Field-emission High-resolution Transmission Electron Microscopy Research Articles

Enhanced corrosion protection for MAO coating on magnesium alloy by the synergism of LDH doping with deposition of 8HQ inhibitor film

The inherent micropores of micro-arc oxidation (MAO) coatings on magnesium alloy often cause poor long-term corrosion resistance. Herein, a low-porosity and high corrosion-resistant 8HQ/LDH/MAO composite coating, comprising a layered double hydroxide (LDH)-doped MAO primer and a top layer of 8-hydroxyquinoline (8HQ) inhibitor film, was deposited onto the magnesium alloy surface. Characterizations such as high-resolution field-emission transmission electron microscopy were performed to observe the synthesized nanoparticles’ morphology, size, composition, and structure. Results confirmed the successful synthesis of nitrate ion intercalated MgAl-LDH nanosheets and demonstrated the increase in thickness and denseness of the MAO coating after LDH doping. Based on electrochemical impedance spectroscopy and Tafel curves, the corrosion current density (jcorr) of the newly fabricated 8HQ/LDH/MAO composite coating was reduced by about three orders of magnitude. The low-frequency impedance modulus (|Z|ƒ=0.1 Hz) increased by nearly four orders of magnitude compared with that of bare Mg alloy. After 14 days of exposure to the corrosive electrolyte, the composite coating maintained a low jcorr, showing significantly enhanced corrosion resistance compared with single MAO coating. These findings demonstrated the synergism of LDH doping with 8HQ sealing to enhance the corrosion protection of MAO coating on magnesium alloy.

WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

Synthesis and Magnetic Properties of FeCo Alloy Nanowires via AC Frequency Conversion Electrodeposition

Binary alloy nanowires of Fe₃CoSUB7/SUB system are synthesized in the highly ordered porous anodic aluminum oxide (PAA) templates by AC frequency (5, 50, 120, and 200 Hz) conversion electrodeposition method. High resolution field emission transmission electron microscope (HRTEM) and Lorenz TEM (LTEM) were used to study the morphology and the magnetic domain structure of the Fe₃CoSUB7/SUB alloy nanowires, respectively. Magnetic measurements showed that the M-H curves presented a discontinuity in a restricted magnetic field, but with high squareness (about 90 %). Quantitative local measurements of the magnetic properties of the nanowires are explored by differential phase contrast (DPC) imaging. The magnetic properties, however, were significantly affected by the AC frequency, which is correlated with the specific magnetic structure formation of Bloch line. We reported herein a detailed investigation on Fe₃CoSUB7/SUB alloy nanowires and their magnetic properties.

Potential core-shell anode material for rechargeable lithium-ion batteries: Encapsulation of titanium oxide nanostructure in conductive polymer

We investigated the effect of a conductive polymer coating on an active material. TiO2-capped conductive polymer (TOCP) is prepared using a simple and effective two-step process, which comprised hydrothermal and polymerization techniques. Structural analysis showed that the as-prepared pristine titanium oxide electrode material prescribed to the rutile phase TiO2. High-resolution field-emission transmission electron microscopy confirmed that the composite electrode material comprised a thin, uniform, and nano-sized polypyrrole layer coated on TiO2. The TOCP core-shell nanostructure exhibited a high reversible specific capacity of 348/318 mAh g−1, which was considerably higher than that of the pristine TiO2 (TO) nanostructure. At a high current density, its specific capacity was 206/205 mAh g−1, which indicated the material’s high integrity. A combination of large surface area and high porosity could facilitate fast ion/electrode transport, and the electrode active material integrity screening the excellence in rate capability and long-term cyclic stability in rechargeable lithium-ion batteries.

Rational design of non-hazardous phytic acid-functionalized graphene oxide for polymer nanocomposites toward reinforcing corrosion resistance performance applications

Corrosion protection of water-borne polyurethane (WPU) containing phytic acid-decorated graphene oxide (PG) for Q235 steel was investigated in this work. Natural and non-hazardous phytic acid (PA) was applied to modify graphene oxide (GO) for enhancing its dispersion and compatibility with WPU. The results of Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Thermalgravimetric analysis, and Atomic force microscopy demonstrated successful decoration of GO by PA. Scanning electron microscopy and Field-emission high-resolution transmission electron microscopy were used to reveal the morphology structures of GO and PG. The electrochemical impedance spectroscopy and polarization curves were applied to investigate the anti-corrosion performance of WPU loaded with PG nanoparticles. Results revealed that the WPU/PG composite coatings presented an excellent enhancement in long-term anti-corrosion performance. The reason was that the modification of GO by PA not only improved compatibility with WPU, enabling the formation of an efficient barrier to play a physical anti-corrosion effect, but also formed stable metal chelate complexes with iron ions. Moreover, WPU/PG0.05 has the best anti-corrosion ability and “self-healing” function to some degree. Therefore, the advantages of PG can be used as an effective anti-corrosion nanofiller in practical application.

Facile and solvothermal synthesis of rationally designed mesoporous NiCoSe2 nanostructure and its improved lithium and sodium storage properties

Rechargeable metal ion batteries have attracted considerable attention in modern society because environmental issues are getting worse over time. They are highly expecting to play a vital role in day-to-day life in portable electronic devices (EVs) as well as hybrid electric vehicles (HEVs). Herein, we report the synthesis of bimetallic dichalcogenide by a solvothermal technique and systematically explore the effect of mesoporous NiCoSe2 (MNCS) nanostructures by controlling the ratio of surface-active agent during the synthesis process. The depth morphological evaluation using high-resolution field-emission transmission electron microscopy (HR FE-TEM) suggests that all the MNCS nanostructures display similar morphology with an extended network of material architecture when the ratio of surface active agent increased and thus interestingly play an important role in enhancement of surface area and porosity of the as-prepared electrode architecture. Interestingly, an obtained MNCS50 nanostructure displays a specific capacity of 557 and 398 mAh g−1 after 100 and 60 cycles for lithium ion batteries (LIBs) and sodium ion batteries (SIBs), respectively. The larger surface area and high porous nature of MNCS50 nanostructure affords more spaces to accommodate larger numbers of lithium (Li) and sodium (Na) ions during the discharge/charge process, and the nanostructured electrode material often enhances the electrical conductivity. These observations are indicating the use of nanostructured anode materials for LIBs and SIBs.

Development of a Novel Method for the Fabrication of Nanostructured Zr(x)Ni(y) Catalyst to Enhance the Desorption Properties of MgH2

The present work involves the development of a novel method for the fabrication of zirconium nickel (Zr(x)Ni(y)) alloy used as a nanocatalyst to improve the hydrogen storage properties of the Mg/MgH2 system. The catalyst was fabricated through the high-pressure reactor and activated under hydrogen prior to being mechanically milled with the MgH2 for 5 h under argon. The microstructure characterisation of the samples was determined via SEM-EDX (scanning electron microscope analysis–energy dispersive X-ray spectroscopy), XRD (X-ray diffraction) and FE-HRTEM (field emission high resolution transmission electron microscopy), and the desorption characteristic of the nanocomposite (10 wt.% Zr(x)Ni(y)–MgH2) was determined via TPD (temperature-programmed desorption). The nanostructured MgH2 powder milled with 10 wt.% of the activated Zr(x)Ni(y) based nanocatalyst resulted in a faster hydrogen release—5.9 H2-wt.% at onset temperature 210 °C/peak temperature 232 °C. The observed significant improvement in the hydrogen desorption properties was likely to be the result of the impact of the highly dispersed catalyst on the surface of the Mg/MgH2 system, the reduction in particle size during the ball milling process and/or the formation of Mg0.996Zr0.004 phase during the milling process.

Phase-dependent structural, optical, phonon and UV sensing properties of ZnS nanoparticles

In order to investigate the influence of crystal structure on the photoresponse properties of ZnS nanoparticles under UV light exposure, electrical measurements on polyvinylpyrrolidone capepd cubic and hexagonal ZnS nanoparticles with average particle size 30–40 nm have been successfully carried out. Low-temperature solvothermal synthesis yields pure and highly crystalline w-ZnS nanoparticles with good stability. Different structures of prepared ZnS nanoparticles have been identified and confirmed with powder x-ray diffraction, high-resolution field-emission transmission electron microscopy and non-resonant Raman spectroscopic techniques, respectively. The energy band gap and emission properties of cubic and hexagonal ZnS have been studied using UV–vis absorption and photoluminescence spectroscopy. The interaction of phonons with free carriers and transport properties has a vital influence on the electronic and optical properties of nanomaterials. Hence, the resonant and non-resonant Raman spectral studies have been carried out for the prepared samples. Studies on the I–V characteristics and the mechanism behind the enhancement of photocurrent for the cubic and hexagonal ZnS nanoparticle-based photodetectors have shown an enhanced photocurrent for hexagonal ZnS nanoparticles rather than the cubic.

Electrospun P–Mo–W–Ni multicomponent composite oxides for hydrogen evolution reaction

Novel crystalline Ni10W12Mo12P2O87 multicomponent composite oxides were synthesized through electrospinning heteropoly acid H3PMo12O40 (PMo12), H3PW12O40 (PW12) and NiAc2-contained polyvinyl alcohol aqueous solution with a PMo12:PW12:NiAc2 ratio of 1:1:10. Then, calcination is performed under mild conditions. The characterization results of the structure, composition and morphology observed from x-ray powder diffraction, thermogravimetric analysis, field-emission high-resolution transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and Fourier transform infrared illustrated that multicomponent composite oxides consisted of MoO3, WO3, NiWO4, NiMoO4 and P2O5. The electrochemical method could explain that the crystalline Ni10W12Mo12P2O87 presented better hydrogen evolution properties than those fabricated from PMo12 to NiAc2 or PW12 to NiAc2 equaling to 1:5, individually, and the corresponding Tafel slope was 40 mV/decade. In addition, the presence of NiMoO4 and NiWO4 compounds was crucial to improve the electrocatalytic hydrogen evolution properties of the catalyst.

Supermagnetically Tuned Halloysite Nanotubes Functionalized with Aminosilane for Covalent Laccase Immobilization.

Halloysite nanotubes (HNTs) were tuned with supermagnetic Fe3O4 (M-HNTs) and functionalized with γ-aminopropyltriethoxysilane (APTES) (A-M-HNTs). Gluteraldehyde (GTA) was linked to A-M-HNTs (A-M-HNTs-GTA) and explored for covalent laccase immobilization. The structural characterization of M-HNTs, A-M-HNTs, and A-M-HNTs-GTA-immobilized laccase (A-M-HNTs-GTA-Lac) was determined by X-ray photoelectron spectroscopy, field-emission high-resolution transmission electron microscopy, a magnetic property measurement system, and thermogavimetric analyses. A-M-HNTs-GTA-Lac gave 90.20% activity recovery and a loading capability of 84.26 mg/g, with highly improved temperature and storage stabilities. Repeated usage of A-M-HNTs-GTA-Lac revealed a remarkably consistent relative activity of 80.49% until the ninth cycle. The A-M-HNTs-GTA-Lac gave consistent redox-mediated sulfamethoxazole (SMX) degradation up to the eighth cycle. In the presence of guaiacol, A-M-HNTs-GTA-Lac gave elevated SMX degradation compared with 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) and syrinialdehyde. Therefore, the A-M-HNTs can serve as supermagnetic amino-functionalized nanoreactors for biomacromolecule immobilization. The obtained A-M-HNTs-GTA-Lac is an environmentally friendly biocatalyst for effective degradation of micropollutants, such as SMX, and can be easily retrieved from an aqueous solution by a magnet after decontamination of pollutants in water and wastewater.

Laccase-Assisted Rapid Synthesis of Colloidal Gold Nanoparticles for the Catalytic Reduction of 4-Nitrophenol

A green method for the rapid preparation of uniform-sized colloidal gold nanoparticles under ambient conditions was presented and validated using laccase as a reduction agent in alkaline medium. UV-Vis spectrophotometry, field-emission high-resolution transmission electron microscopy, X-ray diffraction, selected area electron diffraction, energy dispersive X-ray analysis, zetasizer, and Fourier transform infrared spectroscopy were used to characterize the gold nanoparticles. The gold nanoparticles were spherical, crystalline, uniform, and monodisperse with an average size of 12.24 nm. These nanoparticles were successfully used to reduce 4-nitrophenol in the presence of NaBH4 and exhibited an excellent catalytic activity.

Green synthesis of magnesium ion incorporated nanocrystalline hydroxyapatite and their mechanical, dielectric and photoluminescence properties

Nanocrystalline hydroxyapatite (HAp-Ca10(PO4)6(OH)2, 35nm) and magnesium (Mg2+) ion incorporated HAp were synthesized by microwave technique. XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), FE-HRTEM (Field emission high resolution transmission electron microscopy), DLS (dynamic light scattering), EDXRF (energy dispersive X-ray fluorescence spectrometry), microhardness, permittivity and alternating current (ac) conductivity, besides the PL (photoluminescence), wettability and in vitro bioactivity of the samples were analysed. EDXRF revealed the Mg2+ ion incorporation in HAp. The Mg2+ ion incorporation did not alter the phase but drastically reduced the crystallite size and particle size respectively by 48% and 32%. There was enhanced microhardness (24%) at low level (<13%) and decreased zeta potential of Mg2+ ion incorporation. The permittivity, ac conductivity, PL, wettability and in vitro bioactivity were enhanced on Mg2+ ion incorporation. These properties enable them to be a promising candidate for wound healing, bone replacement applications and also as a biosensor.

Cadmium selenide@sulfide nanoparticle composites: Facile precipitation preparation, characterization, and investigation of their photocatalyst activity

We report a two-step synthesis and structural characterization of CdSe/CdS core/shell nanoparticles by the precipitation method. Besides, the effects of preparation parameters such as reaction temperature, the speed of the reaction stirrer, and the rate of adding sulfide source on the size, morphology, and photocatalyst activity of CdSe/CdS core–shell nanoparticles were studied by SEM images and degradation of methyl orange (MO) dye test. The structure and composition of the obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscope (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), spectra energy dispersive analysis of X-ray (EDS), and ultraviolet–visible (UV–vis) techniques.

Physicochemical characterization of the superhydrophilic, magnesium and silver ions co-incorporated nanocrystalline hydroxyapatite, synthesized by microwave processing

Magnesium (Mg2+) and silver (Ag1+) ions co-incorporated nanocrystalline hydroxyapatite (HAp, 31×19nm) was synthesized by microwave processing. The prepared samples were characterized using XRD (X-ray Diffraction), FTIR (Fourier Transform Infrared), FE-HRTEM (Field Emission-High Resolution Transmission Electron Microscopy), DLS (Dynamic Light Scattering), zeta potential, microhardness, and PL (Photoluminescence). In addition, antimicrobial, wettability and in vitro bioactivity were also analyzed. The Mg2+ and Ag1+ ions co-incorporation did not modify the phase of the HAp; however, there was a significant reduction in the crystallite size (13%) and particle size (31%). The negative zeta potential was decreased with an increase in the Mg2+ and Ag1+ ions co-incorporation. The microhardness (<0.05M), PL (<0.01M), antimicrobial efficacy and in vitro bioactivity were enhanced in the co-incorporated samples. The surface of the co-incorporated sample was superhydrophilic in nature. These multifunctional properties, enable them to be an excellent candidate for bone replacement and biosensing applications.

Simple and surfactant free synthesis and characterization of CdS/ZnS core–shell nanoparticles and their application in the removal of heavy metals from aqueous solution

In the current study, CdS/ZnS core–shell nanoparticles were successfully synthesized from CdSO4·8H2O and Zn(NO3)2·6H2O starting reagents in the presence of ultrasonic irradiation. The effects of preparation parameters such as ultrasonic power, irradiation time, and precursor concentration on the morphology of the CdS/ZnS core–shell nanoparticles and the removal of heavy metals (Hg+2, Pb+2) were studied by SEM and batch adsorption studies. The as-synthesized products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and ultraviolet-visible (UV-Vis) spectroscopy.

Facile and Rapid Synthesis of Ultrafine PtPd Bimetallic Nanoparticles and Their High Performance toward Methanol Electrooxidation

Uniform and sub‐10 nm size bimetallic PtPd nanoparticles (NPs) have been synthesized via a simple and facile method without using any surfactants at an ambient temperature. As a green and clean reductive agent, ascorbic acid (AA) was employed for the coreduction of K2PtCl4 and K2PdCl4 in aqueous solution. The morphology, composition, and structure of PtPd NPs had been characterized by transmission electron microscopy (TEM), field emission high resolution transmission electron microscopy (FE‐HRTEM), energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscope (XPS). Comparing with both the monometallic Pt and Pd, the as‐prepared alloy nanoparticles show superior electrocatalytic activity and better tolerance against poisoning by intermediates generated during methanol electrooxidation, which makes them a promising electrocatalysts for direct methanol fuel cells (DMFCs). Meanwhile, the green and simple approach could be easily extended to the manufacture of bimetallic or trimetallic alloy nanomaterials.

Sonochemical synthesis and characterization of CdS/ZnS core–shell nanoparticles and application in removal of heavy metals from aqueous solution

In the present work, CdS/ZnS core–shell nanoparticles have been successfully synthesized with the aid of Cd(NO3)2 and Zn(NO3)2⋅6H2O as the starting reagents in presence of ultrasonic irradiation. Besides, the effects of preparation parameters such as ultrasonic power, irradiation time and precursor concentration on the morphology CdS/ZnS core–shell nanoparticles and removal of heavy metals (Hg2+, Pb2+) were studied by SEM images and batch adsorption mode. The as-synthesized products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscope (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), spectra energy dispersive analysis of X-ray (EDS) and ultraviolet–visible (UV–Vis) techniques.

Synthesis of LaVO4: Dy3+ luminescent nanostructure and optimization of its performance as down-converter in dye-sensitized solar cells

The effect of downconversion film of LaVO4:Dy3+ nanocrystals, which could absorb UV light and downconvert it to visible light, for increasing the current density of DSSC has been studied. La(CH3CO2)3 as a new source of La was used to synthesis of tetragonal LaVO4:Dy3+ nanocrystals as down shifting material in dye sensitized solar cells by using hydrothermal method. Besides, the optimized Dy3+ concentration and annealing temperature which affect the morphology, particle size, photoluminescence and crystal structure of the produced nanostructures were found for the first time. The as-synthesized products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), spectra energy dispersive analysis of X-ray (EDAX) and ultraviolet–visible (UV–Vis) techniques. The photoluminescence studies of the LaVO4:Dy3+ nanocrystals revealed strong enhancement in emission intensity, when Dy3+ concentration was increased from 0 to 0.08mmol and annealed at 500°C. The lattice structure transforms from tetragonal to monoclinic phase subsequent to annealing at 700 and 900°C. Using this down-conversion material, the current density of solar cell increased by 6.7%, compared to the uncoated solar cell.

Vitamin E TPGS coated liposomes enhanced cellular uptake and cytotoxicity of docetaxel in brain cancer cells

The aim of this work was to develop a drug delivery system of liposomes, which are coated with d-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS), a PEGylated vitamin E, with docetaxel as a model drug for enhanced treatment of brain tumour in comparison with the nude liposomes as well as with the so-called stealth liposomes, i.e. those coated with polyethylene glycol (PEG), which have been intensive investigated in the literature. Docetaxel or coumarin-6 loaded liposomes were prepared by the solvent injection method and characterized for their particle size, polydispersity, zeta potential and drug encapsulation efficiency. C6 glioma cells were employed as an in vitro model to access cellular uptake and cytotoxicity of the drug or coumarin-6 loaded liposomes. The particle size of the PEG or TPGS coated liposomes was ranged between 126 and 191nm. High-resolution field-emission transmission electron microscopy (FETEM) confirmed the coating of TPGS on the liposomes. The IC50 value, which is the drug concentration needed to kill 50% cells in a designated time period, was found to be 37.04±1.05, 31.04±0.75, 7.70±0.22, and 5.93±0.57μg/ml for the commercial Taxotere®, the nude, PEG coated and TPGS coated liposomes, respectively after 24h culture with C6 glioma cells. The TPGS coated liposomes showed great advantages in vitro than the PEG coated liposomes.

Facile preparation and formation mechanism of uniform silver nanoparticles ising OP-10 as emulsifier in reverse microemulsion

Using the polymerizable hydrophobic styrene monomer as the dispersion medium and the traditional nonionic surfactant OP-10 as emulsifier, stable silver nanoparticles of narrow size distribution were prepared by a reverse (w/o) microemulsion method. The powder X-ray diffraction (XRD) pattern indicated that the obtained silver nanoparticles were of face-centered cubic structure. The results of the transmission electron microscopy (TEM) show that the final silver nanoparticles are of spherical structure with an average diameter of 15.2 nm and of a Gaussian distribution. The internal high-ordered structure of silver nanoparticles was characterized by the field-emission high-resolution transmission electron microscopy (FEHRTEM), indicating that the silver is monocrystalline and it has only one nucleation site during the formation process of a nanoparticle. The time-resolved UV-visible absorption spectra was used to monitor the process of the reaction in situ. The results show that the concentration of silver nanoparticles increases but the size changes little and the morphology transforms from obvious ellipsoidal shape to nearly spherical shape during the process. The experimental results indicate that the droplets’ dynamic exchange which is closely related to the nature of surfactant film is the control factor of the kinetics. The dynamic exchange mechanism of silver nanoparticle formation is proposed to involve continual encounter of two separate droplets forming transient fused dimer in which the chemical reaction occurs followed by re-separation without combination. Attributed to the dual role of surfactant in the nanoparticle formation, tailored nanoparticles can be successfully synthesized in control in the premise of a certain stability of reverse microemulsion.