Transmission Electron Microscopy Methods Research Articles

Formation of active phases of Fe/C, Cr/C and Fe–Cr/C catalysts in oxidative dehydrogenation of ethane

The oxidative dehydrogenation of ethane into ethylene using CO2 as an oxidant at temperatures of 650–750 °C was carried out over Fe/C, Cr/C and Fe–Cr/C catalysts deposited on a carbon support. Before and after the reaction the catalysts were investigated by X-ray powder diffraction (XRD), in situ magnetometry and transmission electron microscopy methods. The correlation between activity of Fe/C, Cr/C and Fe–Cr/C catalytic systems and their phase composition was established.

Self-intercalated quasi-2D structured V5Se8 wrapped with multi-walled carbon nanotubes toward advanced sodium ion batteries

Sodium-ion batteries (SIBs) have attracted much focus as electrochemical energy storage devices with unlimited potential for upcoming large-scale energy storage applications. Nevertheless, sodium ions with large radius and high mass can hinder sodium ions from diffusing into the electrode material, resulting in poor energy/power density and cycling stability. Therefore, a highly conductive three-dimensional carbon network composed of V5Se8 with a self-intercalated layer structure and one-dimensional multi-walled carbon nanotubes (MWCNTs) has been prepared using a straightforward one-step selenization process. This three-dimensional structure can increase the reversible sodium ion storage capacity and structural stability during the cycling process. The obtained V5Se8/MWCNTs electrodes have outstanding rate capacity (250 mAh g−1 at 10 A g−1) and tremendous initial reversible capacity (353 mAh g−1 at 0.2 A g−1). After 1000 cycles, they also obtain adequate cycling stability (323 mAh g−1 at 2 A g−1). The reaction mechanism of V5Se8/MWCNTs electrode in SIBs has been studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods, demonstrating that this electrode experiences a reversible phase transition between V5Se8 and V throughout the Na + insertion/extraction procedures. The full cell can offer a discharge plateau of 2.02 V when coupled with a Na3V2(PO4)2F3@reduced graphene oxide cathode. It also has an excellent discharge capacity of 177 mAh g−1 at 0.1 A g−1 and good cycling stability of 79 mAh g−1 after 1000 cycles at 1 A g−1.

A novel design of transitional layer structure between reduced activation ferritic martensitic steels and tungsten for plasma facing materials

Plasma-facing components (PFCs) are among the most critical gaps for fusion energy to establish technical and economic feasibility. Tungsten as a first wall/blanket material in PFCs requires to be integrating with reduced activation ferritic martensitic (RAFM) steels as a structural component. Currently, major drawbacks are the requirement of brazing, the formation of a brittle interface, and a large difference between the coefficients of thermal expansion of tungsten and steel. Here, a novel transitional multilayer structure was designed and investigated to join tungsten and RAFM steels using three interlayers. The composition of each interlayer was selected based on computational thermodynamics and diffusion kinetics to ensure a body-centered cubic (bcc) single-phase structure and prevent the formation of a brittle intermetallic phase region in the temperature range of 600–1150 °C. Although the transitional layer structure was designed for additive manufacturing, spark plasma sintering (SPS) as proof of concept was used to bond the individual layers. Interfaces were investigated using scanning and transmission electron microscopy methods but no layered intermetallic phase was observed. Nanoindentation maps across the interface suggest major hardness differences at the interface between tungsten and the vanadium interlayer, as well as the interface between RAFM steel and the FeCrAl interlayer.

A fluorescence nanoprobe of N-Acetyl-L-Cysteine capped CdTe QDs for sensitive detection of nitrofurazone

A method was established for detecting the content of nitrofurazone (NFZ) by fluorescence quenching of N-Acetyl-L-Cysteine (NAC) coated cadmium telluride quantum dots (CdTe QDs). By means of transmission electron microscopy (TEM) and multispectral methods such as fluorescence and ultraviolet visible spectra (UV–vis), the synthesized CdTe QDs were characterized. The quantum yield (φ) of CdTe QDs was measured as 0.33 by reference method. The CdTe QDs had a better stability, the RSD of fluorescence intensity was 1.51% in three months. NFZ quenching the emission light of CdTe QDs was observed. The analyses of Stern-Volmer and time-resolved fluorescence suggested the quenching was static. The binding constants (Ka) between NFZ and CdTe QDs were 1.14 × 104 (293 K), 0.74 × 104 (303 K) and 0.51 × 104 (313 K) L mol−1. The hydrogen bond or van der Waals force was the dominated binding force between NFZ and CdTe QDs. The interaction was further characterized by UV–vis absorption as well as Fourier transform infrared spectra (FT-IR). Using fluorescence quenching effect, a quantitative determination of NFZ was carried out. The optimal experimental conditions were studied and determined as following: pH was 7 and contact time was 10 min. The effects of reagent addition sequence, temperature and the foreign substances including some metals (Mg2+; Zn2+; Ca2+; K+; Cu2+), glucose, bovine serum albumin (BSA) and furazolidone on the determination were studied. There was a high correlation between the concentration of NFZ (0.40 – 39.63 μg mL−1) and F0/F with the standard curve F0/F = 0.0262c + 0.9910 (r = 0.9994). The detection limit (LOD) reached 0.04 μg mL−1 (3S0/S). The contents of NFZ in beef and bacteriostatic liquid were detected. The recovery of NFZ was 95.13% – 103.03% and RSD was 0.66% – 1.37% (n = 5).

INVESTIGATION OF THE EFFECT OF HEAT TREATMENT ON Cu – Al ALLOYS OBTAINED BY WIRE-ARC ADDITIVE MANUFACTURING

By methods of optical, scanning and transmission electron microscopy, studies have been carried out to establish the influence of Al, Si andMg on the formation and change of the structure, phase composition and distribution of elements of Cu–Al alloys obtained by wire-arc additive manufacturing with cold metal transfer, and after their heat treatment. The main factors determining the mechanical behavior of Cu-Al alloys after the addition of Si and Mg and their heat treat- ment are determined and analyzed. It is shown that the increased strength and hardness of the Cu-Al alloy is explained by grain grinding and the formation of particles of the second phases between the layers of the deposited metal. The features of the distribution of the main elements (Cu, Al) and secondary elements (Si, Mg) in the process of wire-arc additive manufacturing are revealed. Recently, studies of the Cu-Al alloy have been carried out, which have shown that Al as a solid solution element in the Cu-Al alloy can increase the formation of deformation twins and the density of dislocations. In addition, it was found that the addition of micro-alloying elements to the Cu–Al alloy significantly improves its me- chanical properties. The kinetics of the growth of intermetallic compounds such as CuAl2, Cu9Al4, Cu3Al in Cu–Al casting alloys has been studied. As a result of the complex of technological measures, the modes of obtaining additive billets of Si–Al, Cu–Al–Si and Cu–Al–Si–Mg alloys were selected. Technological equipment has been improved to obtain blanks as part of the work. The microstructure, phase composition and mechanical properties of Si–Al, Cu–Al–Si and Cu–Al–Si–Mg alloys obtained bywire-arc additivemanufacturing using coldmetal transfer technology are investigated.

GPIbα shedding in platelets is controlled by strict intracellular containment of both enzyme and substrate

BackgroundA disintegrin and metalloprotease 17 (ADAM17) catalyzes platelet glycoprotein (GP) Ibα ectodomain shedding, thereby releasing glycocalicin in plasma. The spatiotemporal control over the enzyme-substrate interaction and the biological consequences of GPIbα shedding are poorly understood. ObjectivesThis study aimed to determine the spatiotemporal control over GPIbα shedding by ADAM17. MethodsTransmission electron microscopy with immunogold staining, immunoprecipitation, and quantitative western blotting were used. ResultsImmunogold staining showed that all ADAM17 antigen is expressed intracellularly, irrespective of platelet activation. ADAM17 clustered in patches on a tortuous membrane system different from α- and dense granules. Mild activation by platelet adhesion to immobilized fibrinogen did not cause GPIbα shedding, whereas strong and sustained stimulation using thrombin and collagen (analogs) did. Glycocalicin release kinetics was considerably slower than typical hemostasis, starting at 20 minutes and reaching a plateau after 3 hours of strong stimulation. Inhibition of the ADAM17 scissile bond specifically in GPIbα receptors that reside on the platelet’s extracellular surface did not prevent shedding, which is in line with the strict intracellular location of ADAM17. Instead, shedding was restricted to a large GPIbα subpopulation that is inaccessible on resting platelets but becomes partially accessible following platelet stimulation. Furthermore, the data show that proteinaceous, water-soluble ADAM17 inhibitors cannot inhibit GPIbα shedding, whereas membrane permeable small molecule ADAM inhibitors can. ConclusionThe data show that platelets harbor 2 distinct GPIbα subpopulations: one that presents at the platelet’s surface known for its role in primary hemostasis and one that provides substrate for proteolysis by ADAM17 with kinetics that suggest a role beyond hemostasis.

Dislocation toughening in single‐crystal KNbO3

AbstractThe growing research interest in dislocation‐tuned functionality in ceramics is evident, with the most recent proofs‐of‐concept for enhanced ferroelectric properties, electrical conductivity, and superconductivity via dislocations. In this work, we focus on dislocation‐tuned mechanical properties and demonstrate that, by engineering high dislocation densities (up to 1014 m−2) into KNbO3 at room temperature, the fracture toughness can be improved by a factor of 2.8. The microstructures, including dislocations and domain walls, are examined by optical microscopy, electron channeling contrast imaging, piezo‐response force microscopy, and transmission electron microscopy methods to shed light on the toughening mechanisms. In addition, high‐temperature (above the Curie temperature of KNbO3) indentation tests were performed to exclude the influence of ferroelastic toughening, such that the origin of the toughening effect is pinpointed to be dislocations.

Increasing the Thermal Stability and High-Temperature Strength of Vanadium Alloys by Strengthening with Nanosized Non-Metallic Particles

Using the methods of scanning and transmission electron microscopy, the features of the structural-phase state of a vanadium alloy of the V-Cr-Ta-Zr system after a combined treatment, which consisted in cyclic alternation of thermomechanical and chemical-heat treatments, were studied. The values of yield strength and ductility of the V-Cr-Ta-Zr alloy were determined, depending on the stabilization and test temperatures. It was established that, after the combined treatment, the structural-phase state of the V-Cr-Ta-Zr alloy was composite, in which the joint implementation of dispersion and substructural strengthening ensured the formation of a gradient grain structure with a polygonal state, the elements of which were fixed by nanosized ZrO2 particles characterized by a high thermal stability. Such modification of the microstructure was accompanied by an increase in the high-temperature strength and a shift in the upper limit of the temperature stability interval towards high temperatures, of up to 900 °C. It was assumed that the polygonal state inside the grains contributed to the implementation of cooperative mechanisms of the dislocation-disclination type, which ensured the accommodation of the material in the "high-strength state" under loading.

Structural, Optical, Magnetic and Electrochemical Properties of CeXO2 (X: Fe, and Mn) Nanoparticles

CeXO2 (X: Fe, Mn) nanoparticles, synthesized using the coprecipitation route, were investigated for their structural, morphological, magnetic, and electrochemical properties using X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM), dc magnetization, and cyclic voltammetry methods. The single-phase formation of CeO2 nanoparticles with FCC fluorite structure was confirmed by the Rietveld refinement, indicating the successful incorporation of Fe and Mn in the CeO2 matrix with the reduced dimensions and band gap values. The Raman analysis supported the lowest band gap of Fe-doped CeO2 on account of oxygen non-stoichiometry. The samples exhibited weak room temperature ferromagnetism, which was found to be enhanced in the Fe doped CeO2. The NEXAFS analysis supported the results by revealing the oxidation state of Fe to be Fe2+/Fe3+ in Fe-doped CeO2 nanoparticles. Further, the room temperature electrochemical performance of CeXO2 (X: Fe, Mn) nanoparticles was measured with a scan rate of 10 mV s-1 using 1 M KCL electrolyte, which showed that the Ce0.95Fe0.05O2 electrode revealed excellent performance with a specific capacitance of 945 Fּ·g-1 for the application in energy storage devices.

Doxorubicin- and Trastuzumab-Modified Gold Nanoparticles as Potential Multimodal Agents for Targeted Therapy of HER2+ Cancers.

Recently, targeted nanoparticles (NPs) have attracted much attention in cancer treatment due to their high potential as carriers for drug delivery. In this article, we present a novel bioconjugate (DOX-AuNPs-Tmab) consisting of gold nanoparticles (AuNPs, 30 nm) attached to chemotherapeutic agent doxorubicin (DOX) and a monoclonal antibody, trastuzumab (Tmab), which exhibited specific binding to HER2 receptors. The size and shape of synthesized AuNPs, as well as their surface modification, were analyzed by the TEM (transmission electron microscopy) and DLS (dynamic light scattering) methods. Biological studies were performed on the SKOV-3 cell line (HER2+) and showed high specificity of binding to the receptors and internalization capabilities, whereas MDA-MB-231 cells (HER2-) did not. Cytotoxicity experiments revealed a decrease in the metabolic activity of cancer cells and surface area reduction of spheroids treated with DOX-AuNPs-Tmab. The bioconjugate induced mainly cell cycle G2/M-phase arrest and late apoptosis. Our results suggest that DOX-AuNPs-Tmab has great potential for targeted therapy of HER2-positive tumors.

Design and characterization of a novel Cu2.3Al1.3Ni1.7SnCr0.3 multi-principal element alloy coating on magnesium alloy by laser cladding

The evaporation and dilution of substrate seriously limit the performance of laser cladding coatings on magnesium alloys. In order to overcome the above shortcomings, a multi-step ultrasonic assisted laser remelting technology was proposed to improve the performance of the coating. In this work, a novel Cu2.3Al1.3Ni1.7SnCr0.3 multi-principal element alloy coating (MPEAC) was prepared on the surface of magnesium alloy. Characterization techniques such as transmission electron microscopy (TEM), electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM) were employed to characterize the microstructure and phase composition of the coatings. And the phase structure and morphology at the interface between the coating and the substrate were also studied via focus ion beam (FIB) and TEM method. In addition, the corrosion and wear resistance ability of the coatings were monitored by potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), hardness and friction tests. The results show that Cu2.3Al1.3Ni1.7SnCr0.3 MPEAC with ultrasonic assisted is composed of FCC phase and eutectic phases (Cu10Sn3 and Cu2Ni3Sn3). Due to the forced convection generated by ultrasonic waves, some Cu and Ni phases are precipitated around Cu2Ni3Sn3 phases, which is beneficial to enhance the corrosion resistance. Because of the grain refinement effect caused by ultrasonic, the wear resistance of the coating is also improved. Furthermore, ultrasonic vibration can effectively weaken and eliminate the texture density of the Cu2.3Al1.3Ni1.7SnCr0.3 MPEAC fabricated by laser cladding.

Microstructure, mechanical and thermal properties of YSZ thermal barrier coatings deposited by axial suspension plasma spraying

Yttrium-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are indispensable elements of present-day turbine propulsion systems. The ones deposited with atmospheric plasma spraying (APS) are characterized by required low thermal conductivity, but they are unable to survive frequent thermomechanical loading and therefore their application is limited to parts remaining stationary. Expanding capability of TBCs is sought in various areas, but the one realized through modification of most proliferated apparatus used for plasma spraying (PS) (from radial to axial injection) and substituting micrometric powders with the nano-structured suspension needs least changes in the industry established procedures and offers the highest property improvement. The present experiment covered the deposition of ZrO2-8Y2O3 YSZ TBC using both atmospheric and suspension PS processes. They were performed with commercial micrometric and nano-structured YSZ (8% Y2O3) powders. The coatings morphology and microstructure were characterized with 3D profilometry, scanning and transmission electron microscopy (SEM/TEM) methods. Finally, the coating’s hardness and heat conductivity were measured. This complex approach allowed to state that PS of micrometric t’-ZrO2 powder having an admixture of m-ZrO2 phase is capable of only partial improvement in its homogenization. However, the suspension PS process of nano-structured powder eliminated any traces of the monoclinic phase from the coating. The TEM microstructure observations indicated that the suspension PS coating is built by in-flight solidified droplets as well as by the melted ones flattened on arrival. A surface layer of liquefied material on solid droplets increases their adhesion to surface asperities promoting pseudo-columnar growth of the coating. The preservation of monotonic slow increase of thermal conductivity during heating of the suspension PS coating means, that its pseudo-columnar microstructure is better suited to withstand high strains during such treatment.

Uncovering the Optimal Molecular Characteristics of Hydrophobe-Containing Polypeptoids to Induce Liposome or Cell Membrane Fragmentation.

Cellular functions of membrane proteins are strongly coupled to their structures and aggregation states in the cellular membrane. Molecular agents that can induce the fragmentation of lipid membranes are highly sought after as they are potentially useful for extracting membrane proteins in their native lipid environment. Toward this goal, we investigated the fragmentation of synthetic liposome using hydrophobe-containing polypeptoids (HCPs), a class of facially amphiphilic pseudo-peptidic polymers. A series of HCPs with varying chain lengths and hydrophobicities have been designed and synthesized. The effects of polymer molecular characteristics on liposome fragmentation are systemically investigated by a combination of light scattering (SLS/DLS) and transmission electron microscopy (cryo-TEM and negative stained TEM) methods. We demonstrate that HCPs with a sufficient chain length (DPn ≈ 100) and intermediate hydrophobicity (PNDG mol % = 27%) can most effectively induce the fragmentation of liposomes into colloidally stable nanoscale HCP-lipid complexes owing to the high density of local hydrophobic contact between the HCP polymers and lipid membranes. The HCPs can also effectively induce the fragmentation of bacterial lipid-derived liposomes and erythrocyte ghost cells (i.e., empty erythrocytes) to form nanostructures, highlighting the potential of HCPs as novel macromolecular surfactants toward the application of membrane protein extraction.

Au Nanoparticles Functionalized Covalent-Organic-Framework-Based Electrochemical Sensor for Sensitive Detection of Ractopamine

Ractopamine, as a feed additive, has attracted much attention due to its excessive use, leading to the damage of the human nervous system and physiological function. Therefore, it is of great practical significance to establish a rapid and effective method for the detection of ractopamine in food. Electrochemical sensors served as a promising technique for efficiently sensing food contaminants due to their low cost, sensitive response and simple operation. In this study, an electrochemical sensor for ractopamine detection based on Au nanoparticles functionalized covalent organic frameworks (AuNPs@COFs) was constructed. The AuNPs@COF nanocomposite was synthesized by in situ reduction and was characterized by FTIR spectroscopy, transmission electron microscope and electrochemical methods. The electrochemical sensing performance of AuNPs@COF-modified glassy carbon electrode for ractopamine was investigated using the electrochemical method. The proposed sensor exhibited excellent sensing abilities towards ractopamine and was used for the detection of ractopamine in meat samples. The results showed that this method has high sensitivity and good reliability for the detection of ractopamine. The linear range was 1.2-1600 μmol/L, and the limit of detection (LOD) was 0.12 μmol/L. It is expected that the proposed AuNPs@COF nanocomposites hold great promise for food safety sensing and should be extended for application in other related fields.

Radiation-induced structure of austenitic steels with different nickel content under neutron irradiation in SM-3 and BOR-60 reactors

Comparative studies of the radiation-induced structure of austenitic steels with a nickel content of 10, 20 and 25 wt.%, irradiated sequentially in the SM-3 and BOR-60 reactors, as well as to higher damaging doses in the BOR-60 reactor, have been carried out. The phase composition, dislocation structure, pores, and radiation-induced segregations at grain boundaries were studied by high-resolution analytical methods of transmission electron microscopy, scanning electron microscopy, and atomic probe tomography. The formation of radiation-induced phase precipitates based on nickel has been established, and its volume fraction correlates with the level of radiation-induced segregations, and increases, the higher the nickel content in the steel. The values of barrier strength factors for radiation-induced structural elements in the studied steels are adjusted by calculation and experiment, which makes it possible to determine their contribution to radiation hardening.It is shown that the largest contribution to radiation hardening as a result of neutron irradiation in BOR-60 at high irradiation temperature up to 29 dpa is made by large radiation-induced precipitates of (G + γ') phases. It is shown that with an increase in the damaging dose, the main factor limiting the performance of internal devices will be radiation swelling, since the contribution to the change in properties from radiation-induced phases and radiation defects will not increase due to their density reaching saturation. Steel with 25 wt.% Ni exhibits the lowest level of swelling at high radiation doses, which makes it possible to consider it as a material-candidate for internals for promising VVER reactors with higher temperatures and longer service life.

PHYSICO-CHEMICAL AND SORPTION PROPERTIES OF NANOCOMPOSITE AEROGELS BASED ON MODIFIED CARBON NANOTUBES AND GRAPHENE

The paper presents the technology for obtaining nanocomposite aerogels based on oxidized carbon nanotubes (o-CNTs) and reduced graphene oxide (r-GO) modified with polyaniline and phenoldehyde resin. Aerogel was obtained in high-pressure autoclave among supercritical fluid - isopropanol. The complex diagnostic of synthesized nanocomposite was carried out by the methods of scanning and transmission electron microscopy, infrared spectroscopy, X-ray diffractometry, Raman spectroscopy. The parameters of the porous space were evaluated by adsorption of nitrogen. The resulting electron images indicate that the CNTs was as structural formers, concentrating on their surface graphene sheets. It should also be noted that in the samples, particles of spherical polyaniline were found. It was established that nanocomposite aerogel is a mesoporous material with a specific surface of 289 m2/g. A comparison of infrared and Raman spectra, as well as X-ray diffractograms of the initial materials with aerogel spectra was carried out. According to the results, the nanocomposite contains combined peaks of all source materials. After drying in the supercritical isopropanol media, the ordered structure of the carbon frame is preserved. Electronodononic oxygen and nitrogen-containing groups, which are identified according to the IR spectroscopy as part of the composite, can be active centers for adsorption of heavy metals due to the possibility of the formation of coordination bonds. The nanocomposite sorption activity was evaluated by the example of the heavy metals sorption, namely lead, from model aqueous solutions. To determine the contact time and the absorption mechanism, kinetic studies of adsorption were carried out in a limited volume. It was found that 99% of the pollutant was sorbed in the first 15 min with an achievement of the adsorption capacity of 350 mg/g. Using of pseudo-first and second-order models, the Elovich model and intra-particle diffusion models the adsorption mechanism were offered. For citation: Kuznetsova T.S., Burakov A.E., Pasko T.V., Burakova I.V., Dyachkova T.P., Memetova A.E. Physico-chemical and sorption properties of nanocomposite aerogels based on modified carbon nanotubes and graphene. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 66-76. DOI: 10.6060/ivkkt.20236603.6726.

Crystallography and Surface Oxidation of Stoichiometric Arsenopyrite from Šumadija-Kopaonik Pb-Zn/Polymetallic Ore District (Serbia)

The behaviour and stability of arsenopyrite largely depend on its crystal structure, but studies of crystallography and structural defects are scarce. For clarification, we investigated a series of natural arsenopyrite crystals from the polymetallic Pb-Zn-(±Cu,Ag,Au,Sb,Bi,W) Šumadija-Kopaonik ore district (Serbia) by powder X-ray diffraction (XRPD). Among them, samples from the Drenjak gold mineralisation showed near-stoichiometric FeAsS composition and were further investigated by conventional and high-resolution transmission electron microscopy methods. TEM revealed abundant planar crystallographic defects and epitaxial surface oxide layer formation upon air exposure. Our findings present the fundamental work on the prototype arsenopyrite structure and have further implications for studies on ion incorporation into FeAsS structure and its environmental stability and oxidation mechanisms as a source of anthropogenic As release into the environment.

A conformational switch in clathrin light chain regulates lattice structure and endocytosis at the plasma membrane of mammalian cells.

The nanoscale localizations, interactions, and conformations of endocytic proteins are key regulators of clathrin-mediated endocytosis. Although super-resolution microscopy has revealed the detailed organization of endocytic proteins, the resolution of super-resolution imaging cannot assess molecular interaction and conformational changes. Fluorescence resonance energy transfer (FRET) occurs when dyes are separated by less than 10 nm for most fluorescent proteins pairs. Thus, it can be used to map close-range molecular complexes and dynamics. Yet, to understand how endocytosis works, measurements from FRET must be correlated to the distinct stages of endocytosis. To accomplish this, we developed a new correlative lifetime-based FRET (FLIM-FRET) and platinum replica transmission electron microscopy (PREM) method, named FRET-CLEM. Here, FRET-based atomic distances can be mapped directly to individual cellular structures visualized in EM at the plasma membrane. We used this method to measure the conformational changes in clathrin light chain (CLC), a component of the clathrin triskelion and assembled clathrin lattice. CLC conformational changes have been proposed to regulate the assembly of clathrin in solution. However, CLC conformational changes and their effects on clathrin lattice growth, curvature, and endocytosis at the membrane of living cells are unknown. Using FRET-CLEM, we discovered that CLC undergoes a conformational switch as clathrin lattices curve. Preventing this conformational switch with acute chemical tools increased clathrin lattice sizes and inhibited endocytosis. Therefore, a specific conformational switch in CLC regulates lattice curvature and endocytosis in mammalian cells. These new correlative light and EM data will help develop a complete mechanistic model of endocytosis. More generally, FRET-CLEM can map molecular interactions and conformational changes at targeted membrane-associated proteins at identified cellular compartments including exocytic sites and neuronal synapses.

Development of a novel sensor based on Bi2O3 and carbonized UIO-66-NH2 nanocomposite for efficient detection of Pb(Ⅱ) ion in water environment

Development of an efficient monitoring technology for rapid detection of toxic Pb(Ⅱ) ion in water environments is extremely important. Here, a novel and highly sensitive sensor was prepared using one-step calcination technique, based on Bi2O3 nanoparticles and carbonized metal–organic framework (MOF) nanocomposite. Scanning electron microscopy, transmission electron microscopy, contact angle and X-ray photoelectron spectroscopy characterization methods were used to analyze the morphology and structure of the prepared materials. Based on the electrical double-layer capacitance theory and Raman spectroscopy, changes to the active sites of different modified materials were investigated. Besides, differential charge densities and adsorption energies of the different modified materials in Zr-O clusters were calculated using density functional theory (DFT). A Bi2O3 and carbonized UIO-66-NH2 (Bi2O3/C-UIO-66-NH2) -modified glassy carbon electrode was used to detect Pb(Ⅱ) by differential pulse anodic stripping voltammetry. Under optimal experimental parameters, the developed electrochemical sensor has a wide linear range (2–130 μg/L) and a low detection limit (0.05 μg/L). Meanwhile, the sensor has excellent stability, repeatability, and anti-interference properties and has been successfully applied to detect Pb(Ⅱ) in actual water samples. The results of this paper show that our developed sensor an efficient and rapid sensor technology for monitoring lead in water environment.

Nanoscale Mineralogical Characterization of Terrestrial and Extraterrestrial Samples by Transmission Electron Microscopy: A Review

Nanoscale minerals (i.e., nanominerals and mineral nanoparticles) in terrestrial and extraterrestrial materials are difficult to characterize because of their small particle sizes, high surface energy, and/or poor crystallization. Transmission electron microscopy (TEM) is a powerful analytical platform for the characterization of minerals at the nano and even atomic scales, and it can determine their morphology through imaging, derive structural information using multiple electron-diffraction techniques, and investigate chemical compositions. Since the 1990s, the application of TEM to the characterization of nanoscale minerals has developed rapidly into a core technique in nanoscale Earth and planetary science (NEPS). This review introduces a brief history and the general principles of TEM, considers detailed methods of preparing specimens for nanoscale mineralogical characterization by TEM, and emphasizes the contributions of TEM to multiple NEPS research fields in recent decades. These contributions are considered from the perspective of nanoscale mineralogical studies of morphology, structure, and chemistry in complex geological materials. Finally, the work provides an outlook on current opportunities to apply TEM methods to nanoscale mineralogical study. This review aims to provide common and practical TEM methods to NEPS researchers and to support the use of TEM for a wide range of applications in nanoscale mineralogy to promote NEPS development.