High-resolution X-ray Photoelectron Spectroscopy Research Articles

Effect of HF etching on titanium carbide (Ti3C2Tx) microstructure and its capacitive properties

Two-dimensional multi-layered microstructure generated by hydrofluoric acid etching is essential for the high capacitance MXenes. However, the mechanisms dictating the formation, evolution and properties of MXenes during etching remain elusive due to the lack of direct observation. Herein, using ex-situ scanning electron microscopy combined with high resolution transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, we have revealed the fine variation of microstructure and properties of multi-layered titanium carbide Ti3C2Tx etched for different time. The results show that the laminar cracks always formed from the first initial laminar crack at the edge site of the outermost side of the Ti3AlC2 particle, which induces continuous nucleation of other laminar cracks in the nearby area. The early laminar cracks undergo growth accompanying with increased macro-layer density of Ti3C2Tx and the Al(F,O,C)3 precipitation in subsequent etching process. The formation of laminar cracks is revealed to be correlated with the release of local internal stress in Ti3AlC2. In addition, it is found that there are significant changes of Ti valence state, CC and Ti-C bonding as well as Ti-F, CO and Al-O surface groups during etching. Maximum specific capacitance coincides with maximum lattice parameter c of Ti3C2Tx and maximum number of macro-layers, while over-etching produces in-plane microcracks, Ti dissolution, and reduced specific capacitance. The results provide important insight to facilitate optimal synthesis of this material.

Decoration of Reduced Graphene Oxide with Magnesium Oxide during Reflux Reaction and Assessment of Its Antioxidant Properties

The aim of this work is the reduction and decoration of graphene oxide (GO) with magnesium oxide (MgO). In this work, GO was synthesized using modified Hummers’ protocol with (1:2), (1:3) and (1:4) graphite:potassium permanganate mass ratios. Subsequently, all GO samples (GO1:2, GO1:3, GO1:4) were reduced and decorated with magnesium oxide nanoparticles using a reflux technique at 100 °C for 2 h. Sample characterization using X-ray diffraction (XRD) reveals the presence of peaks relative to two different magnesium (Mg) phases: magnesium oxide (MgO) and magnesium hydroxide (Mg(OH)2). The presence of these spectral features, although characterized by a remarkable broadening, confirms the successful synthesis of Mg(OH)2-rGO-MgO nanocomposites. X-ray photoelectron spectroscopy (XPS) spectra indicate the presence of peaks assigned to C, O and Mg. The analysis of the high-resolution XPS spectra of these elements confirms once again the presence of Mg(OH)2-rGO-MgO compounds. The low temperature synthesis of Mg(OH)2-rGO-MgO nanocomposite exhibiting superior catalytic properties compared to MgO–rGO nanoparticles is an important step forward with respect to the current state of the art. The antioxidant activity of six nanocomposites, namely GO1:2, GO1:3, GO1:4, MgO–rGO1:2, MgO–rGO1:3 and MgO–rGO1:4, was determined using standard protocols based on a DPPH radicals scavenging assay, an H2O2 scavenging assay, and a phosphomolybdate assay. All our samples exhibited dose-dependent antioxidant activity. Interestingly, among the different synthesized nanoparticles, GO1:4 and MgO–rGO1:4 showed the best performances.

Valence State Tuning of Gold Nanoparticles in the Dewetting Process: An X-ray Photoelectron Spectroscopy Study.

Gold nanoparticles (AuNPs) are commonly synthesized using the citrate reduction method, reducing Au3+ into Au1+ ions and facilitating the disproportionation of aurous species to Au atoms (Au0). This method results on citrate-capped AuNPs with valence single states Au0. Here, we report a methodology that allows obtaining AuNPs by the dewetting process with three different valence states (Au3+, Au1+, and Au0), which can be fine-tuned with ion bombardment. The chemical surface changes and binding state of the NPs were investigated using core-level X-ray photoelectron spectroscopy (XPS). This is achieved by recording high-resolution Au 4f XPS spectra as a function of ion dose exposure. The results obtained show a time-dependent tuning effect on the Au valence states using low-energy 200 V acceleration voltage Ar+ ion bombardment, and the valence state conversion kinetics involves the reduction from Au3+ and Au1+ to Au0. Proper control of the reduction in the valence states is critical in surface engineering for controlling catalytic reactions.

Synthesis of Cyano-Benzylidene Xanthene Synthons Using a Diprotic Brønsted Acid Catalyst, and Their Application as Efficient Inhibitors of Aluminum Corrosion in Alkaline Solutions.

Novel cyano-benzylidene xanthene derivatives were synthesized using one-pot and condensation reactions. A diprotic Brønsted acid (i.e., oxalic acid) was used as an effective catalyst for the promotion of the synthesis process of the new starting xanthene–aldehyde compound. Different xanthene concentrations (ca. 0.1–2.0 mM) were applied as corrosion inhibitors to control the alkaline uniform corrosion of aluminum. Measurements were conducted in 1.0 M NaOH solution using Tafel extrapolation and linear polarization resistance (LPR) methods. The investigated xanthenes acted as mixed-type inhibitors that primarily affect the anodic process. Their inhibition efficiency values were enhanced with inhibitor concentration, and varied according to their chemical structures. At a concentration of 2.0 mM, the best-performing studied xanthene derivative recorded maximum inhibition efficiency values of 98.9% (calculated via the Tafel extrapolation method) and 98.4% (estimated via the LPR method). Scanning electron microscopy (SEM) was used to examine the morphology of the corroded and inhibited aluminum surfaces, revealing strong inhibitory action of each studied compound. High-resolution X-ray photoelectron spectroscopy (XPS) profiles validated the inhibitor compounds’ adsorption on the Al surface. Density functional theory (DFT) and Monte Carlo simulations were applied to investigate the distinction of the anticorrosive behavior among the studied xanthenes toward the Al (111) surface. The non-planarity of xanthenes and the presence of the nitrile group were the key players in the adsorption process. A match between the experimental and theoretical findings was evidenced.

Kinetic investigation of plasma catalytic synthesis of ammonia: insights into the role of excited states and plasma-enhanced surface chemistry

The present work investigates the kinetics of catalytic ammonia synthesis in a N2/H2 mixture activated by a nanosecond pulsed discharge plasma experimentally and numerically. X-ray diffraction, high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy are combined to characterize the morphology and surface electronic properties of the catalyst. Special attention is placed on the role of excited species in promoting the formation of important intermediates and the plasma-enhanced surface chemistry. A detailed kinetic mechanism consisting of atoms, radicals, excited species, molecules, ions, and surface species is developed and studied by incorporating a set of the electron impact reactions, reactions involving excited species, ionic reactions, direct and dissociative adsorption reactions, and surface reactions. A zero-dimensional model incorporating the plasma kinetics solver is used to calculate the temporal evolution of species densities in a N2/H2 plasma catalysis system. The results show that the coupling of Fe/γ–Al2O3 catalyst with plasma is much more effective in ammonia synthesis than the Fe/γ–Al2O3 catalyst alone and plasma alone. The numerical model has a good agreement with experiments in ammonia formation. The path flux analysis shows the significant roles of excited species N(2D), H2(v1), N2(v) in stimulating the formation of precursors NH, NH2, and adsorbed N(s) through the pathways N(2D) + H2 → NH + H, H2(v1) + NH → NH2 + H and N2(v) + 2Fe(s) → N(s) + N(s), respectively. Furthermore, the results show that the adsorption reaction N + Fe(s) → N(s) and Eley–Ridel interactions N(s) + H → NH(s), N + H(s) → NH(s), NH + H(s) → NH2(s) and NH2 + H(s) → NH3(s) can kinetically enhance the formation of ammonia, which further highlights the plasma-enhanced surface chemistry. This work provides new insights into the roles of excited species and plasma-enhanced surface chemistry in the plasma catalytic ammonia synthesis.

Hydrogen adsorption and interactions in self-reducing shell hosted palladium nanoparticles on magnetite support

The nanoparticles (NP), consisting of hydrazine grafted organo-silica with PdNPs embedded shell on the Fe3O4 core, were prepared to study the adsorption and interactions of hydrogen in PdNPs and their support matrix. This material is expected to find the applications in the hydrogen technology including catalysis. The PdNPs were formed spontaneously in the organo-silica shell on magnetite nanoparticles by the reduction of Pd2+ ions with grafted hydrazine in the organo-silica shell. Thus formed NPs, termed as Fe3O4-GTEOS@PdNPs, were also thermally treated at 1033 K in Ar atmosphere to convert organic components to carbon. The chemical composition, physical structure, and magnetic properties were studied by high resolution transmission electron microscopy, X-rays diffraction, Mössbauer spectroscopy and X-ray photoelectron spectroscopy for the characterizations of physical, chemical and magnetic changes occurred in the Fe3O4-GTEOS@PdNPs after hydrogen adsorption-desorption at varying temperatures with respect to that in unused one. The hydrogen adsorption pressure-composition (PC) isotherms in Fe3O4-GTEOS@PdNPs followed the expected trend from 173 to 303 K as expected from PdNPs. However, thermally treated Fe3O4-GTEOS@PdNPs were found to adsorb lower amount of hydrogen due to oxidation of Pd0 to PdO and morphological changes during heating in Ar atmosphere. The comparison of nH/nPd value (0.49) obtained for the PdNPs in Fe3O4-GTEOS@PdNPs with the values those reported in the literature for different Pd materials showed the decrease in nH/nPd value with decrease in the size of Pd particles. This was attributed to stronger Pd–H bond in a nanoscale palladium, which prevented hydrogen transfer to interior matrix as compared to bigger Pd particles. The hydrogen adsorption PC isotherm at 373 K in Fe3O4-GTEOS@PdNPs could not be obtained as the unknown chemical reaction happened in the sample during the experiment. The considerably higher H2 consumption in the Fe3O4-GTEOS@PdNPs occurred at 373 K than that expected from the hydrogen adsorption in the PdNPs alone.

Effect of ash in biodiesel combustion particulate matter on the oxidation characteristics of carbon soot

This study investigates the effect of ash in biodiesel combustion particulate matter on the oxidation characteristics of carbon soot within a diesel particulate trap. Samples of pigment-U engineered carbon soot were mixed with different biodiesel ashes using an impregnation method. The samples were subjected to 24 h of heating at 120 °C and 2 h of heating at 350 °C before treatment. The oxidation activity, structural properties and the elemental species of the manufactured carbon soot were investigated using thermogravimetric analysis, specific surface area and pore analysis, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The oxidation characteristics of the carbon soot were investigated with different metal elements, masses and metal salt types. The results show that the doping of metal elements and metal salt types can increase the oxidation activity of the carbon soot, with Na elements and nitrate having the greatest effect on the oxidation activity. Doping with metal elements and metal salt species can make the structural orderliness and graphitization of the soot decrease, and the O and CO contents increase to different degrees. Sodium (Na) and nitrate have the greatest influence on the soot structural properties, with the numerical ratios and area ratios between peaks being the largest. Doping with Na results in an ID1/IG value of 1.44, and an AD3/AG value of 1.53. The CO content of soot doped with Na is the greatest, reaching 4.7%. The oxygen content of soot doped with Na carbonate is the largest, reaching 5.5%.

Sequentially evaporated layer deposition stack of CuxS thin films for photonics applications

CuxS(x;1,2) layers were grown on thermal annealing of the sequentially evaporated layer deposition (SELD) stack of Cu/S from 373 to 573 K. The thicknesses of the deposited stacks were fixed at 200 and 600 nm. The 300 K deposited layers possess a CuS (covellite) phase and a few impurity peaks of Sulphur (S). The as-deposited films of both thicknesses provided the CuS (covellite) phase with impurity peaks of Sulphur (S). The CuS single phase was observed at 373 and 473 K. The CuS transformed into a copper-rich Cu2S (chalcocite) phase at 523 K, and the same phase continued at 573 K. The Cu2S phase was obtained on re-evaporation of S from CuS at 523 K. An intermediary digenite phase was also spotted at 523 K. The CuS and Cu2S phases were confirmed from the Raman spectra. The oxidation states of Cu and S of the CuS films were also determined from XPS analysis. The Cu 2p and S 2p levels of CuS (covellite) were established using high-resolution XPS spectra. The phase transformation from CuS to Cu2S and change in stoichiometry at higher temperatures give rise to bandgap variation from 2.30 to 1.20 eV for direct and 2.10–1.34 eV for indirect allowed bandgaps. The absorption coefficient (α) for both thickness values is > 1 × 105 cm-1. Further, the 600 nm films provided higher absorption coefficient (α) values than the 200 nm layers. The unique electrical and optical properties and bandgap tuning make CuS and Cu2S thin films suitable for gas sensors, photodetectors, absorber layers in low-cost PV solar cells, and energy storage applications.

How the Environment Encourages the Natural Formation of Hydrated V2O5.

Herein, we report the microscopic and spectroscopic signatures of the hydrated V2O5 phase, prepared from the α-V2O5 powder, which was kept in deionized water inside an airtight glass container for approximately 2.5 years. The experimental results show an evolution of the V4+ component in V 2p3/2 core energy level spectra, and a peak corresponding to σ-OH– bond appeared in the valence band spectra in the hydrated V2O5 powder sample due to the water intercalation. Vanadium metal oxide particles were found to be self-nucleated into micro/nanorods after a long period of exposure to an extremely humid environment. The distinct features in the spectra obtained with high-resolution transmission electron microscopy, micro-Raman scattering, and X-ray photoelectron spectroscopy confirmed the presence of structural water molecules for the first time in the long-aged naturally hydrated V2O5 phase.

Study of optical, morphological, structural, and chemical properties of CdO thin films synthesized by thermal annealing transformation of CdCO3 thin films

Considering the potential applications of cadmium oxide (CdO) thin films in optoelectronics, this work aims to investigate the structural, optical, compositional, and morphological properties of CdO thin films obtained by converting CdCO3 thin films into CdO by thermal annealing. The established method consists of thermal treatment for 2 h at different temperatures for CdO thin film obtention. The CdO thin films were characterized by ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetry (TGA). The direct band gap of the CdO thin films obtained was 2.39 and 2.43 eV. These values are in the range reported in the literature for CdO thin films and are related to direct transitions of electrons between valence and conduction bands. Furthermore, the HR-TEM and XRD analysis confirmed a cubic crystalline structure for CdO thin films. The low-resolution and high-resolution XPS spectra further confirm the expected chemical composition of CdO thin films.

Role of Materials Chemistry on Transparent Conductivity of Amorphous Nb-Doped SnO2 Thin Films Prepared by Remote Plasma Deposition

In this study, remote plasma sputtering deposition of niobium-doped SnO2 transparent conductive oxides on glass substrates was carried out at ambient temperature with no post-deposition annealing. The microstructure, optical, electrical, and surface morphology of the thin films were characterized using a combination of advanced techniques, such as X-ray diffraction (XRD), UV-Vis spectrophotometer, Hall-effect measurements, as well as field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy, and high-resolution X-ray photoelectron spectroscopy. It was determined that the oxygen defects of the films have a substantial impact on their transparent conductivity. The crystalline films, which were crystallized by annealing at 450 °C, had higher resistivities due to a decreased concentration of oxygen vacancies, which restricted conduction. In comparison, the amorphous films exhibited remarkable conductivity. The best amorphous films (Nb:SnO2) exhibited a resistivity of less than 4.6 × 10−3 Ω·cm, with a 3 × 1020 cm−3 carrier concentration and a 4.4 cm2/(V·S) of Hall mobility. X-ray amorphous Nb:SnO2 films can be used to make conductive and transparent protective layers that can be used to shield semiconducting photoelectrodes used in solar water splitting. These layers can also be used with more conductive TCO films (ITO or AZO) when needed.

Irradiation-induced amorphization of UO2 films prepared by spraying-assisted combustion synthesis

Spraying-assisted combustion synthesis with uranyl nitrate − acetylacetone − 2-methoxyethanol solutions was used to prepare UO2 films on an aluminum alloy substrate. The tuning of the spraying parameters and annealing temperatures allowed the preparation of UO2 films with thicknesses varying from 10–300 nm and 5–10 nm UO2 grain size. High-resolution electron microscopy and X-ray photoelectron spectroscopy showed that increasing the annealing temperature promotes Mg diffusion from the substrate into the films. The incorporation of Mg reduced the overall crystallinity of the films. The irradiation with Ar2+ ions (1.7 MeV energy and a fluence of 2 × 1016 ions/cm2) did not degrade the quality of the films. However, the Mg content significantly influenced the irradiation-induced restructuring of the UO2 films. Irradiated films with low or no Mg content exhibit high crystallinity, and the UO2/Al interfacial layer becomes highly porous. Films with higher Mg content are mostly amorphized after irradiation. The origin of irradiation-induced amorphization was related to the formation of MgyU1-yO2±x solid solutions. Chemically complex, pore-free, and amorphous Mg-Al-O film/substrate interfacial layers enable continuous Mg diffusion during irradiation. Furthermore, the gradual increase in Mg amounts triggers irradiation-induced precipitation of a crystalline MgO-rich phase within the amorphous films.

Optical and interfacial characteristics of a heterojunction between (2¯01)-oriented single-domain β-(In0.072Ga0.928)2O3 and α-Al2O3 crystals

In this article, we determine the band alignment at the thermodynamically stable heterointerface between a ( 2 ¯ 01 )-oriented single-domain β-(In0.072Ga0.928)2O3 crystal and bulk c-plane sapphire, namely, (0001)-oriented α-Al2O3. The β-(In0.072Ga0.928)2O3 layer was deposited on the bulk sapphire crystal using pulsed laser deposition. The β-(In0.072Ga0.928)2O3 and α-Al2O3 valence and conduction band offsets (VBO and CBO, respectively) were found to be 0 ± 0.1 and 4.87 ± 0.1 eV, respectively. Accordingly, we identified a type-I α-Al2O3/β-(In0.072Ga0.928)2O3 heterojunction. X-ray diffraction measurements confirmed ( 2 ¯ 01 )-oriented single-domain β-(In0.072Ga0.928)2O3 high-quality films with in-plane rotations of every 120 ∘ , whereas Rutherford backscattering spectrometry was employed to verify the bulk composition. We employed high-resolution X-ray photoelectron spectroscopy to measure the core level binding energies of Al 2p and Ga 2p3/2 with respect to the valence band maxima of the β-(In0.072Ga0.928)2O3 and α-Al2O3 layers, respectively. Then, we measured the energy separation between the Al 2p and Ga 2p3/2 core levels at the interface of the heterojunction. β-(InGa)2O3 is a wide-bandgap semiconductor, while α-Al2O3 is a well-known dielectric. Together, they can be employed to fabricate reliable and efficient power electronic devices. We also combined high-resolution transmission electron microscopy, X-ray diffraction, and fast Fourier transform algorithms to characterize the dislocations at the interface.

Effect of argon flow rate and direct current bias on the growth of boron nitride coating in low-temperature plasma

A microwave plasma chemical vapor deposition system was used to synthesize cubic boron nitride (cBN) coatings on diamond seeded silicon substrates using direct current (DC) bias. Effects of the argon (Ar) flow rate and bias voltage on the growth of the cBN coatings were investigated. Hydrogen (H2), argon (Ar), a mixture of diborane in H2 (95% H2, 5% B2H6), and N2 were used in the feed gas. A DC bias system was used for external biasing of the sample, which facilitates the goal of achieving sp3 bonded cBN. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) revealed the existence of sp3-bonded BN in the produced samples. With increasing Ar flow, the cBN content in the coating increases and reaches a maximum at the maximum Ar flow of 400 SCCM used in this study. High-resolution XPS scans for B1s and N1s indicate that the deposited coating contains more than 70% cBN. This study demonstrates that energetic argon ions generated in a microwave-induced plasma significantly increase cBN content in the coating.

Homogeneous Spatial Distribution of Deuterium Chemisorbed on Free-Standing Graphene.

Atomic deuterium (D) adsorption on free-standing nanoporous graphene obtained by ultra-high vacuum D molecular cracking reveals a homogeneous distribution all over the nanoporous graphene sample, as deduced by ultra-high vacuum Raman spectroscopy combined with core-level photoemission spectroscopy. Raman microscopy unveils the presence of bonding distortion, from the signal associated to the planar sp configuration of graphene toward the sp tetrahedral structure of graphane. The establishment of D–C sp hybrid bonds is also clearly determined by high-resolution X-ray photoelectron spectroscopy and spatially correlated to the Auger spectroscopy signal. This work shows that the low-energy molecular cracking of D in an ultra-high vacuum is an efficient strategy for obtaining high-quality semiconducting graphane with homogeneous uptake of deuterium atoms, as confirmed by this combined optical and electronic spectro-microscopy study wholly carried out in ultra-high vacuum conditions.

Insitu synthesis, characterization of Z-scheme g-C3N4/Bi2O3 as photocatalyst for degradation of azo dye, Amido black-10B under solar irradiation

Here in, we report the synthesis of Z-scheme g-C3N4/Bi2O3 as an efficient direct solar light-driven photocatalyst using a facile in-situ approach. The characterization of obtained composite using various techniques such as X-ray diffraction (XRD) pattern, field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), TGA/DTA/DTG, and X-ray photoelectron spectroscopy (XPS) revealed successful synthesis of g-C3N4/Bi2O3 composite. Furthermore, photoluminescence (PL), transient photocurrent response (TPR), UV-VIS diffuse reflectance spectroscopy (UV–vis DRS), and BET surface area analysis studies were also carried out. The as-obtained composite g-C3N4/Bi2O3-2 displayed 98.8% degradation efficiency of amido black 10B (AB-10B) dye in 60 min under exposure of direct sunlight and at optimized conditions (dye concentration = 0.01 g L−1, pH = 5, catalyst dose as 0.25 g L−1). The photocatalytic degradation process was compounded with first-order reaction kinetics. The statistical significance of the experimental data received was evaluated and a strong correlation between the process parameters was predicted. Based on inhibitor studies, a mechanism was proposed that revealed the significant contribution of . O2− and . OH in photocatalytic process. Thus, g-C3N4/Bi2O3-2 showed enhanced photocatalytic degradation and can be explored further for various environmental applications.

Chromium-Rich Core-Shell Cr x Ir1-X O2 Nanotubes for Highly Efficient Oxygen Evolution Reaction in Alkaline Solution

Considering the growing attention to oxygen evolution reaction (OER) as a key role in clean energy through electrocatalytic water splitting, advanced materials for water oxidation are central to the area of renewable energy. In general, the OER process, involved four electron and four proton coupled electrochemical reaction, demands higher kinetics to overcome an overpotential than HER (hydrogen evolution reaction). For this aspect, significant research efforts have been devoted to developing efficient OER electrocatalyst with enhanced electrocatalytic kinetics and long-term durability.Here we present the synthetic processes and physical/electrochemical characterization of Cr x Ir1-x O2 nanotubes (NTs). Those NTs are synthesized through electrospinning, a simple way to facilitate 1D nanostructure, and post-thermal annealing process with different annealing speed (°C /min). As-prepared Cr x Ir1-x O2 NTs at the optimized conditions have shown outstanding OER electrocatalytic activity in alkaline media from the viewpoints of overpotential and Tafel slope as well as durability. The morphology and compositions of Cr x Ir1-x O2 were characterized by a field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The crystalline structures of the prepared Cr x Ir1-x O2 are investigated through high-resolution X-ray diffraction (XRD). Electrochemical activities for oxygen evolution reaction (OER) are studied with rotating disk electrode (RDE) voltammetry in N2-saturated 1.0 M KOH (aq); and compared with those of iridium single component oxides (IrOx and IrO2) and commercial iridium (cIr, counterparts in OER electrocatalysts).This work was financially supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT or by the Ministry of Education (NRF-2019R1F1A1059969, NRF-2018R1A6A1A03025340, NRF-2020R1A2B5B01001984, and NRF-2019R1F1A1062799).

Superhydrophobic PDMS coated 304 stainless-steel mesh for the removal of HDPE microplastics

The use of microplastics is a global issue that affects the environment, the economy and human health. Here we describe a superhydrophobic 304 stainless steel obtained by combining chemical etching and PDMS modification. Among other techniques, field emission scanning electron microscopy (FE-SEM) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) were used to identify the hierarchical structure as well as the chemical composition of the surface. The stainless-steel mesh was superhydrophobic (159°) and superoleophilic (0°). The coating presented high stability against abrasion of SiC abrasive paper as well as in the presence of different pH values in acidic or alkaline conditions. In addition, taking advantage of the coating's wetting properties, we show that the superhydrophobic surface can also be used to remove high-density polyethylene microplastics from water. A surface mechanism promoting the removal or microplastics is also proposed, considering the surface properties of the solid pollutants as well as the wetting properties of the superhydrophobic coating.

Improved threshold switching characteristics of vanadium oxide/oxynitride-based multilayer selector in a cross-point array

We developed a selector device with the bi-directional threshold switching characteristics of vanadium oxide (VOx) by implementing vanadium oxynitride (VOx:Ny) in a sandwich structure. The proposed device with the Pt/VOx:Ny/VOx/VOx:Ny/Pt structure as opposed to a cell with a Pt/VOx/Pt structure exhibits lower off-current and stable switching characteristics. The elements of the device were analyzed using high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, and its memory characteristics were verified by applying the Pt/VOx:Ny/VOx/VOx:Ny/Pt selector to amorphous indium-gallium-zinc oxide-based resistive switching (RS) devices in the 1 selector-1 ReRAM structure. Our device shows stable RS properties over 100 DC cycles and> 106 AC cycles, an improved ON/OFF ratio (~67), a high switching speed (<110 ns), and a rectification ratio of ~1 × 103 when the read margin is 10%.

BiO 2-x Nanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO 2 Reduction to Formate

BiO _2-x Nanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO ₂ Reduction to Formate