Selected Area Electron Diffraction Studies Research Articles

Synthesis of copper-reduced graphene oxide nanomaterials using glucose and study of its antibacterial and anticancer activities.

In this work, glucose-capped copper nanoparticles decorated reduced graphene oxide nanomaterial are synthesized at 100°C and 200°C via chemical reduction method and studied for their antibacterial and anticancer activities. Synthesized nanomaterials were characterized using X-ray Diffraction, Fourier-transform infrared, Transmission Electron Microscope, and RAMAN. It is observed in Transmission electron microscopy and Selected area electron diffraction studies that copper nanoparticles deposited onto reduced graphene oxide are smaller than nanoparticles generated in the absence of reduced graphene oxide. Also, the size of copper nanoparticles synthesized at 200°C is smaller than at 100°C. Results suggest that Cu/Glu/rGO synthesized at both temperatures showed significant antibacterial activity against Escherichia coli and Bacillus anthracis, similarly, showed significant cell death in cancer cell lines [Cal33 and HCT-116 p53 (+/+)]. Interestingly, the nanomaterials were seen to be more effective against the cancer cell lines harboring aggregating mutant p53. Tumors with aggregating mutants of p53 are difficult to treat hence, Cu/Glu/rGO can be promising therapeutic agents against these difficult cancers. However, the antibacterial and anticancer activity of Cu/Glu/rGO synthesized at 100°C where Cu2O form is obtained was found to be more effective compared to Cu/Glu/rGO synthesized at 200°C where Cu form is obtained. Though fine-tuning of the material may be required for its commercial applications.

The influence of temperature on structural and third order nonlinear properties of cadmium sulfide nanoparticle films prepared by chemical reaction method

In this work Cadmium sulfide nanoparticles)CdS-NPs(was deposited on glass substrates using a polymerassisted chemical reaction method (CRM) and annealed at different temperatures, 300∘C, 400∘Cand 500∘C. The structural and optical characteristics of CdS-NPs films were investigated using X-ray diffraction (XRD), FTIR analysis, UV–Vis absorption spectroscopy and scanning electron microscopy (SEM). X-ray diffraction (XRD) and selected area electron diffraction studies confirmed the formation of nanocrystalline cubic phase of CdS in the films. The calculation shows that the CdS crystallized in cubic phase and formed NPs with average crystallite sizes of 17.2, 20.1 and 23.3 nm and the microstrain is about 0.034, 0.030 and 0.026 for CdS films annealed at 300∘C, 400∘C and 500∘C. The UV–Vis spectrophotometer measurements showed that the films were highly transparent value of 97 % at annealing temperature of 300∘Cand 400∘C. The direct allowed bandgaps have been determined and they lie in the range 2.49 -205 eV for CdS-NPs film annealed at temperatures of 300 ∘C–500∘C. The thermal non-linear refractive indices (n2) of the CdS-NPs are determined using open and closed aperture Z-scan techniques. The optical limiting (OL) behaviours have been studied. It was shown that the OL efficiency depended on the CdS-NPs temperature. Under laser irradiation, self-diffraction rings were seen in CdS-NPs-300∘C, CdS-NPs-400∘C and CdS-NPs-500∘C. With increased input power, each pattern is created by a rise in the number of rings and the diameter of the outermost ring. The aim of the current project studies is to investigate the linear and nonlinear optical characteristics to find fresh applications for CdS-NPs in the world of optical modulators.

Deformation and failure behavior of nanocrystalline WCu

The technical potential of WCu alloys is limited by the modest fracture characteristics of the material system in its coarse-grained condition. To provide a nanocrystalline microstructure and improve mechanical properties, a W-50 at.% Cu composite was processed using high-pressure torsion deformation at a temperature of 200 °C. Therefore, two specimens were subjected to 100% and 1000% shear strains, respectively. Scanning electron and scanning transmission electron microscopy, including nanoscale energy dispersive X-ray spectroscopy mappings, were used to quantify the resulting microstructures. The average grain sizes for the 100% and 1000% deformed specimens were determined to be 14.7 ± 6.6 nm and 10.5 ± 5.6 nm, with the amount of mechanically intermixed W in the Cu grains increasing from 15.4 at.% to 15.9 at.%. X-ray diffraction and selected area electron diffraction studies both revealed strained lattice parameters of the W and Cu phases, respectively. Mechanical properties were investigated using in-situ notched microcantilever tests. The mean conditional fracture toughness and J-integral values were comparable for both conditions, at 3.7 ± 0.4 MPa√m and 245 ± 58 J/m2, respectively. The related behavior could be attributed to the low fault tolerance of the highly deformed states and was substantiated by cleaved globular W grains along the fractured surfaces. In addition, the detailed relationship between the altered grain boundary conditions, the degree of mechanical intermixing and the influence of the different microstructures on the fracture properties were carefully evaluated and discussed to pave the way for future application of these high-strength nanocomposites.

Hydrothermal Synthesis of Cu0.66‐xZn0.34+xSe Materials and Investigation of Their Structural, Optical, and Magnetic Properties

AbstractIn the current paper, we have prepared Cu0.66‐xZn0.34+xSe materials by varying the concentration of copper and zinc (x=0, 0.085, 0.17, 0.255, 0.34) with the help of a facile one‐step hydrothermal method. The X‐ray diffraction study reveals that the as‐prepared nanomaterials show the polycrystalline property. The crystallinity increases with the variation of Zn concentration, and the average crystallite size was calculated in the 39 to 55 nm range. The morphological analysis shows the uniform and agglomerated particles having an average size of around 596 nm. High‐resolution transmission electron microscopy and selected area electron diffraction study reveal the crystalline phases of the prepared sample. The energy‐dispersive X‐ray analysis confirmed the presence of constituent elements in the sample. The sample shows a high optical bandgap in the range of 3.6 eV to 4.09 eV, which was calculated from absorbance spectra. Photoluminescence measurements of the samples were carried out with 532 nm laser excitation, where the defect‐related emission peaks in the 540–850 nm range are observed. A change in the bandgap and optical emission is observed for different compositions. The magnetic properties analysis through the vibrating sample magnetometer reveals that the prepared sample exhibits ferromagnetic behaviour at room temperature, which can be used in magnetic storage applications. The tuning of the optical properties of the samples by varying the copper and zinc concentrations will be useful for various photonic devices.

Direct Observation of Intragrain Defect Elimination in FAPbI3 Perovskite Solar Cells by Two-Dimensional PEA2PbI4

Two-dimensional perovskites have widely been used to improve the efficiency and stability of perovskite solar cells and are generally believed to passivate defects at the grain boundaries of three-dimensional perovskites. Herein, we studied introducing various combinations of two-dimensional phenyl ethylammonium lead iodide (PEA2PbI4) and methylammonium chloride (MACl) to the formamidinium lead iodide (FAPbI3) precursor solution. Ultralow dose selected area electron diffraction studies prove that the high density of intragrain planar defects in FAPbI3 can be strongly reduced by adding PEA2PbI4 and fully eliminated by adding further MACl. Although PEA+ is too large to incorporate into FAPbI3, PEA2PbI4 not only improves crystallization but also suppresses intragrain defect formation. As a result, a longer charge carrier lifetime, higher photoluminescence quantum yield, lower Urbach energy, and current–voltage hysteresis are achieved, resulting in a champion PCE of 23.69%, with an improvement of humidity stability.

Thermal transport in turbostratic multilayer graphene

The presence of twist angles between layers of two-dimensional materials has a profound impact on their physical properties. Turbostratic multilayer graphene is a system containing a distribution of rotational stacking faults, and these interfaces also have variable twist angles. In this work, we examine the influence of turbostratic single-layer graphene content on the in-plane thermal conductivity of a defect free multilayer graphene system with low defect density. Detailed Raman mode analysis is used to quantify the content of turbostratic single-layer graphene in the system while complementing insight is obtained from selected area electron diffraction studies. Thermal transport in these systems is investigated with Raman optothermal technique supported with finite element analysis simulations. Thermal conductivity of AB-stacked graphene diminishes by a factor of 2.59 for 1% of turbostratic single-layer graphene content, while the decrease at 19% turbostratic content is by an order in magnitude. Thermal conductivity broadly obeys the relation, κ∼exp(−F), where F is the fraction of turbostratic single-layer graphene content in the system.

Effect of molybdenum on structural evolution and thermomechanical behavior of a heat-resistant nickel aluminide-based alloy

Powders of heat-resistant NiAl-8Cr-6Co-xMo-1 Nb-0.9Hf (x = 0, 2, 4 and 6 at% Mo) alloys were successfully obtained by high-energy ball milling (HEBM) and combustion synthesis. Powders with the grain size of 10–55 µm were characterized by high flowability (up to 30 s) and bulk density (up to 3.1 g/cm3) due to the absence of submicron-sized particles. Compacted samples having a finer-grained (<5 µm) structure were produced from the combustion-synthesized powders by hot isostatic pressing (HIP). Molybdenum doping gave rise to a duplex structure consisting of NiAl and (Cr, Mo) grains. High-resolution electron microscopy (HRTEM) and selected area electron diffraction studies of the fine structure of the alloys detected that there are nanoparticles of refractory compounds (Co2Nb, Cr2Nb, (Hfx, Nby)C, and Ni2AlHf) along the grain boundaries and in grain bulk, which improve resistance to viscoplastic strain at temperatures above 800 °C. Molybdenum was shown to affect the mechanical properties of the base alloy in compression tests at 500–1100 °C. Two predominant mechanisms of alloy deformation were identified: glide of matrix dislocations and mechanical twinning.

Practical Route for the Low-Temperature Growth of Large-Area Bilayer Graphene on Polycrystalline Nickel by Cold-Wall Chemical Vapor Deposition.

We report a practical chemical vapor deposition (CVD) route to produce bilayer graphene on a polycrystalline Ni film from liquid benzene (C6H6) source at a temperature as low as 400 °C in a vertical cold-wall reaction chamber. The low activation energy of C6H6 and the low solubility of carbon in Ni at such a low temperature play a key role in enabling the growth of large-area bilayer graphene in a controlled manner by a Ni surface-mediated reaction. All experiments performed using this method are reproducible with growth capabilities up to an 8 in. wafer-scale substrate. Raman spectra analysis, high-resolution transmission electron microscopy, and selective area electron diffraction studies confirm the growth of Bernal-stacked bilayer graphene with good uniformity over large areas. Electrical characterization studies indicate that the bilayer graphene behaves much like a semiconductor with predominant p-type doping. These findings provide important insights into the wafer-scale fabrication of low-temperature CVD bilayer graphene for next-generation nanoelectronics.

Structural and optical studies of colloidal silver nano particles

Colloidal silver nano particles are prepared by biosynthesis using medicinal plants like Ocimum Sanctum and AdhaThodaVasica. Soft gamma ray irradiation is done on the samples. Transmission electron microscopic image of before irradiated silver nano colloid shows the agglomeration of spherical nano clusters while the irradiation results in the reduction of particle size with well defined grains. Selected area electron diffraction studies can explain both the polycrystalline pattern of silver nano colloids. Further, the crystal structure is identified as Face Centered Cubic pattern. The formation and stability of silver nano particles in the colloidal solutions are monitored using uv–visible absorption spectra. Gamma irradiation does not change the band gap value of nano silver. Here the plant extracts served not only as reducing agents but also a good stabilizing agent, which prevents the aggregation of silver nano particles. Gamma ray irradiation helps a better confined morphology for silver nano particle without affecting the structural parameters and optical band gap values.

Green synthesis, characterization and antimicrobial activity of zinc oxide nanoparticles using Artemisia pallens plant extract

The green synthesis of zinc oxide nanoparticles from plant extract is attracting great interest owing to the cost effectiveness and ecofriendly method of synthesis. Crystalline hexagonal shape zinc oxide (ZnO) nanoparticles of approximately 50-100 nm were synthesized through a one-step solution-based technique using alcohol free Artemisia pallens plant extract as a reducing agent. Analysis of the synthesized nanoparticles using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) exhibited homogenous wurtzite structure. TEM and selected area electron diffraction studies showed the zinc oxide nanoparticles are crystalline and hexagonal with growth direction in (101) plane. Fourier transform infrared spectrum showed a single band at 478.34 cm−1 which can be attributed to Zn-O vibrational band. The composition of the synthesized ZnO nanoparticles was then confirmed through energy dispersive X-ray spectroscopy results. In this work, the antimicrobial activity of ZnO nanoparticles was studied. The development of synthesizing metal nanoparticles (MNPs) by plant extracts has become a major focus of research as these nanoparticles have low environmental hazards and low human toxicity. This makes it a commonly used source of nanoparticle synthesis with an efficient, extremely eclectic, relatively cheap and traditional agent that has been used for many years to successfully prepare different organic molecules and compounds.

Fast catalytic reduction of p-nitrophenol by Cu/HAP/ZnFe2O4 nanocomposite

In this study, we reports the synthesis, characterization and application of the novel Cu/HAP/ZnFe2O4 nanocomposite. The composite was synthesized in three steps and well characterized by various characterization techniques such as X-ray photoelectron spectroscopy, fourier transforms infrared spectroscopy, powdered X-ray diffraction analysis, scanning electron microscopy, transmission electron microscope, selected area electron diffraction studies, vibrating sample magnetometer analysis and energy dispersive X-ray spectroscopy. The nanocomposite Cu/HAP/ZnFe2O4 show excellent catalytic reduction of p-nitrophenol in the presence of sodium borohydride at room temperature. Remarkably the catalyst took less than five-second for complete (100%) reduction of p-nitrophenol to the corresponding p-aminophenol. The composite was very stable and show the same catalytic efficiency for five consecutive cycles. This recyclable, environment-friendly, highly stable and low-cost catalyst has the enormous potential in the transformation of p-nitrophenol to the corresponding p-aminophenol as well as to remove the hazardous chemicals such as p-nitrophenol from the environment as a whole.

Microstructural Changes in Inconel 625 Alloy Fabricated by Laser-Based Powder Bed Fusion Process and Subjected to High-Temperature Annealing

The microstructure of the laser powder bed additively manufactured Inconel 625 in post-build stress-relief annealed condition and subsequently annealed at a temperature of 600 °C for 5, 100 and 500 h was investigated by means of light microscopy as well as scanning and transmission electron microscopy. Stress-relieved Inconel 625 exhibited fine cellular–dendritic microstructure characterized by the high dislocation density. Selected area electron diffraction studies allowed to demonstrate that already after 5 h of annealing at a temperature of 600 °C, precipitation of the γ′′ phase in the form of coherent nanoparticles occurred. With the prolongation of the duration of annealing at a temperature of 600 °C from 5 to 500 h, the gradual dissolution of intercellular areas and decrease in the dislocation density were accompanied by enhanced precipitation of the γ′′ phase nanoparticles.

Synthesis, Characterizations and Antimicrobial Activity of Cuprous Oxide (Cu2O) Nanoparticles

Cuprous oxide nanoparticles were synthesized by the reduction of copper sulphate pentahydrate salt at different concentration using sodium borohydride as a reducing agent, polyethylene glycol-6000 as a stabilizer by simple, chemical co-precipitation methods and the effect of concentration on particle size were also studied. The crystalline size and phase of Cu2O nanoparticles (NPs) were authenticated by X-ray diffraction (XRD), morphology and structure by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental analysis was carried out by energy-dispersive X-ray spectroscopy (EDX). The concentration-dependent antimicrobial properties of Cu2O NPs were studied for a different strain of bacteria. XRD and selected area electron diffraction studies (SAED) patterns confirmed the formation of face-centered-cubic Cu2O nanoparticles with size 4.77 nm and 8.02 nm at two different concentrations of 0.01 M and 0.1 M CuSO4, respectively. SEM and TEM images showed that the nanoparticles were uniform, in the form of clusters, and homogeneously distributed. EDX confirmed that synthesized nanoparticles were in pure form having copper and oxygen ratio 3:1 based on the atomic percentage of the chemical species. Cu2O nanoparticles showed excellent antibacterial activity against both bacterial strains Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli). The antibacterial activities of Cu2O NPs were found to be concentration-dependents and large bactericidal effect were seen for Gram-positive (Staphylococcus aureus) bacteria at higher concentrations of Cu2O NPs.

The phase optimization, optical and electrical properties of kesterite Cu2ZnSnS4 thin film prepared by single target RF magnetron sputtering technique for solar cell application

Cu2ZnSnS4 (CZTS) thin film was prepared by RF sputtering technique from a single quaternary target by optimizing RF power, in situ substrate temperature and post deposition annealing temperature. The single phase formation of crystalline CZTS thin film has been verified at a particular optimized condition by characterizing through x-ray diffraction, Raman spectrometer and x-ray photoelectron spectroscopy. The kesterite structure has been further confirmed from the lattice fringes of high resolution transmission electron microscope and selected area electron diffraction study. The surface properties such as particle size, shape and roughness and elemental composition of amorphous and crystalline phase of CZTS studied by atomic force microscope, scanning electron microscope and energy dispersive analysis of x-rays. The optical absorption and photoluminescence studies of post-deposition annealed film prove the defect free and single phase CZTS formation. The band gap calculation for crystalline CZTS showed band gap of 1.49 eV calculated from the Tauc plot. The electrical properties of optimized CZTS thin film has been studied from Hall effect measurement showing P-type conductivity with better carrier concentration and Hall mobility.

Phase-Tunable Synthesis of Ultrathin Layered Tetragonal CoSe and Nonlayered Hexagonal CoSe Nanoplates.

Multiple structural phases in transition metal dichalcogenides have attracted considerable recent interest for their tunable chemical and electronic properties. Herein, a chemical vapor deposition route to ultrathin CoSe nanoplates with tunable structure phases is reported. By precisely tailoring the growth temperature, ultrathin 2D layered tetragonal CoSe nanoplates and nonlayered hexagonal CoSe nanoplates can be selectively prepared as square or hexagonal geometries, with thickness as thin as 2.3 and 3.7 nm, respectively. X-ray diffraction, transmission electron microscopy, and selected area electron diffraction studies show that both types of nanoplates are high-quality single crystals. Electrical transport studies reveal that both the tetragonal and hexagonal CoSe nanoplates show strong thickness-tunable electrical properties and excellent breakdown current density. The 2D hexagonal CoSe nanoplates display metallic behavior with an excellent conductivity up to 6.6 × 105 S m-1 and an extraordinary breakdown current density up to 3.9 × 107 A cm-2 , while the square tetragonal nanoplates show considerably lower conductivity up to 8.2 × 104 S m-1 with angle-dependent magnetoresistance and weak antilocalization effect at lower field. This study offers a tunable material system for exploring multiphase 2D materials and their potential applications for electronic and magnetoelectronic devices.

Facile synthesis and electrochemical investigations of Tin-doped MnO2/carbon nanotube composites

The composites of carbon nanotube (CNT) supported by Sn-doped MnO2 with enhanced capacitance have been fabricated with varying dopant concentrations. The composites have been subjected to physiochemical, configurational, and morphological analyses by FTIR, UV–Vis spectroscopy, X-ray diffraction and field emission scanning electron microscopy, high resolution transmission electron microscopy and selected area electron diffraction studies. The electrochemical performance of the composite has been evaluated by cyclic voltammetry and charge/discharge techniques. Highest specific capacitances of 940 F g−1 at a current density of 0.35 A g−1 and 927 F g−1 at 5 mV s−1 in 1 M Na2SO4 electrolyte solution was achieved in the case of 5% Sn doped composite. Moreover, the electrode demonstrated good cycling performance and retaining 79.7% of the initial capacitance over 3000 cycles. The superior electrochemical performance is accredited mainly to the porous sheath hierarchical architecture, which consist of inter connected MnO2 nanoneedles uniformly coated over the CNT surface. This peculiar architecture is responsible for fast ion/electron transfer and easy access of the active material.

Thermal stability of arc evaporated Al-Cr-O-N coatings

(AlxCr1−x)δ(O1−yNy)ξ coatings were arc evaporated using Al0.70Cr0.30 cathodes and different nitrogen-to-oxygen gas flow ratios and investigated with respect to their phase evolution and thermal stability. The utilization of specific nitrogen-to-oxygen ratios underlies elaborated cross-sectional transmission electron microscopy and selected area electron diffraction studies carried out on (Al,Cr)N–(Al,Cr)2O3–(Al,Cr)N gradient coatings. Based on dynamical differential scanning calorimetry and thermogravimetric analysis up to 1500 °C, in combination with subsequent X-ray powder diffraction, we can conclude, that the thermal stability of (AlxCr1−x)δ(O1−yNy)ξ oxynitrides increase with increasing O content, up to ~81 at.% of the non-metallic sublattice. Especially, the high O-containing coatings are prone for the formation of volatile Cr-oxides. However, the typically observed two-step dissociation process of Cr–N bonds towards Cr (via the formation of Cr2N and N2-release), is delayed to a one-step process (up to 1500 °C) for N-contents below 10 at.% of the non-metallic sublattice.Consequently, by knowledge-driven fine-tuning of the nitrogen-to-oxygen ratio, the thermal stability of (AlxCr1−x)δ(O1−yNy)ξ oxynitrides can be designed for their application-based specific needs.

Novel combustion synthesis of carbon foam‑aluminum fluoride nanocomposite materials

The facile, rapid and bulk production of composite materials consisting of carbon nanostructures doped with metal-based compounds has been a significant challenge for various research areas where such types of materials can be applied, including catalysis, energy storage and water purification. In this work, a carbon foam‑aluminum fluoride composite (C-AlF3) was developed by adopting a combustion synthesis approach, which is an attractive alternative to wet chemical methods usually employed for such purposes. The flame ignition and combustion of a solid-state mixture comprising a fluoropolymer and nano-sized Al powder leads to the formation of a porous carbon foam network doped with dispersed cubic-like AlF3 nanoparticles (100 to 500 nm in size), as observed by high-resolution microscopy methods. Selective area electron diffraction and X-ray diffraction studies revealed a rhombohedral α-AlF3 crystal structure for these embedded particles, while micro-Raman spectroscopy indicated typical carbonaceous features for the foamy matrix. The C-AlF3 composite also showed a combination of micro-, meso- and macro-porous characteristics (i.e. pore sizes in the nanometer scale) based on the analysis of N2 sorption data collected at 77 K. The findings of this study provide useful insights for further research on carbon-based nanocomposite materials prepared via direct combustion synthesis routes.

Incorporation of Alloy-de-Alloy Phase with Conversion Based Manganese Oxide to Enable High and Stable Capacity and Density Functional Theory Study of CdMn2O4

In this work, incorporation of alloying-dealloying based element i.e. Cd due to its high ductility and good wear resistance in manganese based spinel oxides i.e. CdMn2O4 has been studied as Li-ion battery (LIB) anode. This study demonstrates that the Li-alloying phases in such type of compound provides extra assistances of dissemination of these intermetallics element in Li2O matrix which stabilizes the conversion reaction and significantly buffer the accompanying volume variation. As a result, CdMn2O4 exhibits high-capacity (810 (±5) mAh g−1, 100 mA g−1) and -rate capability at different C-rates that signifies the introduction of an alloying element over pure conversion based materials. Further, reduced particle size of ∼ 10 nm supports mechanical integrity of electrode by transferring the developed stress to voids/gaps in spinel CdMn2O4 enabling high performance as LIB anodes. Based on the galvanostatic, cyclic voltammetry data and ex situ –X-ray diffraction,-transmission electron microscope, -selected area electron diffraction studies, a plausible reaction mechanism is also proposed. The reversibility of proposed reaction is further complemented by electrochemical impedance spectroscopy. Furthermore, diffusion of Li ion into spinel CdMn2O4 and associated structural and electronically changes are studied by Density Functional Theory (DFT) and discussed in detail.

Growth of faceted SiC nanostructures using vapor phase condensation: Microstructural analysis

The paper emphasizes the morphological and microstructural analysis of SiC nanostructures grown by thermal plasma assisted gas phase condensation process. High Resolution Transmission Electron Microscopic and Selected Area Electron Diffraction studies are used to analyze the growth directions and the polytypic arrangement with stacking faults in the as synthesized SiC nanoparticles. The results help in understanding the hierarchical poly-types related to the observed geometries and showed the presence of both α- and β-SiC polytypes. The microstructural study is supported by X-Ray diffraction and UV–Visible absorption spectroscopic studies.