Electron Field Emission Research Articles

Synthesis of 3,4-dihydropyrimidines and octahydroquinazolinones by SBA-15 supported schiff-base iron (III) complex as durable and reusable catalyst under ultrasound irradiation

Biginelli-type heterocyclic compounds are particularly important due to their several chemical reactivities and various range of pharmacological activity. Therefore Biginelli reaction has witnessed several modification and numerous investigations are continuing in this field to develop more effective and efficient methodologies. In this research, Iron (III) schiff base immobilized SBA-15 has been prepared as a valuable, efficient, and recoverable catalyst for the Biginelli reaction. The morphology of the prepared catalyst was identified by spectroscopic characterization techniques and structural microscopic analysis including Fourier transform infrared (FT-IR) patterns, X-ray diffraction (XRD) by powder crystal method, Energy-dispersive X-ray spectroscopy (EDS) study, Thermogravimetric-Differential thermal analysis (TGA-DTA), Transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FE-SEM) images. Biginelli compounds containing 3,4-dihydropyrimidines and octahydroquinazolinones were conveniently synthesized by this catalyzed protocol from the cycloaddition of aromatic aldehydes with the 1,3-dicarbonyl substrates and urea via ultrasonic waves. The several advantages of the presented approach are high yields and easy isolation of products, shorter reaction times, and milder conditions, structural stability and reusable catalyst. The combination of heterogeneous catalyst and ultrasonic radiation can make catalytic reactions more efficient than traditional ways attractive for academic researchers and application scholars in the industry.

Formation of core-shell structure MnCo2O4 microspheres and as a bifunctional catalyst for zinc-air batteries

Efficient and stable bifunctional catalysts, facilitating oxygen reduction and oxygen evolution, play a pivotal role in energy conversion and storage fields. In this paper, four core-shell MnCo2O4 catalyst samples are prepared by controlling different solvent heating time, which are 0.5 h, 2 h, 6 h, and 12 h, respectively. The subsequent tests indicate that the sample with a 6 h not only has an ideal core-shell structure, but also exhibits favorable performance. The unique core-shell structure and favorable electrochemical performance are mainly attributed to the prepared precursor spheres. The microspheres have an inherent core-shell structure. Detailed studies of the morphological variations of MnCo2O4 catalysts with the different solvent heating time are performed using transmission electron microscopy and field emission scanning electron microscopy. Furthermore, we analyze the potential formation mechanism of the core-shell structure MnCo2O4 catalyst. The obtained core-shell structured MnCo2O4 catalysts provide a new way for the preparation of cathode catalyst for zinc-air batteries.

Coupled Monte Carlo density functional theory calculations of cold and laser-assisted electron field emission from graphene-coated copper cathode

Field emission is an important process with a variety of applications. Quantitative predictions of such electron emission need to include details of the internal potentials that shape the electronic wavefunctions (and hence the tunneling probability), predictive analysis of the work function barrier (ΦB), and knowledge of the electron distribution at the surface that constitutes the supply function. Here, these various factors were all collectively considered based on a combined Monte Carlo-density functional theory approach. Results were obtained for both the field-dependent cold electron emission current density as well as photoemission from a short laser pulse. The method also allows for calculations of field-dependent emittance. The technique is general and could be extended to include plasmon–polariton modes, different thicknesses of coatings, and role of surface adsorbates and defects.

Analytical modeling of nucleation and growth of graphene layers on CNT array and its application in field emission of electrons

Carbon Nanotube (CNT) arrays and graphene have undergone several investigations to achieve efficient field emission (FE) owing to CNT’s remarkable large aspect ratio and graphene’s exceptional FE stability. However, when dense CNT arrays and planar graphene layers were used as field emitters, their field enhancement factor reduced dramatically. Therefore, in this paper, we numerically analyze the growth of a dense CNT array with planar graphene layers (PGLs) on top, resulting in a CNT-PGL hybrid and the associated field enhancement factor. The growth of the CNT array is investigated using Plasma Enhanced Chemical Vapor Deposition (PECVD) chamber in C2H2/NH3 environment with variable C2H2 flow, Ni catalyst film thickness, and substrate temperature followed by PGL precipitation on its top at an optimized cooling rate and Ni film thickness. The analytical model developed accounts for the number density of ions and neutrals, various surface elementary processes on catalyst film, CNT array growth, and PGLs precipitation. According to our investigation, the average growth rate of CNTs increases and then decreases with increasing C2H2 flow rate and catalyst film thickness. CNTs grow at a faster rate when the substrate temperature increases. Furthermore, as the chamber temperature is lowered from 750 °C to 250 °C in N2 environment and Ni film thickness grows, the number of the graphene layers increases. The field enhancement factors for the CNT array and hybrid are then calculated based on the optimal parameter values. The average height of the nanotubes, their spacing from one another, and the penetration of the electric field due to graphene coverage are considered while computing the field enhancement factor. It has been found that adding planar graphene layers to densely packed CNTs can raise its field enhancement factor. The results obtained match the current experimental observations quite well.

Probing the effect of molar concentration on TiO2 nanorod/nanoflower films toward enhanced field electron emission properties

Probing the effect of molar concentration on TiO2 nanorod/nanoflower films toward enhanced field electron emission properties

The isoniazid drug adsorption on the boron carbide graphene-like monolayer: insights from simulation in the field of medicine

To determine the electrical sensitivity of BC3 nanosheets to isoniazid (IS), DFT simulations were performed. IS molecules were found to have a clear affinity for pure BC3. The adsorption energy of the most stable structure is approximately −22.12 kcal/mol. Reducing the gap between the HOMO and LUMO levels of BC3 nanosheets significantly (from 1.45 to 0.72 V) enhances IS adsorption and consequently improves the electrical conductivity. This finding positions BC3 as a viable choice for applications like IS detection and electronic sensors. Moreover, the adsorption of IS has altered the work function of BC3, suggesting its potential as a function-based sensor capable of detecting IS through significant shifts in field electron emission current levels. BC3 also offers the advantage of rapid IS desorption, with a recovery time of approximately 6.18 ms.

Formation of Diamond Films with Different Grain Sizes on TiO2 Nanotubes and Its Field Emission Properties

Diamond films with different grain sizes are deposited on TiO2 nanotube (TNT) arrays prepared by anodic oxidation using a microwave plasma chemical vapor deposition reactor. The scanning electron microscope, X‐Ray diffractometer, and Raman results indicate that the diamond film is successfully deposited and that the substrate undergoes a phase transition due to the diamond deposition temperature, resulting in the rutile phase becoming dominant with lower energy bandgap and work function. Notably, after 5 h of deposition, a relatively continuous microcrystalline film is formed on the TNTs, and the diamond grains change from spherical to pyramidal and show excellent electron field emission behavior, with a low turn‐on field of 0.5 V μm−1 and a current density of 85.9 μA cm−2. In addition, the deposition environment of the nanocrystalline diamond has a large impact on the substrate morphology, resulting in a blocked electron transport path, which reduces the overall field emission performance. The enhanced performance is attributed to the synergistic effect between the highly efficient 1D electron path of the TNTs, the negative electron affinity of the diamond surface, and the lower work function of rutile TiO2.

Functionalization of silver nanoparticles coating cotton fabrics through hydrothermal synthesis for improved antimicrobial properties

Deposition of silver nanoparticles (AgNPs) on the surfaces of cotton fabric (CF) is an approach for producing antimicrobial textile products. CF-AgNPs composites were fabricated ex situ using a simple hydrothermal synthesis of AgNPs, while the fabric was surface modified using a plasma to improve adhesion prior to coating. The morphology and chemical composition of CF-AgNPs nanocomposites were examined using UV–vis spectrophotometry (UV–vis), x-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Study results show uniform deposition of AgNPs on cotton fabrics. The CF-AgNPs composite material exhibits excellent laundering durability and antimicrobial performance against Gram-positive, Staphylococcus aureus and Gram-negative, Escherichia coli pathogens. These findings indicate that the developed fabric can be used in a wide range of biomedical applications, health care and various packaging systems.

Controlled growth of CuO nanowires on Cu grid via thermal oxidation process with enhanced field electron emission properties

Controlled growth of CuO nanowires on Cu grid via thermal oxidation process with enhanced field electron emission properties

Synthesis and characterization of FMWCNTs/ZnO doped PVDF nanocomposites for enhanced mechanical, dielectric, and radiation shielding properties

This study investigates the enhancement of radiation shielding properties of polyvinylidene fluoride (PVDF) through the incorporation of functionalized multi-walled carbon nanotubes (FMWCNTs) and zinc oxide nanoparticles (ZnONPs), aiming to develop a lightweight, effective, and environmentally friendly shielding material. PVDF-based nanocomposites with varying concentrations of FMWCNTs@ZnO (0.0, 0.5, 1.0, 1.5, and 3.0 wt%) were synthesized using a solution casting method. Morphological analysis via high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) confirmed the uniform dispersion of FMWCNTs@ZnO within the PVDF matrix. X-ray diffraction (XRD) studies revealed an increase in the β-phase crystallinity of PVDF at 1 wt% FMWCNTs@ZnO concentration, with a notable peak shift indicating enhanced polar group development. Vickers microhardness tests showed a significant improvement, with hardness values increasing from 342.5 kg/mm2 for pure PVDF to 391.2 kg/mm2 for nanocomposites containing 3 % FMWCNTs@ZnO. Dielectric analyses demonstrated increased permittivity and a dynamic relaxation behavior indicative of improved charge carrier density and interfacial polarization. Gamma shielding efficiency, assessed through linear attenuation coefficients (GLAC) and mass attenuation coefficients (GMAC), exhibited superior performance at lower photon energies (80 keV), with the highest GLAC and GMAC values observed for the 3 wt% FMWCNTs@ZnO doped samples. These findings underscore the potential of FMWCNTs@ZnO doped PVDF nanocomposites as promising materials for radiation shielding applications, offering a synergistic approach to enhancing mechanical, dielectric, and protective properties against ionizing radiation.

A Comparative Analysis of Field Electron Emission from Carbon Black Embedded within Insulated Copper Hollowed Wires and Glass Tubes

A Comparative Analysis of Field Electron Emission from Carbon Black Embedded within Insulated Copper Hollowed Wires and Glass Tubes

Theory of Field Electron Emission from Nanotextured Cathode

Theory of Field Electron Emission from Nanotextured Cathode

A nanoDiamond/gold nanoparticle-based electrochemical immunosensor for the detection of HER 2 cancer biomarker

We report a highly sensitive electrochemical immunosensor based on a nanohybrid platform for the detection of the breast cancer biomarker human epidermal growth factor receptor 2 (HER 2). NanoDiamond (nanoD) and gold nanoparticles (AuNPs) immobilised by drop coating and electrodeposition methods, respectively, were employed to fabricate an immunosensor for HER 2 detections on a glassy carbon electrode (GCE). Voltammetry and electrochemical impedance spectroscopy (EIS) techniques were used to characterise each step of the modification process of the immunosensor. In addition, transmission electron microscopy (TEM), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques were used to characterise the materials used to fabricate the modified electrode. Under optimal conditions of temperature, time, and pH (35 °C, 50 min, and pH 7.2), different concentrations were investigated within a wide range of 1 pg mL−1 to 50 ng mL−1 using differential pulse voltammetry (DPV). With a low detection limit of 0.29 pg mL−1 from the DPV analysis, the immunosensor showed very good sensitivity and had a high specificity for HER 2. Additionally, the immunosensor demonstrated good applicability in the analysis of HER 2 in human serum samples, demonstrating a potential for use in the early identification of breast cancer.

Field Electron Emission from Point Diamond Cathodes under Continuous Laser Irradiation

Field Electron Emission from Point Diamond Cathodes under Continuous Laser Irradiation

Simulating the Effect of Field Electron Emission from a Cathode with a Thin Dielectric Film on Its Sputtering in a Gas Discharge in an Argon and Mercury Vapor Mixture

Simulating the Effect of Field Electron Emission from a Cathode with a Thin Dielectric Film on Its Sputtering in a Gas Discharge in an Argon and Mercury Vapor Mixture

Nitrogen admixture effects on growth characteristics and properties of carbon nanowalls

The plasma functionalization of carbon nanowalls (CNWs) is of great interest due to their potential applications in electron field emission and energy storage devices. In this study, the effects of nitrogen on the growth and properties of CNWs are thoroughly investigated by varying a wide range of the N2 concentrations in the CH4/H2/N2 discharge plasma. Nitrogen-doped carbon nanowalls (NCNWs) were synthesized in a single-step growth using the hydrogen radical injection plasma-enhanced chemical vapor deposition technique. The formation of dense NCNWs was found to be enhanced by nitrogen and was three times higher in the sample with a 150 sccm N2 flow rate than in the sample without N2 addition (N-0). As the N2 concentration increased from 0 to 200 sccm, the morphology of CNWs changed from relatively straight to curly-like nanowall structures. A high-resolution optical emission spectroscopic observation shows that as N2 flow increased, CN radicals became the dominant species, suppressing the formation of C2 and CH. Photoelectron spectroscopy analysis revealed the nitrogen doping effect on graphene layers at high N2 concentrations. According to Raman and Transmission Electron Microscopy analyses, the NCNWs had more branched and thicker nanowalls with higher defect concentrations than the N-0 sample. The wettability of NCNWs was improved, particularly for the sample with a N2 flow rate of 150 sccm.

Effect of Metal Nanoparticles in the Field Emission of Silicon Nanowires

In this work, an efficient method is reported for creating a metal nanoparticle (silver) / Si composite structure consisting of a vertical array of silicon nanowires (SiNWs) decorated with silver metal nanoparticles. A two-stage metal-assisted etching method is employed to obtain SiNWs and Silver (Ag) metal nanoparticles are decorated on the SiNWs using the electroless deposition method. It allows the good coverage of silver metal nanoparticles over SiNWs. Scanning Electron Microscopy (SEM) analysis revealed that Ag was covered with SiNWs. High-work function metal nanoparticles such as Ag nanoparticles on SiNWs have been utilized in different applications such as photovoltaics and sensors. The size of SiNWs is determined through the Raman shift. The silicon optical phonon peak showed an increase in redshift and a decrease of full-width at half maxima with a decrease in diameter due to the quantum confinement. The Electron Field Emission (EFE) characteristics of the Agdecorated SiNW films were studied based on the current-voltage measurements and analyzed using the Fowler-Nordheim (F-N) equation. The low turn-on field is obtained through the Ag metal nanoparticles which have wider applications in lowpower operational devices.

Modeling of the influence of field electron emission from a cathode with a thin insulating film on its sputtering in a gas discharge in a mixture of argon and mercury vapor

A model of the low-current gas discharge in a mixture of argon and mercury vapor in the presence of a thin insulating film on the cathode surface is proposed. The model takes into account that in such a mixture a substantial contribution to the ionization of the working gas can come from the ionization of mercury atoms during their collisions with metastable excited argon atoms. In the discharge, positive charges accumulate on the film surface, creating an electric field in the film sufficient to cause field emission of electrons from the cathode metal substrate into the insulator. Such electrons are accelerated in the film by the field and can escape from it into the discharge volume. As a result, the effective yield of ion-electron emission from the cathode increases. The temperature dependences of discharge characteristics are calculated and it is shown that, due to a rapid decrease in the concentration of mercury vapor in the mixture with decreasing temperature, the electric field strength in the discharge gap and the discharge voltage increase. The presence of a thin insulating film on the cathode can result in an improvement in its emission characteristics and a significant reduction in the discharge voltage. This causes a decrease in the energies of the ions and atoms bombarding the cathode surface, and, consequently, in the intensity of cathode sputtering in the discharge.

One-dimensional diamond nanostructures: Fabrication, properties and applications

Diamonds exhibit a unique combination of numerous excellent physical and chemical properties, such as the highest hardness, high Young's modulus, wide bandgap, high carrier mobility, negative electron affinity, and high thermal conductivity. Especially, diamond has attracted significant attention in recent years for its outstanding performance in high-frequency and high-power electronic devices and thermal management. Inheriting the intrinsic physical and chemical properties of diamonds, one-dimensional (1D) diamond nanostructures exhibit many additional properties that are unavailable for bulk diamond or thin films, e.g., large specific surface area, ultrahigh elasticity, and some plasticity, tip effect as well as direct transport for photon or photo-induced carriers. These properties make 1D diamond nanostructures an ideal candidate for applications ranging from micro/nano-electromechanical systems (MEMS/NEMS) to field electron emission, optical, electrochemical, and biological areas. This review will first introduce the development of controlled synthesis methods of 1D diamond nanostructure, including bottom-up chemical vapor deposition growth and top-down selective etching of bulk diamond. Subsequently, we will summarize recent advances in the mechanical, electron field emission, optical, and biological properties of 1D diamond nanostructures and their applications in electron and photon emitter, MEMS, sensing, intracellular delivery, etc.

High-energy electron injection in top-gated niobium microbridges for enhanced power efficiency and localized control

This study explores gate-controlled superconductivity in metallic superconductors by employing a top-gate architecture with a 15 nm monocrystalline h-BN as a gate dielectric. The transport properties under gate voltage can be elucidated by injecting high-energy electrons, following the Fowler–Nordheim electron field emission model. In contrast to conventional resistive Joule heating, high-energy electron injection with top-gating exhibits excellent power efficiency in suppressing superconductivity. A nearby superconducting bridge, which serves as a thermometer, indicates that our top-gate device can achieve good local control, well limited within a distance of 0.6 μm due to the very low top-gating power. These findings are essential for advancing efficient and highly integrated tunable superconducting electronic devices.