High-resolution Electron Micrographs Research Articles

Structural features of Qingdao petroleum coke from HRTEM lattice fringes: Distributions of length, orientation, stacking, curvature, and a large-scale image-guided 3D atomistic representation

Structural features of a green Qingdao petroleum coke (produced at ∼ 500 °C) were investigated by image analysis of high-resolution transmission electron micrographs, XRD, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). The fringe length distribution was comprised mostly of fringes <20 Å, with a peak at 5–7 Å. The MALDI-TOF MS data also indicated an abundance of low molecular weight material 250–300 Da. The coke had considerable preferential orientation within the field of view of the micrograph. However, the degree of ordering was poor with fringe stacking occurring for ∼20% for the fringes, with a mean of 2.11 fringes. XRD also indicated low ordering as expected for a lower quality, low temperature coke. The poor nanostructure-level order was a result of small fringe lengths, with curvature (present in 42% of the fringe) likely contributing. It is thus a partially ordered system, with order varying over length scales. An image-guided construction strategy capable of controlling the degree of order (utilizing Fringe3D and Vol3D) was used to construct an atomistic structural representation (C3717H1830N54O134S109) incorporating many experimental parameters. The structure was comprised of preferentially orientated molecules, but with the observed limited stacking, incorporating both curvature frequency and extent.

Pollen morphology of extant Winteraceae: a study allowing SEM-based affiliation of its fossil representatives

AbstractWhen applying high-resolution microscopy, the pollen morphology of extant taxa can be used to classify fossil pollen, that is, to address the latter in the established systematic-phylogenetic framework. Here we investigate tetrads and pollen features of 20 different Winteraceae species, most of them belonging to the early-diverging generic lineagesTasmannia,DrimysandPseudowintera. The tetrads and pollen are grouped into eleven pollen types based on diagnostic features observed by both light and scanning electron microscopy. The high-resolution scanning electron micrographs of recent material allow detailed comparison with fossil material, resulting in a more accurate affiliation of fossil tetrads/pollen to extant lineages. As a case study, early Miocene Winteraceae tetrads from South Africa are re-examined and formally described. The systematic placement of the African fossils is discussed in light of the pollen types presented here.

Bimetallic PdRu/graphene oxide based Catalysts for one-pot three-component synthesis of 2-amino-4H-chromene derivatives

Addressed herein, palladium–ruthenium nanoparticles decorated on graphene oxide (PdRu@GO) has been developed by using ultrasonic double solvent reduction method and efficiently used as a recyclable heterogeneous catalyst for the synthesis of 2-amino-4H-chromene derivatives by one-pot multi-component reaction (condensation) of resorcinol (1), malononitrile (2), and various aromatic aldehydes (3a-n). An advantageous of this method is that the prepared nanocatalyst PdRu@GO can be handily separated and used several times for subsequent runs without any significant decrease of catalytic performance even after 5th cycles. This highly stable and uniformly dispersed bimetallic catalyst has been utilized as novel, highly efficient, easy usage, long lived and isolable catalyst for the synthesis of 2-amino-4H-chromene derivatives from resorcinol, aromatic aldehydes and malononitrile with excellent durability and great catalytic performance. The structure morphology and properties of PdRu@GO nanoclusters were fully characterized by using diverse techniques such as, transmission electron microscopy (TEM), the high resolution electron micrograph (HRTEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) methods. The obtained PdRu@GO nanoparticles have been found to be one of the highest efficient and recyclable heterogeneous catalysts for the synthesis of 2-amino-4H-chromene derivatives with all the combination of these advantageous.

Zn-doped SnO2 nanostructures: structural, morphological and spectroscopic properties

SnO2 is a promising material for optoelectronic, catalytic and sensing applications and is highly sensitive to the small amount of impurities that can change its properties drastically. In the present work, co-precipitation method was employed to synthesize pure and Zn-doped SnO2nanostructures. The effect of Zn doping (1, 3 and 5% molar ratio) on crystallographic and spectroscopic properties of SnO2 nanostructures has been studied. The X-ray diffraction results revealed that SnO2 possesses tetragonal rutile crystal structure with predominant (110) plane and the same structure was retained after doping with Zn. Raman shifts also confirmed the typical feature of the tetragonal rutile phase in all samples. Fourier transform infrared spectra revealed stretching mode of Sn–O bond and vibrational mode of O–Sn–O bond complementing the Raman spectroscopy results. Field emission scanning electron micrographs confirmed the variation in morphology of synthesized samples with Zn-dopant concentration. High-resolution transmission electron micrographs showed that the synthesized nanostructures were nearly spherical and average particle size varies between ~20–26 nm. UV–Visible results revealed that the band gap of the synthesized SnO2 nanoparticles increased with increase in Zn content. Photoluminescence spectroscopic results showed that emission intensity increased with increase in Zn content. The increased intensity of emission peaks may be ascribed to the development of defect states in the band gap of Zn-doped SnO2 nanoparticles.

Self-optimization of plasmonic nanoantennas in strong femtosecond fields

Plasmonic dimer nanoantennas can significantly boost the electric field strength in the gap region, allowing for a modification of the feed gap geometry by femtosecond laser illumination. Using resonant bowtie antennas to enhance the electric field of a low-fluence femtosecond oscillator, here we experimentally demonstrate highly localized reshaping of the antennas, resulting in a self-optimization of the antenna shape. From high-resolution scanning electron micrographs and two-dimensional energy dispersive x-ray maps, we analyze the near-field enhanced subwavelength ablation at the nanotips and the resulting deposition of ablated materials in the feed gap. The dominant ablation mechanism is attributed to the nonthermal transient unbonding of atoms and electrostatic acceleration of ions. This process is driven by surface plasmon enhanced electron emission, with subsequent acceleration in the vacuum. This ablation is impeded in the presence of an ambient gas. A maximum of sixfold enhancement of the third-harmonic yield is observed during the reshaping process.

Microwave Assisted Synthesis of Palladium Nanoparticles in an Aqueous Emulsion of Copolymer: Application to Catalysis

Palladium nanoparticles were prepared in a few minutes using polyol assisted-microwave process. This synthesis based on the reduction of metal salt (k2PdCl4) in ethylene glycol medium in presence of an aqueous emulsion of copolymers (latex) as a reducing and stabilizer agent. The products were characterized by UV–Vis spectroscopy infrared spectroscopy transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, selected area electron diffraction patterns, and high-resolution transmission electron micrographs. We have found spherical homogeneous Pd nanoparticles with narrow particles size distributions. In addition, we used Pd-latex-EG nanofluid emulsion for catalyzing organic reactions including Suzuki, Heck and the Sonogashira reactions. As a result, we have successfully demonstrated the crucial effect of latex copolymer for reducing and capping Pd nanoparticle. We point out that the presence of the polymer molecules don’t affect the catalytic effect which mainly due to the Pd metallic nanoparticles.

One-pot three-component synthesis of 2-Amino-4H-Chromene derivatives by using monodisperse Pd nanomaterials anchored graphene oxide as highly efficient and recyclable catalyst

An efficient and environmentally benign method has been developed for the synthesis of 2-amino-4H-chromene derivatives via one-pot multi component condensation of resorcinol (1), malononitrile (2), and various aromatic aldehydes (3a–j), using highly monodisperse palladium nanoparticles supported with graphene oxide (Pd@GO) as a heterogeneous catalyst. An advantageous of this method is that monodisperse Pd@GO nanoparticles can be easily separated and reused several times for further runs. This highly stable and monodisperse catalyst has been used for the first time as highly efficient, long lived and isolable catalyst for the synthesis of 2-amino-4H-chromene derivatives from resorcinol, aromatic aldehydes and malononitrile with great catalytic performance and easy work-up procedure. The structure and morphology of synthesized catalyst were characterized by using different techniques such as, transmission electron microscopy (TEM), the high resolution electron micrograph (HRTEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The highly crystalline, colloidally stable and highly monodisperse Pd@GO formation were shown by using these techniques. Besides, the Pd@GO has been found to be highly efficient and recyclable heterogeneous catalyst for the synthesis of 2-amino-4H-chromene derivatives.

Controlled Growth, Microstructure, and Properties of Functional Si Quantum Dot Films via Plasma Chemistry and Activated Radicals

Control of plasma and radical generation and associated energy deposition near the growing thin films are still the main challenges in materials fabrication in the plasma-assisted deposition of Si quantum dot (QD) thin film. To control and enhance the material’s performance concerning film properties and application durability, we prepare 2.6 nm sized Si QDs with a fully ordered structure and entrapped them in amorphous silicon nitride using advanced dual frequency capacitively coupled plasmas. Raman and XRD analyses consistent with the high-resolution transmission electron micrographs reveal that the QD size can be controlled and altered from ∼2.6 to 4.0 nm simply by changing the operating pressure, which affects the film’s crystallinity in a broad range from 60% to 72% and the resulting microstructure. Further, a broad visible range ∼ 1.8–3.0 eV photoluminescence, with intense intensity and narrow to broad widths, is observed from Si QDs films. It is also seen that the observed photoluminescence feature...

Inorganic fullerene-type WS2 nanoparticles: processing, characterization and its photocatalytic performance on malachite green

In this work, we have employed a hydrothermal route for the synthesis of fullerene-type tungsten disulfide (WS2) nanoparticles. X-ray diffraction analysis signifies a hexagonal crystal structure of WS2 with the crystallites experiencing preferred orientations along (002) and (103) planes. The agglomerated nanoparticles and inorganic fullerene (IF)-type structures are apparently observable from the high-resolution electron micrographs. Raman spectrum shows prominent $$ E^{1}_{{2{\text{g}}}} $$ and A 1g modes emanating from the IF nano-WS2 system. The Tauc’s plot obtained from the optical absorption data predicts a direct band gap of ~1.91 eV for the nano-WS2 system; whereas, photoluminescence analysis reveals a broad emission peak located at ~638 nm and is ascribed to the associated transition from the indirect to direct nature of the band gap. The photocatalytic decomposition of malachite green (MG) solution (30 mg/l) by WS2 (100 mg/l) under UV and visible light irradiation has been evaluated. The latter condition exhibited a better photocatalytic response with the MG degradation as high as 71.2%, revealed for 120 min. Photocatalytic and optoelectronic features of IF-type nano-WS2 would bring new insights not only to resolve issues related to environmental hazards, but also in functional devices of technological relevance.

Formation of giant atomic clusters in the β-Samson (β-Al3Mg2) phase of the Al-Mg alloy system

The crystallographic features of the (α-Mn → α-Mn + β-Samson) reaction in Al-Mg alloys around the composition of 48 at.% Mg have been investigated mainly by transmission electron microscopy to understand the formation of giant atomic clusters in the β-Samson structure. It was confirmed, for instance, that the state of an Al-48 at.% Mg alloy annealed at 573 K for 24 h could be identified as the (α-Mn + β-Samson) coexistence state, and that metastable states were found locally in α-Mn/β-Samson boundary regions. An analysis of electron diffraction patterns obtained from the coexistence state indicated that the orientation relationship of (3¯ 30)α//(8¯ 80)β-S and [110]α//[110]β-S was established between α-Mn and β-Samson regions, together with a lattice contraction of about 10% along the [001]α direction and an expansion of about 0.4% along the [1¯ 10]α direction in the (α-Mn → β-Samson) structural change. High-resolution electron micrographs of the coexistence state also suggested that some atoms at the Mg (I) and Mg (II) sites in the distorted α-Mn structure could be converted to those at the Mg (23) site of the β-Samson structure as the center site of the Samson cluster. Furthermore, both the features of giant clusters in the β-Samson structure and their formation from the α-Mn structure were discussed on the basis of the experimental data obtained in this study.

Structural characterization of niobium oxide thin films grown on SrTiO3 (111) and (La,Sr)(Al,Ta)O3 (111) substrates

Niobium oxide thin films have been grown by molecular beam epitaxy on SrTiO3 (STO) (111) and (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT) (111) substrates. Transmission electron microscopy (TEM) confirmed the formation of high quality films with coherent interfaces. Films grown with higher oxygen pressure on STO (111) resulted in a (110)-oriented NbO2 phase with a distorted rutile structure, which can be described as body-centered tetragonal. The a lattice parameter of NbO2 was determined to be ∼13.8 Å in good agreement with neutron diffraction results published in the literature. Films grown on LSAT (111) at lower oxygen pressure produced the NbO phase with a defective rock salt cubic structure. The NbO lattice parameter was determined to be a ≈ 4.26 Å. The film phase/structure identification from TEM was in good agreement with in situ x-ray photoelectron spectroscopy measurements that confirmed the dioxide and monoxide phases, respectively. The atomic structure of the NbO2/STO and NbO/LSAT interfaces was determined based on comparisons between high-resolution electron micrographs and image simulations.

Environmental benignity of a pesticide in soft colloidal hydrodispersive nanometric form with improved toxic precision towards the target organisms than non-target organisms

Mosquito-borne diseases are of major concern as they cause devastating health effects, morbidity, and mortality in the human population. Conventional pesticides have failed to curb the mosquito population due to the development of insensitivity in mosquitoes. Hence, higher dosages of pesticides along with their toxic solubilizers have been employed, which have led to raise in pesticide pollution load, environmental toxicity, and human health concerns. As a realisation for the requirement of alternative pesticides, the present study has involved in the formulation of a hydrodispersive nanometric colloidal form of deltamethrin (NDM), a type-II pyrethroid pesticide, from its hydroimmisicible parental form (PDM). The mean hydrodynamic diameter of the droplets was found to be 30.6±4.6nm by dynamic light scattering study (DLS). High-resolution transmission electron micrographs have revealed the spherical structure of the droplets with a size range of 35–40nm. The NDM was found to possess sedimentation resistance, intrinsic and hydrodispersive stability. The toxicity of NDM and PDM was comparatively investigated on target organisms (Culex tritaeniorhynchus and Culex quinquefasciatus mosquitoes) and non-target organisms (Allium cepa – Bioindicator of toxicants and Rhizobium sp. – Soil bacteria). As comparative to PDM, NDM has exerted higher efficacy on adult mosquito and larval population, even at low-level concentrations. However, in the case of non-target organisms, the NDM toxicity was lower than PDM. Comprehensively, the study has concluded the potential advantage of formulating conventional pesticides into nanometric soft colloidal form for the improved toxic precision on target organisms (mosquitoes). This ensures the ability of NDM to combat against the mosquito population even at lower concentrations, thereby reducing the pesticide exposure load towards the environment and human population.

Microstructure and Creep Properties of Silicon- and/or Germanium-Bearing Near-α Titanium Alloys

The effects of Si and/or Ge addition on the microstructure and creep properties at 650°C and 137 MPa were investigated in near-α Ti–Al–Sn–Zr–Mo alloys. Si and/or Ge addition decreased the minimum creep strain rate owing to the solid solution of Si and Ge in the matrix and the precipitation of silicide, germanide, and their solid solutions. The decrease in the minimum creep strain rate in the alloy with 1 wt% Ge without Si was the most significant because of the formation of very fine germanide precipitates. In addition, a marked shift in the lattice parameters of the α and β phases was detected for the alloy with 4 wt% Ge. The Moiré fringe patterns at the α/β interfaces in the alloys were investigated using high-resolution transmission electron micrographs to discuss the alloying effect on the structure of the interfaces.

Patterns and distribution of presynaptic and postsynaptic elements within serial electron microscopic reconstructions of neuronal arbors from the medicinal leech Hirudo verbana.

Microscale connectomics involves the large-scale acquisition of high-resolution serial electron micrographs from which neuronal arbors can be reconstructed and synapses can be detected. In addition to connectivity information, these data sets are also rich with structural information, including vesicle types, number of postsynaptic partners at a given presynaptic site, and spatial distribution of synaptic inputs and outputs. This study uses serial block-face scanning electron microscopy (EM) to collect two volumes of serial EM data from ganglia of the medicinal leech. For the first volume, we sampled a small fraction of the neuropil belonging to an adult ganglion. From this data set we measured the proportion of arbors that contained vesicles and the types of vesicles contained and developed criteria to identify synapses and to measure the number of apparent postsynaptic partners in apposition to presynaptic boutons. For the second data set, we sampled an entire juvenile ganglion, which included the somata and arbors of all the neurons. We used this data set to placd our findings from mature tissue in the context of fully reconstructed arbors and to explore the spatial distribution of synaptic inputs and outputs on these arbors. We observed that some neurons segregated their arbors into input only and mixed input/output zones, that other neurons contained exclusively mixed input/output zones, and that still others contained only input zones. These results provide the groundwork for future behavioral studies. J. Comp. Neurol. 524:3677-3695, 2016. © 2016 Wiley Periodicals, Inc.

Charge Transfer States in Dilute Donor-Acceptor Blend Organic Heterojunctions.

We study the charge transfer (CT) states in small-molecule blend heterojunctions comprising the nonpolar donor, tetraphenyldibenzoperiflanthene (DBP), and the acceptor, C70, using electroluminescence and steady-state and time-resolved photoluminescence spectroscopy along with density functional theory calculations. We find that the CT exciton energy blue shifts as the C70 concentration in the blend is either decreased or increased away from 50 vol %. At 20 K, the increase in CT state lifetime is correlated with the increasing diameter of C70 nanocrystallites in the blends. A quantum confinement model is used to quantitatively describe the dependence of both CT energy and lifetime on the C70 or DBP domain size. Two discrete CT emission peaks are observed for blends whose C70 concentration is >65%, at which point C70 nanocrystallites with diameters >4 nm appear in high-resolution transmission electron micrographs. The presence of two CT states is attributed to coexistence of crystalline C70 and amorphous phases in the blends. Furthermore, analysis of CT dissociation efficiency versus photon energy suggests that the >90% dissociation efficiency of delocalized CT2 states from the crystalline phase significantly contributes to surprisingly efficient photogeneration in highly dilute (>80% C70) DBP/C70 heterojunctions.

Growth of L1-ordered crystal in FePt and FePd thin films on MgO(001) substrate

Formation of L10-oredered structure from disordered A1 phase has been investigated for FePt and FePd films on MgO(001) substrates employing a two-step method consisting of low temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. L10-(001) variant crystal with the c-axis perpendicular to the substrate grows preferentially in FePd films whereas L10-(100), (010) variants tend to be mixed with the L10-(001) variant in FePt films. The structure analysis by X-ray diffraction indicates that a difference in A1 lattice strain is the influential factor that determines the resulting L10-variant structure in ordered thin films. Misfit dislocations and anti-phase boundaries are observed in high-resolution transmission electron micrographs of 10 nm-thick Fe(Pt, Pd) film consisting of L10-(001) variants which are formed through atomic diffusion at 600 °C in a laterally strained FePt/PeFd epitaxial thin film. Based on the experimental results, a nucleation and growth model for explaining L10-variant formation is proposed, which suggests a possibility in tailoring the L10 variant structure in ordered magnetic thin films by controlling the alloy composition, the layer structure, and the substrate material.

Superior Monodisperse CNT‐Supported CoPd (CoPd@CNT) Nanoparticles for Selective Reduction of Nitro Compounds to Primary Amines with NaBH4 in Aqueous Medium

AbstractSuperior carbon nanotube furnished CoPd (CoPd@CNT) nanoparticles (NPs) were reproducibly and easily produced by sonochemical double solvent reduction method in a mild condition and the size of the CoPd NPs was found as 3.63 nm. The prepared novel catalyst were characterized by transmission electron microscopy (TEM), the high resolution electron micrograph (HRTEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The sum of their results showed the formation of highly crystalline, monodisperse and colloidally stable CoPd@CNT. The catalytic performance of these novel NPs were investigated for the first time for highly selective reduction to –NO2 unlike –CN groups, in which they were found to be exceptional reusable, isolable, stable and highly efficient heterogeneous catalyst. All prepared products were obtained with perfect yield by using CoPd@CNT as a heterogeneous catalyst and NaBH4 as a hydrogen source. Our synthesis process provides a facile and eco‐friendly route to CoPd@CNT, allowing further investigation of current catalysts for many other chemical reactions.

Features of noise in ultrathin gold nanowire structures

Bundles of ultrathin gold nanowires (Au NWs, 2 nm in diameter) were fabricated and subsequently assembled onto electrodes. Electrical measurements and noise spectroscopy techniques were applied for sample characterization. The peculiarities of noise behavior in the system of bundles of ultrathin gold nanowires were studied. The measured power spectral density of flicker noise was proportional to current squared, which reflects ohmic behavior in NW structures. Lorentzian-shaped components were revealed in the noise spectra. They are suggested to be the result of the participation of molecules adsorbed on the NW surface in transport phenomena. The presence of molecular interfaces was confirmed by high-resolution transmission electron micrographs. The adsorbed molecules play an important role in charge transport and therefore determine electrical and noise properties of the NW structures. The results should be taken into account for the development of NW devices for sensing and molecular electronics applications.

Highly Efficient and Monodisperse Graphene Oxide Furnished Ru/Pd Nanoparticles for the Dehalogenation of Aryl Halides via Ammonia Borane

AbstractHighly monodisperse graphene oxide‐supported Ru/Pd nanoparticles (RuPd@GO NPs) have been reproducibly and easily synthesized by microwave assisted method. RuPd@GO NPs was performed for dehalogenation of arylhalides in the presence of ammonia borane in a mild condition as novel, highly efficient and exceptional reusable heterogeneous catalyst. The novel materials were characterized by transmission electron microscopy (TEM), the high resolution electron micrograph (HRTEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The results showed that the prepared catalysts are highly crystalline, monodisperse and colloidally stable. The current one‐pot catalytic process was described as a new methodology for dehalogenation of arylhalides which can be assessed as a quite simple, eco‐friendly and highly efficient as well as exceptional reusable. All products were provided with one of the highest yield and the shortest time in the presence of novel RuPd@GO NPs due to the the synergistic effect of Ru and Pd. Our synthesis process comes with a facile and eco‐friendly option to RuPd@GO NPs, allowing further scrutiny of current catalysts for numerous other chemical reactions.

Resistive switching characteristics of a single Zn-doped CuS nanoball anchored with multi-walled carbon nanotubes

We report a new synthesis method to grow Zn-doped CuS (CZS) nanoballs on multi-walled carbon nanotube (MWCNT) surfaces from a single molecular source [Cu(en)2ZnCl4]·DMSO complex. The single precursor acts as the source for both Cu+2 and Zn+2 ions for the formation of nanocrystalline balls. High resolution electron micrographs clearly revealed the formation of crystalline CZS nanoballs on the surface of MWCNT. The chemical composition and local bonding of CZS have been examined by XPS and UPS analysis. A current-voltage (I-V) characteristic on single CZS nanoballs was carried out using conducting probe atomic force microscopy (C-AFM). A clear hysteresis in I-V characteristics demonstrated the bipolar resistive switching in the nanoballs anchored with MWCNTs at low set and reset voltages. The study reveals a novel technique to grow doped semiconductor nanocrystal for its application in resistive switching memory devices.