Structure Of Nano Research Articles

X-Ray diffraction, electronic structure and magnetic characterization of nano and single crystals SrLaAlO4: Mn optical materials

• SrLaAlO 4 : Mn nano and single crystals were examined by XRD method to determine the crystal structure. • SEM/EDX imaging has been done. • XPS electronic structure was examined and discussed. • Experimental effective magnetic moment and the calculated one were compared. The XRD, XPS, SEM and magnetic characterization of the nano and single crystals SrLaAlO 4 doped with Mn were done. The sol–gel method was used to obtain the nanopowder and SEM imaging confirmed the sub-micron size of grains. The single crystals were grown by the Czochralski method. All compounds exhibit excess of strontium and deficiency of aluminium. The unit cell volumes increase with the amount of strontium. The electronic structures measured by XPS of the undoped yellowish single crystals and those nominally doped with 0.02 Mn (amber) and 0.1 Mn (olive) are very similar with comparable ratios of the main to the additional lines. It differs in the case of the nanocrystals, where the surface decomposition is observed. The magnetic measurements indicate the presence of the Mn 4+ ions and are in good agreement with the spectroscopic data.

Synthesis, Characterization and Catalytic Activity of CuO Nanostructures using Schiff Base Copper Complexes as a Precursor

Two Cu(II) complexes, [Cu(L1)2](NO3)2 (1) and [Cu(L2)2] (NO3)2(2), which L1 and L2 Schiff base ligands are 2-(thiophene-2-yl) -1Himidazo [4,5-f] [1,10] phenanthroline and 2-(furane-2-yl)-1Himidazo[4,5-f] [1,10] phenenthroline, respectively, were synthesized and characterized by physico - chemical and spectroscopic methods. Corresponded CuO nanoparticles were prepared by calcination of the obtained complexes at 500˚C. The structure of nano sized copper oxides were characterized by X- ray diffraction (XRD) and scanning electron microscopy (SEM). Electrocatalytic oxidation of acetylcholine (ACh) on copper oxide nanostructures were investigated. The results showed that acetylcholine (ACh) was oxidized irreversibly on copper oxide nanostructures with an excellent catalytic activity.

A novel way to vary the structure of precipitated silica and calcium carbonate aggregates in a wide range by using grinding media during the precipitation process

Certain characteristics of the product quality particularly the aggregate structure of precipitated nano- und micro-particles are relevant depending on the application of precipitated solids. This structure depends on the physicochemical properties of the material as well as on the operating and formulation parameters of the precipitation process and the following process steps. In most of the cases large aggregates are produced by precipitation processes. These aggregates have to be redispersed in a subsequent dispersion step to produce colloidal systems with the desired product properties. In this study the effect of grinding media on the formation of aggregates in a precipitation process was investigated by implementing a basket mill in the precipitation reactor instead of a stirrer. This enables simultaneous precipitation and stirred media milling. The aggregate size range by this method was considerably smaller compared to the one obtained by standard precipitation and dispersion processes. During the following drying step, these aggregates aggregate further forming larger tertiary structures consisting of secondary aggregates. Therefore, compared to the secondary particles obtained from the precipitation process at standard conditions, a new product with a novel tertiary aggregate structure and different micromechanical properties, which can be characterized qualitatively via nanoindentation, was developed. A correlation between the maximum product fineness at the end of the precipitation process and the number of stress events according to the stress model for grinding and dispersing with stirred media mills has been observed.

Structural and morphological characterization of carbon materials by image analysis of microscopic appearances

Techniques for the structural and morphological characterization of carbon materials using microscopy and image processing are reviewed. These techniques are high resolution transmission electron microscopy (HRTEM), three dimensional transmission electron microscopy (3D-TEM) and two dimensional fast Fourier transform (2D-FFT). They are applied to the structural analysis of carbon nanotubes loaded with metal particles, activated carbon, and thin graphite. A HRTEM with C s corrector can achieve a high resolution of less than 0.1 nm even if the acceleration voltage is 80 kV. The more precise three dimensional structure of the carbon nanotubes and activated carbon can be revealed by using 3D-TEM combined with HRTEM. The 2D-FFT of lattice images of HRTEM can analyze the structure of nano structured carbons, like selected area electron diffraction (SAED) which is difficult to apply to the microscopic area. 2D-FFT can be an alternative technique to SAED for nano-size analysis. HRTEM, 3D-TEM, and image processing thus can provide a powerful tool for the analysis of the structure and morphology of nanostructured carbons. [TANSO 2012 (No. 255), 292–304.]

Study of the structure and mechanical properties of nano- and ultradispersed mechanically activated heavy tungsten alloys

Mechanisms of sintering and the structure and mechanical properties of nano- and ultradispersed W-Ni-Fe (WNF) and W-Ni-Fe-Co (WNFC) heavy tungsten alloys are investigated. The effect of tungsten particle sizes on the optimal sintering temperature is studied. The size of particles has been changed by the mechanical activation (MA) of the source W-Ni-Fe coarse-grained (CG) charge and by adding ultradispersed particles obtained using plasmochemical synthesis. Nanodispersed powders and ultradispersed powders (UDPs) have been sintered using the techniques of free sintering and pulse plasma sintering (PPS). It has been revealed that the dependence of the alloy density on heating temperature is nonmonotonic, with the maximum corresponding to the optimum sintering temperature. It has been shown that an increase in the time of MA and acceleration of grinding bodies in the process of MA accompanied by a decrease in the size of alloy particles and formation of nonequilibrium solid solutions lead to a reduction in the optimal sintering temperature. It has been shown that, using planetary high-energy milling methods and high-rate spark plasma sintering, it is possible to obtain ultrastrong tungsten alloys whose mechanical properties (macroelasticity stress and yield stress) substantially exceed analogous properties of commercial alloys.

Effects of DTAB on Performance of Nano Pd/C Catalyst for Purification of Terephthalic Acid

The 0.5 wt.% Pd/C catalysts used for purification of terephthalic acid(TA) were prepared, and the effects of dodecyltrimethylammonium bromide(DTAB) concentration on activity and microstructure of catalysts were investigated by means of SEM, TEM, XRD,HPLC,specific surface area(BET) and porosity test. The results show that DTAB can increase the activity of Pd/C catalysts, and the catalytic activity increases with the increase in DTAB concentration and nearly remains constant with further increase after it exceeds 0.5 wt.%.. DTAB can clean the surface of activated carbon and diminish the palladium size of Pd/C catalysts. The addition of DTAB has effects in crystal structure of nano Pd/C catalysts, and the Pd crystal planes of (111) and (200) was replaced by a broad reflections after DTAB added. DTAB tends to form various meta-stable structures(spherical or cylindrical)at the solid-liquid interface that helps finer grain for mation and hinders subsequent coarsening of the palladium particles.

Temporal dynamics of phytoplankton and heterotrophic protists at station ALOHA

Pico- and nano-sized autotrophic and heterotrophic unicellular eukaryotes (protists) are an important component of open-ocean food webs. To date, however, no direct measurements of cell abundance and biomass of these organisms have been incorporated into our understanding of temporal variability in the North Pacific Subtropical Gyre (NPSG). Based primarily on epifluoresence microscopy augmented with flow cytometry, we assessed the abundance and biomass of autotrophs and heterotrophic protists at Station ALOHA between June 2004 and January 2009. Autotrophic eukaryotes (A-EUKS) were more abundant in both the upper euphotic zone and deep chlorophyll maximum layer (DCML) during winter months, driven mostly by small flagellates. A higher ratio of A-EUKS to heterotrophic protists (A:H ratio) and a structural shift in A-EUKS to smaller cells during the winter suggests a seasonal minimum in grazing pressure. Although Prochlococcus spp. comprised between 30% and 50% of autotrophic biomass in both the upper and lower euphotic zone for most of the year, the community structure and seasonality of nano- and micro-phytoplankon differed between the two layers. In the upper layer, Trichodesmium spp. was an important contributor to total biomass (20–50%) in the late summer and early fall. Among A-EUKS, prymnesiophytes and other small flagellates were the dominant contributors to total biomass in both layers regardless of season (10–20% and 13–39%, respectively). Based on our biomass estimates, community composition was less seasonally variable in the DCML relative to the upper euphotic zone. In surface waters, mean estimates of C:Chl a varied with season—highest in the summer and lowest in the winter (means=156±157 and 89±32, respectively); however, there was little seasonal variability of C:Chl a in the DCML (100m mean=29.9±9.8). Biomass of heterotrophic protists peaked in the summer and generally declined monotonically with depth without a deep maximum. Anomalous patterns of A:H variability during summer 2006 (low mesozooplankton, high A-EUKS and H-dinoflagellates) suggest that top-down forcing is strong enough to impact lower trophic levels in the NPSG. Continued studies of community abundance and biomass relationships are needed for adequate representations of plankton dynamics in ecosystem models and for developing a predictive understanding of both intra- and inter-lower trophic level responses to climate variability in the NPSG.

Influence of structure and properties of colloidal biomaterials on cellular uptake and cell functions.

The molecular structure and physicochemical properties of nano- and colloidal materials have a big impact on their intracellular uptake and cell functions. Elucidation of the cellular uptake and cytotoxicity of the colloidal materials has been recognized recently as one of the paramount prerequisites for their biomedical applications. In this review, the influence of important parameters of colloidal biomaterials such as size, shape, chemical and mechanical properties on cellular uptake and its pathways is summarized. The intracellular distribution and transportation of the colloidal particles are then correlated with their physiochemical properties. The impacts on cytotoxicity and cell functions are also discussed. Finally, more attention is suggested to be paid on the basic understanding of cellular uptake and subsequent influence on cells, which is of great significance for the function implementations and safer applications of nano- and colloidal materials.

Investigations of the Supramolecular Structure of Individual Diphenylalanine Nano- and Microtubes by Polarized Raman Microspectroscopy

Polarized Raman microspectroscopy and atomic force microscopy were used to obtain quantitative information regarding the molecular structure of individual diphenylalanine (FF) nano- and microtubes. The frequencies of the Raman spectral bands corresponding to the amide I (1690 cm(-1)) and amide III (1249 cm(-1)) indicated that the FF-molecules interact by hydrogen bonding at the N-H and not at the C═O sites. The calculated mean orientation angles of the principal axes of the Raman tensors (PARTs) obtained from the polarized Raman spectral measurements were 41 ± 4° for the amide I and 59 ± 5° for amide III. On the basis of the orientation of the PART for the amide I mode, it was found that the C═O bond is oriented at an angle of 8 ± 4° to the tube axis. These values did not vary significantly with the diameter of the tubes (range 400-1700 nm) and were in agreement with the molecular structure proposed previously for larger crystalline specimens.

Structure and electrochemistry of scaling nano C–LiFePO4 synthesized by hydrothermal route: Complexing agent effect

Submicronic particles of LiFePO4 were synthesized by hydrothermal method at 185 °C assisted by carboxylic acid route. In this work, we used citric acid to control the pH of the final products and studied the influence of synthetic conditions on the physical and electrochemical properties of LiFePO4. Structural characterization includes XRD, SEM, TEM and FTIR experiments. The powder quality was investigated by magnetic measurements. Electrochemical features of C–LiFePO4 in Li cell using 1 mol L−1 LiPF6-EC-DEC electrolyte show an excellent capacity retention of 158 mAh g−1 for material prepared with R(citric acid/Fe) = 7 mol%.

Nano silver coated patterned silica thin film by sol–gel based soft lithography technique

We report the fabrication of nano silver coated patterned silica thin film by sol–gel based soft lithography technique. Initially, silica gel film on soda lime silica glass was prepared by dipping technique from a silica sol of moderate silica concentration. A PolydimethylSiloxane elastomeric stamp containing the negative replica of the patterns of commercially available compact disc was used for embossing the film and the embossed film was cured up to 450 °C in pure oxygen atmosphere for oxide film. Finally, a precursor solution of AgNO3 in water containing polyvinyl alcohol as an organic binder was made and used for coating on the patterned silica film by dipping technique and cured the sample up to 450 °C in reducing gas atmosphere to obtain nano silver layer. The formation of only cubic silver (~4.0 nm) and both cubic silver (~5.2 nm) and silver oxide (~3.6 nm) crystallites at 350 and 450 °C film curing temperatures respectively were confirmed by XRD measurements. The % of nano silver metal and silver oxide were 75.4 and 24.6 respectively. The nano-structured surface feature was visualized by FESEM whereas AFM revealed the high fidelity grating structure of the films. Presence of both spherical and rectangular structure (aspect ratio, 2.37) of nano silver/silver oxide was confirmed by TEM. The films were also characterized by UV–Vis spectral study. The patterned film may find application in chemical sensor devices.

Structure and Properties of Nano- and Microcomposite Coating Based on Ti-Si-N/WC-Co-Cr

Using the two technologies: plasma-detonation and vacuum-arc deposition, we fabricated two types of coatings: Ti‐Si‐N/WC‐Co‐Cr/steel and Ti‐Si‐N/steel. We found that the top coating of Ti‐Si‐N was nanostructured one with 12 to 15 nm grain sizes and H = 40 to 38 GPa hardness. A thick coating which was deposited using the pulsed plasma jet, demonstrated 11 to 15.3 GPa hardness, an elastic modulus (E) changing within 176 to 240 GPa, and tungsten carbide grain dimensions varying from 150 to 350 nm to several microns. An X-ray diraction analysis shows that the coating has the following phase composition: TiN, (Ti,Si)N solid solution, WC, W2C tungsten carbides. An element analysis was performed using energy dispersive spectroscopy (microanalysis) and scanning electron microscopy, as well as the Rutherford backscattering of 4 He + ion and the Auger electron spectroscopy. Surface morphology and structure were analyzed using scanning electron microscopy and scanning tunnel microscopy. Tests friction and resistance (cylinder-plane) demonstrated essential resistance to abrasive wear and corrosion in the solution. The decrease of grain dimensions • 10 nm occurring in the top Ti‐Si‐N coating layer increased the sample hardness to 42§2:7 GPa under Ti72‐Si8‐N20 at.% concentration.

Relation between conductance, photoluminescence bands and structure of ITO nanoparticles prepared by various chemical methods

To study the relation between conductance, photoluminescence bands and structure of indium tin oxide (ITO), nano- and microparticles of ITO were synthesised using various methods, including hydrothermal, oxalate precursor decomposition and Pechini type sol–gel combustion methods. The resultant powders were analysed by X-ray diffraction (XRD), resistance measurement, photoluminescence (PL) spectroscopy and scanning electron microscopy techniques. The crystallographic and microstructural parameters of samples were refined from the XRD patterns utilising Rietveld method. Two PL bands were observed in 475 and 560 nm and it was found that the low-energy PL band intensity presents direct relation with conductivity of samples while the other one shows inverse relation. Pechini samples demonstrated the highest conductivity and low-energy PL band intensity, while hydrothermal sample has low conductivity. It was suggested that the low-energy PL band is the characteristics of excitons trapped in oxygen vacancy while the high-energy PL band is attributed to the excitons trapped in other defects centre. The colour of samples and data resulted from XRD pattern refinement were also validated. According to the refinement results and Popa's model, all samples show anisotropic micro-strain and crystallite size. It was also deduced that hydrothermal sample was textured in the 〈111〉 direction.

Mesoscale variability modulates seasonal changes in the trophic structure of nano- and picoplankton communities across the NW Africa-Canary Islands transition zone

The variability of picoplankton and nanoplankton autotrophic ( A) and heterotrophic ( H) communities was studied along a zonal gradient extending from the NW African shelf to 500 km offshore in two contrasting seasons of the year: early spring (spring) and summer (summer). Plankton abundance was significantly higher in summer than in spring. In particular, heterotrophic prokaryotes (HP) and Prochlorococcus (Proc) were an order of magnitude more abundant in summer, presumably due to a higher loading of dissolved organic matter and higher temperatures. The average ratio of A to H biomass was lower during the summer. Over the African shelf, picoplankton was lowest during summer, while both the autotrophic and heterotrophic nanoflagellates (ANF and HNF) showed the highest abundances. In contrast, in spring, the highest abundance of Picoeukaryotes (PE) and Synechococcus (Syn) was found over or close to the shelf. The offshore sampling sections intersected a complex area of strong mesoscale variability, which affected the plankton distribution. In summer, the entrainment of an upwelling filament around a cyclonic eddy provoked the increase of HP and Syn abundances by about one order of magnitude over the surrounding waters, while PE were more abundant over the core of the eddy (probably due to nutrient pumping). In spring, HP and Syn were more abundant at the boundaries of an anticyclonic eddy and in the filament (where PE also increased). Proc abundance increased up to one order of magnitude in the core of the eddy and in the eddy-oceanic waters front. ANF and HNF showed the highest abundances in the filament and the eddy. In summary, although seasonality affects the background variability in microplankton communities, the mesoscale variability found in the Canary Islands transition zone strongly modulates the patterns of distribution, abundances and changes in community structure, altering the A to H ratio and concomitantly playing a key role modifying the carbon pathways within the food web in the region.

Comparative Investigations of Structure and Absorptive Capacity of Nano- and Microsized Magnetic-Operated Particles for their Application in Medicine and Biology

For the first time, the comparative investigations of structure and sorption efficiency of nano- and microsized magnetic-operated particles in respect to both the antigen and virus hepatitis B and also to the substance-markers (low-, middle- and highmolecular substances) were carried out. The sorption efficiency of magnetic particles: magnetite (Fe3O4), cobalt-ferrite (CoFe2O4), composite ferro-carbon (FeC) to the substances of different molecular weight was evaluated in vitro experiments. The high absorptive capacity to low- and highmolecular substance-markers has been observed for microsized composites of FeC. Absorptive capacity of the nanosized Fe3O4 and CoFe2O4 particles to the substance-markers was low. But the nanosized Fe3O4 and CoFe2O4 particles had a good absorptive capacity to virus of hepatitis B and its antigen (HBsAg). The sorption efficiency results of nano- and microsized magnetic particles correlate with the structure of their surface.

Thermal conductivity of polymer composites with close-packed structure of nano and micro fillers

Thermal conductivity of polymer composites with nano and micro fillers has been investigated numerically and experimentally. The nano fillers used were multi-walled carbon nanotubes (MWNTs) and alumina nanoparticles, and the spherical alumina particles were selected as the micro fillers. A periodic unit cell with a random close-packed structure was created using a packing algorithm that treat the micro filler as spheres. Finite element analyses were also performed to predict the potential of nano fillers to enhance thermal conductivity of the composites and to analyze the effect of microstructure of micro fillers. Additionally, the polymer composites with nano and micro fillers were made and the thermal conductivity of the composites were measured. The results showed that the addition of MWNTs to the matrix lead to a large increase in thermal conductivity of the composites. The proposed thermal model predicted a thermal conductivity in good agreement with experiment.

Structure of Na2O–CaO–P2O5–SiO2 Glass–Ceramics with Multimodal Porosity

We have investigated the evolution of the structure of nano–macro porous CaO–Na2O–P2O5–SiO2 bioactive glass–ceramics by Fourier transform infrared (FTIR) and Raman spectroscopies, and X‐ray diffraction (XRD). A controlled devitrification, followed by a chemical leaching treatment is used to produce a multimodal distribution of nano/macro pores that are expected to improve cell attachment. Data show that the leaching process removes the sodium‐ and calcium‐containing crystalline phases that are formed during the ceramming heat treatment. The primary Si–O peaks in the infrared spectra blue shift with leaching, indicating that the sample becomes SiO2 rich. In parallel, the fraction of nonbridging oxygen decreases. These results suggest a restructuring of the glass network far below the glass transition temperature. The stresses from leaching, capillary forces, and subsequent restructuring develop and grow, eventually producing cracks in the sample.

Study on ultraviolet emission mechanism of micro-nano multi-scale ZnO structures

The micro-nano multi-scale ZnO structure was synthesized by the vapor phase transport process onto Si (100) substrate. A typical scanning electron microscope (SEM) image of the sample clearly showed the surface has the complex structure of hexagonal micro and nano- rods. Photoluminescence (PL) spectra at room temperature showed an intense near-band-gap ultraviolet (UV) emission peak but no deep level emission related to impurities or defects, indicating that the sample has good optical quality. The temperature (83—307K) dependence of the PL spectra showed that the room-temperature UV emission resulted from two optical transitions, one related to the ZnO free exciton and the other related to the free-to-bound (FB) transition of the free cawier with the binding energy of about 124.6meV.

Differences in glow curves structure of nano- and microcrystals of CaSO 4:Dy measured at a low heating rate

The glow curves of nano- and microcrystals of CaSO 4:Dy were measured at a low heating rate. The glow peak maximum temperatures were almost the same for the nano- and microcrystals. However, the glow peak intensity and the peak ratio of the main peaks at 90 and 160 ∘ C ( β = 0.04 ∘ C s - 1 ) were different. The TL peak parameters determined with the heating rate method ( β = 0.01 – 0.4 ∘ C s - 1 ) were found to be the same for both types of crystals. For nanocrystals the main peak at 160 ∘ C ( β = 0.04 ∘ C s - 1 ) was strongly reduced. This effect is related to the annealing procedure.

Seasonal variation in the community and size structure of nano- and microzooplankton in Gyeonggi Bay, Yellow Sea

To investigate the seasonal variation and community structure of nano- and microzooplankton in Gyeonggi Bay of the Yellow Sea, the abundance and carbon biomass of nano- and microzooplankton were evaluated at 10-day intervals from January 1997 to December 1999. Four major groups of nano- and microzooplankton communities were classified: heterotrophic ciliates, heterotrophic dinoflagellates (HDF), heterotrophic nanoflagellates (HNF), and copepod nauplii. The total carbon biomass of nano- and microzooplankton ranged from 10.2 to 168.8 μg C L −1 and was highest during or after phytoplankton blooms. Nano- and microzooplankton communities were composed of heterotrophic ciliates (7.4–81.4%; average 41.7% of total biomass), HDF (0.1–70.3%; average 26.1% of total biomass), copepod nauplii (1.6–70.6%; average 20.7% of total biomass), and HNF (0.8–59.5%; average 11.5% of total biomass). The relative contribution of individual components in the nano- and microzooplankton communities appeared to differ by seasons. Ciliates accounted for the most major component of nano- and microzooplankton communities, except during summer and phytoplankton blooming seasons, whereas HDF were more dominant during the phytoplankton blooming seasons. The abundance and biomass of nano- and microzooplankton generally followed the seasonal dynamics of phytoplankton. The size and community distribution of nano- and microzooplankton was positively correlated with size-fractionated phytoplankton. The carbon requirement of microzooplankton ranged from 60 to 83% of daily primary production, and was relatively high when phytoplankton biomass was high. Therefore, our result suggests that the seasonal variation in the community and size composition of nano- and microzooplankton appears to be primarily governed by phytoplankton size and concentration as a food source, and their abundance may greatly affect trophic dynamics by controlling the seasonal abundance of phytoplankton.