Transmission Electron Microscopy Studies Research Articles

Potential larvicidal bioefficacy of copper sulfide-based hybrid nanoemulsions of eucalyptus oil against Aedes aegypti (Linnaeus).

Nanotechnology, an emerging field, has acquired considerable attention for the control of vectors. The present study aimed to synthesize, characterize copper sulfide- and eucalyptus oil-based hybrid nanoemulsions and investigate their larvicidal potential against Aedes aegypti by studying larvicidal bioassay, morphological aberrations, histopathological alterations, biochemical analysis and evaluation of risk assessment in non-target organisms. Hybrid nanoemulsions were prepared by mixing aqueous copper sulfide nanoparticles (CuSNPs) with non-polar eucalyptus oil in five ratios (1:1, 1:2, 1:3, 1:4 and 1:5) by sonication, screened and characterized using Transmission electron microscopy (TEM). Larvicidal activity was recorded and toxicity values were calculated by log-probit method. Morphological, histological and biochemical changes were examined in Aedes aegypti larvae after treatment. Nanohybrids were also tested under simulated conditions and against non-target organism. The nanohybrid ratio of 1:5 was found to be stable after thermodynamic stability tests. TEM studies revealed average size of 90±7.90 nm with globular shape. LC50 and LC90 toxicity values of prepared CuSNPs were calculated out to be 5.00 and 5.81ppm after 24 hours treatment. Effective concentration of prepared nanohybrid (6.5ppm) tested under simulated conditions showed maximum larvicidal mortality after 48 hours of exposure. No toxicity towards the Mesocyclops spp. was observed after treatment of these nanohybrids even up to 21 days. Copper sulfide based hybrid nanoemulsions were found to show efficient larvicidal property which can be used for the formulation of ecofriendly bio-larvicide against Aedes aegypti.

Thermal atomic layer deposition of Er2O3 films from a volatile, thermally stable enaminolate precursor.

Thin films of Er2O3 films were grown by atomic layer deposition using the Er precursor tris(1-(dimethylamino)-3,3-dimethylbut-1-en-2-olate)erbium(III) (Er(L1)3), with water as the co-reactant. Saturative, self-limited growth was observed at a substrate temperature of 200 °C for pulse lengths of ≥4.0 s for Er(L1)3 and ≥0.2 s for water. An ALD window was observed from 175 to 225 °C with a growth rate of about 0.25 Å per cycle. Er2O3 films grown at 200 °C on Si(100) and SiO2 substrates with a thickness of 33 nm had root mean square surface roughnesses of 1.75 and 0.75 nm, respectively. Grazing incidence X-ray diffraction patterns showed that the films were composed of polycrystalline Er2O3 at all deposition temperatures on Si(100) and SiO2 substrates. X-ray photoelectron spectroscopy revealed stoichiometric Er2O3, with carbon and nitrogen levels below the detection limits after argon ion sputtering to remove surface impurities. Transmission electron microscopy studies of Er2O3 film growth in nanoscale trenches (aspect ratio = 10) demonstrated conformal coverage.

Formulation, Optimization and Evaluation of Cytarabine-Loaded Iron Oxide Nanoparticles: From In Vitro to In Vivo Evaluation of Anticancer Activity.

Innovative drug delivery systems based on iron oxide nanoparticles (INPs) has generated a lot of interest worldwide and have prime biomedical benefits in anticancer therapy. There are still issues reported regarding the stability, absorption, and toxicity of iron oxide nanoparticles (INPs) when administered due to its rapid surface oxidation and agglomeration with blood proteins. To solve this problem, we have synthesized trehalose-coated stabilized iron oxide nanoparticles (TINPs) by a co-precipitation technique. The surface coating of INPs with trehalose helps to improve the stability, prevents protein binding, and increase absorption uptake inside the body. Developed TINPs was then loaded with anticancer drug cytarabine by chemical crosslinking encapsulation method using suitable solvent. Engineered cytarabine-loaded trehalose-coated stabilized iron oxide nanoparticles (CY-TINPs) were optimized for particle size, zeta potential (-13.03 mV), and solid-state characterization such as differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and transmission electron microscope (TEM) studies. The particle size of 50 nm was achieved for developed CY-TINPs. The developed CY-TINPs was further evaluated for in vitro cell line investigations which confirmed potential cytotoxic activity. Developed CY-TINPs show remarkable enhancement in in vivo pharmacokinetic parameters Cmax as 425.26 ± 2.11 and AUC0-72 as 11,546.64 ± 139.82 as compared to pure drug. Compared to traditional drug delivery, the CY-TINPs formulation can effectively delay release, improve bioavailability, and boost cytotoxic activity against tumors.

Templated Synthesis of SiO2 Nanotubes for Lithium-Ion Battery Applications: An In Situ (Scanning) Transmission Electron Microscopy Study.

One of the weaknesses of silicon-based batteries is the rapid deterioration of the charge-storage capacity with increasing cycle numbers. Pure silicon anodes tend to suffer from poor cycling ability due to the pulverization of the crystal structure after repeated charge and discharge cycles. In this work, we present the synthesis of a hollow nanostructured SiO2 material for lithium-ion anode applications to counter this drawback. To improve the understanding of the synthesis route, the crucial synthesis step of removing the ZnO template core is shown using an in situ closed gas-cell sample holder for transmission electron microscopy. A direct visual observation of the removal of the ZnO template from the SiO2 shell is yet to be reported in the literature and is a critical step in understanding the mechanism by which these hollow nanostructures form from their core-shell precursors for future electrode material design. Using this unique technique, observation of dynamic phenomena at the individual particle scale is possible with simultaneous heating in a reactive gas environment. The electrochemical benefits of the hollow morphology are demonstrated with exceptional cycling performance, with capacity increasing with subsequent charge-discharge cycles. This demonstrates the criticality of nanostructured battery materials for the development of next-generation Li+-ion batteries.

Polyphenol-Based Nanoscale Iron Exchangers for Regulating Anticancer Chemotherapy by Modulating the Activity of Intracellular Glutathione.

The elevated glutathione (GSH) level in cancer cells contributes to the poor response to chemotherapy and necessitates the use of maximum tolerated drug doses, leading to myriad side effects. We have developed a biocompatible and fluorescently trackable nanosystem, iron(III)-bound nanocarbonaceous polyphenol (FeNCP), to modulate the available GSH pool in cancer cells for synergistic effects in treatments with a cytotoxic anticancer drug, doxorubicin (Dox). This nanosystem was designed using a nanoscale carbon system as a platform to generate a GSH-responsive gallic acid-iron complex. The effective interaction between FeNCP and GSH was probed in PBS (pH 7.4) and cell lysates using UV-Vis, fluorescence spectrophotometry, 1H NMR, flow cytometry, and confocal and transmission electron microscopic studies. The concurrent treatment of cancer cells with subcytotoxic FeNCP and Dox leads to dose reduction indices of Dox of ∼6.1 for HepG2 (hepatocellular carcinoma) and 6.7 for B16F0 (melanoma) to kill ∼50% of the cell population, which is suggestive of the requirement of a multifold lower dose of Dox. Notably, this combination was relatively more cytotoxic toward cancer cell lines than the model normal cell line, Vero. The increased reactive oxygen species levels in combinatorial treatment reveal that FeNCP serves as a potential candidate for modulating glutathione activity and potentiating cytotoxic effects of Dox. The intelligent multifold design of this nanosystem might enable the applicability in optical detection of GSH and imaging-assisted surgery in the future, in addition to the potential to advance treatment regimens in anticancer chemotherapy.

Synthesis, spectroscopic characterization, biological activity, and conducting properties of functionalized Ni(II) dithiocarbamate complexes with solvent extraction studies of the ligands

A series of new nickel(II) dithiocarbamate complexes of general formula [M L2], (where L = benzyl(4-fluorobenzyl)carbamodithioate (L1), benzyl(4-cyanobenzyl)carbamodithioate (L2), ethyl(4-methylbenzyl)carbamodithioate (L3), (4-methoxybenzyl) (naphthalen-1-ylmethyl)carbamodithioate (L4) and ethyl(4-methoxybenzyl)carbamodithioate (L5)) have been synthesized, and characterized via elemental analysis, FT-IR, electronic spectra, 1H NMR, 13C NMR, Mass spectrometry and Thermogravimetric analysis (TGA). The continuous variation method (Job's method) was used to determine the stoichiometry of the complexes. TGA was used to analyze the thermal decomposition behavior of metal complexes in nitrogen atmosphere. As a result of the thermal decomposition process, all of the complexes produced NiS as the final product. X-ray Diffraction (XRD), Energy dispersive X-ray analysis (EDAX), and Transmission electron microscopy (TEM) studies confirm the formation of NiS nanomaterial. Crystalline size of NiS was obtained between 19.97 to 21.35 nm range by applying the Scherrer equation using XRD. Solid-state electrical conductivities reveal that all the complexes behave as a semiconductor at room temperature. All the synthesized dithiocarbamate ligands and complexes were screened against five human bacterial pathogens (Escherichia coli, Staphylococcus aureus, Salmonella typhi, Aeromonas hydrophila, and Shigella boydii) by disc diffusion method. Solvent extraction studies show that the ligand has strong extractability towards metal ions in a basic medium (pH = 10).

Contrasting Pr1–xCaxMnO3 OER Catalysts with Different Valences and Covalences

Perovskite oxides are promising materials for catalyzing the oxygen evolution reaction (OER). However, understanding the properties of active sites that enable high OER activity without corrosive electrode reduction is still elusive. In this work, we use combined electrochemical and environmental transmission electron microscopy (ETEM) studies to compare the OER stability of the (001) surfaces of Pr1–xCaxMnO3 perovskite films with doping of x = 0.1 and x = 0.33. Notably, electrochemical analysis in alkaline conditions, as well as ETEM studies in H2O vapor, shows parallel trends in the stability of both systems: Mn leaching for the Pr1–xCaxMnO3 (PCMO) x = 0.33 system due to oxygen vacancy formation at the surface and higher stability of PCMO x = 0.1, where the oxygen vacancy redox peak is absent in cyclovoltammetry. Electron energy loss spectroscopy reveals the preservation of the Mn valence state in H2O for the PCMO x = 0.1 system, whereas for x = 0.33, Mn is reduced. We interpret this enhanced stability for the low-doped system in terms of a modified Mn 3d–O 2p hybridization, i.e., covalence. For a system with charge localization due to Jahn–Teller polarons, the covalence determines to what degree redox processes of lattice oxygen can arise that can finally lead to corrosive oxygen vacancy formation.

Interaction of N-acyltaurines with phosphatidylcholines

N-acyltaurines (NATs) are biologically active amphiphilic lipids. They come under the group of compounds known as N-acyl amino acids. NATs were first detected in the brain and other tissues in mice lacking the enzyme fatty acid amide hydrolase FAAH (−/−). N-arachidonoyltaurine (20:4 NAT) acts as an excellent ligand for the subset of transient receptor potential (TRP) channels, especially vanilloid type channels TRPV1 and TRPV4. Also, hydrophobic and hydrophilic regions of NATs enable them to interact with membrane lipids. Here, we have investigated the interaction of NATs, N-myristoyltaurine (NMT), and N-palmitoyltaurine (NPT) with their corresponding diacyl phosphatidylcholines (PCs), dimyristoylphosphatidylcholine (DMPC), and dipalmitoylphosphatidylchoine (DPPC). The miscibility and phase behavior of the hydrated binary mixtures have been investigated by differential scanning calorimetry (DSC). Studies on the interaction of NMT/NPT with DMPC/DPPC revealed that the two amphiphiles mix well up to 50 mol% of NAT and phase separation is observed at higher contents of the NAT. The phase transition of the equimolar mixtures of NAT:PC (50:50) studied by fluorescence, also supported the DSC results. PXRD and FTIR analysis show that the NAT:PC equimolar mixture (50:50) forms different supramolecular structures when compared to that of individual NATs and PCs. From transmission electron microscopic studies it is observed that the equimolar mixtures of NMT and NPT with their corresponding diacylphosphatidylcholines (50:50, mol/mol) forms unilamellar vesicles whose diameter range between 30 and 50 nm.

Practice of electron microscopy on nanoparticles sensitive to radiation damage: CsPbBr3 nanocrystals as a case study.

In-depth and reliable characterization of advanced nanoparticles is crucial for revealing the origin of their unique features and for designing novel functional materials with tailored properties. Due to their small size, characterization beyond nanometric resolution, notably, by transmission electron microscopy (TEM) and associated techniques, is essential to provide meaningful information. Nevertheless, nanoparticles, especially those containing volatile elements or organic components, are sensitive to radiation damage. Here, using CsPbBr3 perovskite nanocrystals as an example, strategies to preserve the native structure of radiation-sensitive nanocrystals in high-resolution electron microscopy studies are presented. Atomic-resolution images obtained using graphene support films allow for a clear comparison with simulation results, showing that most CsPbBr3 nanocrystals are orthorhombic. Low-dose TEM reveals faceted nanocrystals with no in situ formed Pb crystallites, a feature observed in previous TEM studies that has been attributed to radiation damage. Cryo-electron microscopy further delays observable effects of radiation damage. Powder electron diffraction with a hybrid pixel direct electron detector confirms the domination of orthorhombic crystals. These results emphasize the importance of optimizing TEM grid preparation and of exploiting data collection strategies that impart minimum electron dose for revealing the true structure of radiation-sensitive nanocrystals.

Vertically aligned nanocomposite films by self‐assembled epitaxial nucleation for super‐broadband transparent conductors

AbstractDesigning super‐broadband transparent conductors is challenging because of the exclusive nature of conductivity and infrared transmittance. Here, using a one‐step process, we created vertically aligned nanocomposite conducting films with high transparency across a super‐broad wavelength range. Vertically aligned transparent Ba3V2O8 nanocolumns with lateral ~100‐nm widths enable high transmittance (>50%, even at a 4‐μm wavelength) for all incident light and outperform that of Sn‐doped In2O3, while the conducting SrVO3 matrix retains low resistivity (<0.56 mΩ cm at room temperature). A combined study of scanning transmission electron microscopy, scattering scanning near‐field infrared microscopy, and X‐ray diffraction revealed that spontaneous phase separation of Ba3V2O8 nanocolumns in a SrVO3 matrix film occurs via self‐assembled epitaxial nucleation. Our vertically aligned nanocomposite films provide a fertile platform for next‐generation optoelectronics.

Nickel-doped TiO2 and thiophene-naphthalenediimide copolymer based inorganic/organic nano-heterostructure for the enhanced photoelectrochemical urea oxidation reaction

To overcome the global challenges of energy crises and environmental threats, urea oxidation is a hopeful route to utilize urea-rich wastewater as an energy source for hydrogen production. Herein, we report an inorganic/organic type of nano-heterostructure (NHs–Ni-TiO2/p-NDIHBT) as a photoanode with excellent urea oxidation efficiency driven by visible light. This heterostructured photoanode consists of nickel (Ni)-doped TiO2 nanorods (NRs) arrays as an inorganic part and a D-A-D type organic polymer i.e p-NDIHBT as an organic part. The as-prepared photoanode was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The morphological studies of TEM confirm the coating of p-NDIHBT on Ni–TiO2 NPs (∼1 μm). The consequence of heterostructure formation on optical and photoelectrochemical (PEC) properties of photoanode were explored through photoelectrochemical responses under visible light irradiation. The photoelectrochemical activity of Ni–TiO2 and Ni–TiO2/p-NDIHBT photoanode from linear sweep voltammetry (LSV) shows the ultrahigh photocurrent density of 0.36 mA/cm2 and 2.21 mA/cm2, respectively measured at 1.965 VRHE. Electrochemical impedance spectroscopy (EIS) of both photoanodes shows a highly sensitive nature toward the urea oxidation reaction. The hybrid photoanode also exhibits high photostability, good solar-to-hydrogen conversion efficiency, and high faradaic efficiency for urea oxidation.

Activation energy study on nanostructured niobium substituted Mg2Ni intermetallic alloy for hydrogen storage application

The magnesium-based metallic alloys have been exhibited to be the improved hydrogen storage materials. In the present investigation, a nanostructured Mg67Ni33 and Niobium substituted intermetallic compound was prepared by a high-energy ball milling technique for hydrogen storage application. Niobium substitution on the pure crystalline intermetallic compound changed the structure of the crystalline to semi-amorphous as well as changed the interplanar spacing after 30 h of milling. Furthermore, the effect of Nb substitution on the inter-planar shift and its corresponding implications on lattice strain, crystallite size, and unit cell volume of the Mg2Ni compound were also discussed. Transmission electron microscope studies confirm the particle size was reduced to less than 100 nm for 30 h of milling. However, SEM images confirm the agglomeration of these nanoparticles and form spherical particles of size around 3–5 μm. XRD and EDS authenticate the presence of oxides. Kissinger’s analysis confirmed that Mg2Ni powder exhibited lower activation energy of 64.101 kJ mol−1 than niobium-substituted alloy powders. The hydrogen charge and discharge potential of these compounds are discussed in detail.

Conversion of gaseous effluents of power plant to sodium carbonate: A value-added material for powder detergent

The CO 2 emission from thermal power plants is one of the major causes of Global warming. Various CO 2 capture technologies such as chemical absorption and adsorption, solvent scrubbing, and membrane processes have been proposed; however, these approaches are expensive and energy-intensive. Here, we have developed a new process for the conversion of gaseous effluents from thermal power plants into nanostructured materials without producing secondary waste. The process includes passing the gaseous industrial effluent (flue gas) in three different aqueous-based solvents (neutral, acidic and alkaline). After completing the reaction, the alkaline solvent was evaporated to get a solid mass. A powder X-ray diffraction study confirms the formation of sodium carbonate. Transmission electron microscopic studies show the formation of a spherical particle of size ~150 nm. Further, gas absorption study reveals high absorption of CO 2 . The as-obtained sodium carbonate was used for the detergent formulation. The result shows grade I detergent has been prepared with improved detergency power (> 65%), having less than 15% active alkalinity, ~19% active ingredient and less than 1% ash. The above work shows a new approach for the scientific as well as the industrial community to convert pollutants into useful products. Design of new process for conversion of power plant effluent into cleaning productKeywords • Flue gas generated from the coal power plant has been captured • Treatment of captured flue gas has been done for the conversion into valuable sodium carbonate • Extracted sodium carbonate has been used for making powder detergent • No by-product has been obtained at the end of conversion

Applications ofPeristrophe paniculataDerived Plasmonic Nanoparticles for DNA Binding and Photocatalytic Degradation of Cationic Dyes

AbstractResearch on plasmonics and their applications in diverse fields has increased significantly over the last decade. The present work primarily aimed to bio‐fabricate silver and gold plasmonic nanoparticles and to study their potential as photocatalysts and as DNA binders. To achieve this, Ag and Au NPs were derived employingPeristrophe paniculataand their optical, morphological and structural properties were investigated by standard analytical techniques. The formation rate constant k was 2.58×10−2 min−1and 3.56×10−2 min−1for Ag and Au NPs correspondingly. FT‐IR analysis showed that the water‐soluble alkaloid, 5‐amino‐3,4‐dihydro‐2H‐pyrrole‐2‐carbonitrile was responsible for the stabilization of nanoparticles. Transmission electron microscopic studies disclosed the formation of uniform spherical AgNPs and irregularly shaped AuNPs and the diameter was 9.32 nm and 27.85 nm respectively which was again corroborated by XRD studies (16.64 nm and 36.08 nm). The interaction of ct‐DNA with Ag and Au NPs was investigated using absorption spectroscopy in the UV‐Vis range and the binding constant values were 2.2×105 M−1and 8.1×106 M−1respectively. The degradation of methylene blue and malachite green by AgNPs was almost 100 % and 65 % respectively in 3 h under sunlight and neutral pH (pseudo first order rate constants were 7.9×10−3 min−1and 1.9×10−3 min−1). Moreover, the derived AgNPs exhibited mitigate activity against targeted pathogens. Thus, this green technique could be implicit for the eco‐friendly synthesis of Ag and Au NPs, and the prepared nanoparticles may be explored as photocatalysts for the degradation of cationic dyes without any added oxidants.

Physical Vapor Transport Growth of Antiferromagnetic CrCl3 Flakes Down to Monolayer Thickness.

The van der Waals magnets CrX3 (X=I, Br, and Cl) exhibit highly tunable magnetic properties and are promising candidates for developing novel two-dimensional (2D) spintronic devices such as magnetic tunnel junctions and spin tunneling transistors. Previous studies of the antiferromagnetic CrCl3 have mainly focused on mechanically exfoliated samples. Controlled synthesis of high quality atomically thin flakes is critical for their technological implementation but has not been achieved to date. This work reports the growth of large CrCl3 flakes down to monolayer thickness via the physical vapor transport technique. Both isolated flakes with well-defined facets and long stripe samples with the trilayer portion exceeding 60µm have been obtained. High-resolution transmission electron microscopy studies show that the CrCl3 flakes are single crystalline in the monoclinic structure, consistent with the Raman results. The room temperature stability of the CrCl3 flakes decreases with decreasing thickness. The tunneling magnetoresistance of graphite/CrCl3 /graphite tunnel junctions confirms that few-layer CrCl3 possesses in-plane magnetic anisotropy and Néel temperature of 17K. This study paves the path for developing CrCl3 -based scalable 2D spintronic applications.

Preparation, Characterization and Thermal Studies of Polypyrrole - Gold Nanocomposites

Background: Understanding nanocomposites' morphological characteristics is important for explaining their properties and their usefulness. Method: In this review, we present the method for interfacial synthesis of polypyrrole and its gold nanocomposites with varying concentrations of polymer. The bonding involved in the nanocomposites is understood from Fourier transform infrared spectroscopy and X-ray diffraction studies confirmed the crystalline nature of the particles. Result: Scanning electron microscope and transmission electron microscopy studies showed that the spherical and globular nature of the particles is mutually connected to form nanocomposites compared with virgin polymer. Conclusion: Catalytic behavior of gold nanoparticles in polymer composites is observed from the thermal analysis.

Bias‐Free Graphene Solid Cell to Realize the Real‐Time Observation on Dynamical Changes of Electrodes

AbstractTo realize the development of high‐performance electrodes materials, real‐time observation tool that can visualize dynamical changes of electrode materials upon lithiation and sodiation is highly critical. Recently, in situ transmission electron microscopy (TEM) has gained much attraction as it provides rich information on both phase and morphological transitions of electrode materials upon lithiation and sodiation in an atomic scale. Nevertheless, two significant limitations are present for current in situ TEM study: i) most of the in situ TEM experiments use a specially designed TEM holder, which is costly and suitable for use in only selective types of TEM; and ii) recently developed in situ TEM techniques with no applied bias have inherent limitations in the size of the sample (difficult for a size above 50 nm). Overcoming these two aforementioned issues, bias‐free graphene solid cells (GSCs) are now introduced, which can conduct real‐time observation of electrode materials in any size dimensions and morphologies without using bias. In this work, dynamical changes of hollow SnO2 nanotubes (NTs) are visualized upon lithiation and sodiation in real time using GSCs, where rich information is obtained on the morphology‐dependent, ion‐dependent characteristics of dynamical changes.

Citric acid functionalized reduced graphene oxide containing bio‐based waterborne polyester thermoset as an excellent anticorrosive material

AbstractProtection of metal surfaces from corrosion by environmentally friendly coating is found to be an interesting and useful research topic. In this milieu, the authors presented an environment friendly bio‐based waterborne polyester thermoset as an anticorrosive organic coating. The polyesters comprise renewable resource based citric acid, dimer acid and glycerol along with citric acid functionalized reduced graphene oxide. Three different compositions of the polyester were produced by varying the amount (0.1, 0.5, and 1 weight%) of functionalized reduced graphene oxide. The structural and morphological attributes of these polyesters were evaluated by Fourier transform infrared spectroscopic, X‐ray diffraction, Raman spectroscopic, scanning electron microscopic, and transmission electron microscopic studies. The thermosets of the resinous polyesters were obtained by curing them with bio‐based glycerol containing epoxy and fatty acid modified poly(amido amine). The thermosets exhibited high tensile strength (18.68–26.94 MPa), elongation at break (176%–471%), toughness (22.74–86.5 MJ/m3), thermal stability (up to 222°C), biodegradability and chemical resistance. Potentiodynamic polarization and electrochemical impedance spectroscopic studies clearly revealed excellent corrosion resistance (impedance of the order of 107 ohm cm2 and highest phase angle of 88.2°) of the mild steel coated plates. Thus, the formulated polyester thermosets could be used as a promising environment friendly high performing anticorrosive material.

Heteroepitaxy Growth and Characterization of High-Quality AlN Films for Far-Ultraviolet Photodetection.

The ultra-wide bandgap (~6.2 eV), thermal stability and radiation tolerance of AlN make it an ideal choice for preparation of high-performance far-ultraviolet photodetectors (FUV PDs). However, the challenge of epitaxial crack-free AlN single-crystalline films (SCFs) on GaN templates with low defect density has limited its practical applications in vertical devices. Here, a novel preparation strategy of high-quality AlN films was proposed via the metal organic chemical vapor deposition (MOCVD) technique. Cross-sectional transmission electron microscopy (TEM) studies clearly indicate that sharp, crack-free AlN films in single-crystal configurations were achieved. We also constructed a p-graphene/i-AlN/n-GaN photovoltaic FUV PD with excellent spectral selectivity for the FUV/UV-C rejection ratio of >103, a sharp cutoff edge at 206 nm and a high responsivity of 25 mA/W. This work provides an important reference for device design of AlN materials for high-performance FUV PDs.

Controlled Synthesis of Tellurium Nanowires.

One-dimensional tellurium nanostructures can exhibit distinct electronic properties from those seen in bulk Te. The electronic properties of nanostructured Te are highly dependent on their morphology, and thus controlled synthesis processes are required. Here, highly crystalline tellurium nanowires were produced via physical vapour deposition. We used growth temperature, heating rate, flow of the carrier gas, and growth time to control the degree of supersaturation in the region where Te nanostructures are grown. The latter leads to a control in the nucleation and morphology of Te nanostructures. We observed that Te nanowires grow via the vapour-solid mechanism where a Te particle acts as a seed. Transmission electron microscopy (TEM) and electron diffraction studies revealed that Te nanowires have a trigonal crystal structure and grow along the (0001) direction. Their diameter can be tuned from 26 to 200 nm with lengths from 8.5 to 22 μm, where the highest aspect ratio of 327 was obtained for wires measuring 26 nm in diameter and 8.5 μm in length. We investigated the use of bismuth as an additive to reduce the formation of tellurium oxides, and we discuss the effect of other growth parameters.