Surface Binding Energy Research Articles

Determining the carbon detection limit with magnetic sector dynamic secondary ion mass spectrometry (SIMS)

Dynamic SIMS is often used to evaluate the concentration of impurities in solids because of its high sensitivity, depth profiling capabilities, good depth resolution, and high throughput. Continuous ion beam sputtering with a high-density primary beam provides high sensitivity and reduces the background contribution from residual gases within the analytical chamber. Dynamic SIMS experiments performed with several magnetic sector instruments using various sputtering rate conditions demonstrated a slow decrease of the carbon detection limit with the increase of sputtering rate (SR), when it was varied by changing the sputtering beam density. The dependence data, within the scatter limits, can be fit by a power function of SR with the exponent of about −1/2. The observed detection-limit-dependence curve is common for magnetic sector SIMS instruments, owing to contamination and the design of the analytical chamber. The depth resolution of light-element SIMS analysis (except for oxygen) performed using Cs+ sputtering is limited and cannot be improved by reducing the impact energy of the sputtering beam. A segregation-type depth profile with a long trailing edge was observed in the B, C, and N depth profiles when Cs+ sputtering was employed under ultra-high vacuum conditions. This effect is plausibly associated with preferential sputtering owing to the difference in the surface binding energy, along with the large difference in the mass of the interacting atoms within the collision cascade during sputtering. The depth resolution improved with surface oxidation when Cs + sputtering was combined with backfilling of the analytical chamber using O2. The analytical chamber backfilled with oxygen can be sufficiently replaced with a very low-impact energy-focused oxygen beam, enabling simultaneous oxygen and cesium co-sputtering SIMS analysis. The practical feasibility of using a co-sputtering with focused Cs+ and O2+ sputtering beams to achieve a high depth-resolution for carbon analysis under ultrahigh vacuum conditions was demonstrated.

Simulation of ion beam sputtering with OKSANA and SRIM: A comparative study

The energy distributions and average energies of sputtered particles are calculated using simulation codes OKSANA and SRIM-2013. Most simulations refer to an amorphous Ni target bombarded by normally incident Ar ions of keV energies. Sputtering of Si, Ti, V and Nb targets is also considered. It is shown that SRIM can strongly overestimate the contribution of fast ejected atoms, especially for targets irradiated with lighter ions. The effect is amplified by using the surface binding energies found to fit the measured sputter yields. It is concluded that the enhanced ejection of fast particles is associated with sputtering due to backscattered ions. The role of the first collision of an incident ion with a target atom is particularly noted. A comparison of the OKSANA calculated results with the data of other codes (TRIM.SP, ACAT) and experimental data showed their reasonable agreement.

Damage analysis caused by 60Co ions in functionally graded materials

Functionally graded composite/hybrid materials (FGCM/FGHCM) were produced by adding B4C, TiO2, and B4C+TiO2 ceramic materials at various ratios (0–50%) into the AA6082 matrix. The analysis of the damage caused by 60Co ions' (1.173–1.1332 MeV) on the material was examined using the SRIM/TRIM Monte Carlo simulation software. In the simulation, the following data regarding the atoms of the target materials were obtained: ion distribution, target ionization, total displacements, surface binding energy, lattice binding energy, and displacement energy. Among the studied four materials, the one with the highest ion range value was found to be AA6082 with 8550 Å. TiO2 was found to be the reinforcement material that reduced the ion range the most in the material. Due to its high binding energy, B4C reinforced AA6082+(0–50%) B4C FGCM was found to have the least vacancy with 4782/ion.

Sputtering yield increase with fluence in low-energy argon plasma-tungsten interaction

The increase of tungsten sputtering yield with fluence was investigated during plasma (≤100 eV) irradiation. This analysis focused on the combined effects of surface binding energy and surface morphology caused by Ar retention. As post-mortem analysis, Ar concentration was measured with SIMS (Secondary Ion Mass Spectroscopy) and TDS (Thermal Desorption Spectroscopy). The Ar concentration saturated at 21 % of W number density during the sputtering process. The corresponding change in surface morphology causes a change in the local ion incident angle, which leads to a sputtering yield increase of 10 %. The increased Ar concentration leads to a decrease in surface binding energy and a change in surface morphology which increases W sputtering yield from 0.02 to 0.03 by ion energy 80 eV. Over time, W sputtering yield reaches saturation as a function of saturated Ar concentration. This result implies that the synergistic role of Ar concentration and surface morphology on sputtering yield. This sputtering yield enhancement occurs more seriously in the realistic condition of plasma-facing materials that face low-energy plasma.

Calculation of Surface Binding Energy in NixPdy Alloys Using Density Functional Theory

In the study, surface binding energies for pure Ni and Pd metals were calculated using density functional theory. The values obtained were 5.32 eV and 4.65 eV, respectively, which represents good accuracy for ab initio calculations. The work also included calculations of surface binding energy for different configurations of NiPd alloys with nickel and palladium concentrations of 66%, 50%, and 33%. Calculations were performed for each type of lattice for both Ni and Pd surface binding energies. Several types of lattices were simulated, and it was found that the average surface binding energies for Ni and Pd are: 5.02 eV and 4.36 eV respectively in the alloy with a Ni concentration of 50%; 4.89 eV and 4.22 eV respectively in the alloy with a Ni concentration of 66%; 5.12 eV and 4.40 eV respectively in the alloy with a Ni concentration of 33%.

Monte Carlo simulations of W-Ta alloys under helium ion bombardment

In this study, Monte Carlo simulations were conducted using the SDtrimSP software to explore the sputtering and vacancy distribution of W1-xTax (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) alloys with (110), (100), and (111) surfaces under helium ion bombardment. The results indicate that the (110) surface exhibits the highest SBE among the three surfaces. Under the same conditions, the sputtering yield and number of vacancies of the alloy gradually increase with increasing Ta concentration for each surface. This suggests that the damage resistance of the alloy decreases with increasing Ta concentration, but the difference is not significant. Furthermore, it was also observed that the sputtering yields of W (Ta) atoms show a linear relationship with their respective concentrations in the alloy. Additionally, the molecular dynamics software LAMMPS was used to recalculate the Surface Binding Energy (SBE), which significantly affect the sputtering. These findings provide a theoretical foundation for the application and development of materials in nuclear fusion environments.

Monte Carlo simulations of W-Re alloys under helium ion bombardment

Based on the Monte Carlo simulation method, this study used the SDTrimSP software to explore the sputtering and vacancy distribution of W1−xRex (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) alloys with (110), (100), and (111) surfaces under helium ion bombardment. Since the surface binding energy in the SDTrimSP software is replaced by cohesive energy, this causes certain difference. So we used LAMMPS to re-scan the surface binding energy of three crystal planes with an index of one at different W-Re alloy ratios to enhance computational accuracy. Subsequently we input this value into the SDTrimSP software to compute the sputtering and vacancy under different incident energies and angles. The results show that (110) crystal plane has the smallest sputtering yield which is related to the surface binding energy. With the increasing concentration of Re atoms in the alloys, the sputtering yield of W-Re alloy linearly increases. Compared with pure W, the difference in sputtering yields and vacancies of W-Re alloys in three crystal planes are not significant. These findings can be valuable when selecting materials for plasma-facing applications in fusion reactor design.

La0.5Sr0.5Fe0.5Ti0.5O3 as a Bifunctional Catalyst for H2/O2 Fuel Cells: Towards Enhanced Stability and Electroactivity

To address the rising demand for H2 for fuel cells, hydrogen is produced through water splitting (electrochemically/photoelectrochemically).Although perovskite-structured materials show promise for the oxygen reduction reaction (ORR), their effectiveness in the oxygen evolution reaction (OER) poses a challenge. Consequently, there’s a growing demand for bifunctional catalysts exhibiting high electroactivity across a broad pH range. One potential candidate for exploration as a negative electrode in batteries and fuel cells is LaFeO3. With co-substitution of Sr and Ti, La0.5Sr0.5Fe0.5Ti0.5O3 (LSFT) is formed and explored as an air electrode. In this study, we systematically assess LSFT as a bifunctional catalyst across a broad pH spectrum of electrolytic solutions. LSFT displays increased current densities in both the OER and hydrogen evolution reaction (HER) domains, alongside improved stability, notably in neutral conditions. Our investigation incorporates Density Functional Theory (DFT) simulations to determine surface binding energies and construct a Pourbaix diagram. The results underscore the robustness of LSFT as a perovskite-based bifunctional catalyst, achieving a cycle stability exceeding 600 cycles and a chronopotentiometric stability of 1500 h with a stable potential of ∼2 V at the current density of 150 mA/cm2 in the neutral environment.

Effect of air-annealing on the structure, surface morphology, and supercapacitive properties of the 2D-BiOCl nanosheets

Upright-standing nanosheets of bismuth oxychloride (BiOCl), synthesized via a facile chemical synthesis method and air-annealed from 50 to 600 ℃ temperatures (named BOC-50–600), are envisaged as electrochemical supercapacitor electrodes. These electrodes are initially screened for their surface morphology, elemental configuration, phase purity, and binding energy by various means. Due to changes in the surface morphology, phase, charge transfer resistance, and binding energy, the one annealed at 150 ℃ i.e., BOC-150 has offered targeted supercapacitive performance due to quasi-faradaic redox reactions in 6 M KOH electrolyte solution. The specific capacitance of the BOC-150 electrode, measured at 1.40–5.0 A/g current densities, varies from 264.6 to 95 F/g. The as-assembled BOC-150//BOC-150 symmetric supercapacitor device (SSD) demonstrates an efficient supercapacitive performance with a maximum 86.87 Wh/kg energy density and 3735 W/kg power density. Additionally, the as-designed SSD endows an admirable capacity retention of 81.6% for 5000 charge-discharge cycles, approving moderate chemical stability and considerable mechanical robustness for use in commercial electronic items.

The relationship between hydrogen storage capacity and 4d transition metal-carbon surface binding energy

This study explores the correlation between the strength of 4d-transition metal (TM)/surface binding energy (BE) and the hydrogen storage capacity in decorated (TM@CNF) and doped (TM/CNF) carbon nanoflakes. The findings reveal smaller TM-CNF distances and larger BE for doped cases. These TM-CNF bond characteristics impact the storage capacity, with doped cases outperforming in Mo/CNF and Tc/CNF and decorated in Y@CNF and Zr@CNF scenarios. This contrasting performance underscores the difficulty in finding a surface/dopant combination for efficient storage, where the BE cannot be weak due to its stability and also cannot be too strong due to the loss of storage capacity.

Data-Driven Evolutionary Design of Multienzyme-like Nanozymes.

Multienzyme-like nanozymes are nanomaterials with multiple enzyme-like activities and are the focus of nanozyme research owing to their ability to facilitate cascaded reactions, leverage synergistic effects, and exhibit environmentally responsive selectivity. However, multienzyme-like nanozymes exhibit varying enzyme-like activities under different conditions, making them difficult to precisely regulate according to the design requirements. Moreover, individual enzyme-like activity in a multienzyme-like activity may accelerate, compete, or antagonize each other, rendering the overall activity a complex interplay of these factors rather than a simple sum of single enzyme-like activity. A theoretically guided strategy is highly desired to accelerate the design of multienzyme-like nanozymes. Herein, nanozyme information was collected from 4159 publications to build a nanozyme database covering element type, element ratio, chemical valence, shape, pH, etc. Based on the clustering correlation coefficients of the nanozyme information, the material features in distinct nanozyme classifications were reorganized to generate compositional factors for multienzyme-like nanozymes. Moreover, advanced methods were developed, including the quantum mechanics/molecular mechanics method for analyzing the surface adsorption and binding energies of substrates, transition states, and products in the reaction pathways, along with machine learning algorithms to identify the optimal reaction pathway, to aid the evolutionary design of multienzyme-like nanozymes. This approach culminated in creating CuMnCo7O12, a highly active multienzyme-like nanozyme. This process is named the genetic-like evolutionary design of nanozymes because it resembles biological genetic evolution in nature and offers a feasible protocol and theoretical foundation for constructing multienzyme-like nanozymes.

Bismuth sulfide micro flowers decorated nickel foam as a promising electrochemical sensor for quantitative analysis of melamine in bottled milk samples

Here, we demonstrate hydrothermally grown bismuth sulfide (Bi2S3) micro flowers decorated nickel foam (NF) for electrochemical detection of melamine in bottled milk samples. The orthorhombic phase of hydrothermally grown Bi2S3 is confirmed by the detailed characterization of x-ray diffraction and its high surface area micro flowers-like morphology is investigated via field emission scanning electron microscope. Furthermore, the surface chemical oxidation state and binding energy of Bi2S3/NF micro flowers is analyzed by x-ray photoelectron spectroscopy studies. The sensor exhibits a wide linear range of detection from 10 ng l−1 to 1 mg l−1 and a superior sensitivity of 3.4 mA cm−2 to melamine using differential pulse voltammetry technique, with a lower limit of detection (7.1 ng l−1). The as-fabricated sensor is highly selective against interfering species of p-phenylenediamine (PPDA), cyanuric acid (CA), aniline, ascorbic acid, glucose (Glu), and calcium ion (Ca2+). Real-time analysis done in milk by the standard addition method shows an excellent recovery percentage of ̴ 98%. The sensor’s electrochemical mechanism studies reveal that the high surface area bismuth sulfide micro flowers surface interacts strongly with melamine molecules through hydrogen bonding and van der Waals forces, resulting in a significant change in the sensor’s electrical properties while 3D skeletal Nickel foam as a substrate provides stability, enhances its catalytic activity by providing a more number /of active sites and facilitates rapid electron transfer. The work presented here confirms Bi2S3/NF as a high-performance electrode that can be used for the detection of other biomolecules used in clinical diagnosis and biomedical research.

The Molecular Structural Analysis of Biologically Important Catechol Molecule: An Integrative Perspective from Experiments and Futuristic Tools

Background: Catechol is a phenolic molecule found naturally in plants. It is also known as pyrogallic acid or 1, 2-dihydroxybenzene. Catechol is currently produced commercially by decarboxylating gallic acid at high temperatures and pressures. Aims and Objectives: This research aimed to understand the biological importance of catechol and perform molecular structural analysis on catechol molecules. Methods: Catechol (1, 2, dihydroxy benzene) was studied via computational analysis by employing the use of DFT and B3LYP methods. Hirshfeld analysis was carried out to investigate crystal intermolecular interactions, and the NBO study was performed to study chemical donating and accepting interactions. Moreover, the computational study was performed using FTIR, HNMR and other instrumentation like AIM theory for circular dichroism data. Results: Furthermore, the surface iso-projection study and binding energy results did prove to run in alignment with experimentally obtained values from the computational studies. Fukui functional study and molecular electrostatic potential were utilized in the study to investigate interactions between anionic and cationic sites of catechol. In addition, molecular dynamic simulations revealed that biomolecular stability was also present. Thus, the antibiotic efficacy of catechol displayed chemical oxidative interactions that exhibited close chemical correlations with ascorbic acid, ellagic acid, and gallic acid. Conclusion: The catechol has been examined experimentally and theoretically. The results were compared with catechol spectra, including IR and UV-visible spectra generated through computer analysis. The experimentally observed spectra were found to be in parallel with theoretical data. According to drug-likeness investigations, the following compounds, gallic acid, ellagic acid, and ascorbic acid, were found to be closely related to catechol as an antibiotic. Hence, it can be concluded that catechol, whether in its entirety or in a portion, is a potent antibacterial, anti-inflammatory, and anti-malarial drug.

Calculation of oxide sputter yields

An existing semi-empirical model to calculate the compound sputter yields is used to fit a large set of literature data on oxide sputter yields which consists of data for 21 different materials, and 65 datasets. The dedicated fitting procedure enables to link the surface binding energy of the metal and oxygen atoms with the oxide cohesive energy. This approach resolves a long standing problem in the research community on the accurate prediction of oxide sputter yields.

Anion-tuning in cobalt chalcogenides for a comparative study on electro-oxidation of glucose

Electronic structure modulation is of great important to enhance the electrocatalytic ability for glucose oxidation and follow up the electrochemical sensing performance. In this work, Co3X4 (X = O, S, Se) synthesized by oxidation, sulfurization and selenylation of ZIF-67 precursor, respectively, are served as electrocatalysts and then modified on conductive indium tin oxide (ITO) to construct sensing electrodes. The Co3S4/ITO electrode shows a highest sensitivity of 1109.9 μA−1 mM−1 cm−2 when compared with those of the Co3Se4/ITO electrode (515.9 μA−1 mM−1 cm−2), Co3O4/ITO electrode (227.7 μA−1 mM−1 cm−2), and even the relative reported sensing electrodes, enabling more efficient electro-oxidation of glucose by S substitution in Co3X4. The experimental characterization and theoretical calculation elucidate that tuning the anion components in cobalt chalcogenides can modulate their electrochemical active surface area, hydrophilicity, electrical conductivity and binding energies for glucose adsorption, in turn, the electrocatalytic ability. This work provides not only an effective strategy for performance improvement but also a significant understanding of how the anion component of electrocatalyst affect their glucose oxidation ability.

Growth dynamics of nanocolumnar thin films deposited by magnetron sputtering at oblique angles

The morphology of numerous nanocolumnar thin films deposited by the magnetron sputtering technique at oblique geometries and at relatively low temperatures has been analyzed for materials as different as Au, Pt, Ti, Cr, TiO2, Al, HfN, Mo, V, WO3 and W. Despite similar deposition conditions, two characteristic nanostructures have been identified depending on the material: a first one defined by highly tilted and symmetric nanocolumnar structures with a relatively high film density, and a second one characterized by rather vertical and asymmetric nanocolumns, with a much lower film density. With the help of a model, the two characteristic nanostructures have been linked to different growth dynamics and, specifically, to different surface relaxation mechanisms upon the incorporation of gaseous species with kinetic energies above the surface binding energy. Moreover, in the case of Ti, a smooth structural transition between the two types of growths has been found when varying the value of the power used to maintain the plasma discharge. Based on these results, the existence of different surface relaxation mechanisms is proposed, which quantitatively explains numerous experimental results under the same conceptual framework.

A Predictive Model for Monolayer‐Selective Metal‐Mediated MoS2 Exfoliation Incorporating Electrostatics

AbstractThe metal‐mediated exfoliation (MME) method enables monolayer‐selective exfoliation of van der Waals (vdW) crystals, improving the efficacy of large monolayer production. Previous physical models explaining monolayer‐selective MME propose that the main contributors to monolayer‐selectivity are vdW crystal/metal surface binding energy and/or vdW crystal layer strain resulting from lattice mismatch. However, the performance of some metals for MME is inconsistent with these models. Here, a new model is proposed using MoS2 as a representative vdW crystal. The model explains how the MoS2/metal interface electrostatics, in combination with strain, determines monolayer‐selectivity of MME by modulating the MoS2 interlayer energy. Monolayer MoS2/metal interfaces are characterized using in situ Raman spectroscopy and density functional theory calculations to estimate the electrostatics and strain of MoS2 in contact with different metals. The model successfully demonstrates the dependence of MME monolayer‐selectivity on the MoS2/metal interface electrostatics and highlights the significance of electrostatics in nanomaterial vdW interactions.

Mechanistic Implications of Low CO Coverage on Cu in the Electrochemical CO and CO2 Reduction Reactions.

Electrochemical CO or CO2 reduction reactions (CO(2)RR), powered by renewable energy, represent one of the promising strategies for upgrading CO2 to valuable products. To design efficient and selective catalysts for the CO(2)RR, a comprehensive mechanistic understanding is necessary, including a comprehensive understanding of the reaction network and the identity of kinetically relevant steps. Surface-adsorbed CO (COad) is the most commonly reported reaction intermediate in the CO(2)RR, and its surface coverage (θCO) and binding energy are proposed to be key to the catalytic performance. Recent experimental evidence sugguests that θCO on Cu electrode at electrochemical conditions is quite low (∼0.05 monolayer), while relatively high θCO is often assumed in literature mechanistic discussion. This Perspective briefly summarizes existing efforts in determining θCO on Cu surfaces, analyzes mechanistic impacts of low θCO on the reaction pathway and catalytic performance, and discusses potential fruitful future directions in advancing our understanding of the Cu-catalyzed CO(2)RR.

Enhancement mechanism of micro-iron ore tailings on mechanical properties and hydration characteristics of cement-steel slag system

The limited cementitious activity of steel slag (SS) powder restricts its large-scale utilization as a replacement material for Portland cement and even more so for inert iron ore tailings (IOT). The micro-IOT (MIOT) were utilized as additives to improve the compressive strength and hydration degree of a binary system containing SS and PC. Compressive strength, flowability, and setting time were measured. The mechanism of MIOT on the hydration properties and microstructure of the cement–SS binary system was investigated using XRD, TG, FTIR, SEM, and MIP. The results revealed that the 28-d compressive strength of composite mortar S20M10 (20% SS and 10% MIOT) with MIOT added to the cement–SS system was 50.32 MPa, which was 93.41% of that of the cement samples and 16.16% higher than the compressive strength of the cement-SS system. Wet grinding of IOT lowered the crystallinity and surface binding energy, increased the reactivity, and facilitated the participation of MIOT in the hydration reaction with the reactive silica-alumina phases in SS, producing more C–S–H. The formation of carbonate AFm phases in the composite system improved the strength. MIOT in suitable dosage can limit the maximum possible pore and porosity of the composite system, increasing the structure's complexity and making the hardened slurry denser. This study provides a solution for IOT activity activation and promotes high-value utilization of SS and IOT.

Temperature dependence of surface microstructure of 316 L stainless steel exposed to low-energy hydrogen ion irradiation

The austenitic 316 L stainless steel (316LSS) is an important metal for nuclear installations due to its high strength, good plastic toughness and excellent corrosion resistance, and is commonly used as the plasma-facing and structural material. In this study, 316LSS samples are irradiated with low-energy hydrogen ions (35 eV) at the temperature of 400–1300 K to investigate the surface microstructure evolution. The experimental results show that the surface of 316LSS samples remains relatively smooth at 400 K and 600 K after irradiation. Significant surface roughening including spherical protrusions is formed on the surface at 800 K and 1100 K, and step-like streaks are observed at 1300 K. However, no drastic change in the surface morphology is observed in the separate annealing experiments at 800–1300 K. It has been shown that hydrogen ion irradiation mainly causes the surface microstructure evolution of 316LSS samples. After hydrogen plasma exposure, a large number of adatoms are first formed on the surface of 316LSS because of bubble growth. The adatoms then preferentially reach the defects by diffusion at certain temperatures, and aggregate into spherical protrusions with low surface energy. The qualitative simulation results show that the irradiation temperature affects the diffusion and aggregation of adatoms on the surface, and the radius of the spherical protrusions gradually increases due to the decrease of the surface binding energy and the increase of the irradiation fluence.