Selected Area Electron Diffraction Analysis Research Articles

Enhanced Absorption and Photoemission from TiO2 Nanowire/Graphene Oxide Thin-Film Heterostructure

Vertically oriented TiO2 nanowires (NWs) have been fabricated on graphene oxide (GO) thin film (TF) using a catalytic free growth technique called glancing-angle deposition. GO TF was spin coated on Si substrate at different rotation speeds and the surface roughness measured by atomic force microscopy. Field-emission scanning electron microscopy confirmed formation of a heterostructure consisting of GO TF with thickness of ∼ 300 nm and TiO2 NWs with length of ∼ 800 nm. Selected-area electron diffraction analysis in transmission electron microscopy showed that the TiO2 NWs grown on the GO TF were amorphous in nature, as confirmed by x-ray diffraction analysis. A bandgap close to ∼ 4.1 eV was obtained for GO TF, whereas a main band transition edge at 3.3 eV was obtained for a TiO2 NW/GO TF heterostructure sample, related to TiO2. Two subband transitions at 2.9 eV and 2.4 eV were also observed for the heterostructure sample, corresponding to oxygen and Ti3+ defect transitions for the TiO2 NWs. Enhanced photoluminescence and absorption were observed for the heterostructure sample as compared with the GO TF sample.

Thermal nanosizing: Novel route to synthesize manganese oxide and zinc oxide nanoparticles simultaneously from spent Zn–C battery

Abstract Spent batteries are one of the fast-growing waste streams in electronic waste due to their low cost, maintenance and versatile applications. In this study, a novel thermal route, using spent waste battery is proposed for synthesis of manganese oxide (MnO) and zinc oxide (ZnO) nanoparticles simultaneously instead of metal separation approaches. Thermal transformation of zinc-carbon (Zn C) battery black mixture at 900 °C under argon atmosphere in horizontal quartz tube furnace facilitated the formation of ZnO nanoparticles, after condensation, leaving behind the MnO nanoparticle in the residue. MnO nanoparticles are known to be high capacity anode materials for lithium ion batteries. ZnO has wide band gap and can be used in sensor and electronics applications. Mechanism of MnO and ZnO nanoparticles formation from spent Zn C battery called “Thermal nanosizing”, is established. Characterization of spent Zn C battery was conducted and synthesized nanoparticles are confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and energy dispersive spectroscopy techniques. Morphological analysis was conducted by field emission scanning electron microscopy, transmission electron microscopy and selected area electron diffraction analysis. Both MnO and ZnO nanostructures were spherical shape and within 50 nm in size. “Thermal nanosizing” a novel route, proposed in this study could be a path breaking approach to synthesize MnO and ZnO nanoparticles simultaneously from spent battery and could represent an economic value for industries along with environmental benefits.

Impact of Different Morphological Structures on Physical Properties of Nanostructured SnSe

Nanostructured SnSe samples with specific morphologies like rods, rod-flowers, flakes, and flake-flowers were synthesized using the same reactants but with a control over various growth parameters involved in a hydrothermal reaction process. The morphology and detailed microstructure of the obtained samples have been studied by means of field-emission scanning electron microscopy (FE SEM) and high resolution transmission electron microscopy (HR-TEM). The sample quality, homogeneity, and phase purity have been thoroughly studied by selective area electron diffraction (SAED) and X-ray diffraction (XRD) analysis. Crystal structure study by refinement of powder XRD profiles using the least-squares fitting strategy indicates all samples to be pure single phase and provides its lattice parameters. The impact of changing morphology on the electrical, optical, and sensing properties of SnSe has been systematically evaluated. Temperature dependent electrical transport measurements highlight the increasingly 2D nat...

Low-energy ion beam synthesis of Ag endotaxial nanostructures in silicon

Coherently, embedded metal nanostructures (endotaxial) are known to have potential applications concerning the areas of plasmonics, optoelectronics and thermoelectronics. Incorporating appropriate concentrations of metal atoms into crystalline silicon is critical for these applications. Therefore, choosing proper dose of low-energy ions, instead of depositing thin film as a source of metal atoms, helps in avoiding surplus concentration of metal atoms that diffuses into the silicon crystal. In this work, 30 keV silver negative ions are implanted into a SiO x /Si(100) at two different fluences: 1 × 1015 and 2.5 × 1015 Ag− ions/cm2. Later, the samples are annealed at 700 °C for 1 h in Ar atmosphere. Embedded silver nanostructures have been characterized using planar and cross-sectional TEM (XTEM) analysis. Planar TEM analysis shows the formation of mostly rectangular silver nanostructures following the fourfold symmetry of the substrate. XTEM analysis confirms the formation of prism-shaped silver nanostructures embedded inside crystalline silicon. Endotaxial nature of the embedded crystals has been discussed using selected area electron diffraction analysis.

Investigation of Boron Containing AlN and AlGaN Layers Grown by MOVPE

In this work we investigate the epitaxial growth of boron containing (Al,Ga)N layers and superlattices for applications in the active region of UV‐LEDs. For AlBN layers containing 5% of boron as quantified by secondary ion mass spectrometry, columnar growth has been observed. Transmission electron microscopy (TEM) studies revealed B‐lean, crystalline columns, separated by highly boron containing amorphous intermediate regions. However, in the first few nanometers of AlBN growth, no evidence of columnar growth can be found. Indeed, first layers of AlBGaN/AlN superlattice stacks do not show any sign of columnar growth. However, for increasing thickness, 3D‐like growth develops through formation of pyramidal structures. TEM‐based selective area electron diffraction analysis does not show evidence of lattice tilting, proving that the observed inclined facets are not a result of lattice twinning. Thin AlBGaN layers with different thickness containing 1% boron show similar photoluminescence (PL) spectra with slightly reduced intensity as compared to similar B‐free AlGaN layers. Although small grainy structures develop and increase in density for AlBGaN layers with a thickness of 10 nm and more, the PL intensity increases steadily with layer thickness, showing that these grains do not drastically deteriorate their luminescence properties.

Investigation on improved performance of Erbium doped TiO2 nanowire based UV detector

Undoped TiO2 and Erbium doped TiO2 nanowires (Er:TiO2 NWs) were synthesized on respective thin films using e-beam cum glancing angle deposition technique onto n-type silicon substrates. The length of the NWs was ∼182 nm as calculated from field emission gun scanning electron microscopy images. Transmission electron microscopy showed an average NW length of 173 nm. Polycrystalline nature of both samples was obtained from the selected area electron diffraction analysis as well as from the X-ray diffraction (XRD) analysis. Energy dispersive X-ray spectroscopy and variation in the grain size (calculated from XRD) confirmed the doping of Erbium in case of Er:TiO2 NWs. Increased absorption, as well as enhanced bandgap, was observed for Er:TiO2 NWs compared to the undoped TiO2 NWs. Superior device performance in terms of detectivity, sensitivity and photoswitching was obtained for Er:TiO2 NWs as compared to the undoped TiO2 NWs in the UV region.

Single-Crystal Electrospun Plasmonic Perovskite Nanofibers

Hexagonal single-crystal perovskite-like (A3B8O21) nanofibers were synthesized via the electrospinning technique. High-resolution transmission electron microscopy imaging showed that each single nanofiber is composed of several interconnected small crystals. The selected-area electron diffraction analysis reveals a single crystalline nature of the fabricated nanofibers. The fabricated nanofibers showed surface plasmon resonance characteristics. Theoretical and computational calculations using the Mie–Gans theory were performed to investigate the plasmonic and optical properties of the obtained nanofibers, which were also confirmed experimentally and compared to gold nanoparticles. The fabricated nanofibers were tested as novel substrate materials for surface-enhanced Raman spectroscopy, showing exceptional performance.

Comparison of gold nanoparticles biosynthesized by cell-free extracts of Labrys, Trichosporon montevideense, and Aspergillus.

Biosynthesis of gold nanoparticles (AuNPs) by microbes has received much attention as an efficient and eco-friendly process. However, the characteristics of AuNPs biosynthesized by different microbial cell-free extracts are rarely comparatively studied. In this study, three locally isolated strains, i.e., bacteria Labrys sp. WJW, yeast Trichosporon montevideense WIN, and filamentous fungus Aspergillus sp. WL-Au, were selected for AuNPs biosynthesis. UV-Vis absorption bands at 538, 539, and 543nm confirmed the formation of AuNPs by these strains. Transmission electron microscopy and selected area electron diffraction analyses revealed that the as-synthesized AuNPs were crystalline with spherical or pseudo-spherical shapes. However, the average sizes of these AuNPs were diverse, which were 18.8, 22.2 and 9.5nm, respectively. The biomolecules involved in nanoparticles stabilization were demonstrated by Fourier transform infrared spectroscopy analysis. Four common functional groups such as -N-H, -C=C, -N=O, and -S=O groups were detected in these AuNPs, while a distinct -C=O group was involved in WL-Au-AuNPs. The catalytic rate of WL-Au-AuNPs toward 4-nitrophenol reduction (0.37min-1) was much higher than those of others (WJW-AuNPs 0.27min-1 and WIN-AuNPs 0.23min-1). This research would provide useful information for exploring efficient microbial candidates to synthesize AuNPs with excellent performances.

Melanin-Mediated Synthesis of Silver Nanoparticles and Their Affinity Towards Tyrosinase

The bacterial strain Pseudomonas sp. SSA has capacity to produce extracellular melanin that sequesters heavy metals. The brown-black melanin pigment was observed in the culture liquid and mediated synthesis of silver nanoparticles (AgNPs). The AgNPs were characterized using UV–visible, dynamic light scattering, energy dispersive X-ray, Fourier transform infrared and surface plasmon resonance spectroscopy, scanning electron and transmission electron microscopy and selected area electron diffraction analysis. The synthesized nanoparticles were found to be spherical in shape with size in the range of 14–30 nm and showed high antimicrobial activity against pathogenic bacteria and fungi. These nanoparticles revealed binding affinity towards fungal and human tyrosinases with KD 4.601 × 10–10 and 2.816 × 10–5 M, respectively. In addition, produced nanoparticles did not show any toxic effect towards HeLa cells up to 20 μg/mL. These nanoparticles could find application in medicine and cosmetics due to their enzyme inhibition and antimicrobial activities.

Eco-friendly synthesis of Solanum trilobatum extract-capped silver nanoparticles is compatible with good antimicrobial activities

This study focused on the evaluation of antimicrobial activity of silver nanoparticles (AgNPs) after their green synthesis by means of a Solanum trilobatum bark extract. The obtained product with an intense surface plasmon resonance band at ∼442 nm with UV–visible spectroscopic analysis indicated the formation of AgNPs. The morphology of AgNPs was observed under transmission electron microscopy and field emission scanning electron microscopy, displayed that the eco-friendly synthesized AgNPs have a spherical shape with an average size of ∼25 nm in diameter. X-ray powder diffraction and selected area electron diffraction analyses confirmed that the AgNPs are crystalline in nature. Fourier transform infrared spectroscopy indicated that the AgNPs capped with active ingredients of the bark extract. X-ray photoelectron spectroscopy revealed elemental composition of the AgNPs. The performance of S. trilobatum bark extract-capped AgNPs in terms of inhibition of microbial growth was studied by disc diffusion and well diffusion assays. Eco-friendly synthesized S. trilobatum extract-capped AgNPs were found to possess enhanced antimicrobial properties: growth inhibition of gram-negative and gram-positive bacteria and of fungal species. These results demonstrated the potential applications of the indigenous medicinal plants to the field of nanotechnology.

Mesoporous TiO2 spheres as a photoanodic material in dye-sensitized solar cells

Mesoporous TiO2 films with spherical architectures and promising performance in dye-sensitized solar cells (DSSCs) were prepared. The morphology of the films was investigated by scanning electron microscopy. Transmission electron microscopy analysis of the spheres disclosed the elongated shape of sub-20 nm primary particles, while BET analysis revealed their high surface area of 135m2/g. Anatase presence was observed in the films based on X-ray diffractometry, selected-area electron diffraction analysis and Raman spectroscopy analyses. Increased light scattering of the spheres in visible region was observed by UV-VIS-NIR spectroscopy. Photovoltaic performance of the operating N719-sensitized cells was tested using electrochemical impedance spectroscopy and current density-voltage (J-V) curves under simulated AM1.5 spectrum. The 0.25 cm2 cells exhibited photo-to-electric power efficiency of 4.9%, which is among noteworthy values for DSSCs with similar photoanodic structures.

Novel MOF shell-derived surface modification of Li-rich layered oxide cathode for enhanced lithium storage

Li-rich layered oxide materials have attracted increasing attention because of their high specific capacity (>250 mAh g−1). However, these materials typically suffer from poor cycling stability and low rate performance. Herein, we propose a facile and novel metal-organic-framework (MOF) shell-derived surface modification strategy to construct NiCo nanodots decorated (∼5 nm in diameter) carbon-confined Li1.2Mn0.54Ni0.13Co0.13O2 nanoparticles (LLO@C&NiCo). The MOF shell is firstly formed on the surface of as-prepared Li1.2Mn0.54Ni0.13Co0.13O2 nanoparticles via low-pressure vapor superassembly and then is in situ converted to the NiCo nanodots decorated carbon shell after subsequent controlled pyrolysis. The obtained LLO@C&NiCo cathode exhibits enhanced cycling and rate capability with a capacity retention of 95% after 100 cycles at 0.4 C and a high capacity of 159 mAh g−1 at 5 C, respectively, compared with those of LLO (75% and 105 mAh g−1). The electrochemical impedance spectroscopy and selected area electron diffraction analyses after cycling demonstrate that the thin C&NiCo shell can endow LLO with high electronic conductivity and structural stability, indicating the undesired formation of the spinel phase initiated from the particle surface is efficiently suppressed. Therefore, this presented strategy may open a new avenue on the design of high-performance electrode materials for energy storage.

Oxygen-assisted synthesis of hexagonal boron nitride films for graphene transistors

We grow high-quality two-dimensional hexagonal boron nitride (h-BN) films on copper pockets by chemical vapor deposition. A piece of sapphire embedded in the pocket serves as an oxygen supply during the growth process. To obtain clean h-BN films, source powders are placed in a U-shaped quartz tube and heated up in a water bath without the carrier-gas flow. These films are characterized by using SEM, Raman, XPS, and selected area electron diffraction analyses. As dielectric substrates, h-BN films significantly enhance the charge-carrier mobility of graphene transistors. This facile and robust method can be a scalable approach to synthesize large-area high-quality h-BN films for related electronic applications.

Structural and electrochemical properties of iron- and nickel-substituted Li2MnO3 cathodes in charged and discharged states

Structural change and the charge compensation mechanism of lithium-rich layered cathode (Li1.23Fe0.15Ni0.15Mn0.46O2) in charged and discharged states were investigated. Selected area electron diffraction analysis revealed that in discharged state, an initial structure composed of a single phase of monoclinic layered rock-salt changed to a mixture of hexagonal layered rock-salt and spinel-like structures. In charged state, the spinel-like phase became dominant as transition-metal ions migrate. 57Fe Mössbauer spectroscopy, X-ray absorption spectroscopy (XAS), and Soft-XAS showed that the valence of Fe and Ni ions approximately changed from Fe3+ to Fe3.2+ and Ni2+ to Ni3.5+ during charge-discharge, although Mn ions remained as Mn4+. Various oxidation states of oxide ions such as superoxide, peroxide, and hole states have also been detected in charged state. Considering that actual discharge capacity was 255 mAh/g, the contribution to charge compensation from the valence change of Fe and Ni ions was extremely small, and it only contributed to about one-third of total capacity. Therefore, the mechanism to yield high capacity of the Li1.23Fe0.15Ni0.15Mn0.46O2 cathode relates strongly to the redox reaction of oxide ions. Moreover, the decrease in capacity during charge-discharge cycling was mainly due to the irreversible redox reaction of Mn, Fe, and oxide ions.

Structural investigation of phase segregation in Mn2CrGa-based alloys

Alloys with nominal compositions of Mn2CrGa1-xAlx (x = 0.0, 0.2, 0.5, 1.0) have been studied by X-ray powder diffraction (XRD). Detailed structural investigation of the alloys with x = 0.2 and 0.5 has been further carried out using transmission electron microscopy (TEM). The alloys, in the typical Heusler composition, were prepared using rapid quenching and subsequent annealing. The XRD analysis revealed that a disordered cubic phase was present in the alloys with x = 0.0 and 1.0 while a spinodal decomposition with phase separation has been observed in the alloys with x = 0.2 and 0.5. TEM study confirms a segregation of two crystalline phases, one of them a cubic phase with the β–Mn prototype structure and the other a new crystalline phase with a tetragonal structure. Energy-dispersive X-ray spectroscopy (EDS) analysis was used to determine the compositions of the two crystalline phases. The mass ratio of the tetragonal phase and the β–Mn prototype cubic phase is derived as t/c ≈ 2.41 by fitting the average compositions of the two crystalline phases to the nominal composition. The orientational relationship of two crystalline structures has been determined by selected-area electron diffraction (SAED) and stereogram analysis. The structures of the two crystalline phases have been investigated by high-resolution transmission electron microscopy (HRTEM) and image simulation. The structural model of the tetragonal phase is proposed and compared with the experimental results in SAED and HRTEM studies.

Conducting π-Conjugated Bis(iminothiolato)nickel Nanosheet

A π-conjugated coordination nanosheet (CONASH) comprising bis(iminothiolato)nickel moieties, NiIT, was synthesized by a reaction of Ni2+ with 1,3,5-triaminobenzene-2,4,6-trithiol (L) in the presence of ferrocenium ions. A bulk material, bulk-NiIT, prepared in a homogeneous solution was characterized by XPS, IR, and SEM. A liquid–liquid interfacial reaction using bis(2,4-pentanedionato)nickel(II) in CH2Cl2 and L in H2O afforded a semiconducting nanosheet, nano-NiIT. AFM, SEM, and TEM observation of nano-NiIT revealed the uniform and flat nature of a stacked layer nanosheet. Selected-area electron diffraction (SAED) analysis indicated the formation of a two-dimensional hexagonal crystal structure.

Laser irradiation of iron, cobalt, and nickel targets in liquid nitrogen: A facile approach for nitride nanoparticle fabrication of ferromagnetic transition metals

Nitride nanoparticles of ferromagnetic metal elements were produced by laser irradiation from metallic targets immersed in liquid nitrogen using Nd:YAG lasers with wavelengths of 532 and 1024 nm. Transmission electron microscopy analyses of the precipitated nanoparticles from the suspensions on microscopy grids reveal agglomerates consisting of polydisperse particles with sizes in the tens of nanometers range. Some particles with size of several hundreds of nanometers indicate that laser irradiation promotes cryoablation together with plasma erosion of the targets. Selected area electron diffraction analyses corroborated by Raman measurements indicate the formation of crystalline metal nitrides with spheroidal and acicular morphologies. Regardless of the laser radiation wavelength, nanoparticles with similar nitride phases are found: Fe4N and Fe16N2 for Fe target, Co2N and Co3N for Co target, Ni4N with Ni8N for Ni target. All nanoparticles show superparamagnetic-like behavior with a blocking temperature varying significantly with the nanoparticle size. Such single-step method is a promising green route for nanoparticle production of these metal nitrides, which are commonly obtained using more complex and multi-step processes.

Complex and Hierarchical 2D Assemblies via Crystallization-Driven Self-Assembly of Poly(l-lactide) Homopolymers with Charged Termini.

Poly(l-lactide) (PLLA)-based nanoparticles have attracted much attention with respect to applications in drug delivery and nanomedicine as a result of their biocompatibility and biodegradability. Nevertheless, the ability to prepare PLLA assemblies with well-defined shape and dimensions is limited and represents a key challenge. Herein we report access to a series of monodisperse complex and hierarchical colloidally stable 2D structures based on PLLA cores using the seeded growth, "living-crystallization-driven self-assembly" method. Specifically, we describe the formation of diamond-shaped platelet micelles and concentric "patchy" block co-micelles by using seeds of the charge-terminated homopolymer PLLA24[PPh2Me]I to initiate the sequential growth of either additional PLLA24[PPh2Me]I or a crystallizable blend of the latter with the block copolymer PLLA42-b-P2VP240, respectively. The epitaxial nature of the growth processes used for the creation of the 2D block co-micelles was confirmed by selected area electron diffraction analysis. Cross-linking of the P2VP corona of the peripheral block in the 2D block co-micelles using Pt nanoparticles followed by dissolution of the interior region in good solvent for PLLA led to the formation of novel, hollow diamond-shaped assemblies. We also demonstrate that, in contrast to the aforementioned results, seeded growth of the unsymmetrical PLLA BCPs PLLA42-b-P2VP240 or PLLA20-b-PAGE80 alone from 2D platelets leads to the formation of diamond-fiber hybrid structures.

Simple green production of silver nanoparticles facilitated by bacterial genomic DNA and their antibacterial activity

Green synthesis of AgNPs has gained many research interests as a low cost and eco-friendly approach. This work reported on the use of bacterial genomic DNA as the alternative biopolymer for a green production of AgNPs under a neutral pH. Although both ssDNA and dsDNA could function as stabilizing agents during the synthesis process, the ssDNA, generated by pre-heating the dsDNA at 100 °C, was more efficient to produce AgNPs with higher yield as determined by the intensity of the surface plasmon resonance (SPR) peak of silver at 475 nm. The obtained AgNPs were spherical with the average diameter of 15.0 ± 7.6 nm, which their identity was confirmed by X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction analyses. The synthesized AgNPs exhibited the potent antibacterial activity against both Escherichia coli and Staphylococcus aureus with the minimum bactericidal concentrations at 250 and 500 μg/ml, respectively, suggesting their potential antibacterial activity against both Gram-negative and Gram-positive bacteria.

Biosynthesis, Characterization and Antibacterial Efficacy of Silver Nanoparticles Derived from Endophytic Fungi against P. gingivalis.

Microbial resistance to existing antimicrobial agents in periodontal therapy is a growing problem. Therefore, there is a need for development of new antimicrobial agents. To biosynthesize and characterize Silver Nanoparticles (AgNPs) using endophytic fungi and to evaluate the antibacterial efficacy against P. gingivalis. Cut leaf segments of Withania Somnifera (Ashwagandha) were used to isolate the fungi. Fresh cultures of fungi were inoculated in Erlenmeyer flask of 100 ml Malt Glucose Yeast Peptone (MGYP) broth and incubated at 29°C for 72 hours for the biomass to grow. Biomass was filtered and cell free fungal filtrate was used further. Biosynthesized AgNPs were characterized by visual observation, Ultraviolet-Visible (UV-Vis) spectrophotometer, Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction Analysis (SAED) and Fourier Transform Infrared Spectroscopy (FTIR). Antibacterial efficacy was evaluated by agar diffusion method measuring the zone of inhibition. The study groups included different concentrations of AgNPs: A (20 μl), B (40 μl), C (60 μl), D (80 μl) and E (100 μl) of AgNPs, F (0.2% CHX), G (2% CHX), H (Ampicillin) and I (sterile distilled water). The data collected for inhibition zones were statistically analysed using One-way Anova followed by Tukey post-hoc multiple comparison tests. The fungi were identified as Fusarium semitectum. Characterization studies showed the colour change from colourless to reddish brown; U-V spectrum showed peak 420 nm, TEM revealed the particles spherical in shape and 10-20 nm in size. FTIR analysis revealed the presence of functional groups. AgNPs 80 μl and 100 μl showed mean zone of inhibition 17.33 and 18 mm against P. gingivalis. CHX (0.2%) 17.85 and CHX (2%) 19.97 mm, Ampicillin 20.5 mm and no zone for sterile distilled water. Biosynthesized AgNPs showed efficient antibacterial efficacy against P. gingivalis hence, creates a new horizon in periodontal therapy.