Transmission Electron Microcopy Research Articles

Ethanol Sensing Properties of Tungsten Oxide Nanocubes Prepared by a Urea-Assisted Hydrothermal Method

A facile hydrothermal process has been employed to synthesize WO3nanocubes using urea as an assistant agent. The crystal structure and morphology of WO3nanocubes have been characterized by X-ray diffraction (XRD), scanning electron microcopy (SEM) and transmission electron microcopy (TEM). XRD, SEM and TEM images of the products illustrate that WO3square nanostructures have a single orthorhombic phase, length of ~ 100-200 nm and thickness of ~ 40 nm. The ethanol sensing property of as-prepared tungsten oxide nanocubes is studied at ethanol concentration of 10-1000 ppm and working temperature of 160-400 °C. The result shows that the WO3 nanocubes have high sensitivity to ethanol because of their small size and special morphology.

One‐Step Fabrication of Multifunctional Core‐Shell Fibres by Co‐Electrospinning

AbstractIn the present study, multifunctional core‐shell fibre mats were designed by co‐electrospinning. These core‐shell fibre mats have three different functionalities: 1) they are magnetic, 2) they change their optical properties with the pH of the media, and 3) they are sensitive to O2. The shell is formed by a fluorescent pH‐sensitive co‐polymer which was previously synthesised and characterized by our research group. The core is a suspension formed by magnetic nanoparticles in a solution made up by a lipophilic indicator dye (oxygen indicator; PtOEP) and, poly‐methyl methacrylate, in THF. The magnetic nanoparticles were prepared by encapsulation of magnetite within a cross‐linked polymeric matrix (MMA‐co‐EDMA). To our knowledge, this is the first time that three functionalities (magnetic properties, sensitivity to pH, and response to O2 concentration) were successful conjugated on the same micro‐ or nano‐material via a facile one‐step process with high yield and cost effectiveness.The morphology of the well‐organized core‐shell fibres were characterized by high resolution scanning electron microcopy (HRSEM), transmission electron microcopy (TEM), and confocal laser microscopy. The luminescent properties of core‐shell fibre mats were analysed and successfully used for simultaneously monitoring pH (from 6 to 8) and O2, showing complete reversibility, high sensitivity (i.e., Ksv = 7.07 bar−1 for determining O2 in aqueous media), high magnetic susceptibility, and short response times.

Investigation of Photocatalytic Activities over Bi2WO6/ZnWO4 Composite under UV Light and Its Photoinduced Charge Transfer Properties

Bi(2)WO(6)/ZnWO(4) composite photocatalysts have been successfully synthesized by a facile hydrothermal process. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microcopy (TEM), and UV-vis diffuse reflectance spectrum (DRS). The results show that Bi(2)WO(6) nanoparticles grow on the primary ZnWO(4) nanorods. The Bi(2)WO(6)/ZnWO(4) composites have better UV light photocatalytic activities compared to single ZnWO(4) nanorods. Furthermore, the photoinduced charge transfer properties of Bi(2)WO(6)/ZnWO(4) composites were investigated by means of transient photovoltage (TPV) technique in detail. The interconnected interface of Bi(2)WO(6)/ZnWO(4) composites led to the low recombination ratios of photoinduced electron-hole pairs and enhanced photocatalytic activities.

Characterization and synthesis of KTa0.1Nb0.9O3 particles via high temperature mixing method under hydrothermal conditions

KTa0.1Nb0.9O3 (KTN) particles with an orthorhombic perovskite structure have been synthesized via a high temperature mixing method (HTMM) under hydrothermal conditions. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microcopy (HRTEM). The influence of alkaline concentration and solvent composition on the phase structure and morphology of the obtained powders was investigated. The results show that the well-crystallized KTN powders with sizes of 200–500nm are successfully prepared at temperatures as low as 240°C when the KOH concentration is 2.0M and the isopropanol/water (I/W) volume ratio equals to 100/0.

Synthesis, Characterization and Capacitive Behaviors of Nanoporous Carbons Obtained by Using the Template of Zeolite-13X/MCM-48 Biporous Molecular Sieve

Zeolite-13X/MCM-48 biporous molecular sieve has been synthesized in the mode of overgrowth of MCM-48 on the surface of pre-added zeolite 13X. This kind of biporous molecular sieve has been taken as the template to prepare nanoporous carbons by a two-step casting process with furfuryl alcohol and acetonitrile as the precursors. The structures and textures are characterized by X-ray diffraction, nitrogen sorption at 77 K and high-resolution transmission electron microcopy. The electrochemical performances of the as-prepared porous carbons were tested by cyclic voltammetry and galvanostatic charge-discharge cycling in aqueous electrolyte. One of the carbon samples (labeled as C3-3) which is prepared by adding 5% zeolite-13X in the MCM-48 sol as the template and conducting acetonitrile chemical vapor deposition for 4 h after the impregnation of furfuryl alcohol. The C3-3 nanoporous carbon keeps the structure ordering and has the capacitance of 197 F g-1 at 2 mV s-1. The cycling performance of this carbon sample is excellent, which can maintain above 90% capacitance after 1000 cycles at 1 A g-1.

Hydrothermal synthesis and characterization of Lanthanum-doped NaTaO3 with high photocatalytic activity

Lanthanum-doped NaTaO3 (NaTaO3:La) nanocrystals have been synthesized by a hydrothermal method. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microcopy (TEM), inductive coupled plasma atomic absorption spectrometric analysis, volumetric adsorption method (BET) and UV–vis spectroscopy were used to characterize the samples. The NaTaO3:La nanocubes show a higher photocatalytic activity than that of the pure NaTaO3 in the degradation of the safranine T dye under UV irradiation. The highest photocatalytic activity was achieved when 2 mol% lanthanum was doped.

Hydroxycamptothecin‐loaded Fe3O4 nanoparticles induce human lung cancer cell apoptosis through caspase‐8 pathway activation and disrupt tight junctions

10-Hydroxycamptothecin (HCPT) elicits strong anti-cancer effects and is less toxic than camptothecin (CPT), making it widely used in recent clinical trials. However, its low solubility limits its application as an effective anti-cancer therapy. In the present study we investigate the hypothesis that the unique water dispersible oleic acid-Triton X-100-coated Fe3O4 nanoparticles loaded with HCPT disrupt epithelial cell-cell junctions and induce human lung cancer cell apoptosis through the caspase-8 pathway. We characterized the HCPT-loaded nanoparticles and determined their effects on lung cancer cell viability and apoptosis by using immunofluorescence light microscopy and SDS-PAGE/immunoblots. We found that HCPT-loaded nanoparticles elicited an anti-proliferative effect in a dose-dependent manner. HCPT-loaded nanoparticles reduced the expression of cell-cell junction protein claudins, E-cadherin and ZO-1, and transmission electron microcopy demonstrated a disrupted tight junction ultrastructure. Transepithelial electric resistance was also reduced, indicating the reduction of tight junction functions. The HCPT-loaded nanoparticles increased phosphorylation of p38 and SAPK/JNK while it showed no effects on p42/44 MAP kinase. Compared with void Fe3O4 nanoparticles or HCPT drug alone, HCPT drug-loaded nanoparticles evoked synergistic effects by increasing cell apoptosis with enhanced activation of the caspase-8 pathway. Therefore, our current study highlights the potential of HCPT drug-loaded nanoparticles as a chemotherapeutic agent for increasing anti-cancer drug efficacy.

Besnoitiosis in a Southern Plains Woodrat (Neotoma micropus) from Uvalde, Texas

Recently, Besnoitia neotomofelis was described from a southern plains woodrat (Neotoma micropus) from southern Texas. During May 2010, 1 of 55 southern plains woodrats trapped in Uvalde County, Texas, was diagnosed with besnoitiosis. Grossly, the woodrat had bilateral swellings of the cheeks, and numerous Besnoitia sp.-like cysts were observed in the tongue, facial region, musculature of the limbs, and subcutis of the dorsum and flanks. Little to no inflammation was noted around cysts. The cysts were morphologically similar to B. neotomofelis based on light and transmission electron microcopy. The sequence of the internal transcribed spacer region-1 was identical to the type isolate of B. neotomofelis. Attempts to isolate Besnoitia sp. in laboratory mice failed; however, Toxoplasma gondii was isolated in a Swiss Webster mouse. This represents the first report of besnoitiosis caused by B. neotomofelis in a southern plains woodrat and the first concurrent Besnoitia sp. and T. gondii infection in any host species.

Amphiphilic block glycopolymers via atom transfer radical polymerization: Synthesis, self-assembly and biomolecular recognition

In this work the synthesis of poly(butyl acrylate)-b-poly(2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate) (PBA-b-PHEMAGl) diblock glycopolymer and poly(2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate)-b-poly(butyl acrylate)-b-poly(2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate) (PHEMAGl-b-PBA-b-PHEMAGl) was performed via atom transfer radical polymerization. Monofunctional and difunctional poly(butyl acrylate) macroinitiators were used to synthesize the well-defined diblock and triblock glycopolymers by chain extension reaction with the glycomonomer HEMAGl. The self-assembly of these glycopolymers in aqueous solution was studied by dynamic light scattering and transmission electron microcopy, showing the coexistence of spherical micelles and polymeric vesicles. In addition, the biomolecular recognition capacity of these micelles and vesicles, containing glucose moieties in their coronas, was investigated using the lectin Concanavalin A, Canavalia Ensiformis, which specifically interacts with glucose groups. The binding capacity of Concanavalin A with glycopolymer is influenced by the copolymer composition, increasing with the length of HEMAGl glycopolymer segment in the block copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Effect of Single Femtosecond Pulses on Gold Nanoparticles

Gold nanoparticles find a wide range of applications in optics and photonics; however, their detailed interaction with intense laser light is only partially understood. Previous works have studied the effect of intense pulse trains on gold nanoparticles at a wide range of illumination parameters and observed diverse optical and morphological changes. In this work we study, for the first time, the interaction between single femtosecond pulses and gold nanoparticles. Using transmission electron microcopy and optical spectroscopy, we have found that nanoparticles illuminated by 50 fs pulses with fluence of less than 0.15 J/cm2 per pulse (3 TW/cm2) undergo morphological changes that affect their extinction spectra. Experimentation with particles of different diameters show similar qualitative effects, which are more pronounced for larger particles. Pulses at different excitation wavelengths were found to induce different effects for resonance and off-resonance conditions. The presented results provide valuable experimental data on the complex pulse−particle interaction and would be helpful for better understanding of the physical processes that are involved.

Growth evolution of rapid grown aligned carbon nanotube forests without water vapor on Fe/Al 2O 3/SiO 2/Si substrate

This paper presents the growth evolutions in terms of the structure, growth direction and density of rapid grown carbon nanotube (CNT) forests observed by scanning and transmission electron microcopies (SEM/TEM). A thermal CVD system at around 700 °C was used with a catalyst of Fe films deposited on thin alumina (Al 2O 3) supporting layers, a very fast raising time to the growth temperature below 25 °C/s, and a carbon source gas of acetylene diluted with hydrogen and nitrogen without water vapor. Activity of Fe catalyst nanoparticles was maintained for 5 min during CVD process, and it results in CNT forests with heights up to 0.6 mm. SEM images suggest that the disorder in CNT alignment at the initial stage of CNTs plays a critical role in the formation of continuous CNT growth. Also, the prolonged heating process leads to increased disorder in CNT alignment that may be due to the oxidation process occurring at the Fe nanoparticles. TEM images revealed that both double- and few-walled CNTs with diameters of 5–7 nm were obtained and the CNT density was controlled by thickness of Fe catalytic layer. The number of experiments at the same conditions showed a very good repeatability and reproducibility of rapid grown CNT forests.

Simple method for the layer-by-layer surface modification of multiwall carbon nanotubes

A simplified method for the surface modification of multiwall carbon nanotubes (MWCNTs) using the layer-by-layer (LbL) technique is proposed. In this approach, the minimum polyelectrolyte content was added to the solution in order to eliminate the tedious centrifugation step. The one pot LbL deposition of poly (diallyldimethylammonium chloride) (PDADMAC), and poly (sodium 4-styrenesulfonate), (PSS) is presented. UV–Vis spectroscopy and zeta potential measurements were used to determine the minimum PDADMAC and PSS concentration needed for the deposition of each polyelectrolyte layer. The deposition cycle was repeated until six layers of PDADMAC/PSS were deposited. The film growth was confirmed by transmission electron microcopy and was found to increase as a function of the number of deposited layers with a final thickness of 18 nm. Evidence of the alternate deposition of oppositely charged polyelectrolytes was further investigated by measurement of the zeta potential values which were found to reverse from positive to negative as a function of the number of deposited layers thus confirming the overcompensation of the surface charge at each adsorption step. This simple method could be useful for the fast preparation of large volumes of MWCNTs solutions in a single batch without the need for centrifugation step.

APPROACHES FOR A RELIABLE COMPOSITIONAL ANALYSIS OF ALKALINE-BASED LEAD-FREE PEROVSKITE CERAMICS USING MICROANALYTICAL METHODS

The article describes the approaches for a reliable, quantitative compositional analysis of lead-free perovskite ceramics in powder and bulk forms that contain volatile alkaline compounds. The combination of scanning electron microscopy (SEM) and transmission electron microcopy (TEM) with electron-probe analytical techniques, such as energy-dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDS) and electron-energy-loss spectroscopy (EELS) makes it possible to determine the true chemical composition, from precursor powders to synthesized ceramics or single crystals. The microscale (SEM) and nanoscale (TEM) analytical methods also give an insight into the local variations of the chemical composition.

Radiation induced hardening of ion irradiated RPV steels

It is well known that radiation hardening and embrittlement of A533B steels is very sensitive to minor solute content. To investigate the effect on microstructural evolution of these materials, A533B steels with different Cu levels were irradiated by 2.4MeV Fe ions. The ion irradiation was performed at 290°C and also at room temperature up to a dose of 2dpa. After the irradiation, the microstructure of the specimens was observed by transmission electron microcopy. Small dislocation loops formed in the matrix and also in the vicinity of dislocation were identified as interstitial dislocation loops, using additional electron irradiation at room temperature in the HVEM.

Preparation and mineralization of three-dimensional carbon nanofibers from bacterial cellulose as potential scaffolds for bone tissue engineering

Nanofibers exist widely in human tissue and designing three-dimensional (3-D) nanofibrous tissue engineering has important implications. For the first time to our knowledge, this article described the construction of 3-D nanofibrous carbon scaffolds for potential bone tissue regeneration which are composed of carbon nanofiber (CNF) and hydroxyapatite (HAp). CNFs were obtained by carbonization under inert conditions with 3-D bacterial cellulose nanofibers as starting carbon sources. The resulting CNFs showed 3-D fibrous structural features with diameter ranging from 10 to 20 nm. In vitro biomineralization process was performed on the surface-treated 3-D CNFs. The resultant CNF/HAp composites were investigated using scanning electron microscopy, transmission electron microcopy, Raman spectroscopy, and X-ray diffraction. The results showed that surface treatment of CNFs in nitric acid promoted the mineralization and changed the morphology of HAp formed on CNFs.

Spermatozoa of an Old World Ricinulei ( Ricinoides karschii, Ricinoidae) with notes about the relationships of Ricinulei within the Arachnida

The ultrastructure of spermatozoa is a valuable tool for phylogenetic and systematic studies. Ricinulei are enigmatic and poorly studied arachnids. So far, spermatozoa are only known from New World ricinuleids. The goals were to study, by means of light and transmission electron microcopy, the spermatozoa of an Old World species with regard to their phylogenetic implications, e.g., does the sperm structure contribute to the debated sister-group relationship of Acari and Ricinulei. The spermatozoa are coiled-flagellate and characterized by a cap-like acrosomal vacuole covered by electron-dense material, an elongated nucleus covered by a manchette of microtubules during spermiogenesis, an axoneme with a 9 + 2 microtubular pattern, a nuclear tube and axonemal basis which both originate underneath the acrosomal vacuole and cleistospermia as transfer form equipped with three intracellular plates. The data of the present study did not support a close relationship of Ricinulei and Acari which have aflagellate sperm with various synapomorphies as e.g., lacking nuclear envelopes/membranes in Actinotrichida (very similar to Solifugae) or vacuolated spermatozoa in Anactinotrichida. Affinities of Ricinulei are discussed in the light of the ultrastructure of arachnid spermatozoa.

Processing, structure, and mechanical properties of alumina-nanofilled polystyrene composites

Binary composites composed of polystyrene (PS) and a synthetic boehmite alumina were produced by using the water-mediated melt compounding (WMC) and direct melt compounding (DMC) techniques. The alumina particles were dispersed in water at ambient temperature. The aqueous alumina suspension was injected into molten PS in a twin-screw extruder to prepare reinforced polymer composites. The dispersion of the alumina was studied by transmission and scanning electron microcopy techniques (TEM and SEM, respectively). The mechanical and thermomechanical properties of the composites were determined by employing a dynamic-mechanical thermal analysis (DMTA) and short-time creep and uniaxial static tensile tests. It was found that the direct melt compounding of the alumina with PS resulted in microcomposites, whereas the water-mediated melt compounding technique gave rise to nanocomposites. The incorporation of alumina into the PS nanocomposites increased their stiffness, tensile strength, and creep resistance. However, the elongation of the PS nanocomposites at break was smaller than that of the PS microcomposites.

In situ etching WO3 nanoplates: Hydrothermal synthesis, photoluminescence and gas sensor properties

Abstract A novel hydrothermal process using p-nitrobenzoic acid as structure-directing agent has been employed to synthesize plate-shaped WO3 nanostructures containing holes. The p-nitrobenzoic acid plays a critical role in the synthesis of such novel WO3 nanoplates. The morphology, structure and optical property of the WO3 nanoplates have been characterized by transmission electron microcopy (TEM), scanning electron microcopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). The lateral size of the nanoplates is 500–1000 nm, and the thickness is about 80 nm. The formation mechanism of WO3 nanoplates is discussed briefly. The gas sensitivity of WO3 nanoplates was studied to ethanol and acetone at different operation temperatures and concentrations. Furthermore, the WO3 nanoplate-based gas sensor exhibits high sensitivity for ethanol and acetone as well as quick response and recovery time at low temperature.

Preparation, characterization, and properties of sodium montmorillonite clay/poly(styrene–butadiene–styrene) containing quaternary ammonium cations and photoinitiator nanocomposites via ultraviolet exposure

AbstractA functionalized graft copolymer {poly(styrene–butadiene–styrene) (SBS)‐g‐4‐benzoyl‐N,N‐dimethyl‐N‐[2‐(2‐methyl‐1‐oxo‐2‐propenyloxy)ethyl]benzenemethanaminium bromide (4‐BBPDMAEMA)}, containing a photoinitiator, quaternary ammonium cations, and many CC double bonds, was synthesized to modify clays, such as Na+–montmorillonite (MMT) clay, for the preparation of organic–inorganic nanocomposite resins via radical photoinduced crosslinking polymerization. The structure of SBS‐g‐4‐BBPDMAEMA was characterized by Fourier transform infrared and 1H‐NMR spectroscopy. The corresponding SBS‐g‐4‐BBPDMAEMA was found to have two functions: the capability to ionically exchange with sodium ions in the silicate gallery and the capability to synthesize exfoliated SBS/MMT nanocomposites by the UV crosslinking of intercalation polymerization. The results from the X‐ray diffraction primarily reveal that the clay platelets should have been exfoliated or completely disordered. However, the results from transmission electron microcopy confirmed that a mixture of partially exfoliated and intercalated structures presented in the nanocomposites. Dynamic mechanical thermal analysis testing indicated that the glass‐transition temperature of the polybutadiene phase and polystyrene phase moved to a lower temperature. Data of thermogravimetric analysis and testing of the mechanical properties showed that the thermal stability and mechanical properties of SBS‐g‐4‐BBPDMAEMA could be regulated by the crosslinking and content of MMT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Hierarchical porous carbon obtained using the template of NaOH-treated zeolite β and its high performance as supercapacitor

Alkaline-treated zeolite β (AT-β) has been taken as the template to prepare hierarchical porous carbons by a two-step casting process. The structures are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen sorption at 77 K and high-resolution transmission electron microcopy. The electrochemical performances of the supercapacitors tested by cyclic voltammetry and galvanostatic charge–discharge cycling are conducted in both aqueous and organic electrolytes. The carbon samples starting from AT-β (CN1 to CN3) exhibit higher capacitance retentions than the sample started from zeolite β (CN) due to the different pore structures. In aqueous electrolyte, CN2 presents the best electrochemical performance which could be attributed to the highest accessible specific surface area. In organic electrolyte, CN shows the highest capacitance at low scan rate (or current load) consisting with the highest pseudocapacitance contribution of C–O quinone type groups (O-I), pyrrolic/pyridone (N-5) and pyridinic (N-6).