Ultra-high Resolution Transmission Electron Microscope Research Articles

Study the influence of the crystal structure of the co-precipitated brownmillerite CaFeO2.5+δ sample on optical and magnetic properties

In this study, the brownmillerite CaFeO2.5+δ sample has been prepared by co-precipitation method. The brownmillerite CaFeO2.5+δ sample crystallizes in a distorted orthorhombic (Pcmn space group) structure as confirmed by Rietveld analysis of the X-ray diffraction (XRD). Structural characterization also of the brownmillerite CaFeO2.5+δ sample has been carried out by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and ultra-high resolution transmission electron microscopy (UHR-TEM). Mössbauer spectroscopy revealed that the brownmillerite CaFeO2.5+δ sample contained Fe3+ in both octahedral and tetrahedral sites. Furthermore, there is Fe3.5+ in the octahedral site because of the excess oxygen content (δ = 0.0185). The UV-Vis. absorption spectrum of the brownmillerite CaFeO2.5+δ sample exhibits two absorption peaks in the UV range and two broad absorption peaks in the visible range. The hysteresis loop M (H) of the brownmillerite CaFeO2.5+δ sample indicated the presence of antiferromagnetic ordering with a small amount of weak ferromagnetic. Present results support that the brownmillerite CaFeO2.5+δ sample is useful for industrial applications.

Human lactoferrin-clay mineral nanohybrids as emerging green biomaterials: A physicochemical characterization

Herein montmorillonite and halloysite have been exploited to prepare advanced lactoferrin-loaded nanohybrid biomaterials for potential biomedical applications. Nanohybrids were prepared following two methodologies: a traditional procedure which induces spontaneous drug-clay interactions to take place in aqueous environment and by spray drying, as alternative and preferred industrial technique for protein processing. Structural assembly of the obtained nanohybrids was assessed by solid state characterization techniques and determination of their surface charge properties. Full microscopy studies, including scanning electron microscopy and ultra-high resolution transmission electron microscopy coupled with EDS were also carried out. Cytotoxicity assays were performed to assess biocompatibility of nanohybrids towards human fibroblast cell cultures. Results showed that both intercalation-solution and spray drying procedures led to the effective formation of nanohybrids structures, with greater extent of peptide-clay mineral interactions in those obtained by spray drying. All the samples exhibited cell viability % higher than 80%, with best results for halloysite coupled with spray drying technique.

Analyses of ultraviolet-excitable high-efficiency phosphorescent RGB phosphors with various Eu2O3 doping concentrations for fabricating white Light–Emitting diodes

In this study, we fabricated white light–emitting phosphors by applying a 350-nm excitation wavelength to Eu2O3-doped [YBi0.1]VO4 (red), SrAl12O19 (green), and Sr3MgSi2O8 (blue) phosphors. The Eu3+-doped [YBi0.1]VO4 phosphor was synthesized using a high-temperature solid-state reaction method in an air environment, and the Eu2+-doped SrAl12O19 and Sr3MgSi2O8 phosphors were synthesized in a reducing environment. The morphological characteristics, crystal structures, and luminescence performance of the phosphors were investigated using X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), ultra-high-resolution transmission electron microscopy (UHR-TEM), and photoluminescence emission (PL). The white light–emitting phosphor was successfully fabricated at the molar ratio of [Y0.8 Bi0.1Eu0.1]VO4:[Sr0.88Eu0.12]Al12O19:[Sr0.99Eu0.01]3MgSi2O8 phosphors of 1:1.5:1. Its Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were (0.3422, 0.3398), which is close to the coordinates of pure white light at ([0.33, 0.33]).

Impact-formed complex diamond-graphite nanostructures

AbstractShock waves resulting from asteroidal and laboratory impacts convert sp2-bonded graphitic material to sp3-bonded diamond. Depending on the shock pressure and temperature conditions, complex nanostructures can form that are neither graphite nor diamond but belong to the diaphite material group, which are characterized by structurally intergrown layered sp2- and sp3-bonded carbon domains. Our ultrahigh-resolution transmission electron microscopy images combined with density functional theory calculations demonstrate that diaphites have two related but distinct structural families. Here, we describe diaphite nanostructures from natural and laboratory shocked samples, provide a framework for classifying the members of these materials, and draw attention to their excellent mechanical and electronic material properties.

Effect of the Preparation Conditions on the Catalytic Properties of CoPt for Highly Efficient 4-Nitrophenol Reduction.

CoPt alloys with Pt contents from 15 to 90% were prepared using low-cost electrochemical deposition. Different samples were synthesized from electrochemical baths at pH = 2.5 and 5.5 in a solution with and without saccharin as an additive. The morphology, composition and crystalline structure of the as-prepared samples were investigated by High Resolution—Scanning Electron Microscopy (HR-SEM), Atomic Force Microscopy (AFM), Ultra-high Resolution—Transmission Electron Microscopy (UHR-TEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). XRD investigations revealed that fcc crystalline structure transforms into hcp crystalline structure when the pH of the electrochemical bath is increased from 2.5 to 5.5 as well as when saccharin is added to the electrochemical bath. The catalytic performance of the CoPt alloys for the nitro to amino phenol compounds conversion was investigated for all the prepared samples, and the results show that the conversion degree increases (from 11.4 to 96.5%) even though the Pt content in the samples decreases. From the samples prepared from the electrochemical bath with saccharin, a study regarding the effect of contact time was performed. The results indicated that after only 5 min, the CoPt sample prepared at pH = 5.5 in the presence of saccharin completely converted the nitro compound to an amino compound.

Microstructure and Anisotropic Order Parameter of Boron-Doped Nanocrystalline Diamond Films

Unconventional superconductivity in heavily boron-doped nanocrystalline diamond films (HBDDF) produced a significant amount of interest. However, the exact pairing mechanism has not been understood due to a lack of understanding of crystal symmetry, which is broken at the grain boundaries. The superconducting order parameter (Δ) of HBDDF is believed to be anisotropic since boron atoms form a complex structure with carbon and introduce spin-orbit coupling to the diamond system. From ultra-high resolution transmission electron microscopy, the internal symmetry of the grain boundary structure of HBDDF is revealed, which can explain these films’ unconventional superconducting transport features. Here, we show the signature of the anisotropic Δ in HBDDF by breaking the structural symmetry in a layered microstructure, enabling a Rashba-type spin-orbit coupling. The superlattice-like structure in diamond describes a modulation that explains strong insulator peak features observed in temperature-dependent resistance, a transition of the magnetic field-dependent resistance, and their oscillatory, as well as angle-dependent, features. Overall, the interface states of the diamond films can be explained by the well-known Shockley model describing the layers connected by vortex-like structures, hence forming a topologically protected system.

Biotechnological use of the ubiquitous fungus Penicillium sp. 8L2: Biosorption of Ag(I) and synthesis of silver nanoparticles

In this work, the efficiency of the ubiquitous fungus Penicillium sp. 8L2 to remove Ag(I) ions from synthetic solutions and its potential to synthesize silver nanoparticles (AgNPs) was evaluated. Using a Rotatable Central Composite Design pH and biomass concentration were optimized. Maximum biosorption capacity 51.53 mg/g, by Langmuir model, comparing favourably with other reports. The fungal biomass was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and analyzed before and after the biosorption process by different techniques: X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Ultra-High Resolution Transmission Electron Microscopy and Energy Dispersive X-ray (HR-TEM-EDX) and Ultraviolet–Visible Spectrophotometry (UV–vis). The results showed that the fungus applied several mechanisms to remove Ag(I) ions from the solution and that some of them induced the synthesis of AgNPs. This fact could be verified in the synthesis tests from the cell extract in which aqueous suspensions with high concentrations of AgNPs were obtained. These nanoparticles had diameters between 2 and 9 nm and therefore a high potential for their use as biocidal agents. The results indicated that the synthesis of nanoparticles could be an added value to the heavy metal biosorption process.

Investigation on the Voltage Hysteresis of Mn3O4 for Lithium-Ion Battery Applications.

In lithium-ion batteries (LIBs), conversion-based electrodes such as transition-metal oxides and sulfides exhibit promising characteristics including high capacity and long cycle life. However, the main challenge for conversion electrodes to be industrialized remains on voltage hysteresis. In this study, Mn3O4 powder was used as an anode material for LIBs to investigate the root cause of the hysteresis. First, the electrochemical reaction paths were found to be dominated by Mn/Mn2+ redox couple after the first lithiation from galvanostatic charging/discharging (GCD) and cyclic voltammetry (CV) measurements. Then, the voltage hysteresis was proposed to be composed of reaction overpotential (∼0.373 V) and intrinsic overpotential (∼0.377 V), which were related to the diffusion behaviors according to CV, galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS) analyses. Furthermore, results revealed that the formation of disparate phase distribution during lithiation and delithiation could be the root cause of the intrinsic overpotential of Mn3O4. These results were based on ultrahigh-resolution transmission electron microscopy (UHRTEM) and molecular dynamics (MD) simulation. It was expected that improving the diffusion behaviors of the systems could eliminate the voltage hysteresis of Mn3O4. In summary, this paper provides an explicit insight into the hysteresis for conversion-based Mn3O4 that could also be applied to other oxide systems and very crucial to reduce energy loss for commercializing oxides as anode materials in LIBs.

Biogenic Silver Nanoparticles for Trace Colorimetric Sensing of Enzyme Disrupter Fungicide Vinclozolin.

We report a novel, simple, efficient, and green protocol for biogenic synthesis of silver nanoparticles (AgNPs) in aqueous solution using clove (Syzygium aromaticum) extract as a reducing and protecting agent. Ultraviolet-visible (UV-Vis) spectroscopy was employed to monitor the localized surface plasmon resonance (LSPR) band of clove extract-derived AgNPs prepared under various conditions. Fourier-transform infrared (FTIR) spectroscopy analysis provided information about the surface interaction of the clove extract with the AgNPs. Ultrahigh-resolution transmission electron microscopy (UHRTEM) results confirmed the formation of spherical, uniformly distributed clove extract-capped AgNPs with sizes in the range of 2–20 nm (average size: 14.4 ± 2 nm). Powder X-ray diffractometry analysis (PXRD) illustrated the formation of pure crystalline AgNPs. These AgNPs were tested as a colorimetric sensor to detect trace amounts of vinclozolin (VIN) by UV-Vis spectroscopy for the first time. The AgNP-based sensor demonstrated very sensitive and selective colorimetric detection of VIN, in the range of 2–16 µM (R2 = 0.997). The developed sensor was green, simple, sensitive, selective, economical, and novel, and could detect trace amounts of VIN with limit of detection (LOD) = 21 nM. Importantly, the sensor was successfully employed for the determination of VIN in real water samples collected from various areas in Turkey.

Efficacious Electrochemical Oxygen Evolution from a Novel Co(II) Porphyrin/Pyrene-Based Conjugated Microporous Polymer.

Oxygen evolution reaction (OER) is energetically challenging from the platform of making many photovoltaic devices such as metal-air batteries and water splitting systems because of its poor kinetics even when precious metals are used. Herein, a Co(II)-porphyrin/pyrene-comprised conjugated microporous polymer Co-MPPy-1 has been developed which shows efficient OER in alkaline medium. The material was characterized by Fourier transform infrared, solid-state 13C cross-polarization magic angle spinning nuclear magnetic resonance, N2 volumetric adsorption/desorption analysis, scanning electron microscopy, ultra high resolution-transmission electron microscopy, X-ray photoelectron spectroscopy, and other physical studies. Co-MPPy-1 showed Brunauer-Emmett-Teller surface area of ∼501 m2 g-1. Co-MPPy-1 achieved a current density of 1 and 10 mA/cm-2 at 340 and 420 mV, respectively. The turnover frequency calculated for the OER is 0.43 s-1. The heterogeneity of this electrocatalyst was tested by chronoamperometric measurement and 1000 cycle recyclability test with retainment of the excellent electrochemical catalytic activity. This can be attributed to the presence of high density of Co(II) porphyrin unit and efficient charge transport in the π-conductive conjugated polymeric backbone.

Changes in the Crystal Lattice Parameters of Montmorillonite during Its Modification by Cobalt and Aluminum Cations

The effect the modification (pillarization) of montmorillonite clays from different locations has on the crystallographic lattice parameters of montmorillonite is determined. It is revealed through ultrahigh resolution transmission electron microscopy and analyzing microdiffraction patterns that pillarization raises the distance between montmorillonite structural units to 2.2 nm, while the intracrystal distance between the atoms grows by 0.4 nm. The catalytic activity of specimens in the oxidation reaction between organic dyes and hydrogen peroxide is enhanced 2–3 times.

Mesoporous Zirconium Oxophosphate: An Efficient Catalyst for the Synthesis of Cyclic Acetals and Cyclic Carbonates under Solvent‐Free Conditions

AbstractMesoporous zirconium oxophosphate (MZrP‐1) composed of porous interconnected network and high specific surface area has been synthesized by using Pluronic P123 as template under evaporation‐induced self‐assembly (EISA) method. The prepared mesoporous material has been characterized by small‐angle powder X‐ray diffraction, UHR‐TEM (Ultra‐high Resolution‐Transmission Electron Microscopy) image analysis, and N2 adsorption‐desorption, FTIR (Fourier‐transform Infrared Spectroscopy) and FE‐SEM (Field Emission‐Scanning Electron Microscopy) analysis. Mesoporous MZrP‐1 catalyst exhibited excellent catalytic activity for the synthesis of cyclic acetals from glycerol and cyclic carbonates from epoxide as starting under solvent‐free green conditions. High surface area and abundant acid sites present at the surface of the mesoporous zirconium oxophosphate is responsible for high catalytic activity. The catalyst can be reusable for several reaction cycles without any significant loss in its catalytic activity.

SWCNT-TiO2 Nanocomposite Photo-Anode for Improved Thermal Performances of Dye-Sensitized Solar Cells

In this study, we report a novel single-wall carbon nanotube (SWCNT)-TiO2 composite photoanode with enhanced thermal conductivity for photovoltaic applications. Thermal chemical vapor deposition technique was used for the growth of high quality SWCNTs. Structural and morphological properties of as synthesized SWCNT and SWCNT-TiO2 composites were inspected using ultra-high resolution transmission electron microscope (UHRTEM) and Raman spectroscopy. Thermal conductivity of pure titania (TiO2) and SWCNT-TiO2 composites were estimated by an optothermal method. Photovoltaic performance of Dye-sensitized solar cell (DSSC) containing composite photoanodes was studied at various temperatures (ranging from room temperature-323K). We observed a notable decline in the overall photovoltaic performance of the DSSC containing pure TiO2 photoanode at elevated temperatures. Whereas, DSSC with composite photoanodes showed a significant improvement in overall photovoltaic performance consistently at room temperature as well as at elevated temperatures that is believed to be due to the existence of SWCNT and provides a conducting pathway to electrons in trap states and which are released at higher temperature and thus, quench recombination more effectively.

Silver nanoparticles supported over mesoporous alumina as an efficient nanocatalyst for N-alkylation of hetero (aromatic) amines and aromatic amines using alcohols as alkylating agent

We have successfully embedded rhombohedral crystallites of silver nanoparticles (Ag-NPs) over mesoporous alumina (Ag@Al2O3) material for the first time. The Ag@Al2O3 has been characterized by powder X-ray diffraction (PXRD), ultra high resolution transmission electron microscopy (UHR-TEM), scanning electron microscopy (SEM), N2 adsorption/desorption isotherm, Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible absorption spectra (UV–Vis), and thermogravimetric analysis (TGA). The PXRD confirms the presence of the rhombohedral phase of Ag nanoparticles. The agglomeration of the silver nanoparticle having a dimension of 80–90nmhas been clearly observed from UHR-TEM images. This novel nanocatalyst showed excellent catalytic activity towards the N-alkylation of hetero (aromatic) amines and aromatic amines using alcohols as the alkylating agent. The catalyst is heterogeneous in nature and can be recovered and recycled more than five reaction cycles without any noticeable loss in its catalytic activity.

NASICON type ordered mesoporous lithium-aluminum-titanium-phosphate as electrode materials for lithium-ion batteries

An ordered 2D-hexagonal mesoporous Lithium-Aluminum-Titanium-Phosphate (LATP-1) material has been synthesized by using cetyltrimethylammonium bromide (CTAB) as the structure directing agent (SDA) thorough hydrothermal route. After acid-ethanol extraction of the as-synthesized LATP-1 material, the extracted white solid product has been characterized thoroughly using small and wide angle powder X-ray diffraction (XRD), nitrogen adsorption/desorption analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), Ultra-high resolution transmission electron microscopy (UHR-TEM) and thermogravimetric analysis (TGA). Elemental analysis revealed 2.53% Li, 2.02% Al, 4.84% Ti, 28.16% P, 62.44% O in the mesoporous LATP-1 material. The template-extracted LATP-1 material has been employed as anode and cathode materials for lithium ion batteries: as an anode material, the LATP-1 electrode exhibits stable discharge-charge performances with delivered capacity of 121 mAh.g−1 and 117 mAh.g−1, respectively and a high coulombic efficiency.

SWCNT-TiO2 Nanocomposite Photo-Anode for Improved Thermal Performances of Dye-Sensitized Solar Cells

In this study, we report a novel single-wall carbon nanotube (SWCNT)-TiO2 composite photoanode with enhanced thermal conductivity for photovoltaic applications. Thermal chemical vapor deposition technique was used for the growth of high quality SWCNTs. Structural and morphological properties of as synthesized SWCNT and SWCNT-TiO2 composites were inspected using ultra-high resolution transmission electron microscope (UHRTEM) and Raman spectrosctopy. Thermal conductivity of pure titania (TiO2) and SWCNT-TiO2 composites were estimated by an optothermal method. Photovoltaic performance of Dye-sensitized solar cell (DSSC) containing composite photoanodes was studied at various temperatures (ranging from room temperature-323K). We observed a notable decline in the overall photovoltaic performance of the DSSC containing pure TiO2 photoanode at elevated temperatures. Whereas, DSSC with composite photoanodes showed a significant improvement in overall photovoltaic performance consistently at room temperature as well as at elevated temperatures that is believed to be due to the existence of SWCNT and provides a conducting pathway to electrons in trap states and which are released at higher temperature and thus, quench recombination more effectively.

Self-assembled sulfated zirconia nanocrystals with mesoscopic void space synthesized via ionic liquid as a porogen and its catalytic activity for the synthesis of biodiesels

Self-assembled ZrO2 nanocrystals have been synthesized through a facile chemical route via steam-assisted ionothermal method using 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) as a porogen. The template-free material has been sulphonated by 1(N) H2SO4 at room temperature followed by calcination in air at 723K. Both ZrO2 and the sulfonated zirconia materials are thoroughly characterized by powder X-ray diffraction (PXRD), ultra high-resolution transmission electron microscopy (UHR-TEM), Fourier transform infrared spectroscopy (FT-IR), FE-SEM, N2 sorption, and NH3-TPD analyses. The sulfonated material has been employed as efficient and environmentally benign heterogeneous catalyst for the synthesis of biodiesels based on long chain fatty acid esters. The catalyst can be easily recovered and reused at least for five times without significant decrease in its catalytic activity.

Plasmon Enhanced Photovoltaic Performance in Graphene Oxide-TiO2 Composite Based Dye-Sensitized Solar Cells

Dye sensitized solar cells (DSSCs) have engendered great research interest with promising potentials in solar cell technology for their high power conversion efficiencies. In this study, we report a plasmon enhanced reduced graphene oxide (RGO)-TiO2 nanocomposite electron injection layer towards the improved performance of DSSCs. Graphene oxide was synthesized using modified Hummer's method and further treated with hydrazine hydrate to obtain reduced graphene oxide (RGO). Structural and morphological properties of as synthesized RGO, RGO- TiO2 and RGO-TiO2-Au nanopaticle (Au NP) composites were investigated using Raman spectroscopy and ultra-high resolution transmission electron microscope (UHRTEM). Raman mapping was performed to further characterize the composite photoanodes.. Photovoltaic performance of DSSC containing composite photoanodes were studied, on keeping the RGO concentration constant and varying the Au NP concentration. A systematic increment in the short circuit current density was noticed while the open circuit voltage (VOC ~ 0.72 V) of DSSC was observed to be constant by increasing Au NP concentration up to an optimal value, probably due to the combined effect of slight rise in quasi-Fermi level and higher carrier transport rate in the resultant composite. Thus, a significant enhancement in the overall photovoltaic performance was observed in DSSCs with RGO- TiO2-Au NP composite photoanode.

Enhanced photovoltaic properties in graphitic carbon nanospheres networked TiO2 nanocomposite based dye sensitized solar cell

In this work, we report a novel carbon based TiO2 nanocomposite electron injection layer (photoanode) toward the improved performance of DSSCs. Graphitic carbon nanospheres (GCNSs) were synthesized by a unique acidic treatment of multi-wall carbon nanotubes. GCNS–TiO2 nanocomposites with different concentrations of GCNSs (ranging from 5 to 20μL) were prepared to use as photoanodes in DSSCs. Structural and morphological properties of GCNS–TiO2 nanocomposites were analyzed by Raman spectroscopy and ultra-high resolution transmission electron microscopy techniques, respectively. A systematic increment in the short circuit current density (JSC) and open circuit voltage (VOC) of DSSC was observed by increasing GCNS concentration up to an optimal value, possibly due to the combined effect of slight rise in quasi-Fermi level and higher carrier transport rate in the resultant composite. Thus, a significant enhancement of ∼47% in the efficiency of DSSC containing GCNS–TiO2 photoanode was observed as compare to DSSC with pure TiO2 photoanode.

Plasmon Enhanced Photovoltaic Performance in TiO2-Graphene Oxide Composite Based Dye-Sensitized Solar Cells

Dye sensitized solar cells (DSSCs) have engendered great research interest with promising potentials in solar cell technology for their high power conversion efficiencies. In this study, we report a plasmon enhanced graphene oxide (GO)-based TiO2-GO-Au composite photo-anode toward the improved performance in our DSSCs. The structural and morphological properties of as synthesized GO and TiO2-GO-Au composites were investigated using Raman spectroscopy and ultra-high resolution transmission electron microscope (UHRTEM). Photovoltaic performances of DSSC containing TiO2-GO-Au composite photoanodes were studied on keeping the constant GO concentration (5 μL) and by varying the concentration of Au-nanoparticles (NP) [1, 3, 5 μL]. A systematic increment in the short circuit current density (JSC) was noticed while incorporating more Au NP to the photoanode probably due to the increased light absorption, higher optical path of absorbed light and faster electron transfer as a combined effect of GO and Au NP. Thus, a significant enhancement in the overall photovoltaic performance was observed in DSSCs with TiO2-GO-Au composite photoanode.