Selected Area Diffraction Patterns Research Articles

Raman spectroscopy, phase transitions, microstructures, and mechano‐luminescence in Ca‐Sr feldspars (CaAl2Si2O8‐SrAl2Si2O8)

AbstractThe Raman spectra of Ca1‐xSrxAl2Si2O8 (0 ≤ x ≤ 1) feldspars have been measured, to investigate at a short‐range scale the effect of changing composition on the P ➔ I and I ➔ I2/c phase transitions and how phase transitions affect the mechano‐luminescence found in these feldspars. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were done on the same samples, to pinpoint the transitions, by the analysis of selected area diffraction patterns (SAED) and of the spontaneous strain. Natural anorthite (CaAl2Si2O8) shows a large number of well‐resolved peaks, together with sharp h + k even, l odd diffractions (c‐type) in SAED patterns, indicative of a P symmetry. In synthetic anorthite, the Raman spectrum is similar to that of natural anorthite, but the peaks are broader, and c‐type reflections are elongated. As Sr increases, the c‐type reflections become more diffuse and elongated, as the Raman peaks do. At x > 0.6, new peaks appear in Raman spectra, and other peaks show a change in their wavenumber. Moreover, the c‐type reflections disappear completely, and the lattice becomes I‐centred. Between x ~ 0.6 and x = 0.86(3), the XRD patterns prompt for a triclinic structure, with S.G. I. The transition to the monoclinic I2/c structure is well constrained by the ferroelastic strain, whereas the Raman spectra are more similar between the monoclinic and triclinic I and I2/c than between I and P. The absence of mechano‐luminescence in triclinic I compositions suggests that this property is enhanced in local P configurations at conditions close to the P to I transition. A possible mechanism for mechano‐luminescence involving a compression induced P to I transition in local Eu2+ bearing P configurations is proposed.

Intervention-Free Graphitization of Carbon Microspheres from a Non-Graphitizing Polymer at Low Temperature: Nanopores as Dynamic Nanoreactors.

Graphitizability of organic precursors is the topic of numerous investigations due to the wide applications of graphitic materials in the industry and emerging technologies of supercapacitors, batteries, etc. Most polymers, such as polydivinyl benzene (PDVB) are classified as non-graphitizings that do not convert to Graphite even after heating to 3000℃. Here, for the first time, the development of graphitic structure in the hierarchal porous sulfonated-PDVB microspheres without employing specific equipment or additives like metal catalysts, organic ingredients, or graphite particles, at 1100°C is reported. The abnormal additive-free graphitic structure formation is confirmed by Raman spectroscopy (ID /IG = 0.87), high-resolution transmission electron microscopy (HRTEM), and selected area diffraction patterns (SAED), as well as x-ray diffraction patterns (XRD), while preservation of aromatic compounds from the carbonization is detected by Fourier transform infrared (FTIR) analysis. Polymer evolution from room temperature to 1100°C is also studied by FTIR, Raman spectroscopy, and XRDtechniques. Based on the obtained results, it is suggested that the hierarchal and complicated ink-bottle pore network with a high surface area besides super micropores in the sulfonated-PDVB microspheres has served as nano-sized reaction media. These pores, hereafter referred as "dynamic nanoreactors", are expected to have confined the in-situ produced thermal decomposition products containing broken bond benzene rings, while changing dimensionally and structurally during the designed carbonization regime. This confinement has led to the benzene rings fusion at 250°C, a remarkable extension of them at 450°C, their growth to graphene sheets at 900°C and finally, the stacking of curved graphene layers at 1100°C. The results of this research put stress on the capability of nanopores as nanoreactors to facilitate reactions of decomposition products at low temperatures and ambient pressures to form stacked layers of graphene; A transformation that normally requires catalysts and very high pressures for only specific polyaromatic hydrocarbons.

Distinct microbial characteristics of the robust single-stage coupling system during the conversion from anammox-denitritation to anammox-denitratation patterns

Simultaneous anammox-denitrification is effectively operated in two types, i.e., the anammox-denitritation (SAD pattern) and the anammox-denitratation (PDA pattern). The nitrate derived from inevitable nitrite oxidization likely determines the practical operational pattern of the coupling system, while little information is available regarding the microbial characteristics during the pattern conversion. Here, the single-stage bioreactor coupling anammox with denitrification was operated under conditions with a changed ratio of influent nitrite and nitrate. Results showed that the bioreactor exhibited a robust performance during the conversion from SAD to PDA patterns, corresponding with the total nitrogen removal efficiency ranging from 89.5% to 92.4%. Distinct community structures were observed in two patterns, while functional bacteria including the genera Denitratisoma, Thauera, Candidatus Brocadia, and Ca. Jettenia steadily co-existed. Meanwhile, the high transcription of hydrazine synthase genes demonstrated a stable anammox process, while the up-regulated transcription of nitrite and nitrous oxide reductase genes indicated that the complete denitrification process was enhanced for total nitrogen removal during the PDA pattern. Ecologically, stochastic processes dominantly governed the community assembly in two patterns. The PDA pattern improved the interconnectivity of communities, especially for the cooperative behaviors between dominant denitrifying bacteria and low-abundant species. These findings deepen our understanding of the microbial mechanism underlying the different patterns of the coupling system and potentially expand its engineering application.

Development of Polymer-Cored Akaganeite Adsorbent for Phosphate Adsorption

Environmental issues related to phosphate and resource depletion have recently emerged as serious problems. This study focuses on solving the problems of phosphate removal and recovery using synthesized granular akaganeite (GAK). This study identified that akaganeite, which possesses an FeOOH structure in iron oxyhydroxide, can be synthesized and used as a reusable material. Immobilization with the core–shell method using polyethersulfone was applied as a strategy to recover phosphate anions from a trace of phosphate solution. GAK was successfully analyzed using SEM/TGA/BET to understand its physical properties. XRD and SAD pattern analyses suggested that the GAK powder form was amorphous in nature. The powdered akaganeite had a surface area of 231 mg2/g and a maximum adsorption capacity of 21.27 mg/g. To prevent the dispersion of powder during granulation, polyethersulfone was used as a scaffold since akaganeite particles can be effectively immobilized onto PES polymer scaffolds, as substantiated by the SEM/EDS results. Moreover, a lack of changes in the pore sizes suggested that physical properties remained unchanged. Furthermore, compared to the granular akaganeite, the surface area of powdered akaganeite decreased 4–5-fold. The adsorption kinetic of granular akaganeite fit the pseudo-second-order model. The powdered form displayed high removal efficiency, intimate with phosphate anions, when n > 1.0, instead of lower KF. On the other hand, granular akaganeite showed lower affinity when n < 1.0, but appeared positive for an adsorbate with higher KF. This implies that the granulation of akaganeite with the PES polymer did not change its adsorption property, with the maximum adsorption capacity for granular akaganeite being 3.65 mg/g.

Variations in the Crystal Lattice of Tb-Dy-Fe Magnetostrictive Materials: The Lattice Constant Disturbance.

In Tb-Dy-Fe alloy systems, Tb0.29Dy0.71Fe1.95 alloy shows giant magnetostrictive properties under low magnetic fields, thus having great potential for transducers, microsensors, and other applications. The C15 cubic crystal structure of Tb-Dy-Fe has long been thought to be the source of giant magnetostriction. It is surprising that such a highly symmetrical crystal structure exhibits such a large magnetostrictive strain. In this work, the lattice parameters of Tb0.29Dy0.71Fe1.95 magnetostrictive materials were studied by processing atomic-resolution images. The selected area diffraction patterns show a face-centered cubic structure, but the fast Fourier transform diagram shows that the cubic structure has obvious distortion. The lattice parameters obtained by geometric phase analysis (GPA) and Gaussian model-based fitting and calculation show that the lattice constants a, b, and c are not strictly equal, and small disturbance of the lattice constants occurs based on the cubic structure. The actual crystal structure of the Tb-Dy-Fe material is a slightly disturbed cubic structure. This variation in the crystal lattice is mainly caused by the inhomogeneous composition and may be related to the giant magnetostrictive properties of Tb-Dy-Fe alloy.

Investigation of the high-temperature fatigue mechanism related to altered local short-range order in AL6XN austenitic stainless steel

An increase in crystal local short-range order (SRO), characterized by obvious diffuse intensity maxima at 1/3{422} in the [111]-axis selected area diffraction pattern, is observed in AL6XN austenitic stainless steel subjected to high-temperature low-cycle fatigue deformation. SRO is an ordered fcc structure with nanometer size, which can be well explained by the ordered arrangement of Cr/Mo atomic layers segregated on the {422} crystal plane in austenite. Many planar slip bands are observed in the fatigue sample, the distribution of SROs is highly related with the distribution of dislocations. In situ high-energy X-ray diffraction (HE-XRD) experiments are performed to investigate the deformation behavior of both as-received and fatigued samples under uniaxial loading. The lattice strain evolution reveals an interesting lattice expansion in the initial elastic stage, which provides direct evidence of a decrease in SRO during further uniaxial tensile deformation, indicating that the deformation modes greatly affect the SRO transition. We believe that the high-temperature fatigue damage originates mainly from the accumulation of planar slip bands, accompanied by a local increase in SRO, which promotes work hardening near the final fatigue fracture.

Use of repeated indenter sliding coupled with finite element computations to investigate the tribological response of nano-twinned 316L stainless steel

The wear response of dynamically deformed 316 L austenitic stainless steels with varying percentages of compressive strain has been investigated. A relatively high strain rate of 80 s−1 has been used while compressing 316 L at engineering strains of 20 % and 80 %. Nano-indentation coupled with inverse algorithm approaches were used to extract the yield strength and strain hardening exponent of all the specimens. The strain hardening exponent decreased with deformation percentage while the strength enhanced, and these properties have been used in the finite element model (FEM) to find out the stresses and strains during repeated sliding to make scratches. A depth-sensing instrumented nano-indenter with a conical tip was used to make multiple scratches on all the specimens, and the damage in the form of scratch groove depth and width was characterized using a combination of profilometry and scanning electron microscopy. The results showed that the 80 %deformed sample exhibited the least wear damage evident in the form of thinnest scratch profiles, shallowest scratch depths and hence the least specific wear rate. However, after multiple cycles of sliding, undeformed and 20 % deformed samples showed similar wear rates. The friction coefficient decreased with an increase in the percentage deformation, but the dynamic friction coefficient for all the specimens saturated after about 30 passes of sliding. Cross-sectional scanning electron microscopic (SEM) imaging of the scratches revealed refinement and alignment of the microstructure along the shape of the bottom of the groove after repeated sliding. We discovered through the utilization of transmission electron microscopy imaging and selected area diffraction pattern that the region affected by scratching exhibited partial transformation of the initial austenitic phase into martensitic phase.

On the origin of diffuse intensities in fcc electron diffraction patterns.

Interpreting diffuse intensities in electron diffraction patterns can be challenging in samples with high atomic-level complexity, as often is the case with multi-principal element alloys. For example, diffuse intensities in electron diffraction patterns from simple face-centred cubic (fcc) and related alloys have been attributed to short-range order1, medium-range order2 or a variety of different {111} planar defects, including thin twins3, thin hexagonal close-packed layers4, relrod spiking5 and incomplete ABC stacking6. Here we demonstrate that many of these diffuse intensities, including [Formula: see text]{422} and [Formula: see text]{311} in ⟨111⟩ and ⟨112⟩ selected area diffraction patterns, respectively, are due to reflections from higher-order Laue zones. We show similar features along many different zone axes in a wide range of simple fcc materials, including CdTe, pure Ni and pure Al. Using electron diffraction theory, we explain these intensities and show that our calculated intensities of projected higher-order Laue zone reflections as a function of deviation from their Bragg conditions match well with the observed intensities, proving that these intensities are universal in these fcc materials. Finally, we provide a framework for determining the nature and location of diffuse intensities that could indicate the presence of short-range order or medium-range order.

Hybrid thermo-physical modelling and experimentation of ultrafast laser-based fabrication of polycrystalline core–amorphous shell nitinol nanoparticles

Ultrafast lasers pulses induced ablation of nickel-titanium (NiTi) alloy substrates immersed in deionized water yielded a high-throughput of polycrystalline core - amorphous shell NiTi nanoparticles (NPs) owing to the high pulse energy of femtosecond (fs) lasers. In this study, the alloy NPs were fabricated by varying the laser fluences from 15 to 45 J/cm2. The polycrystalline core - amorphous shell NiTi were confirmed by selected area diffraction patterns via High resolution – Transmission Electron microscopy. Theoretical investigations were carried out via hybrid simulation approach of molecular dynamics simulation and analytical modelling. Molecular dynamics study revealed the spatial and temporal evolution of electron and lattice temperature of NiTi melt pool due to ablation at various laser fluences. The subsequent temporal dynamics of melt-pool temperature along the depth revealed the phase separation via spinodal decomposition process after 40 picoseconds post irradiation of NiTi with ultrafast laser pulse. The analytical modelling incorporating phase explosion theory estimated the thermo-physical expansion of ablated chunks and subsequent fragmentation of NiTi melt pool in liquid–vapor co-existing phase. The parameters of mathematical modelling were evaluated in-conjunction with the experimental results of size distribution of NPs at the laser fluence of 15 J/cm2. Later, the hybrid mathematical model was employed to predict the size of NiTi NPs ablated at higher laser fluences of 30 J/cm2 and 45 J/cm2 and the results were experimentally verified.

Reacting Mn3O4 powders with quaternary ammonium hydroxides to form two-dimensional birnessite flakes

There is a current interest in synthesis of two-dimensional (2D) materials that would be cost-efficient to scale to industry production. In this study, we report on a bottom-up approach to convert a manganese oxide (Mn3O4) powder into crystalline, 2D layered birnessite flakes. The Mn3O4 precursor powder, is reacted with aqueous solutions of, tetramethyl-, tetraethyl- or tetrabutylammonium hydroxide in a shaker oven at 80 °C for 4 days. X-ray diffraction confirmed that in all cases, upon filtration of colloidal suspensions, well-stacked, crystalline, 2D MnO2 birnessite layers formed, that upon characterization were found to be quite similar. The major differences were the spacings between the flakes that depended on cation size. Selected area diffraction patterns in a transmission electron microscope confirmed both the structure and the polycrystallinity of the flakes. Raman spectroscopy confirmed the structure. The zeta-potentials of the 2D flakes were measured to be ≈−35 ± 2 mV. When UV–Vis spectra were converted to Tauc plots, direct and indirect band gap energies of ≈2.15 and ≈2.60 eV were obtained, respectively. Additionally, the oxygen evolution reactivity of our birnessite flakes significantly are better than those found for Pt/C, demonstrating a high degree of catalytic reversibility. The facile conversion of a relatively inexpensive, earth-abundant oxide, Mn3O4, into a highly value-added 2D birnessite using a one-pot, simple hugely scalable, protocol at near ambient temperatures and pressures with various quats can be considered a breakthrough in the production of these nanomaterials.

Atomic-scale in situ observation of electron beam and heat induced crystallization of Ge nanoparticles and transformation of Ag@Ge core-shell nanocrystals.

Crystallization of amorphous materials by thermal annealing has been investigated for numerous applications in the fields of nanotechnology, such as thin-film transistors and thermoelectric devices. The phase transition and shape evolution of amorphous germanium (Ge) and Ag@Ge core-shell nanoparticles with average diameters of 10 and 12nm, respectively, were investigated by high-energy electron beam irradiation and in situ heating within a transmission electron microscope. The transition of a single Ge amorphous nanoparticle to the crystalline diamond cubic structure at the atomic scale was clearly demonstrated. Depending on the heating temperature, a hollow Ge structure can be maintained or transformed into a solid Ge nanocrystal through a diffusive process during the amorphous to crystalline phase transition. Selected area diffraction patterns were obtained to confirm the crystallization process. In addition, the thermal stability of Ag@Ge core-shell nanoparticles with an average core of 7.4 and a 2.1nm Ge shell was studied by applying the same beam conditions and temperatures. The results show that at a moderate temperature (e.g., 385°C), the amorphous Ge shell can completely crystallize while maintaining the well-defined core-shell structure, while at a high temperature (e.g., 545°C), the high thermal energy enables a freely diffusive process of both Ag and Ge atoms on the carbon support film and leads to transformation into a phase segregated Ag-Ge Janus nanoparticle with a clear interface between the Ag and Ge domains. This study provides a protocol as well as insight into the thermal stability and strain relief mechanism of complex nanostructures at the single nanoparticle level with atomic resolution.

ZnO-ZnFe2O4 Catalyst for Hydrogen Production from Methanol Steam Reforming

In this study, ZnFe2O4 and ZnO-ZnFe2O4 catalysts were prepared using the glycine–nitrate process (GNP). The prepared ZnFe2O4 and ZnO-ZnFe2O4 catalyst powders were characterized using a scanning electron microscope, transmission electron microscope, XRD diffraction studies, and selected area diffraction pattern studies. In addition, the specific surface area was measured using a Brunauer–Emmett–Teller specific surface area analysis. The hydrogen reduction in different temperature ranges was analyzed using the H2 temperature-programmed reduction technique. The specific surface area of the ZnFe2O4 was 5.66 m2/g, and the specific surface area of the ZnO-ZnFe2O4 was 8.20 m2/g at a G/N ratio of 1.5 and at a G/N ratio of 1.7, respectively. The specific surface area of the ZnFe2O4 was 6.03 m2/g, and the specific surface area of the ZnO-ZnFe2O4 was 11.67 m2/g. The ZnFe2O4 and ZnO-ZnFe2O4 were found to have the best catalytic effect at 500 °C. In particular, the highest H2 generation rate of the ZnO-ZnFe2O4 (GN = 1.7) at 500 °C was 7745 mL STP min−1 g-cat−1. Moreover, the ZnO-ZnFe2 O4 catalyst demonstrated good H2 selectivity and stability during the process of steam reforming methanol. Therefore, the ZnO-ZnFe2O4 catalyst powder exhibited high catalytic activity due to the good dispersibility of the ZnO, which increased the specific surface area of the catalyst. In the future, the catalyst can be applied to the steam reforming of methanol for industrial purposes.

Preparation and photothermal effect of Chitosan-Alginate-Molybdenum diselenide nanocomposite scaffolds for cancer therapy

Transition metal dichalcogenides (TMDs) have gained significant attention for biological and biomedical applications due to their biocompatible properties and photothermal effects. In the current study, TMD nanosheets were fabricated with poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PPP) triblock copolymer using the liquid exfoliation method. This study prepared TMD nanosheets of PPP-molybdenum sulfide (PPP-MoS2), PPP-tungsten disulfide (PPP-WS2), PPP-molybdenum diselenide (PPP-MoSe2), and PPP-tungsten diselenide (PPP-WS2). The synthesized PPP-TMD nanosheets were characterized using DLS, FT-IR, XRD, SEM, TEM, XPS, and photothermal studies. The DLS results indicated that the nanosheets were 165.1 ± 2.2 to 217.7 ± 2.8 nm and had a zeta potential of −40.9 ± 0.6 to −43.3 ± 0.4 mV and a polydispersity index (PDI) of 0.2. The FT-IR results showed that the fabricated nanosheets contained polymeric substances, and the UV results confirmed that each PPP-TMD had surface plasmon resonance peaks. The XRD patterns of the nanosheets were consistent with those of the International Centre for Diffraction Data. The SEM and TEM results determined that the PPD-TMD sheets were 150 ± 20 nm wide and were single-layer nanosheets with selective area diffraction patterns. The photothermal effects of the PPP-MoSe2 nanosheets at a 30 µg/mL concentration were evaluated at 808 nm with a 1 W cm−2 current. PPP-MoSe2 exhibited the strongest photothermal effect at > 55 °C for 5 min of laser exposure. In addition, the cytotoxicity effects of PPP-MoSe2 were measured with breast cancer cells (MDA-MB-231) with a 5 min laser treatment. At a 30 µg/mL concentration, PPP-MoSe2 inhibited cancer cells by up to 95 %. Further, alginate-chitosan-PPP-MoSe2 composites were developed and evaluated for their photothermal effect. We believe that PPP-MoSe2 will be an excellent material in cancer therapy.

Influence of Si on the microstructure and C redistribution in martensitic steels

In martensitic steels the distribution of C is fundamental for the technological material properties. However, the effect of Si on C segregation is not known in detail. In this study, the impact of Si on the microstructure of martensitic steels is investigated using scanning electron microscopy and the martensite/austenite orientation relationships are determined using electron backscatter diffraction and transmission Kikuchi diffraction. Transmission electron microscopy and selected area diffraction pattern analysis were used to analyse the intragranular substructure of the martensitic phase. Further, the effect of Si on the redistribution of C is investigated by atom probe tomography in combination with transmission Kikuchi diffraction measurements in order to obtain the local C distribution and correlate it with the crystallography. It was found that the Si addition forms a sigmoidal distribution at the phase boundary and functions as a barrier for C segregation, hence reduces C partitioning into the austenite, while a Si free alloy shows clear C partitioning. Further it was observed that stable C cluster formation occurs along fine twin boundaries in the martensite, inhibiting carbide formation and partitioning of the C into the austenite.

CuO Nanorods Immobilized Agar-Alginate Biopolymer: A Green Functional Material for Photocatalytic Degradation of Amaranth Dye.

The contamination of water is increasing day by day due to the increase of urbanization and population. Textile industries contribute to this by discarding their waste directly into water streams without proper treatment. A recent study explores the treatment potential of copper oxide nanorods (CuO NRs) synthesized on a green basis in the presence of a biopolymer matrix of agar (AA) and alginate (Alg), in terms of cost effectiveness and environmental impact. The synthesized bio nanocomposite (BNC) was characterized by using different instrumental techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), ultra-violet spectroscopy (UV-Vis), scanning electron microscopy-energy dispersive X-ray-elemental analysis (SEM-EDX), transmission electron microscopy (TEM), selected area diffraction pattern (SAED) and X-ray photoelectron spectroscopy (XPS). The optical studies revealed that immobilization of CuO NRs with Alg-Agar biopolymer blend resulted in an increase in light absorption capacity by decreasing the energy bandgap from 2.53 eV to 2.37 eV. The bio nanocomposite was utilized as a photocatalyst for the degradation of amaranth (AN) dye from an aquatic environment under visible light irradiation. A statistical tool known as central composite design (CCD) associated with response surface methodology (RSM) was taken into consideration to evaluate the optimized values of process variables and their synergistic effect on photocatalytic efficiency. The optimized values of process variables were found to be irradiation time (45 min), AN concentration (80 ppm), catalyst dose (20 mg), and pH (4), resulting in 95.69% of dye degradation at 95% confidence level with desirability level 1. The rate of AN degradation was best defined by pseudo-first-order reaction based on the correlation coefficient value (R2 = 0.99) suggesting the establishment of adsorption-desorption equilibrium initially at the catalyst surface then photogenerated •O2- radicals interacting with AN molecule to mineralize them into small non-toxic entities like CO2, H2O. The material used has high efficiency and stability in photocatalytic degradation experiments up to four cycles of reusability.

Identification of 6R martensite in aged Cu-Al-Ni after pseudoelastic mechanical cycles

Martensitic transformations in Cu-Al-Ni shape memory alloys can be induced by temperature or mechanical stress. Several martensitic phases have been reported in Cu-Al-Ni single crystals, depending on chemical composition, crystallographic orientation, temperature and applied mechanical stress. In tensile tests, the morphology of stress vs. strain curves is directly related to the martensitic transitions taking place in the sample, which provides evidence as to which phases are formed under different conditions. In this work, we studied aged Cu-Al-Ni single crystals and found unusual morphology in some stress vs. strain curves. These samples were studied with electron microscopy and we confirmed the presence of 6R martensite due to the extra spots in the selected area diffraction patterns. The formation of 6R martensite from the β phase in Cu-Al-Ni during tensile tests is mentioned in the literature, but this is the first time that twinned 6R retained martensite is confirmed experimentally in samples that also present γ precipitation due to ageing thermal treatments.

Precipitation sequence in Al-Sc-Zr alloys revisited

Sc and Zr additions to Al provide significant strengthening through the formation of Al3(Sc,Zr) L12 dispersoids. Fe impurities are always present in commercial Al alloys and the effect of these impurities on precipitation mechanisms in Al-Sc-Zr alloys remain poorly understood. This is particularly relevant when considering recycled aluminium as recycling results in the build-up of impurities. We used a combination of resistivity and thermo-electric power (TEP) measurements to monitor the evolution of solid solution during ageing of an Al-Sc, Al-Zr and Al-Sc-Zr alloy. Sc first comes out of solution to form Al3Sc dispersoids, followed by Zr to form Al3Zr. A range of Al3Sc-core/Al3Zr-shell faceted morphologies were observed with high angular annular dark field scanning transmission electron microscopy (HAADF-STEM). The presence of a new class of Fe-rich plate-like precipitates in the {100}Al was revealed via HAADF-STEM. The ordered positions of the precipitate and matrix reflections in the selected area diffraction pattern and in high-resolution TEM images reveal that these precipitates display a multi-layered structure. The centre of the plates is pseudo-icosahedral with apparent five-fold symmetry, and is rich in Fe. The outside layer has a L12 structure and is rich in Sc and Zr. The layered structure allows complete coherency with the aluminium matrix. These precipitates are highly anisotropic with a thickness of 5-10 nm and a length up to ∼1000 nm. This is the first report of the formation of this type of coherent pseudo-icosahedral precipitates in isothermal conditions which is named the D-phase.

Synthesis of Tin oxide nanoparticles using Nelumbo nucifera leaves extract for electrochemical sensing of dopamine

In this investigation, SnO2 nanoparticles are prepared through environmental benign method using Nelumbo nucifera (lotus leaf) leaves extract as a reducing agent without any other reagents. The phase formation and the morphology of the as-synthesized SnO2 nanoparticles are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The nanoparticle size is obtained using selected area diffraction patterns of transmission electron microscope (TEM). The synthesized material modified glassy carbon electrode (GCE) is used for electrochemical detection of the dopamine (DA). In cyclic voltammetry (CV), the modified GCE shows effective electrochemical sensing performance than the bare GCE electrode. The limit of detection (LOD) and limit of quantification (LOQ) of DA were calculated by differential pulse voltammetry (DPV). Aforementioned material has high sensitivity and selectivity towards DA oxidation through electrochemical sensing.

Intrinsic defect-induced magnetism and enhanced photocatalytic activity in Zn1−xZrxO (0.0 ≤ x ≤ 0.07) nanoparticles for spintronic device and photocatalytic application

In this study, ZnO nanoparticles were synthesized by sol-gel auto combustion technique with and without Zr4+ doping. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), selected area diffraction pattern (SAED), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR). A rietveld refinement analysis was performed using fullprof software on the XRD patterns of ZnO and Zr4+ doped ZnO nanoparticles, analysis showed a hexagonal wurtzite structure with an average crystallite size between 19 and 15 nm. SEM were employed to examine the surface morphology. TEM used to determine the particle size and size distribution histogram. SAED pattern confirmed the single-crystalline wurtzite structure. The compositional stoichiometry was verified by energy dispersive spectroscopy (EDAX). The PL spectrum reveals UV emission at the near band edge, as well as defect-related blue and green emission. In the PL spectrum, the green emission of Zr doped ZnO nanoparticles correlates strongly with their magnetic properties.An oxygen vacancy defect was confirmed by EPR studies for Zr doped ZnO nanoparticles. Sample (x = 0.03) exhibited very high coercivity value due to higher oxygen vacancies (Vo). X-ray photoelectron spectroscopy showed the oxidation state of Zn and Zr4+ atoms exist as Zn2+ and Zr4+ in the ZnO structure respectively. A vibrating sample magnetometer (VSM) was used to quantify the magnetic properties. Field-dependent magnetization measurements show diamagnetic behavior for pristine and Zr (x = 0.01 mol) doped ZnO. However, other doped samples (x = 0.03, 0.05, and 0.07 mol) exhibited ferromagnetic behavior at room temperature due to intrinsic defects (Zni and Vo). A UV–visible absorption spectrum was used to determine the energy band gap. Compared with pristine ZnO nanoparticles, doped samples exhibit a redshift in absorption edge. In addition, the photocatalytic activity of synthesized samples was determined by degrading the dye methylene blue (M.B.) in the presence of sunlight. An extensive evaluation of the effect of Zr concentrations on photocatalytic degradation was conducted. Zr4+ doped ZnO nanoparticles exhibit emission peaks detected at 424, 446, and 573 nm. These emission peaks result from electron movement from the deep donor level, zinc interstitial (Zni), and oxygen vacancy(Vo), which ultimately leads to higher photocatalytic efficiency.

Photocatalytic and antimicrobial activities of pure and Mn doped ZnO nanoparticles synthesised by Annona Muricata leaf extract

ABSTRACT The present work aim to investigate the photocatalytic, antibacterial and antifungal activities of Zn1-xMnxO (x = 0.0, 0.03, 0.05 and 0.07) nanoparticles synthesised using the leaf extract of Annona Muricata via green synthesis method. The effect of Mn doping in the obtained nanopowder were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), selected area diffraction pattern (SAED), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and UV-visible spectroscopy techniques. XRD pattern confirms hexagonal wurtzite structure of ZnO nanoparticles. Incorporation of Mn into the ZnO host lattice was confirmed by XPS measurement. Morphology of nanoparticles shows irregular, spherical shapes with agglomeration. Presence of Zn, Mn and O elements in the EDAX reveals the perfect nature of nanostructures. The synthesised pure and Mn-doped ZnO nanoparticles were found to be significant antibacterial activity against gram positive Bacillus subtilis, Staphylococcus aureus and gram negative Pseudomonas aeruginosa bacterial pathogens as well as the fungal strain of Candida albicans and Aspergillus Niger. The minimum zone of inhibition observed for bacterial and fungal pathogens confirms better antimicrobial activity of ZnO nanoparticles. The Mn-doped nanoparticle shows comparatively enhanced removal of methylene blue (MB), malachite green (MG) and Congo red (CR) dye under sunlight. These results indicates the green synthesised pure and Mn-doped ZnO nanoparticles have valuable applications in environmental and biomedical fields.