Transmission Electron Microscopy Investigations Research Articles

Synthesis and Fungicidal Activities of Coumarin Derivatives as Succinate Dehydrogenase Inhibitors.

Succinate dehydrogenase inhibitors (SDHIs) have been developed to the fastest growing family of fungicides. To develop novel SDH inhibitors, twenty-seven novel non-amides coumarin derivatives were designed, synthesized and characterized .The bioassay revealed that most of the target compounds exhibited significant antifungal activity against Botrytis cinerea in vitro. Notably, compounds 1a and 2c with EC50 values of 0.92 μg/mL and 0.52 μg/mL, respectively，which were better than that of positive control chlorothalonil (EC50 =3.14 μg/mL).Moreover, in vivo antifungal assay results showed that compound 2c could observably inhibit the growth of B. cinerea on Kuerla pears with remarkable protective at a dosage of 200 μg/mL. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigation indicated that compound 2c significantly damaged the cell structures of B. cinerea mycelium. 3D-QSAR models were analyzed structure-activity relationships of all target compounds. Furthermore, molecular docking revealed that compound 2c was able to bind closely to the receptor protein of SDH. These results demonstrated that compound 2c may be potential candidate for novel SDH inhibitors.

New trends in mycosynthesis of cellulose nanocrystals promoted by gamma irradiation of sugarcane bagasse

AbstractThe biological synthesis of cellulose nanocrystals (CNCs) involves utilizing cellulose-degrading microorganisms or their hydrolytic enzymes as catalysts for the controlled degradation of cellulose, yielding CNCs. Chemical synthesis of CNCs involves acid hydrolysis conducted for 45 min at 45 °C using sulfuric acid (64%). Neurospora intermedia (Assiut University Mycological Center (AUMC) 14,359), Fusarium verticillioides (AUMC 14360), and Rhizopus oryzae (AUMC 14361) were employed in the preparation of CNCs. Before both chemical and biological treatments, sugarcane bagasse (SCB) was irradiated with doses of 100, 200, and 300 kGy, enhancing the yield of nanocellulose from the cellulosic feedstock. The resultant nanocellulose was initially assessed using UV–Vis spectroscopy, and the characterization was further refined through Dynamic Light Scattering analysis to delineate particle size distribution within the nanoscale and to evaluate stability. CNCs and chemically purified cellulose (CPC) displayed analogous Fourier Transform Infrared Spectroscopy but were markedly different from SCB. X-ray Diffraction patterns revealed a notably higher crystallinity of cellulose in nanocellulose, with larger crystallite dimensions compared to CPC and SCB. Transmission Electron Microscope investigations elucidated the morphology of the synthesized nanoparticles. In summary, the selection of F. verticillioides for nanocellulose production represents a promising and sustainable approach that combines effectiveness, environmental friendliness, and cost-efficiency in the synthesis of this valuable nanomaterial. Graphical abstract

In-situ transmission electron microscopy (TEM) investigation of the reduction process in graphene oxide

In-situ transmission electron microscopy (TEM) investigation of the reduction process in graphene oxide

CO2 Interaction Mechanism of SnO2-Based Sensors with Respect to the Pt Interdigital Electrodes Gap

The tuning sensitivity towards CO2 detection under in-field-like conditions was investigated using SnO2-sensitive material deposited onto Al2O3 substrates provided with platinum electrodes with interdigital gaps of 100 µm and 30 µm. X-ray diffraction, low-magnification and high-resolution transmission electron microscopy, and electrical and contact potential difference investigations were employed to understand the sensing mechanism involved in CO2 detection. The morpho-structural analysis revealed that the SnO2 nanoparticles exhibit well-defined facets along the (110) and (101) crystallographic planes. Complex phenomenological investigations showed that moisture significantly affects the gas sensing performance. The experimental results corroborated the literature evidence, highlighting the importance of Pt within the interdigital electrodes subsequently reflected in the increase in the CO2 sensing performance with the decrease in the interdigital gap. The catalytic efficiency is explained by the distribution of platinum at the gas-Pt-SnO2 three-phase boundary, which is critical for enhancing the sensor performance.

Staggering cytotoxic effects of manganese oxide nanoparticles from Bacillus thuringiensis

The current study describes the biological synthesis of manganese oxide nanoparticles from Bacillus thuringiensis, as well as their characterization, biological activity, and toxicity. Nanoparticles may be synthesized in multiple ways, but the biogenic process is the most environmentally friendly and cost-effective. The optical, structural, and crystalline properties of the nanoparticles were investigated. A distinctive peak at 246 nm with a band gap of 3.7eV indicates manganese oxide nanoparticle production. A strong peak at 563.09 cm−1 indicates Mn-O stretching in Fourier Transform Infrared Spectroscopy analysis. X-ray diffraction revealed that the crystalline grain size of manganese oxide nanoparticles was 11.23 nm. The agglomerated spherical shape is seen in the Scanning Electron Microscope and High-Resolution Transmission Electron Microscope investigations. The presence of manganese was verified by the EDAX. Manganese oxide nanoparticles have a significant zeta potential peak of −23.4 mV. This work explored the biological activity of manganese oxide nanoparticles, including antibacterial, anti-inflammatory, antioxidant, and biofilm inhibition studies. To investigate cytotoxicity, Allium cepa root tips are treated with manganese oxide nanoparticles.

Synthesis and Characterization of Iron Nanoparticles from a Bioflocculant Produced by Pichia kudriavzevii Isolated from Kombucha Tea SCOBY.

The intriguing characteristics of nanoparticles have fueled recent advancement in the field of nanotechnology. In the current study, a microbial-based bioflocculant made from the SCOBY of Kombucha tea broth was purified, profiled, and utilized to biosynthesize iron nanoparticles as a capping and reducing agent. UV-visible absorption spectroscopy, transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and TGA were used to characterize the Fe nanoparticles. The FT-IR spectra showed functional groups such as hydroxyl, a halogen (C-Br), and carbonyl, and the alkane (C-H) functional groups were present in both samples (bioflocculant and FeNPs) with the exception of the Fe-O bond, which represented the successful biosynthesis of FeNPs. The TEM investigation revealed that the sizes of the produced iron nanoparticles were between 2.6 and 6.2 nm. The UV-vis spectra revealed peaks at 230 nm for the bioflocculant and for the as-fabricated FeNPs, peaks were around 210, 265, and 330 nm, which confirms the formation of FeNPs. X-ray diffraction presented planes (012), (104), (110), (113), (024), (116), and (533) and these planes correspond to 17.17, 32.58, 33.75, 38.18, 45.31, 57.40, and 72.4° at 2Ө. The presence of Fe nanoparticles presented with 0.82 wt% from the EDX spectrum of the biosynthesized FeNPs. However, Fe content was not present from the bioflocculant. SEM images reported cumulus-like particles of the bioflocculant, while that of FeNPs were agglomerated and hexagonal with sizes between 18 and 50 nm. The TGA of FeNPs showed thermal stability by retaining above 60% of its weight at high temperatures. It can therefore be deduced that the purified bioflocculant produced by a yeast Pichia kudraivzevii can be utilized to synthesize FeNPs with the current simple and effective method.

Microstructural Evolution and High‐Temperature Tensile Properties of 15Cr‐Reduced Activation Ferritic Steel Processed by Hot Powder Forging of Mechanically Alloyed Powders

Reduced activation ferritic steels are being explored as possible cladding tube materials for nuclear reactors because of their low activation and excellent irradiation resistance. In the current investigation, reduced activation ferritic steel (Fe–15Cr–2W) is processed by mechanical alloying of elemental powders followed by hot powder forging. Mechanical alloying is carried out in a Simoloyer attritor mill (Zoz GmbH), after which the powders are placed in a mild steel can and forged at 1200 °C in H2 atmosphere. X‐ray diffraction and transmission electron microscopy (TEM) investigation reveal that 10 h of mechanical alloying is required to achieve complete dissolution of Cr and W in the Fe matrix powder. The relative density and hardness distribution of the forged slab is evaluated in longitudinal as well as transverse direction to optimize the powder forging operation. Electron backscatter diffraction analysis showed dynamic recrystallization to take place during the course of hot powder forging. Tensile tests are performed at room temperature as well as at elevated temperatures (600 and 700 °C). The yield strength and ultimate tensile strength at room temperature as well as at elevated temperatures are found to be higher than those reported in literature for reduced activation ferritic steels consolidated by other techniques.

Synthesis and characterization of core–shell magnetic molecularly imprinted polymer nanocomposites for the detection of interleukin-6

Interleukin-6 (IL-6) belongs to the cytokine family and plays a vital role in regulating immune response, bone maintenance, body temperature adjustment, and cell growth. The overexpression of IL-6 can indicate various health complications, such as anastomotic leakage, cancer, and chronic diseases. Therefore, the availability of highly sensitive and specific biosensing platforms for IL-6 detection is critical. In this study, for the first time, epitope-mediated IL-6-specific magnetic molecularly imprinted core–shell structures with fluorescent properties were synthesized using a three-step protocol, namely, magnetic nanoparticle functionalization, polymerization, and template removal following thorough optimization studies. The magnetic molecularly imprinted polymers (MMIPs) were characterized using dynamic and electrophoretic light scattering (DLS and ELS), revealing a hydrodynamic size of 169.9 nm and zeta potential of +17.1 mV, while Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy techniques showed characteristic peaks of the polymer and fluorescent tag, respectively. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) investigations confirmed the successful encapsulation of the magnetic core within the ca. 5-nm-thick polymeric shell. The MMIP-based electrochemical sensing platform achieved a limit of detection of 0.38 pM within a linear detection range of 0.38–380 pM, indicating high affinity (dissociation constant KD = 1.6 pM) for IL-6 protein in 50% diluted serum samples. Moreover, comparative investigations with the non-imprinted control polymer demonstrated an imprinting factor of 4, confirming high selectivity. With multifunctional features, including fluorescence, magnetic properties, and target responsiveness, the synthesized MMIPs hold significant potential for application in various sensor techniques as well as imaging.

Using In situ Transmission Electron Microscopy to Study Strong Metal-Support Interactions in Heterogeneous Catalysis.

Precisely controlling the microstructure of supported metal catalysts and regulating metal-support interactions at the atomic level are essential for achieving highly efficient heterogeneous catalysts. Strong metal-support interaction (SMSI) not only stabilizes metal nanoparticles and improves their resistance to sintering but also modulates the electrical interaction between metal species and the support, optimizing the catalytic activity and selectivity. Therefore, understating the formation mechanism of SMSI and its dynamic evolution during the chemical reaction at the atomic scale is crucial for guiding the structural design and performance optimization of supported metal catalysts. Recent advancements in in situ transmission electron microscopy (TEM) have shed new light on these complex phenomena, providing deeper insights into the SMSI dynamics. Here, the research progress of in situ TEM investigation on SMSI in heterogeneous catalysis is systematically reviewed, focusing on the formation dynamics, structural evolution during the catalytic reactions, and regulation methods of SMSI. The significant advantages of in situ TEM technologies for SMSI research are also highlighted. Moreover, the challenges and probable development paths of in situ TEM studies on the SMSI are also provided.

Palladium-Functionalized Nanostructured Nickel-Cobalt Oxide as Alternative Catalyst for Hydrogen Sensing Using Pellistors.

To meet today's requirements, new active catalysts with reduced noble metal content are needed for hydrogen sensing. A palladium-functionalized nanostructured Ni0.5Co2.5O4 catalyst with a total Pd content of 4.2 wt% was synthesized by coprecipitation to obtain catalysts with an advantageous sheet-like morphology and surface defects. Due to the synthesis method and the reducible nature of Ni0.5Co2.5O4 enabling strong metal-metal oxide interactions, the palladium was highly distributed over the metal oxide surface, as determined using scanning transmission electron microscopy and energy-dispersive X-ray investigations. The catalyst tested in planar pellistor sensors showed high sensitivity to hydrogen in the concentration range below the lower flammability limit (LFL). At 400 °C and in dry air, a sensor response of 109 mV/10,000 ppm hydrogen (25% of LFL) was achieved. The sensor signal was 4.6-times higher than the signal of pristine Ni0.5Co2.5O4 (24.6 mV/10,000 ppm). Under humid conditions, the sensor responses were reduced by ~10% for Pd-functionalized Ni0.5Co2.5O4 and by ~27% for Ni0.5Co2.5O4. The different cross-sensitivities of both catalysts to water are attributed to different activation mechanisms of hydrogen. The combination of high sensor sensitivity to hydrogen and high signal stability over time, as well as low cross-sensitivity to humidity, make the catalyst promising for further development steps.

Synthesis, Structural, Morphological, and Optical Properties of Promising Lead-Free Double Perovskite Na2CuBiBr6: A Sustainable Material for Photovoltaic Applications

This work primarily focuses on synthesizing and evaluating the structure, morphology, and optical features of double perovskite Na2CuBiBr6 forphotovoltaic devices. In the present investigation, Na2CuBiBr6 is created by a solution-based antisolvent recrystallization approach. A comprehensive experimental investigation is conducted on the Na2CuBiBr6 double perovskite, encompassing its structural configuration, morphology, and optical features. X-ray diffraction analysis verifies the creation of Na2CuBiBr6 double perovskite and showcases its exceptional phasestability in the cubic phase. Scanning electron microscopy reveals the presence of multidirectional crystals ofNa2CuBiBr6crystals. The presence of polycrystalline cubic Na2CuBiBr6 is confirmed using transmission electron microscopy and electron diffraction investigation. In addition, energy-dispersive X-ray spectroscopy demonstrates the consistent distribution of elements within Na2CuBiBr6. UV–vis spectroscopy reveals a band gap of 1.37 eV. The optical characteristics demonstrate that Na2CuBiBr6 exhibits a greater absorbance level and a lower reflectivity level within the visible spectrum. The results of this study suggest that the Na2CuBiBr6 double perovskite, which is both lead-free and environmentally benign, has significant potential for applications in photovoltaic and thermoelectric devices.

TEM investigation of the interface formation during transfer of 3C-SiC(001) layer onto 6H-SiC(0001) wafer

At present, intensive research is underway in the field of vacuum-sublimation growth of 3C-SiC. Transfer of a thin (001)3C-SiC layer onto a 6H-SiC wafer is a promising way to fabricate a 3C-SiC/6H-SiC substrate for growing device-quality homoepitaxial films of low defect density. The article presents the results of the structural characterization of an interface formed during the transfer of a 3C-SiC layer onto a 6H-SiC(0001) wafer, performed with transmission electron microscopy (TEM). A 3C-SiC film with a thickness of about 10 μm, grown by chemical vapor deposition (CVD) on a Si(001) substrate, was utilized in the study. Silicon acted as a bonding material in the transfer process. The morphology and microstructure of the interface between a 6H-SiC substrate and a 3C-SiC (001)-oriented layer are under consideration. TEM investigation reveals an effect of “self”-orientation of the layer with respect to the wafer during the transfer process: an interaction between the molten silicon layer and silicon carbide throughout crystallization results in the generation of defined orientation relationships with respect to substrate axes. An analysis of selected area electron diffraction patterns taken from interfaces showed the relationships to be 3C-SiC{001}‖ 6H-SiC(0001) and 3C-SiC⟨11¯0⟩∼‖ 6H-SiC⟨112¯0⟩.

Determination of the average crystallite size and the crystallite size distribution: the envelope function approach EnvACS.

A procedure is presented to exactly obtain the apparent average crystallite size (ACS) of powder samples using standard in-house powder diffraction experiments without any restriction originating from the Scherrer equation. Additionally, the crystallite size distribution within the sample can be evaluated. To achieve this, powder diffractograms are background corrected and long-range radial distribution functions G(r) up to 300 nm are calculated from the diffraction data. The envelope function f env of G(r) is approximated by a procedure determining the absolute maxima of G(r) in a certain interval (r range). Fitting of an ACS distribution envelope function to this approximation gives the ACS and its distribution. The method is tested on diffractograms of LaB6 standard reference materials measured with different wavelengths to demonstrate the validity of the approach and to clarify the influence of the wavelength used. The latter results in a general description of the maximum observable average crystallite size, which depends on the instrument and wavelength used. The crystallite site distribution is compared with particle size distributions based on transmission electron microscopy investigations, providing an approximation of the average number of crystallites per particle.

Using In situ Transmission Electron Microscopy to Study Strong Metal‐Support Interactions in Heterogeneous Catalysis

AbstractPrecisely controlling the microstructure of supported metal catalysts and regulating metal‐support interactions at the atomic level are essential for achieving highly efficient heterogeneous catalysts. Strong metal‐support interaction (SMSI) not only stabilizes metal nanoparticles and improves their resistance to sintering but also modulates the electrical interaction between metal species and the support, optimizing the catalytic activity and selectivity. Therefore, understating the formation mechanism of SMSI and its dynamic evolution during the chemical reaction at the atomic scale is crucial for guiding the structural design and performance optimization of supported metal catalysts. Recent advancements in in situ transmission electron microscopy (TEM) have shed new light on these complex phenomena, providing deeper insights into the SMSI dynamics. Here, the research progress of in situ TEM investigation on SMSI in heterogeneous catalysis is systematically reviewed, focusing on the formation dynamics, structural evolution during the catalytic reactions, and regulation methods of SMSI. The significant advantages of in situ TEM technologies for SMSI research are also highlighted. Moreover, the challenges and probable development paths of in situ TEM studies on the SMSI are also provided.

Microstructural and morphological studies of TiCrC nanopowders produced by mechanical alloying

Nanocrystalline Ti0.7Cr0.3C powders were synthesized by mechanical alloying (MA) at room temperature from an elemental mixture of Ti, Cr, and C powders. The samples were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDX). The novelty of our study is to advance our knowledge of the effect of milling time on the evolution of microstructural and morphological changes in the Ti0.7Cr0.3C powders. The XRD results revealed that nanostructured (Ti, Cr)C carbide with an average crystallite size of 11 nm was obtained after 20 h of MA. The SEM results showed that during MA, the morphology process implies repeated cold welding, fracturing, and re-welding of powder particles. TEM investigation revealed that the particles of TiCrC powder ranged in size from 50 to 250 nm.

A study of the spinodal decomposition of AgC[sbnd]u alloy films using in situ transmission electron microscopy

We performed in situ transmission electron microscopy (TEM) investigations to understand spinodal decomposition in AgCu alloy thin films. The decomposition of a homogeneous nanocrystalline morphology into a heterogeneous two-phase structure when annealed in situ from room temperature to 400 °C was investigated with different imaging modes in the TEM. These studies reveal phase transformation proceeds in stages: between 180 and 200 °C, onset of phase separation via spinodal decomposition is observed. Then, prominent phase separation occurs between 200 and 250 °C with minimal grain growth. Next, between 250 and 300 °C, grain growth primarily occurs via coalescence, with no apparent phase separation. From 300 to 350 °C, we observe significant phase separation and Ostwald Ripening. Finally, between 350 and 400 °C, further coarsening occurs via coalescence. STEM-HAADF mode reveals the onset of phase separation from domains as small as 5 nm and these results are also supported by electron diffraction and compositional mapping.

Polydopamine functionalized FeTiO3 nanohexagons for selective and simultaneous electrochemical determination of dopamine and uric acid.

Herein we report the simultaneous detection of dopamine (DA) and uric acid (UA) using polydopamine (PDA) functionalized FeTiO3 nanohexagons. The nanohexagons were hydrothermally synthesized and subsequently functionalized with PDA in a Tris-buffer solution. The PDA functionalized nanostructure was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR), respectively. The SEM and TEM investigations revealed the presence of FeTiO3 nanohexagons along with a peripheral coating of PDA over the nanostructures. The XRD pattern confirmed the formation of the ilmenite structure, while the chemical structure was investigated through XPS and FTIR respectively. Using cyclic voltammetry (CV) the efficacy of FeTiO3-PDA electrode was evaluated toward DA oxidation. The enhanced activity of the functionalized electrode in DA oxidation, as compared to the untreated FeTiO3, may be attributed to the significant presence of hydroxyl, amine, and imine functional groups over the polymer layer. Differential pulse voltammetry (DPV) was utilized for the detection of DA and UA. With a linear range of 50 μM to 250 μM, the detection limits of 0.30 μM and 4.61 μM were determined for DA and UA, respectively. The peak separation of 263 mV between DA and UA demonstrates the sensor's remarkable selectivity. In addition, the study displayed the ability to detect both DA and UA simultaneously, and the validity of the sensor was evaluated in serum samples, respectively.

In Situ Formation of SnSe2/SnSe Vertical Heterostructures toward Polarization Selectable Band Alignments.

2D van der Waals (vdW) layered semiconductor vertical heterostructures with controllable band alignment are highly desired for nanodevice applications including photodetection and photovoltaics. However, current 2D vdW heterostructures are mainly obtained via mechanical exfoliation and stacking process, intrinsically limiting the yield and reproducibility, hardly achieving large-area with specific orientation. Here, large-area vdW-epitaxial SnSe2/SnSe heterostructures are obtained by annealing layered SnSe. These in situ Raman analyses reveal the optimized annealing conditions for the phase transition of SnSe to SnSe2. The spherical aberration-corrected transmission electron microscopy investigations demonstrate that layered SnSe2 epitaxially forms on SnSe surface with atomically sharp interface and specific orientation. Optical characterizations and theoretical calculations reveal valley polarization of the heterostructures that originate from SnSe, suggesting a naturally adjustable band alignment between type-II and type-III, only relying on the polarization angle of incident lights. This work not only offers a unique and accessible approach to obtaining large-area SnSe2/SnSe heterostructures with new insight into the formation mechanism of vdW heterostructures, but also opens the intriguing optical applications based on valleytronic nanoheterostructures.

Adapting Conductivity and Mechanical Properties through Layer Thickness Variation in Copper Niobium Laminated Metallic Composites

Cu/Nb laminated metallic composites (LMCs) exhibit extraordinary mechanical strength while electrical conductivity is maintained at a high level. In this research, Cu‐based LMCs with varying volume fraction of niobium are produced via accumulative roll bonding (ARB) and additionally cold‐rolled and heat‐treated to identify the role of these heterogeneous phase boundaries on the overall sheet properties. Deformation structures in these layered materials are studied through scanning transmission electron microscopy investigations. The existence of an interface‐affected zone at the phase boundaries and mechanical intermixing is attributed to decreasing electrical and increasing mechanical properties, especially in very thin layered LMCs. Atom probe tomography measurements show that mechanical alloying occurs due to severe plastic deformation during ARB processing of the laminates. An additional subsequent heat treatment leads to chemical demixing at the interfaces of the phase boundaries.

Atomistic phase transition mechanism of zero-strain electrode material: Transmission electron microscopy investigation of Li4Ti5O12 spinel lattice upon lithiation

The lithiation mechanism of electrode materials is important for understanding the basic reactions in Li-ion batteries. In particular, zero-strain materials have garnered interest owing to their stable charge–discharge performances. In this study, we investigated the atomistic phase transition mechanism of spinel Li4Ti5O12, a well-known zero-strain material, using high-resolution transmission electron microscopy. A single-crystalline Li4Ti5O12 (100) specimen was prepared and observed in situ at a lattice resolution under electron-beam-assisted lithiation. The lattice fringes originating from the Li plane of the spinel crystal were anisotropically altered during phase transition, suggesting the asymmetrical site shifting of Li atoms during lithiation. This spontaneous symmetry-breaking mechanism for the phase transition is considered essential for the lithiation of spinel lattice.