like morphology. These findings show that Ni2Co-CHH electrode material demonstrates great potential as electrode material for supercapacitor device fabrication.

Higher-order effects and validity of the point-dipole approximation for conjugated extended molecular emitters near plasmonic nanostructures.

Rapid advancements in nanotechnology have allowed for the characterization of single molecules by placing them in the vicinity of nanoplasmonic structures that are known to confine light to sub-molecular scales. In this study, we introduce a theoretical framework that captures higher-order effects, and we explore the limits of the standard description of a molecular emitter as a point-dipole. We particularly focus on the role played by the emitter chain length and electron conjugation. Strong deviations are observed from the point-dipole approximation, demonstrating that higher-order effects are essential to fully capture the emission rate of extended molecules in the vicinity of nanoparticles. This deviation strongly depends on the orientation of the conjugated chain relative to the nanoplasmonic structure. Finally, we propose a simple rationalization that qualitatively assesses the difference from the point-dipole approximation.

Tetrahedral Al20O30 Cage: A Superchalcogen Atom.

Superatoms are stable clusters that mimic the chemical behavior of individual atoms in the periodic table. Many endeavors have been devoted to the design and characterization of various superatoms, while engineering superatoms to mimic the chemistry of chalcogens remains a challenge. In this paper, we present a new superchalcogen by evaluating a hollow tetrahedral Al20O30 cluster with theoretical calculations. By comparing the Al20O30 with its daughter dianion (Al20O30)2- in terms of stability, aromaticity, electronic properties, and chemical behavior in compounds, we find that this cluster tends to get two additional electrons to reach a more stable electronic state, which is the origin of the identity of superchalcogens. The adaptive natural density partitioning (AdNDP) analysis illustrates that this Al20O30 cluster accommodates two electrons by a 4-center-2-electron bond formed between the four face-centered Al atoms. Moreover, the Al20O30 cluster has exothermic first and second adiabatic electron affinity (EA), indicating that the dianion (Al20O30)2- is stable against spontaneous electron emission and fragmentation in the gas phase. This reflects the size advantage of superchalcogens when compared with chalcogens. Interestingly, we further study a cluster with one more electron than the superchalcogen Al20O30, namely, H@(Al20O30) and find that it is a superhalogen due to its large vertical and adiabatic EA.

Radiocobalt-Labeling of a Polypyridylamine Chelate Conjugated to GE11 for EGFR-Targeted Theranostics.

The overexpression of the epidermal growth factor receptor (EGFR) in certain types of prostate cancers and glioblastoma makes it a promising target for targeted radioligand therapy. In this context, pairing an EGFR-targeting peptide with the emerging theranostic pair comprising the Auger electron emitter cobalt-58m (58mCo) and the Positron Emission Tomography-isotope cobalt-55 (55Co) would be of great interest for creating novel radiopharmaceuticals for prostate cancer and glioblastoma theranostics. In this study, GE11 (YHWYGYTPQNVI) was investigated for its EGFR-targeting potential when conjugated using click chemistry to N1-((triazol-4-yl)methyl)-N1,N2,N2-tris(pyridin-2-ylmethyl)ethane-1,2-diamine (TZTPEN). This chelator is suitable for binding Co2+ and Co3+. With cobalt-57 (57Co) serving as a surrogate radionuclide for 55/58mCo, the novel GE11-TZTPEN construct was successfully radiolabeled with a high radiochemical yield (99%) and purity (>99%). [57Co]Co-TZTPEN-GE11 showed high stability in PBS (pH 5) and specific uptake in EGFR-positive cell lines. Disappointingly, no tumor uptake was observed in EGFR-positive tumor-bearing mice, with most activity being accumulated predominantly in the liver, gall bladder, kidneys, and spleen. Some bone uptake was also observed, suggesting in vivo dissociation of 57Co from the complex. In conclusion, [57Co]Co-TZTPEN-GE11 shows poor pharmacokinetics in a mouse model and is, therefore, not deemed suitable as a targeting radiopharmaceutical for EGFR.

Emission of electrons and photons and formation of cascade ions during the decay of 125I radionuclide

Emission of electrons and photons and formation of cascade ions during the decay of 125I radionuclide

Electron emission performance analysis and application of carbon nanotube cold cathode prepared by cold pressing process

In this work, a carbon nanotube (CNT) cold cathode electron emitter fabricated by the cold pressing process was developed and studied. The electron emission performance was investigated and the application of pulse x-ray emission and imaging was explored by this cold cathode. The results indicated that the electron emission performance was excellent with electric intensities of turn-on and threshold of 0.47 and 1.17 V/μm@1 mA/cm2, respectively, and the field enhancement factor reached 17 514. The application research results showed that the pulse x-ray waveform has a great corresponding well with the grid voltage, and the imaging of a screw was clear, whose thread and pitch could be seen clearly. This article proposed a cold pressing process prepared for the CNT cold cathode, providing a new technical approach for the development of field emission cold cathode preparation processes.

Enhanced field electron emission of formamidine lead triiodide induced by strong electric field assisted morphology reconstruction

Enhanced field electron emission of formamidine lead triiodide induced by strong electric field assisted morphology reconstruction

Enhanced field emission performance of gold nanoparticle decorated Bi2S3 nanoflowers.

Au nanoparticles (NPs) are decorated on hydrothermally synthesized Bi2S3 nanorods (NRs) to enhance the field electron emission (FEE) performance as compared to bare Bi2S3 nanorods, resulting in reduction in turn-on field from 3.7 to 2.7 V μm-1 (at the current density of 1.0 μA cm-2) with significant increment in maximum emission current density from 138 to 604.8 μA cm-2 (at a field of 7.8 V μm-1) respectively. FESEM/TEM reveals that Bi2S3 nanoflowers are assembled from Bi2S3 NRs of a typical diameter of 120 ± 10 nm, and Au NPs of diameter about 5-10 nm are uniformly decorated onto the surface of NRs to form an Au/Bi2S3 composite. XRD analysis suggests that the as-synthesized product consists of orthorhombic Bi2S3 NRs decorated with face-centered cubic Au NPs. The XPS spectrum shows the elemental mapping of the as-synthesized Au/Bi2S3. Improvement in field emission properties is mainly attributed to a reduction in work function and increasing emitting sites due to Au NP decoration.

Selective laser processing of particle accelerator beam screen surfaces for electron cloud mitigation

Laser-induced surface roughening is a technique that facilitates the reduction of secondary electron emission (SEE) from materials, which is crucial for mitigating electron cloud (EC) formation in particle accelerators, that...

Comparison of [125I]I-labeled trastuzumab and pertuzumab for targeted Auger electron therapy of cancers overexpressing HER2 receptors

Objectives: The HER2 receptor is often overexpressed in various cancers, particularly in breast and ovarian cancers, and this overexpression significantly contributes to the growth and spread of these tumours. Trastuzumab (Herceptin) and pertuzumab (Perjeta) are widely used humanized monoclonal antibodies (mAbs) that have shown promise in treating patients with HER2-positive breast cancer. To enhance their effectiveness, mAbs have recently been combined with chemotherapeutic agents and radionuclides. The aim of our studies was to investigate the potential therapeutic use of trastuzumab and pertuzumab labelled with the Auger electron emitter - 125I. Methods: The radioimmunoconjugates synthesized using 125I and 131I were tested in various in vitro studies on SKOV-3 cells. These studies included tests for specificity, binding affinity, internalization, cytotoxicity (MTS assay), and confocal imaging. Results: The results confirmed that radioiodinated mAbs have high affinity and internalization properties in HER2+ cell line. In contrast to trastuzumab, significant localization of iodinated pertuzumab on the cell membrane was observed. MTS assay and spheroid studies demonstrated minor toxic effects from both radioconjugates, resulting from the combination of the mAbs' immunotoxic effect and the interaction of Auger electrons. However, [125I] I-pertuzumab exhibited higher cytotoxicity. Conclusions: Despite high internalization, both radiobioconjugates showed low cytotoxicity due to the lack of radionuclide localization in the cell nucleus. However, [125I] I-pertuzumab accumulated in the cell membrane, resulting in slightly higher cytotoxicity. To improve therapeutic efficacy, modifying [125I] I-trastuzumab and [125I] I-pertuzumab to transport them to the cell nucleus, e.g., using nuclear localization signal (NLS) peptides is crucial.

Diocotron modes in pure electron plasmas in the APEX levitating dipole trap

Abstract Observations of persistent toroidal modes in dipole-trapped pure electron plasmas are presented. Non-neutral electron plasmas were confined by the poloidal magnetic field of the APEX (A Positron Electron eXperiment) levitating dipole trap. The negative bias of the electron emitter was gated to control the filling time. Large amplitude, narrow-band oscillations were consistently observed in wall probe measurements after the fill. The oscillatory image-charge currents induced by the trapped electron plasma typically persisted for many seconds with fundamental frequencies, f 0 = 50 to 500 kHz, that scale with the E → × B → drift velocity. We attribute this feature to the dipole-equivalent of the diocotron mode that is commonly observed in non-neutral plasmas in linear traps.

Decreased Secondary Electron Emission from Aluminum Surface by a Fluorocarbon-Titanium Composite Film.

Multipactor, a vacuum discharge under microwave conditions triggered by secondary electron emission (SEE), plays a critical role in managing the power level of microwave devices. In this study, we developed a fluorocarbon-titanium composite film on aluminum by cosputtering polytetrafluoroethylene (PTFE) and titanium via a controlled temperature and sputtering power ratio (RF power for PTFE to DC power for Ti) to suppress the SEE of Al. The evolution of microtopography and chemical composition of the composite film was evaluated. An increasing power ratio varying from 0.5 to 3.0 is found to change the film surface from scattered island-like bumps to a prominent peak-valley pattern and eventually to a smooth surface with few flat swellings. Elemental analysis revealed that the fluorine-to-carbon (F/C) mole ratio in samples was more significantly influenced by the sputtering power ratio than by the substrate temperature. The SEE yield indicates that the peak-valley pattern prepared by a power ratio of 2 leads to the maximum of the SEE yield curve reducing steeply from 2.99 to 1.23, which is attributed not only to the roughed pattern but also to the high F/C mole ratio owing to the higher capacity of electron trapping by the fluorine atoms.

Synthesis and Characterization of Thallium-Texaphyrin Nanoparticles and Their Assessment as Potential Delivery Systems for Auger Electron-Emitting 201Tl to Cancer Cells.

Thallium-201 is an Auger electron-emitting radionuclide with significant potential for targeted molecular radiotherapy of cancer. It stands out among other Auger electron emitters by releasing approximately 37 Auger and Coster-Kronig electrons per decay, which is one of the highest numbers in its category. It has also a convenient half-life of 73 h, a stable daughter product, established production methods, and demonstrated high in vitro radiotoxicity. However, its full potential in targeted radiotherapy remains unexplored, primarily due to the lack of available efficient chelators for [201Tl]Tl+ or [201Tl]Tl3+. This study aims to assess texaphyrin for macrocycle chelation of [201Tl]Tl3+. Texaphyrins are known for effective binding of trivalent metals with similar ionic radii, such as indium and gadolinium. Optimization of [201Tl]Tl+ to [201Tl]Tl3+ oxidation and subsequent chelation with texaphyrin-lipid conjugate were assessed using thin-layer chromatography. The formation and stability of nonradioactive Tl-texaphyrin-lipid complexes were confirmed by UV-Vis spectroscopy and ultrahigh performance liquid chromatography-mass spectrometry. [201Tl]Tl/Tl-texaphyrin-lipid nanoparticles (nanotexaphyrins) were assembled by using a microfluidic system, and their morphology and stability were evaluated by using dynamic light scattering and transmission electron microscopy. The uptake of these nanotexaphyrins in lung cancer and ovarian cancer cells was evaluated using both radioactive and nonradioactive methods. The conversion of [201Tl]Tl+ to [201Tl]Tl3+ in 0.25 M HCl achieved an average yield of 91.8 ± 3.1%, while the highest radiolabeling yield of the texaphyrin-lipid with [201Tl]Tl3+ was 25.5 ± 4.5%. Tl-texaphyrin-lipid conjugates were stable at room temperature for at least 72 h. These conjugates were successfully assembled into homogeneous nanotexaphyrins with an average hydrodynamic diameter of 147.4 ± 1.4 nm. Throughout a 72 h period, no changes in size or polydispersity of the synthesized nanoparticles were observed. [201Tl]Tl-nanotexaphyrins were synthesized with an average radiochemical purity of 77.4 ± 10.3% and a yield of 5.1 ± 4.4%. The release of [201Tl]Tl+ from [201Tl]Tl-nanotexaphyrins in phosphate-buffered saline exhibited a time- and temperature-dependent pattern, with a faster release observed at 37 °C than at room temperature. Additionally, the uptake of Tl-nanotexaphyrins and [201Tl]Tl-nanotexaphyrins in cancer cells was similar to that of unbound Tl+ and [201Tl]Tl+. This is the first time that texaphyrins have been investigated as chelators for radiothallium. Although [201Tl]Tl-nanotexaphyrins were found to be thermodynamically and kinetically unstable, we successfully synthesized stable texaphyrin-lipid complexes with natTl3+. This opens up opportunities for further refinements in the nanotexaphyrin-lipid structure to enhance [201Tl]Tl3+ stability and prevent its reduction to a 1+ oxidation state. Future research should consider further modifications to the texaphyrin structure or using texaphyrins without the lipid component.

Secondary electron emission from gold microparticles in a transmission electron microscope: comparison of Monte Carlo simulations with experimental results

Abstract We measure the electron beam-induced current to analyze the electron-induced secondary electron (SE) emission from micron-sized gold particles illuminated by 80 and 300 keV electrons in a transmission electron microscope. A direct comparison of the experimental and simulated SE emission (SEE) employing Monte Carlo scattering simulations based on the GEANT4 toolkit yields overall good agreement with a noticeable discrepancy arising from the shortcoming of the GEANT4 scattering cross sections in the low-loss regime. Thus, the electron beam-induced current analysis allows to quantify the inelastic scattering including SEE in the transmission electron microscope and provides further insight into the charging mechanisms.

Deformation Behavior and Microstructural Evolution Coordinated Regulation by Compression Deformation for Metastable Ti Alloy.

In this paper, in order to investigate the harmonious relationship between the compression deformation behavior of metastable β titanium alloy and the microstructure evolution, the β solution-treated Ti-10V-2Fe-3Al (Ti-1023) alloy was compressed at room temperature and its deformation behavior was analyzed. Optical microscopy (OM) and field emission electron microscopy (FESEM) were used to study the microstructure evolution of alloys at different strain rates. The results show that the stress-induced martensite transformation (SIMT) is more easily activated by low strain rate compression deformation, which is conducive to improving its comprehensive mechanical properties. With the decrease in strain rate, the α″ martensite content increases significantly, the average grain size decreases substantially, and the Low Angle Grain Boundary (LAGB) volume fraction decreases correspondingly. In addition, after compression at different strain rates, the misorientation angle (MA) of the β matrix is mainly concentrated in the LAGBs. The change is small with the decrease in strain rate, but the α″ martensite orientation difference angle shows some peaks, which are ~60°, ~85°, and ~95°, respectively. Simultaneously, the strain rate has an important effect on the content and type of martensitic twins. Finally, the fracture morphology analysis shows that with the increase in strain rate, the fracture mode changes from ductile fracture to brittle fracture. The fracture surface presents a significantly elongated cavity along the direction of maximum shear stress.

MEASUREMENT OF THE RATES OF THE 102Pd(𝑛, γ)103Pd AND 102Ru(𝑛, γ)103Ru REACTIONS IN THE HORIZONTAL CHANNEL OF THE IR-8 REACTOR AT NRC “KURCHATOV INSTITUTE”

Metastasis is one of the main causes of relapse and subsequent high mortality from cancer. Metastases can contain very few cells and spread throughout the body. Despite the existing variety of diagnostic imaging methods, in practice, the resolution of none of them allows one to unambiguously diagnose the presence of a tumor (clump of cancer cells) smaller than 1–2 mm in size. After surgery and tumor removal, patients are typically offered chemotherapy, external beam radiation therapy, or α- or β-emitter radionuclide therapy. This therapy has side effects that lead to additional risks and may interfere with continued treatment. Recently, a number of works, in contrast to the traditional approach, have proposed using “short-range” radionuclides instead of α- or β-emitters [1–3]. It is convenient to use Auger or conversion electron emitters as “short-acting” therapeutic agents. Auger electrons and conversion electrons have a short range and high specific linear energy loss in biological tissue; they are capable of damaging cells within a few tens of microns, but do not have a radiotoxic effect over l ng distances, without damaging healthy cells and tissues. The most efficient and convenient Auger and conversion electron emitters for practical use include 103mRh (𝑇1/2 = = 56.1 min), which has the lowest ratio of the number of γ quanta to electrons [1] and can be obtained by a generator method. The predecessors of 103mRh (𝑇1/2 = 56.1 min) in the generator can be 103Ru (𝑇1/2 = = 39.247 days) or 103Pd (𝑇1/2 = 16.99 days). In order to clarify the prospects for producing these precursors, we have measured the rates of reactions 102Ru(𝑛, γ)103Ru and 102Pd(𝑛, γ)103Pd upon neutron irradiation of metal ruthenium of natural isotopic composition and metal palladium, enriched in the 102Pd isotope to 96.36%, in a horizontal experimental channel of the IR-8 reactor.

Strong field induced ion and electron emission from size-selected metal clusters

Strong field induced ion and electron emission from size-selected metal clusters