X-ray Photoelectron Spectroscopy Spectra Research Articles

Structural, morphological, optical and antibacterial performances of rare earth (Sm)-doped ZnO nanorods

The significant rise of ultra-violet (UV) radiation and pathogenic infectious bacteria poses a serious threat to global health. Numerous researchers’ interests are attracted by novel materials with strong UV-blocking ability, antibacterial activity and low toxicity to other species. In this case, a simple wet chemical method with different annealing temperatures (400, 500, and 600 °C) was employed to create highly effective rare earth (Sm)-doped ZnO nanorods. The (101) plane of wurtzite ZnO shifts towards a lower angle with increasing annealing temperature, according to the X-ray diffraction (XRD) study findings, which additionally establishes the consequence of lattice expansion. Occurrence of doublet peaks of Sm 3d (Sm 3d5/2 and Sm 3d3/2) in the X-ray photoelectron spectroscopy (XPS) spectrum clearly validates the substitution of Sm3+ ions in the 500 °C-annealed samples. The 500 °C-annealed nanorods exhibit combined performances of the wide band gap, improved UV absorbance, and vivid green luminescent emission (563 nm). Additionally, the nanorods have favorable UV-blocking execution of 96 % for UVA at 360 nm, 92 % for UVB at 320 nm, and 57 % for UVC at 225 nm, which is greater than the majority of ZnO-related materials that have been reported up to this date. Sm doping is also appropriate for improving bacterial inhibition against the two studied strains (Escherichia coli and Staphylococcus aureus), in addition to the intriguing features discussed above. Furthermore, with maximum inhibition zone diameters of 20 ± 0.72 and 18 ± 0.57 mm, respectively, these nanorods exhibit high inhibitory action against E. coli and S. aureus bacterial strains. The rare earth-doped material developed during the current experiment, which was annealed at 500 °C, could potentially serve as an effective replacement for UV-blocking and antibacterial material, especially for biomedical applications.

Plasma-assisted annealing of Pt-doped rutile TiO2 nanoparticles for enhanced decomposition and bacterial inactivation under general lighting

Enhanced photocatalytic activity of rutile-based TiO2 materials under general lighting is practically desired. O2 plasma-assisted annealing (PAA) effects on Pt-doped rutile TiO2 nanoparticles were clarified along with its visible-light-driven photocatalytic activity enhancement. The PAA-treated samples were mainly analyzed using optical spectroscopy and x-ray photoelectron spectroscopy (XPS). The photocatalytic activity was assessed by decomposing methylene blue dye and inactivating Bacillus subtilis under general lighting. The PAA treatment changed the O 1s, Ti 2p, and Pt 4f spectra of XPS from those of the pristine sample. This change indicated that the PAA treatment introduced more oxygen deficiency or oxygen vacancies and more oxygen groups adsorbed on the surface. The introduced oxygen vacancies and adsorbed oxygen groups would change the band structure, which primarily narrowed the bandgap energy or broadened the valence band edge, increased the number of electron-trapping sites from the shallow to midgap levels, and enhanced the upward band-bending at the surface. The PAA-induced change in the band structure enhanced the decomposition and bacterial inactivation because it facilitated the separation and concentration of photoexcited carriers. The findings provide a new perspective on enhancing the photocatalytic activities of rutile-based TiO2 nanoparticles under general lighting.

Light-enhanced oxygen degradation of MAPbBr3 single crystal.

Organometal halide perovskites are promising materials for optoelectronic applications, whose commercial realization depends critically on their stability under multiple environmental factors. In this study, a methylammonium lead bromide (MAPbBr3) single crystal was cleaved and exposed to simultaneous oxygen and light illumination under ultrahigh vacuum (UHV). The exposure process was monitored using X-ray photoelectron spectroscopy (XPS) with precise control of the exposure time and oxygen pressure. It was found that the combination of oxygen and light accelerated the degradation of MAPbBr3, which could not be viewed as a simple addition of that by oxygen-only and light-only exposures. The XPS spectra showed significant loss of carbon, bromine, and nitrogen at an oxygen exposure of 1010 Langmuir with light illumination, approximately 17 times of the additive effects of oxygen-only and light-only exposures. It was also found that the photoluminescence (PL) emission was much weakened by oxygen and light co-exposure, while previous reports had shown that PL was substantially enhanced by oxygen-only exposure. Measurements using a scanning electron microscope (SEM) and focused ion beam (FIB) demonstrated that the crystal surface was much roughened by the co-exposure. Density functional theory (DFT) calculations revealed the formation of superoxide and oxygen induced gap state, suggesting the creation of oxygen radicals by light illumination as a possible microscopic driving force for enhanced degradation.

Selenium bio-nanocomposite based on extracellular polymeric substances (EPS): Synthesis, characterization and application in alleviating cadmium toxicity in rice (Oryza sativa L.)

Selenium nanoparticles (SeNPs) have gained significant attention owing to their favorable bioavailability and low toxicity, making them widely applications in the fields of medicine, food and agriculture. In this study, bacterial extracellular polymeric substances (EPS) were used as a novel stabilizer and capping agent to prepare dispersed SeNPs. Results show that EPS-SeNPs presented negative potential (−38 mV), spherical morphologies with average particle size about 100–200 nm and kept stable at room temperature for a long time. X-ray diffraction (XRD) analysis demonstrated that the synthesized nanoparticles were pure amorphous nanoparticles, and X-ray photoelectron spectroscopy (XPS) spectrum showed a spike at 55.6 eV, indicating the presence of zero-valent nano‑selenium. Fourier-transform infrared spectroscopy (FTIR) and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy analysis confirmed proteins and polysaccharides in EPS played a crucial role in the synthesis of EPS-SeNPs. Compared to EPS or sodium selenite (Na2SeO3), EPS-SeNPs showed a relatively moderate result in terms of scavenging free radicals in vitro. In contrast, EPS-SeNPs demonstrated lower toxicity to rice seeds than Na2SeO3. Notably, the exogenous application of EPS-SeNPs effectively alleviated the growth inhibition and oxidative damaged caused by cadmium (Cd), and significantly reduced Cd accumulation in rice plants.

Structural, optical and electrical properties of Al-doped CdO nanoparticles by solid state reaction

In the present study, aluminium doped cadmium oxide (Cd1-xAlxO) nanoparticles at (x = 0.00, 0.03, 0.05 & 0.07) concentrations were prepared using solid-state reaction and synthesized nanoparticles were subjected to different characterisations such as X-ray diffractometer (XRD), UV–Vis-Spectrophotometer (UV–Vis–NIR), field emission scanning electron microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and I–V measurements. The X-ray diffraction patterns confirm the polycrystalline nature of the Cd1-xAlxO nanoparticles with cubic structure. From the XRD patterns, the crystallite size and other structural parameters were calculated. The diffuse reflectance spectra were used to calculate the optical bandgap of the Cd1-xAlxO nanoparticles and it increased with increase of aluminium (Al) concentration (2.00 eV–2.04 eV). The FT-IR spectra confirm the Cd–O vibrational bands in the Cd1-xAlxO nanoparticles.The morphological studies revealed the spherical shape of the synthesized nanoparticles. The XPS spectra confirm the presence of aluminium (Al), cadmium (Cd) and oxygen (O) in the desired ratios. The current versus voltage characteristics of the Cd1-xAlxO nanoparticles were studied using Keysight source metre.

Preparation of Co–CaCO3 catalysts for improved hydrogen production from sodium borohydride

Ca1-xCoxCO3 nanoparticle catalysts (x = 0.0, 0.1, 0.2 and 0.3 %) were prepared by the sol-gel method. The samples were characterized using various techniques such as X-ray diffraction (XRD), attenuated total reflectance spectroscopy (ATR), environmental scanning electron microscopy (ESEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analysis. The XRD peaks of Ca1-xCoxCO3 displayed a significant level of conformity with the rhombohedral calcite structure. The average crystal size of Ca1-xCoxCO3 nanoparticles was found to be 14 nm. The ESEM micrographs of Ca1-xCoxCO3 showed rhombic calcite shapes. The most prominent peaks in the XPS spectra of Ca1-xCoxCO3 are the Ca 2p, C 1s, Co 2p and O 1s peaks. The sample Ca1-xCoxCO3 has the highest surface area (58.27 m2/g) and large pore size (20.25 Å). The rates of hydrogen production for CaCO3, Ca0.9Co0.1CO3, Ca0.8Co0.2CO3 and Ca0.7Co0.3CO3 were 5204, 4381, 6666 and 6136 mL/g.min. The Ca0.8Co0.2CO3 catalyst revealed an activation energy for hydrogen catalytic reaction of 34.56 kJ/mol. The recyclability tests of Ca1-xCoxCO3 catalysts showed a reduction of efficiency by 7 % over 5 reaction cycles. Accordingly, the prepared Ca1-xCoxCO3 catalysts are promising for improved hydrogen production systems. This research contributes to advancements in hydrogen production technology.

Effect of Annealing Temperature on the Electrochemical Behavior of Hydrothermal Assisted Bismuth Phosphate Nanostructures

: In the present scenario, society requires various energy sources due to the depletion of fossil fuels. In the current work, Bismuth Phosphate nanostructures are synthesized via the hydrothermal method at different aging periods and were further annealed at 300 These samples are abbreviated as BP6300, BP12300, BP18300, and BP24300. Further, we analyzed the synthesized samples' structural, morphological, and electrochemical behavior. X-ray Diffraction Technique is used to analyze the phase and crystal structure of all the synthesized samples. A field emission scanning electron microscope (FESEM) is used to analyze the morphology. Raman and FTIR spectra also approved the structure of materials and functional groups of all the synthesized samples. EDX spectra analysis confirmed the results quantitatively by detecting all the elements present in the synthesized material. High–resolution X-ray photoelectron spectroscopy (XPS) spectra confirmed the oxidation states of the synthesized samples. Various aging period treatments with annealing temperatures play a significant role in tuning the electrochemical behavior of working electrodes for battery or hybrid energy storage applications. The drop casting method was adopted for the fabrication of working electrodes, and all the electrochemical analysis of these electrodes was done in the 2 M KOH electrolyte solution. Cyclic Voltammetry (CV), Galvanostatic Charge Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) of all the samples were analyzed in the 3-electrode setup and exhibited a high potential window of 1.4 V. The specific capacity is found to be maximum for BP12300 samples. The investigation revealed that synthesized material could be used as an electrode for various energy storage device applications. Keywords: Bismuth Phosphate, Cyclic Voltammetry, Galvanostatic charge-discharge, and hydrothermal method.

Modified MnO2-Based Cathode for Zinc-Ion Batteries Using Facile Processing and Easily Available Materials

With the fast development of diverse electronics, the demand for safe energy storage systems with high energy density and high stability has increased rapidly. So far, lithium-ion batteries (LIBs) have dominated the market, from small smart electronics to electric vehicles. Nevertheless, LIBs have several limitations, such as high cost, limited raw material resources, high flammability, and harsh environmental impact. Therefore, novel rechargeable batteries which can mitigate these shortcomings must be explored. Aqueous zinc-ion batteries (ZIBs) have shown a promising future. Zinc with high theoretical volumetric capacity (5855 mAh cm-3) and high stability in aqueous electrolytes should enable high-performing, safe, and low-cost batteries. Additionally, the simple assembly of ZIBs in the ambient environment results in low capital costs. Despite these attractive merits, developing cathode materials with high capacity, rate performance, and stability in order to build commercial high-performing ZIBs, remains a great challenge.Cathode materials directly influence the electrochemical performance of ZIBs. Manganese oxide (MnO2) has been investigated as a promising cathode in ZIBs research due to its good specific capacity, low cost and high safety. However, the low ionic conductivity, slow diffusion kinetics, and low stability of MnO2 severely deteriorate the electrochemical performance and cycling stability of zinc-ion batteries. Recently, a series of studies have revealed the high effectiveness of coating on improving MnO2 cathode stability, including polymer coatings, carbon-based material coatings, artificial cathode-electrolyte interfaces, and metal oxide coatings.[1] Nevertheless, the improvement of other parameters, such as the rate performance, could be further improved for practical usage. In this research, we develop a novel modification method combining coating and doping strategies to induce MnO2 cathode with high capacity, high rate performance and low capacity decay after long-term operation. First, we utilize a facile one-step hydrothermal synthesis for Ag-doped α-MnO2. Different amounts of AgNO3 are added into reactors with KMnO4 and MnSO4 (n(Ag):n(Mn)=1:100-4:100) to investigate the influence of doping on capacity and rate performance. Subsequently, the doped tunnel-type MnO2 cathodes are mixed with precursor solutions of Al2O3 and then thoroughly stirred. Finally, an annealing process is conducted to achieve a nanoscale Al2O3 coating on the tunnel type MnO2. The coating configurations influence the electrochemical performance of cathodes;[2] thus, we test precursor solutions with different concentrations (1-3 wt% Al2O3) and annealing temperatures (500-700 °C) to investigate the influence of coating thickness and annealing treatment.With the assistance of scanning and transmission electron microscopes, the nanoscale Al2O3 layer coating on the doped active material is verified. The stable Al2O3 coating protects active materials from dissolution and structural collapse, improving cycling stability and resulting in high capacity retention after long-term operation. Moreover, a significant improvement in rate performance compared to unmodified MnO2 is verified through electrochemical tests. The X-ray photoelectron spectroscopy (XPS) and EPR spectra showed that the doped Ag+ ions lead to oxygen vacancies due to the formation of Ag-O-Mn.[3] The abundant vacancies act as active sites, significantly improving conductivity and ion insertion rates. The ex-situ X-ray diffractometer (XRD) and electrochemical tests are used to investigate the ion insertion mechanism during charging/discharging operations. The Ag-MnO2 @ Al2O3 cathode is synthesized through a facile methodology with environment-friendly materials. The modified cathode exhibits promising performance, especially regarding cycling stability and rate performance, which will be a crucial step for developing high-performing cathodes in aqueous zinc-ion batteries.Reference:[1] Shi, W., Lee, W. S. V., & Xue, J. (2021). Recent development of Mn‐based oxides as zinc‐ion battery cathode. ChemSusChem, 14(7), 1634-1658.[2] Zhou, A., Xu, J., Dai, X., Yang, B., Lu, Y., Wang, L., ... & Li, J. (2016). Improved high-voltage and high-temperature electrochemical performances of LiCoO2 cathode by electrode sputter-coating with Li3PO4. Journal of Power Sources, 322, 10-16.[3] Pu, X., Li, X., Wang, L., Maleki Kheimeh Sari, H., Li, J., Xi, Y., ... & Wu, Y. (2022). Enriching Oxygen Vacancy Defects via Ag–O–Mn Bonds for Enhanced Diffusion Kinetics of δ-MnO2 in Zinc-Ion Batteries. ACS Applied Materials & Interfaces, 14(18), 21159-21172. Figure 1

Mitigating Chemo-Mechanical Degradation in Sulfide-Based All-Solid-State Batteries Comprising Sulfur Composite Cathode and Li–Si Alloy Anode

In this study, all-solid-state batteries consisting of an Li2S5–P2S5 (LPS) glass electrolyte, a sulfur/LPS glass/carbon composite cathode, and an Li–Si anode are prepared and tested under high cut-off voltage conditions (0.5–3.7 V) to elucidate the effect of LPS redox activity on the chemo-mechanical stability of LPS-based cells. The cell cycled in the voltage range 0.5–3.7 V exhibits unstable charging behaviors and voltage noise, with substantial LPS oxidative decomposition. X-ray photoelectron spectroscopy and impedance spectra analyses of a three-electrode system reveal that the cathode resistance is remarkably increased by the oxidative decomposition of LPS when the cell is charged to 3.7 V, which induces dendritic lithium growth at the anode side, resulting in a micro-short circuit through the electrolyte. Composite anodes of Li3PS4 glass+Li–Si alloy (Type 1) and Li3N+LiF+Li–Si alloy (Type 2) are also prepared for all-solid-state batteries (ASSBs) with LPS glass electrolyte and sulfur/LPS glass/carbon composite cathode. Using a three-electrode system, the anode and cathode potentials are separated, and their polarization resistances are individually traced. Even under high-cutoff-voltage conditions (3.7 V), Type 1 and 2 cells are stably cycled without voltage noise for >200 cycles. Although cathode polarization resistance drastically increases after 3.7 V charge owing to LPS oxidation, LPS redox behavior is fairly reversible upon discharge–charge unlike the non-composite alloy anode cell. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis reveals that the enhanced cyclability is attributed to uniform Li–Si alloying throughout the composite anode, providing more pathways for lithium ions even when these ions are over-supplied via LPS oxidation. These results imply that LPS-based cells can be reversibly cycled with LPS redox even under high-cutoff voltages, as long as non-uniform alloying (lithium dendrite growth) is prevented.

(Invited) Metal-Organic Chemical Vapor Deposition of WS2 on Patterned Substrate

Transition metal dichalcogenides (TMDs) have attracted much attention in recent years due to their excellent electrical properties and unique nature. Tungsten disulfide (WS2) , as a representative TMD, is a typical two-dimensional stacking material with moderately wide band gap (single layer: 2.03 eV, bulk: 1.32 eV) and, therefore, has led to active application research in various fields. In particular, large-area, few-layer WS2 is expected to have high potential as a channel material for MOSFETs in the next-generation LSIs because of relatively high carrier mobility even in the extremely thin film. Recently, we have succeeded in fabricating continuous WS2 thin films on Si substrates at low temperatures using newly developed organometallic precursor [1]. In this study, we further report the film characteristics and our attempts to deposit films on Fin structures in order to evaluate their applicability to the next-generation channel materials, which should have complicated 3-dimesional structure.In the experiment, n-BuNC-W(CO)5 was synthesized for WS2 deposition. This novel precursor is a liquid above 35 °C with stable vapor supply. It is also expected to interact with the substrate efficiently due to its polarity in the molecule. The vapor pressure is 1.2 torr at 115 °C, which is an appropriate for a CVD precursor. As a sulfur precursor, (t-C4H9)2S2, which is non-toxic in contrast to H2S, was adopted. WS2 thin films were grown by MOCVD in a cold-wall reactor, using the organic compounds introduced above as precursors for W and S, respectively, on flat and patterned silicon (001) substrates at 300 to 350 °C for 5 to 15 minutes. The deposited films were evaluated by X-ray photoelectron spectroscopy (XPS), UV-Raman spectroscopy (excitation wavelength: 355 nm), and transmission electron microscopy (TEM).Figure 1 summarizes the evaluation results of the WS2 film deposited on the flat substrate. W 4f XPS spectrum (Fig. 1 (a)) show that the film is mostly composed of 2H with a possible slight amount of 1T/1T' structure. In conjunction with S 2p spectrum (Fig. 1 (b)), it can be calculated using the relative sensitivity coefficient that the composition ratio of W to S is approximately 2.1, which is close to the stoichiometric ratio. Moreover, it was confirmed the film was stable more than 6 month in the room atmosphere. In the Raman spectrum shown in Fig. 1(c), two peaks appeared at approximately 350 cm-1 and 420 cm-1 corresponding to in-plane and out-of-plane vibrations, respectively, which are consisted of 2H-WS2 specific peaks of A1g (418 cm-1) and E1 2g (351 cm-1). Here, E1 2g might be broadened by the presence of another smaller mode called 2LA(M) (second-order longitudinal elastic mode), which may be attributed to the various distortions in the grown WS2 thin film. These results are also consistent with previous reports. This Raman results indicating the 2H structure of the film is also consistent with the XPS results as well as the previously reported literatures. Fig. 1(d) shows bright-field TEM images. It can be observed that the film continuously covers the substrate, with no voids larger than micrometer scale. The higher magnification image also shows approximately 10 layers of WS2 film grown with a layered structure parallel to the surface. The WS2 layers are stacked with a face spacing of approximately 0.7 nm, whose distance correlates well with the theoretical tungsten-tungsten interlayer distance of 0.62 nm for the bulk material. The domain size can be estimated to be roughly 50-100 nm.Figure 2 shows cross-sectional TEM images of WS2 thin films deposited on Si Fin structures. It can be observed that a continuous layered film is formed along the 3D Fin structure, and the layered structure is parallel to the surface all over the entire Fin structure. However, the number of layers differs depending on the position, with fewer layers on the sidewalls than those on the top surface, and even fewer layers toward the bottom. This may be due to the insufficient supply of precursor deep in the Fin structure. To improve the uniformity and controllability of layer number, further optimization of the deposition conditions such as precursor supply and deposition temperature, including atomic layer deposition technique, is desired.This research was supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) under the project JPJ011438 for the creation of a center for the creation of next-generation X-nics semiconductors.[1] C. Kirito, K. Yamazaki, Y. Hibino, Y. Hashimoto, H. Machida, M. Ishikawa, H. Sudoh, H. Wakabayashi, R. Yokogawa and A. Ogura, ECS Trans. 104, 3 (2021). Figure 1

Differences between Using Mortars and Solutions When Testing Sodium Silicate as Corrosion Inhibitor for Construction Steel

Corrosion inhibitors are regularly used to minimize corrosion progress in reinforced concrete. Nitrite ions are very effective inorganic inhibitors but not environmentally friendly, since they can leach and contaminate the surrounding soil and water [1, 2]. Among other promising inorganic ions, silicate ions are of particular interest due to their low cost and low toxicity, although most results have been reported in pore simulating solutions. There is little information in the literature where silicate ions are evaluated as corrosion inhibitors in mortar or cement pastes. The purpose of this study is to show some contrasts between the effectiveness of silicate ions as carbon steel inhibitors when they are tested in solution or in mortar.The results in solution (ASCl) were obtained in an alkaline electrolyte (pH=13) that simulates good quality concrete contaminated with chloride ions [3,4]. ASCl contains KOH 0.08 mol/L, NaOH 0.02 mol/L, Ca(OH)2 0.001 mol/L and NaCl 0.3 mol/L, so that [Cl-]/[OH-]=3. The solution containing silicate ions (SSCl) incorporates Na2SiO3.5H2O 0.3 mol/L, corresponding to [inhibitor]/[Cl-]=1. The electrochemical evaluation included standard tests such as cyclic voltammograms, polarization curves, electrochemical impedance spectroscopy (EIS) and weight loss tests involving long exposure times. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to investigate the composition of the surface films. The findings for bare rebars demonstrate that the presence of silicate ions in solution may effectively prevent carbon steel corrosion, with an inhibition efficiency greater than 99% and no localized attack seen after 30 days of immersion. It has also been observed that a 24-hour pretreatment at open circuit potential (OCP) in silicate solutions (SS) improves the corrosion resistance of construction steel when tested in SSCl. The polarization curves show higher pitting potential and lower corrosion current intensities when compared to untreated electrodes. XPS spectra show that silicate ions are incorporated into the surface film. Pretreatments in SS produce passive films that are rich in Fe(II), present mainly as oxohydroxides. EIS shows that the film is more resistive and compact. In contrast, the reference pretreatment in the absence of silicates led to surface films composed mainly of Fe(III) oxides and oxohydroxoxides.Tests in mortars were carried out including reinforcement bars (rebars) in mortar prepared with water/Portland cement=0.6 and sand/cement ratio =3. Mix R (for reference) had no admixed inhibitor and mix S incorporated Na2SiO3.5H2O using a 0.3 mol/L solution to replace the water in the mix. Also, samples P contained rebars pre-treated by previous immersion in silicate ions solutions, in mortars with the same composition as mix R. Once cured for 7 days, the mortar samples were immersed in aerated 0.3 mol/L NaCl solution for 3 months. The electrochemical follow-up included periodical evaluation by EIS and Rp. The alkaline reservoir in the mortar (which is the content of insoluble Ca(OH)2) was investigated by thermogravimetric analysis. Also, a lixiviation test was designed using pH indicators to verify changes in basicity after a lixiviation process. In mortars R and S, charge transfer and polarization resistance (Rt and Rp) remained lower than 50 kΩ cm2 after the first 15 days. However, Rt and Rp higher 100 kΩ cm2 were measured for rebars P after 15 and 60 days of exposure. The differences between P and R tend to flatten after 90 days of exposure. This shows that the inhibitor effect of pretreating the rebars (P) is lost over a longer period of time. According to the results from thermogravimetric tests, silicate ions in mortar consume Ca+2 ions, producing NaOH. Since this is more soluble than Ca(OH)2 it lixiviates quicker, causing the pH to decrease. Lixiviation tests support this theory.In summary, silicate ions are very effective corrosion inhibitors when tested in alkaline solutions. When silicates are used to pretreat the rebars the beneficial effect is lost after 90 days. When solutions containing silicate ions replace water in the mortars´ preparation, the inhibitory effect is lost faster due to the consumption of portlandite and the consequent acidification of the mortars.References Gaidis, J.M., Chemistry of corrosion inhibitors. Cement & Concrete Composites, 2004. 26(3): p. 181. Elsener B., Corrosion inhibitors for steel in concrete. State of the art report. London, ed. M. Publishing. 2001. Montes, F., et al., Silicate Ions as Corrosion Inhibitors for Carbon Steel in Chloride-Contaminated Concrete Pore Simulating Solutions. Corrosion, 2020. 76(12): p. 1147-1154.Rolandi A.C. et al. Corrosion Engineering, Science and Technology 57(5) (2022) 455–463. Figure 1

Atomic distribution, electron transfer, and charge compensation in artificial iron-bearing colusites Cu26-xFexTa2-γSn6S32

The crystal and electronic structures of synthetic Cu26−xFexTa2Sn6S32 (0 ≤ x ≤ 4.0) colusites were studied by single-crystal X-ray diffraction, 57Fe and 119Sn Mössbauer spectroscopy, and X-ray photoelectron spectroscopy (XPS). It has been shown that iron-bearing colusites contain a maximum of 3.5 ÷ 4.0 iron atoms per formula unit, with iron substituting copper only on the Cu(1) site of the cubic lattice. Presence of localized mixed-valence states Fe3+/Fe2+ for colusites with x ≥ 2 has been confirmed by 57Fe Mössbauer spectroscopy at low temperatures (T < 40 K). Increasing temperature leads to the valence-averaged spectral component corresponding to the electron hopping Fe2+ + Cu2+ ↔ Fe3+ + Cu+. XPS data have shown that Ta5+, Sn4+ and S2- do not change their valence states in any samples, whereas Cu2+/Cu+ and Fe3+/Fe2+ ratios increase with increasing the iron content (x). The Cu 2p core XPS spectra analyzed by the charge transfer (CT) approach revealed mixing of the d9 (Cu2+) and d10L (Cu+) configurations. This was attributed to the 3d-Cu and 3d-Fe hybridization mediated by the S-3p orbitals, which can initiate the intersite electron hopping between iron and copper atoms. The mechanisms of charge compensation at different levels of heterovalent iron doping are discussed.

Fabricating the multibranch carboxyl-modified cellulose for hemorrhage control

Excessive bleeding is associated with a high mortality risk. In this study, citric acid and ascorbic acid were sequentially modified on the surface of microcrystalline cellulose (MCAA) to increase its carboxyl content, and their potential as hemostatic materials was investigated. The MCAA exhibited a carboxylic group content of 9.52 %, higher than that of citric acid grafted microcrystalline cellulose (MCA) at 4.6 %. Carboxyl functionalization of microcrystalline cellulose surfaces not only plays a fundamental role in the structure of composite materials but also aids in the absorption of plasma and stimulation of platelets. Fourier -transform infrared (FT-IR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) spectra confirmed that carboxyl groups were successfully introduced onto the cellulose surface. Physical properties tests indicated that the MCAA possessed higher thermal stability (Tmax = 472.2 °C) compared to microcrystalline cellulose (MCC). Additionally, in vitro hemocompatibility, cytotoxicity and hemostatic property results demonstrated that MCAA displayed good biocompatibility (hemolysis ratio <1 %), optimal cell compatibility (cell viability exceeded 100 % after 72 h incubation), and impressive hemostatic effect (BCIMCAA = 31.3 %). Based on these findings, the hemostatic effect of covering a wound with MCAA was assessed, revealing enhanced hemostatic properties using MCAA in tail-amputation and liver-injury hemorrhage models. Furthermore, exploration into hemostatic mechanisms revealed that MCAA can significantly accelerate coagulation through rapid platelet aggregation and activation of the clotting cascade. Notably, MCAA showed remarkable biocompatibility and induced minimal skin irritation. In conclusion, the results affirmed that MCAA is a safe and potentially effective hemostatic agent for hemorrhage control.

Oxygen vacancies mediated changes in ferromagnetic, optical, Photoluminescent and electronic structure properties of Ho-doped CeO2 nanoparticles

The undoped CeO2 and Ce1-xHoxO2 (x = 0.03, 0.05 and 0.07) nanoparticles prepared using microwave assisted co-precipitation route are investigated using X-Ray Diffraction (XRD), UV–Vis–NIR, Raman, photoluminescence, X-ray Photoelectron Spectroscopy (XPS) and SQUID-VSM magnetometer. The XRD validates the inclusion of Ho3+ at the Ce3+/Ce4+ site while maintaining the crystal structure with development of defects and oxygen vacancies with expansion of the CeO2 nanolattice. The composition of the elements with desired stoichiometry is confirmed by Energy Dispersive X-ray spectra analysis. The absorption spectroscopy analysis reports the Urbach energy along with refractive index increases with Ho3+ doping and the optical band gap is decreased indicating red shift. All the nanoparticles are subjected to PL investigations to ascertain the oxygen vacancy and defect structure of nanoparticles. Raman active modes at ∼500 - 630 cm−1 verifies the existence of oxygen vacancies (Vo)., which are seen to rise with concentration of Ho-doping in the CeO2 lattice. When Ce4+ transforms into Ce3+, oxygen vacancies are generated in the lattice to maintain the charge neutrality, as can be seen by the Ce-3d, O-1s, and Ho-4d core level XPS spectra. To demonstrate that Ho3+ doping favours ferromagnetic ordering in the CeO2 lattice, the magnetic properties using the Bound Magnetic Polaron model and F centre exchange mechanism are discussed. The development of various complexes that involve host and doped cations are mediated by Vo suggests the existence of F0, F+, and F2+ centres. The weak ferromagnetic behaviour in Ho3+-doped CeO2 nanoparticles reinforce the relationship between Vo to explain the observed magnetic properties of nanoparticles.

Insight into the role of Mg/B and Mg/Cu dual dopant on the properties of ZnO nanoparticles prepared by facile one-step combustion route for photocatalytic and antibacterial application

ZnO semiconductors are widely known to have benefits in photocatalytic and antibacterial applications. In this study, (Mg/B)–ZnO and (Mg/Cu)–ZnO were synthesized using the combustion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The XRD results confirmed a decrease in the crystal size and an increase in the crystallinity of the doped ZnO samples. SEM analysis confirmed the morphological changes in the structure from rod-shaped to spherical, and the particle size decreased in the doped ZnO samples. EDS analysis validated the nanoparticle composition of Zn, O, Mg, B, and Cu without impurities. Raman spectra confirmed the formation of defects due to the substitution of dopants in the ZnO lattice. All samples for FTIR analysis showed functional chemical group vibrations from Zn–O, C–H, and O–H stretching. The existence of dopant bonds with oxygen was also validated from this analysis. The change in band gap energy was observed from 3.13 to 3.10 eV in Mg/Cu–ZnO and 3.12 eV in Mg/B–ZnO sample due to the influence of the addition of dopant ions. The XPS spectra show the chemical composition of the nanoparticle samples and the oxidation numbers that correlate with the results of EDS and XRD analyses. A decrease in the emission intensity in the PL measurement was observed in the green emission region in the Mg/B–ZnO sample, which correlated with the decrease in electron recombination. The Photocatalytic application was performed by measuring its ability to degrade methyl violet dye under visible-light irradiation. The maximum deterioration after 120 min of irradiation was obtained for the Mg/Cu–ZnO, Mg/B–ZnO, and ZnO samples at 92.62 %, 92.20 %, and 80.89 %, respectively. Antibacterial activity increased against S. aureus bacteria in co-doped ZnO samples with inhibition zones of 12.15 mm, 8.15 mm, and 6.45 mm for Mg/B–ZnO, Mg/Cu–ZnO, and ZnO samples, respectively.

Facile one-step deposition of nanosized Ni(OH)2–MoS2 heterostructure electrodes for efficient oxygen evolution reaction

There is an increasing need for environmentally friendly and sustainable energy sources that rely on efficient and abundant electrocatalysts for the oxygen evolution reaction (OER). OER plays a key role in energy conversion and storage applications. Using a vacuum kinetic spray technique operating at room temperature, electrocatalysts based on nano-sized Ni(OH)2–MoS2 nanocomposites (NCs) on nickel foam are fabricated from the corresponding micron powders. The Ni(OH)2–MoS2 NC modified working electrodes were exploited to investigate the OER at different weight ratios of MoS2 (25, 50, and 75 wt%). To comprehensively investigate and elucidate the surface state and morphology of the electrode, x-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were assessed. SEM images showed that the micro-sized particles were fragmented into smaller nanoscale particles. XPS spectra revealed the synergy enhancement in the Ni(OH)2–MoS2 NCs that resulted in a strong improvement in the OER activity. Ni(OH)2–MoS2 hybrid NCs with 75 wt% MoS2 exhibited the lowest overpotential of 282 mV at 10 mA cm−2 and a small Tafel slope of 54 mV⋅dec−1. Alongside, the prolonged OER durability at 50 mA cm−2 is verified for up to 50 h.

A brief overview of X-ray photoelectron spectroscopy characterization of thin films

Preparation and characterization of nanostructured thin films have been reported by many researchers. X-ray photoelectron spectroscopy (XPS) method has been used over few decades in different fields such as superconductor, semiconductor, metallurgy and catalysis. In this work, elemental oxidation state, electronic state, chemical structure and chemical composition were investigated for metal sulfide, metal selenide, metal oxide and metal telluride films. Evaluation of binding energy for the obtained samples was reported. XPS spectra showed that annealing treatment has a very strong effect on the composition of the films. The elemental oxidation state and electronic state were strongly dependent on the specific experimental conditions.

Improvement in the structural, magnetic and electromagnetic behaviour of barium hexaferrites with yttrium doping for EMI shielding

Electromagnetic interference (EMI) shielding is critical for protecting electronic devices from interference generated by various sources such as power lines, radio waves, microwaves, and electronic devices. In this current study, we present a thorough investigation of the structural, magnetic, and electromagnetic properties of Y3+ doped M-type barium nano hexaferrites. Polycrystalline BaFe12−xYxO19 (x = 0.0, 0.3, 0.5, 0.7, and 0.9) hexaferrites are prepared using the citrate precursor method. The results of X-ray diffraction (XRD), Rietveld refinement and Raman spectroscopy confirmed that all samples have a single-phase, and pure hexagonal crystalline structure with space group P69/mmc. This result is consistent for all the prepared compositions. The structure and dopant materials in different chemical states of the sample are determined based on the X-ray photoelectron spectroscopy (XPS) spectrum. Field emission scanning electron microscopy (FESEM) analysis showed that the particles had a distinct hexagonal morphology. The chemical composition of the prepared hexaferrites is investigated using energy dispersive X-ray analysis (EDAX). UV spectroscopy showed an inverse relationship between the molar ratio of yttrium and the band gap. Vibrating sample magnetometer (VSM) results showed a decrease in saturation magnetization (Ms) and coercivity (Hc) with increasing fraction of yttrium ions. The shielding efficiency (SE) of the synthesized hexa materials against EMI is evaluated using a vector network analyser (VNA). In particular, effective EMI shielding was observed in the frequency spectra of 8–12 GHz (X-band region). Among the tested compositions, BaFe12–0.7Y0.7O19 with a thickness of 3 mm exhibited highest SE of 80.07 dB in the X-band region. The proposed yttrium-substituted barium M-type hexagonal ferrites exhibit significant reflection loss with enhanced absorption spectrum even when applied to an extremely thin 3 mm material, making it a possible preference as the radar-absorbed compound for EMI attenuators for weather monitoring, radar tracking, air traffic management, and gigahertz antennas. Furthermore, commercial applications including long-term magnetic media for recording, storing information, etc. are possible uses of the synthesised magnetic yttrium-doped barium M-type hexagonal ferrites.

Bandgap design of fabricated BN/ZnO/Al2O3/TiO2 doped graphene using XPS approach

This study investigates the use of BN/ZnO/Al2O3/TiO2 nanoparticles as dopants for Graphene nanoparticles. The sintering process was employed to manufacture semiconductor materials. The bandgap serves as the central feature of an atomic heterojunction, playing a crucial role in determining the characteristics or overall quality of the semiconductor materials involved. X-ray photoelectron spectroscopy (XPS) was employed to ascertain the bandgap values of Boron (B), Nitrogen (N), and Carbon (C) at the interfaces of BN/Graphene, BN/ZnO/Graphene, BN/Al2O3/Graphene, and BN/TiO2/Graphene. The survey spectra were examined to provide evidence of atoms' presence and their respective atomic proportions. The analysis of the narrow spectra of XPS was employed to determine the binding energy of atoms within various materials. The conduction band offset (CBO) and valence band offset (VBO) of the aforementioned heterojunctions were computed. The estimation of the ratio between the conduction band offset (CBO) and the valence band offset (VBO), is denoted as ΔEc/ΔEv,. The significant change in the energy gap in the valance band concerning the change in conduction band energy demonstrates that this material possesses the characteristics of an exemplary semiconductor. The present investigation reveals that the BN/TiO2/Graphene heterojunction exhibits the highest values of ΔEv/ΔEc, namely 13.07 for nitrogen (N) and 15.07 for boron (B). The results suggest that the combination of BN/TiO2/Graphene semiconductors holds promising potential for applications in nanoelectronics.

Effect of synthesis temperature on crystal structure, optical and magnetic properties of SmCuO3-δ ceramic phosphor

Effect of synthesis temperature on crystal structure, optical and magnetic properties of SmCuO3-δ ceramic phosphor is investigated in this work. The SmCuO3-δ ceramic has been synthesized using a sol-gel method. Rietveld analysis reveals that SmCuO3-δ ceramic crystallizes into coexisting tetragonal (I4/mmm) and monoclinic (C2/c) crystal structures. The phase fraction of the tetragonal and monoclinic phases strongly depends on the synthesis temperature. The crystallite size and particle size increase with increasing calcination temperature. The X-ray photoelectron spectroscopic spectra reveal the presence of (Cu2+, Cu3+) and (Sm2+, Sm3+) ions alongwith the oxygen vacancy centres in the phosphor. The SmCuO3-δ ceramic shows multiple magnetic phase transitions. The FTIR spectra show the presence of vibrational bands due to Cu-O and Sm-O groups. The optical band gap of the SmCuO3-δ phosphor decreases with an increase in calcination temperature and crystallite size. The photoluminescence excitation spectra show the peaks at 363, 402, 505 and 542 nm at the fixed emission wavelength of 609 nm, whereas the photoluminescence emission spectra contain peaks at 465, 515 and 609 nm at the fixed excitation wavelength of 402 nm. The photoluminescence emission intensity of the sample increases with the rising calcination temperature upto 900 °C and finally, it quenches at 1000 °C. Therefore, the SmCuO3-δ ceramic phosphor may be useful for solid state lighting, LEDs and magnetic devices.