To Transmission Electron Microscopy Research Articles

Characterisation of PVL-Positive Staphylococcus argenteus from the United Arab Emirates.

Staphylococcus argenteus is a recently described staphylococcal species that is related to Staphylococcus aureus but lacks the staphyloxanthin operon. It is able to acquire both resistance markers such as the SCCmec elements and mobile genetic elements carrying virulence-associated genes from S. aureus. This includes those encoding the Panton-Valentine leukocidin (PVL), which is associated mainly with severe and/or recurrent staphylococcal skin and soft tissue infections. Here, we describe the genome sequences of two PVL-positive, mecA-negative S. argenteus sequence type (ST) 2250 isolates from the United Arab Emirates in detail. The isolates were found in a dental clinic in the United Arab Emirates (UAE). Both were sequenced using Oxford Nanopore Technology (ONT). This demonstrated the presence of temperate bacteriophages in the staphylococcal genomes, including a PVL prophage. It was essentially identical to the published sequence of phiSa2wa_st78 (GenBank NC_055048), a PVL phage from an Australian S. aureus clonal complex (CC) 88 isolate. Besides the PVL prophage, one isolate carried another prophage and the second isolate carried two additional prophages, whereby the region between these two prophages was inverted. This "flipped" region comprised about 1,083,000 bp, or more than a third of the strain's genome, and it included the PVL prophage. Prophages were induced by Mitomycin C treatment and subjected to transmission electron microscopy (TEM). This yielded, in accordance to the sequencing results, one or, respectively, two distinct populations of icosahedral phages. It also showed prolate phages which presumptively might be identified as the PVL phage. This observation highlights the significance bacteriophages have as agents of horizontal gene transfer as well as the need for monitoring emerging staphylococcal strains, especially in cosmopolitan settings such as the UAE.

Linewidth characterization of a self-traceable grating by SEM

To achieve high-precision nanometrology, a self-traceable grating reference material has been reported and prepared using atom lithography and soft x-ray interference techniques (Liu et al 2021 Nanotechnology 32 175 301). In this work, we employ a Monte Carlo simulation method to investigate the scanning electron microscopy (SEM) image contrast and linewidth characterization of the grating linewidth. The 3D structure of mushroom-shaped grating lines made of multilayers (Pt, SiO2 and Si) is modeled according to transmission electron microscopy (TEM) images, enabling the SEM linescan profiles of secondary electron signals to be obtained for different values of structural linewidth parameters from Monte Carlo simulations. Using the principle of the model-based library method, a model database of Monte Carlo-simulated SEM linescan profiles is thus constructed by varying the incident electron beam conditions and the grating linewidths; then, the grating linewidth is successfully characterized using experimental SEM images. The comparison with the TEM measurement reveals that the measurement accuracy is verified to within 0.3% for the linewidth of ∼25 nm.

Cellulose nanocrystals extracted from rice husk using the formic/peroxyformic acid process: isolation and structural characterization.

Cellulose derived from biomass is a renewable resource with numerous applications. Using formic/peroxyformic acid at atmospheric pressure, cellulose nanocrystals (CNC) were isolated from rice husk (RH) in this study. This method was an excellent way to get rid of lignin and hemicelluloses from RH. The cellulose was subsequently acid hydrolyzed by H2SO4 (64%) for 30 minutes at 45 °C. The chemical and microstructure analysis showed that the lignin and hemicellulose contents of raw RH had been eliminated, and the crystallinity content of CNC was 67.16%. According to transmission electron microscopy (TEM) morphological analysis, CNC measured 19 ± 3.3 nm in diameter, 195 ± 24 nm in length, and 10.2 ± 6.8 in aspect ratio. The thermal stability of RH and CNC was also investigated using thermogravimetric analysis (TGA). These encouraging findings demonstrated the potential for reusing RH agricultural waste to create CNC and include nanocomposites as a reinforcing material.

Conformal growth of GaP on high aspect ratio Si structured surface via plasma-enhanced atomic layer deposition

This article is concerned with the study of conformal growth of thin gallium phosphide (GaP) layers by plasma-enhanced atomic layer deposition (PE-ALD) on a Si structured surface. GaP layers were deposited on (100) silicon wafers with a structured surface in the form of silicon microcolumns and black silicon. Deposition process were carried out at temperature of 380 °C using trimethylgallium and phosphine precursors. According to transmission electron microscopy (TEM), GaP layers deposited by this method conformally grown on the high aspect ratio structured silicon surface. The energy-dispersive X-ray spectroscopy (EDX) study show that the distribution of the main components of the GaP layer is uniform alongside surface of the silicon microcolumns and wires. High resolution TEM study confirms that GaP layers on the surface of silicon microcolumns and wires are epitaxial with the inclusion of twin lattice defects. Therefore, this deposition method can be used for the conformal deposition of thin crystalline layers of GaP on structured silicon surfaces with a high aspect ratio.

Hydrogen Production via Methane Decomposition over Alumina Doped with Titanium Oxide-Supported Iron Catalyst for Various Calcination Temperatures.

The decomposition of methane has been chosen as an alternative method for producing hydrogen. In this study, 20 % Fe was used as the active metal part of the catalyst. To better comprehend the impact of the supporting catalytic properties, alumina and titania-alumina composite were investigated as supports. Iron-based catalysts were prepared by impregnation method and then calcined at different temperatures (300 °C, 500 °C, and 800 °C). The catalysts were examined at 800 °C under atmospheric pressure with a 15 mL/min total flow rate and 2 : 1 CH4 to N2 feed ratio. The textural and morphological characteristics of the fresh calcined and spent catalysts were investigated. The catalytic activity and stability data demonstrated that Fe supported over TiO2-Al2O3 calcined at 500 °C performed the best of all evaluated catalysts with a more than 80 % hydrogen yield. The Raman spectra result showed that graphitic carbon was produced for all used titanium dioxide catalysts. Moreover, according to transmission electron microscopy (TEM) results, the carbon deposited on the catalysts' surface is carbon nanotubes (CNT).

A Next-Generation qPlus-Sensor-Based AFM Setup: Resolving Archaeal S-Layer Protein Structures in Air and Liquid.

Surface-layer (S-layer) proteins form the outermost envelope in many bacteria and most archaea and arrange in two-dimensional quasicrystalline structures via self-assembly. We investigated S-layer proteins extracted from the archaeon Pyrobaculum aerophilium with a qPlus sensor-based atomic force microscope (AFM) in both liquid and ambient conditions and compared it to transmission electron microscopy (TEM) images under vacuum conditions. For AFM scanning, a next-generation liquid cell and a new protocol for creating long and sharp sapphire tips was introduced. Initial AFM images showed only layers of residual detergent molecules (sodium dodecyl sulfate, SDS), which are used to isolate the S-layer proteins from the cells. SDS was not visible in the TEM images, requiring more thorough sample preparation for AFM measurements. These improvements allowed us to resolve the crystallike structure of the S-layer samples with frequency-modulation AFM in both air and liquid.

Quantified Uniformity and Selectivity of TiO2 Films in 45‐nm Half Pitch Patterns Using Area‐Selective Deposition Supercycles

AbstractArea‐selective deposition (ASD) shows great promise for sub‐10 nm manufacturing in nanoelectronics, but significant challenges remain in scaling to ultrasmall dimensions and understanding feature‐dependent nonuniformity and selectivity loss. This work addresses these problems by simultaneously quantifying uniformity and selectivity for passivation/deposition/etch supercycles in 45 nm half‐pitch TiN/SiO2 line/space patterns. This work employs three selective processes that are uniquely suited for supercycle processing: dimethylamino‐trimethylsilane (DMA‐TMS) inhibition, TiO2 atomic layer deposition (ALD), and HBr/BCl3 plasma etch. The DMA‐TMS inhibition selectively passivates the SiO2 nongrowth surface without affecting deposition on the TiN and TiO2 growth surfaces. The plasma etch removes TiO2 defect particles at a faster rate than the conformal TiO2 film or SiO2 lines. Using three supercycles of this process, this work demonstrates 8 nm of TiO2 with 88% uniformity and ≈100% selectivity according to transmission electron microscopy (TEM), a 2×improvement in film thickness from previous reports in similar nanoscale patterns. Integrated consideration of uniformity and selectivity at specific feature scales will facilitate the effective design of selective deposition processes for nanoscale electronic devices.

Tuning the structural, optical, electrical, and dielectric properties of PVA/PVP/CMC ternary polymer blend using ZnO nanoparticles for nanodielectric and optoelectronic devices

Nanocomposite films made of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and carboxymethylcellulose (CMC) and filled with different concentrations of zinc oxide nanoparticles (ZnO NPs) were created using the solution casting technique. Investigation and discussion were conducted about the effect of ZnO NPs on the pure PVA/PVP/CMC mixture's structural, optical, and electrical features. According to transmission electron microscopy (TEM) and X-ray diffraction (XRD) examinations, the size of the ZnO NPs produced is between 6 and 17 nm and has a hexagonal phase. The X-ray studies of the filled films revealed that the crystallinity of the ZnO NPs has grown at the expense of the PVA/PVP/CMC matrix. According to Fourier Transform Infrared (FTIR) analysis, the main vibrational peaks of PVA, PVP, CMC, and Zn–O varied after filling randomly. For the pure blend, the UV/Vis-NIR transmittance spectra displayed a large absorption peak at 210 nm that could be attributed to the π→π* transitions. After filling, the prepared composites showed a significant decrease in the average transmittance percentage and the appearance of a new small peak at 370 nm that related to the absorption of ZnO NPs. The optical energy gap (Eg), calculated using the indirect and direct allowed transition, was discovered to be reduced as the ZnO NPs content increased. At room temperature, the samples' dielectric characteristics, impedance, and AC conductivity were investigated over a wide frequency range (10−1 to 107 Hz). When the ZnO NPs content was raised, it was seen that the AC conductivity, dielectric loss, and dielectric constant were enhanced. In order to determine the equivalent electrical circuit for each sample, Z′ and Z″ impedance components were analyzed. Due to these remarkable improvements in electrical and optical properties, these nanocomposite films are a potential competitor for use in optoelectronic devices like sensors.

Enhanced Antibacterial Activity of Novel Fluorescent Glutathione-Capped Ag Nanoclusters.

Ag nanomaterials are promising candidates for the discovery of next-generation antibiotics with a high antibacterial effect against multi-drug resistant strains. This paper reports a simple synthesis of novel water-soluble glutathione-capped silver nanoclusters (GSH-Ag NCs) with an enhanced antibacterial activity. According to thin layer chromatography (TLC), the synthesized GSH-Ag NCs are an individual fraction of the same composition without any impurities. According to matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and energy dispersive X-ray (EDX) analyses, the silver core of the GSH-Ag NCs contains approximately 35 silver atoms, and the molecular weight of these nanoclusters is about 11 kDa. The fabricated silver nanoclusters have a reddish fluorescence (λex/λem = 509/645 nm), with a large Stokes shift (>130 nm), and ultra-small size (less than 2 nm) according to transmission electron microscopy (TEM) data and dynamic light scattering (DLS) analysis. The antibacterial activity and minimal inhibitory concentrations of the silver nanoclusters towards Escherichia coli, Staphylococcus aureus, Bacillus cereus and Enterobacter cloacae were evaluated using the agar well-diffusion method and resazurin metabolism assay. The antibacterial activity of chelated silver in the nanoclusters was found to be significantly higher compared to the activity of free silver ions. To explain the possible mechanisms underlying the antibacterial actions of the GSH-Ag nanoclusters, molecular docking was performed, and prospective bacterial targets were identified using AutoDock.

Enhancement of Photocatalytic Activity and Microstructural Growth of Cobalt-Substituted Ba1−xCoxTiO3 {x = 0, …, 1} Heterostructure

The photocatalytic degradation process and absorption kinetics of the aqueous solution of the Cibacron Brilliant Yellow 3G-P dye (Y) were investigated under UV-Vis light. Pure barium titanate BaTiO3 (BT) and cobalt ion-substituted barium Ba1−xCoxTiO3 (x = 0, …, 1) nano-compound powders (BCT) were synthesized using the sol–gel method and colloidal solution destabilization, and utilized as photocatalysts. The powder X-ray diffraction (PXRD) crystal structure analysis of the BT nanoparticles (NPs) revealed a prominent reflection corresponding to the perovskite structure. However, impurities and secondary phase distributions were qualitatively identified in the PXRD patterns for x ≥ 0.2 of cobalt substitution rate. Rietveld refinements of the PXRD data showed that the BCT nano-compound series undergoes a transition from perovskite structure to isomorphous ilmenite-type rhombohedral CoTiO3 (CT) ceramic. The nanoparticles produced displayed robust chemical interactions, according to a Fourier transform infrared spectroscopy (FTIR) analysis. The BT and BCT nanoparticles had secondary hexagonal phases that matched the PXRD results and small aggregated, more spherically shaped particles with sizes ranging from 30 to 114 nm, according to transmission electron microscopy (TEM). Following a thorough evaluation of BCT nano-compounds with (x = 0.6), energy-dispersive X-ray (EDX) compositional elemental analysis revealed random distributions of cobalt ions. Through optical analysis of the photoluminescence spectra (PL), the electronic structure, charge carriers, defects, and energy transfer mechanisms of the compounds were examined. Due to the cobalt ions being present in the BT lattice, the UV-visible absorption spectra of BCT showed a little red-shift in the absorption curves when compared to pure BT samples. The electrical and optical characteristics of materials, such as their photon absorption coefficient, can be gathered from their UV-visible spectra. The photocatalytic reaction is brought about by the electron–hole pairs produced by this absorption. The estimated band gap energies of the examined compounds, which are in the range of 3.79 to 2.89 eV, are intriguing and require more investigation into their potential as UV photocatalysts. These nano-ceramics might be able to handle issues with pollution and impurities, such as the breakdown of organic contaminants and the production of hydrogen from water.

Pulsed electrodeposition of MXenes/HAp multiple biological functional coatings on 3D printed porous Ti-6Al-4V bone tissue engineering scaffold

Titanium and its alloys have been widely used as bone tissue engineering scaffold due to their excellent biocompatibility and mechanical strength. In order to promote bone ingrowth, integration and match the mechanical properties of natural bone tissue, this study proposed diamond-like microstructure porous Ti-6Al-4V scaffolds for personalized bone defect repair. In order to prepare the multiple biological functional coatings on the curve surface inside of the 3D printed porous scaffolds, pulsed electrodeposition method was proposed to obtain multiple layers of Ti3C2Tx/HAp composited coatings. Delaminated Ti3C2Tx has an ultra-thin microstructure according to transmission electron microscopy (TEM) observation and is well dispersed in electrolyte. X-ray diffraction (XRD) characterization shows that Ti3C2Tx has been synthesized and regulates more CaHPO4‧2H2O (DCPD) to Hydroxyapatite (HAP) conversion, which is confirmed by Fourier transform infrared spectroscopy (FTIR) at 0.2 mg/mL concentration. Scanning electron microscopy (SEM) shows that the morphologies of composite coatings are closely related to Ti3C2Tx content due to the availability of effective voltages for electrodeposition. By means of finite element method, deposition thickness and distribution of coatings were simulated to explore the precipitation kinetics and selection of electrodeposition parameters and a current density of 15 mA/cm2 was ultimately used. In vitro electrochemical corrosion of Ti3C2Tx/HAp coatings were tested in human simulated body fluid (SBF) to verify its corrosion resistance in physiological environment and Ti3C2Tx/HAp composited coatings possess the best corrosion resistance according to linear scanning voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) tests. In vitro MC3T3-E1 cell culturing studies were investigated to evaluate cell behaviors and biocompatibility of these coatings. The results indicate that cells grow well on the surface of composite coatings without showing cytotoxicity and cell morphologies show a good spreading state and a trend of inward growth.

Inhibition of the Fibrillation of Amyloid Aβ1-40 by Hybrid-Lipid-Polymer Vesicles.

The transformation of functional proteins into amyloidic plaques is responsible for the impairment of neurological functions in patients fallen victim to debilitating neurological conditions like Alzheimer's, Parkinson's, and Huntington's diseases. The nucleating role of amyloid beta (Aβ1-40 ) peptide into amyloids is well established. Herein, lipid hybrid-vesicles are generated with glycerol/cholesterol-bearing polymers aiming to alter the nucleation process and modulate the early phases of Aβ1-40 fibrillation. Hybrid-vesicles (±100nm) are prepared by incorporating variable amounts of cholesterol-/glycerol-conjugated poly(di(ethylene glycol)m acrylates)n polymers into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membranes. The in vitro fibrillation kinetics coupled to transmission electron microscopy (TEM) is employed to investigate the role of hybrid-vesicles on Aβ1-40 fibrillation without destroying the vesicular membrane. Both polymers, when embedded in hybrid-vesicles (up to 20%) significantly prolonged the fibrillation lag phase (tlag ) compared to a small acceleration in the presence of DOPC vesicles, irrespective of the amount of polymers inside the hybrid-vesicles. Along with this notable retardation effect, a morphological transformation of the amyloid's secondary structures to amorphous aggregates or the absence of fibrillar structures when interacting with the hybrid-vesicles is confirmed by TEM and circular dichroism (CD) spectroscopy.

Photothermal Hyperthermia Study of Ag/Ni and Ag/Fe Plasmonic Particles Synthesized Using Dual-Pulsed Laser

Magneto-plasmonic Ag/Ni and Ag/Fe nanoparticles (NPs) were synthesized in this work using the environmentally safe and contaminant-free dual-pulsed Q-switched Nd:YAG 1064 nm laser ablation method. The optical and magnetic characteristics of synthesized nanomaterials were investigated using a vibrating sample magnetometer and an ultraviolet-visible absorption spectrometer. According to transmission electron microscopy (TEM), the shape of Ag/Ni and Ag/Fe NPs seems to be spherical, with mean diameters of 7.3 nm and 11.5 nm, respectively. X-ray diffraction (XRD) was used in order to investigate and describe the phase structures of the synthesized nanomaterials. The synthesized NPs reached maximum temperatures such as 48.9, 60, 63.4, 70, 75, and 79 °C for Ag/Ni nanofluid and 52, 56, 60, 68, 71, and 72 °C for Ag/Fe nanofluid when these nanofluids were subjected to an NIR 808 nm laser with operating powers of 1.24, 1.76, 2.36, 2.91, 3.5, and 4 W, respectively. Because of the plasmonic hyperthermia properties of nanoparticles, nanofluids display higher temperature profiles than pure water. According to these findings, plasmonic nanoparticles based on silver might be used to treat hyperthermia.

Primary Ciliary Dyskinesia in a Portuguese Bronchiectasis Outpatient Clinic

Primary ciliary dyskinesia (PCD) is a rare hereditary condition characterized by decreased mucociliary clearance of the airways and a compromised reproductive system, resulting in male and female infertility. Several mutations with varied clinical and pathological features have been documented, making diagnosis a challenging process. The purpose of this study is to describe the clinical and pathological features of Portuguese patients with PCD and to examine their genetic variants. A retrospective observational analysis was conducted with patients who were being monitored at a bronchiectasis outpatient clinic in 2022 and had a confirmed or high-likelihood diagnosis of PCD. In total, 17 patients were included in the study, with 12 (66.7%) having PCD confirmed and 5 (29.4%) having a high-likelihood diagnosis. Furthermore, 12 patients were subjected to transmission electron microscopy (TEM), with 7 (58.3%) exhibiting one hallmark defect. Genetic test data was obtained for all 17 patients, with 7 of them (41.2%) displaying a pathogenic/likely pathogenic mutation in homozygosity. To summarize, PCD is an uncommon but significant hereditary illness with consequences regarding morbidity and mortality. Despite the lack of a specific treatment, it is critical to confirm the diagnosis with genetic testing in order to effectively manage the disease and its accompanying disorders.

Overcoming the challenges of preserving lipid-rich Cannabis sativa L. glandular trichomes for transmission electron microscopy.

Cannabis glandular trichomes produce and store an abundance of lipidic specialised metabolites (e.g. cannabinoids and terpenes) that are consumed by humans for medicinal and recreational purposes. Due to a lack of genetic resources and inherent autofluorescence of cannabis glandular trichomes, our knowledge of cannabinoid trafficking and secretion is limited to transmission electron microscopy (TEM). Advances in cryofixation methods has resulted in ultrastructural observations closer to the 'natural state' of the living cell, and recent reports of cryofixed cannabis trichome ultrastructure challenge the long-standing model of cannabinoid trafficking proposed by ultrastructural reports using chemically fixed samples. Here, we compare the ultrastructural morphology of cannabis glandular trichomes preserved using conventional chemical fixation and ultrarapid cryofixation. We show that chemical fixation results in amorphous metabolite inclusions surrounding the organelles of glandular trichomes that were not present in cryofixed samples. Vacuolar morphology in cryofixed samples exhibited homogenous electron density, while chemically fixed samples contained a flocculent electron dense periphery and electron lucent lumen. In contrast to the apparent advantages of cryopreservation, fine details of cell wall fibre orientation could be observed in chemically fixed glandular trichomes that were not seen in cryofixed samples. Our data suggest that chemical fixation results in intracellular artefacts that impact the interpretation of lipid production and trafficking, while enabling greater detail of extracellular polysaccharide organisation.

PEMFC Platinum-Based Catalysts Recycling Using an Electrochemical Process

Hydrogen is one of the most promising energy carriers. Currently, the most used technology to produce electricity from hydrogen, particularly for green mobility, is the technology based on the use of Proton Exchange Membrane Fuel Cells (PEMFC). Platinum, pure or alloyed with another element, remains essential in the design of efficient catalysts either for anode or cathode catalytic layer in PEMFC. This metal is rare and expensive hence recycling it becomes an important issue for the hydrogen sector development.Chemical ways to recover platinum from PEMFC have been already studied 1-2 based on Pt leaching using either a mix of HCl/HNO3 or HCl/H2O2. In our project, we investigate an electrochemical process to leach platinum contained in aged Pt based catalysts to further resynthesize catalysts from the recovered Pt salts. The electrodissolution of platinum becomes significant with the oxidation of the metal (around 1.1 V vs RHE) but particularly when the oxidized platinum is reduced (around 0.7 V vs RHE) 3. Moreover, the dissolution is enhanced when a complexing agent as chloride anion is introduced 4. The idea of our process is to study the impact of different protocol of steps between high potential (to oxidize platinum) and low potential (to reduce platinum oxide). The improvement of the process is linked to the upper and lower potential values, the number of steps and the nature of the electrolyte and the complexing agent. Our main parameter to monitor the dissolution is the changes in electrochemical real surface area (ECSA) associated to transmission electron microscopy (TEM) images of the catalyst at different stages of the protocol as illustrated in Figure 1.In terms of methodology a model study on fresh commercial Pt/C catalyst has been first performed to determinate the optimal conditions of Pt dissolution followed by the application of the protocol on membrane electrode assemblies (MEA) aged in real conditions. 1 L. Duclos, L. Svecova, V. Laforest, G. Mandil, et P.-X. Thivel, « Process development and optimization for platinum recovery from PEM fuel cell catalyst », Hydrometallurgy, vol. 160, p. 79-89, mars 2016, doi: 10.1016/j.hydromet.2015.12.013. 2 L. Duclos, M. Lupsea, G. Mandil, L. Svecova, P.-X. Thivel, et V. Laforest, « Environmental assessment of proton exchange membrane fuel cell platinum catalyst recycling », J. Clean. Prod., vol. 142, p. 2618-2628, janv. 2017, doi: 10.1016/j.jclepro.2016.10.197. 3 S. Cherevko, A. R. Zeradjanin, G. P. Keeley, et K. J. J. Mayrhofer, « A Comparative Study on Gold and Platinum Dissolution in Acidic and Alkaline Media », J. Electrochem. Soc., vol. 161, n° 12, p. H822-H830, 2014, doi: 10.1149/2.0881412jes. 4 S. Geiger, S. Cherevko, et K. J. J. Mayrhofer, « Dissolution of Platinum in Presence of Chloride Traces », Electrochimica Acta, vol. 179, p. 24-31, oct. 2015, doi: 10.1016/j.electacta.2015.03.059. Figure 1

A comparison of silver nanoparticles made by green chemistry and femtosecond laser ablation and injected into a PVP/PVA/chitosan polymer blend

Due to their antibacterial effect, silver nanoparticles (AgNPs) are attracting more and more attention for various applications in biomedicine. The production of nanomaterials from organometallic precursors requires the use of a capping agent that acts as a stabilizer and provides colloidal stability while preventing agglomeration and excessive growth. In this research, we studied the optical properties and antibacterial activity of AgNPs loaded in a blend of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and chitosan, which were used as capping agents to control the shape and size of the nanoparticles and to impart stability to the synthesized Ag nanomaterials. Characterization studies showed that the blend provides a uniform and controlled distribution of AgNPs inside the polymeric matrix without the addition of any more stabilizers. The mean particle size for green and laser-ablated AgNPs was found to be ~ 50 nm according to transmission electron microscopy (TEM) studies. Fourier transform infrared (FTIR) studies showed the presence of characteristic main peaks corresponding to the vibrational groups which characterize the prepared samples. The interactions between the AgNPs and the blend were marked by changes in the intensity of vibrational peaks and spectral positions. X-ray diffraction (XRD) confirmed the crystallographic modification within the PVP/PVA/chitosan matrix because of AgNPs filling. The change in the absorbance has been studied with the help of measured ultraviolet–visible spectroscopy (UV–Vis.) and therefore the optical band gap was calculated. The filling of AgNPs in the blend shows a broad peak at 427 nm because of the phenomenon of surface plasmon resonance (SPR) and its intensity increases with increasing filler concentration. The blend and the Ag nanocomposite showed remarkable antibacterial activity and caused a significant decrease in microbial growth (Escherichia coli) in 24 h. These outcomes demonstrate the suitability and promise of the nanocomposites for various applications, including biomedical labels, sensors, and detectors.

Study on the high temperature creep deformation and fracture behaviors of Inconel 625 deposited metal

The creep behaviors of as-welded Inconel 625 deposited metal were studied over broad ranges of temperature (600 °C–900 °C) and stress (50 MPa–500 MPa), and the corresponding deformation mechanisms and fracture behaviors after rupture were investigated by various techniques. The results showed that the average slope of the creep life and the stress fitting curve was −0.159 (600 °C–800 °C), which was almost the same as that of the cast 625 alloy (−0.16). However, the slope decreased at 900 °C. According to transmission electron microscopy (TEM) observations, the dominant creep deformation mechanism transformed from shearing and climbing of dislocations at 600 °C, 700 °C and 800 °C/200 MPa to cross-slip of dislocations at 800 °C/80 MPa and 900 °C. The fracture behaviors were characterized by optical microscopy (OM) and scanning electron microscopy (SEM). With increasing temperature, the fracture behavior changed from mixed to intergranular. Similarly, the fracture behavior changed with increasing applied stress at 800 °C. At 600 °C, 700 °C and 800 °C/200 MPa, the carbides and intermetallic compounds produced microcracks, which eventually led to fractures. However, at 900 °C and 800 °C/80 MPa, the aggregation of micropores was the main cause of grain boundary failure.

Ellipsoidal α-Fe2O3@SnO2/Ti3C2 MXene core-shell nanoparticles for photodegradation of organic dyes

Photodegradation is a green and economical route to decompose organic dyes utilized by photocatalysts. Herein, ellipsoidal α-Fe2O3@SnO2/Ti3C2 MXene core-shell nanoparticles (NPs) were successfully fabricated by modified Stöber method and hydrothermal treatment for photodegradation of rhodamine B (rhB) dye. According to transmission electron microscopy (TEM), α-Fe2O3@SnO2 nanoparticles were homogenously coated with Ti3C2 MXenes. When the dosage of MXenes is about 3.5 mg, the as-prepared α-Fe2O3@SnO2/MXene-3.5 sample exhibits the excellent photodegradation capacity of rhB dye. The E140 (photodegradation efficiency for 140 min) can rapidly rise to 72.43 %, which is much higher than that of pure α-Fe2O3, SnO2, or Ti3C2 MXene samples. Furthermore, the α-Fe2O3@SnO2/MXene-3.5 also displayed the cycle stability only with a decreasing of 6.88 % after 6 times. As a proposal photocatalytic mechanism, both of Ti3C2 MXene and SnO2 could form the Schottky barrier to reduce the recombination probability of photogenerated electrons and holes due to the metal-like conductivity of Ti3C2 MXene. Meanwhile, Ti3C2 MXene could also accelerate the migration rate of electrons to greatly improve the photocatalytic efficiency.

The effect of the elastic energy on the shape and orientation relations of η-Ni3Ti precipitates in lath martensite

Understanding the elastic interaction between the precipitates may assist in controlling their distribution and help design new steels with enhanced mechanical properties. Custom 465® stainless steel contains only η-Ni3Ti precipitates, making it an ideal steel to study the interaction and orientation relation (OR) between precipitates, which are known to grow in arrays parallel to the four closed-packed axes,< 111 >bcc, and closed-packed planes, {110}bcc, of the matrix. This forms 144 possible orientation pairs, raising the question whether there are preferred relations between neighboring precipitates.In this work we tackle this question by calculating the elastic fields and interaction between η-Ni3Ti precipitates in bcc lath martensite in order to study the effect of elastic energy on the shape and orientation of the precipitates. The results of the calculations are compared to transmission electron microscopy (TEM) observations of Custom 465® stainless steel in different aging conditions. The calculations predict that the η-Ni3Ti precipitates will favor an ellipsoidal morphology with a high aspect ratio. Experimentally, needle-shaped precipitates of b/a = 3 are observed in the steel in the peak-aged condition. Careful examination of the 144 possible orientation pairs reveals that they may be classified into five groups of crystallographically independent pairs of precipitates. The interaction energy of two precipitates reaches up to ~ 7% of the self-energy, higher than the typical interaction energy of precipitates in Ni-based superalloys. Here, the ORs between the precipitate is expected to occur in a more sophisticated manner along the four< 111 > branches. We provide evidence that effective interactions exist inside branches and between interpenetrating branches inclined at 109.5°, although they are not very clear since not all of the favored sites are occupied.