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 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A preliminary insight into metal cycling within the urban sewer was obtained by determining both the heavy metal concentrations (Cu, Zn, Pb, Cd, Ni, Cr) in sewage and sediments, and the nature of metal-bearing particles using TEM-EDX, SEM-EDX and XRD. Particles collected from tap water, sump-pit deposits, and washbasin siphons, were also examined to trace back the origin of some mineral species. The results show that the total levels in Cu, Pb, Zn, Ni, and Cr in sewage are similar to that reported in the literature, thus suggesting that a time-averaged heavy metal fingerprint of domestic sewage can be defined for most developed cities at the urban catchment scale. Household activities represent the main source of Zn and Pb, the water supply system is a significant source of Cu, and in our case, groundwater infiltration in the sewer system provides a supplementary source of Ni and Cd. Concentrations in heavy metals were much higher in sewer sediments than in sewage suspended solids, the enrichment being due to the preferential settling of metal-bearing particles of high density and/or the precipitation of neoformed mineral phases. TEM and SEM-EDX analyses indicated that suspended solids, biofilms, and sewer sediments contained similar heavy metal-bearing particles including alloys and metal fragments, oxidized metals and sulfides. Copper fragments, metal carbonates (Cu, Zn, Pb), and oxidized soldering materials are released from the erosion of domestic plumbing, whereas the precipitation of sulfides and the sulfurization of metal phases occur primarily within the household connections to the sewer trunk. Close examination of sulfide phases also revealed in most cases a complex growth history recorded in the texture of particles, which likely reflects changes in physicochemical conditions associated with successive resuspension and settling of particles within the sewer system.
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PMID:Sources, nature, and fate of heavy metal-bearing particles in the sewer system. 1973 36

Carbon nanofibers were obtained by thermo-catalytic decomposition of methane at 700 degrees C over Ni and Ni-Cu catalysts prepared by different methods (co-precipitation, impregnation and fusion) and using either Al or Mg as textural promoter. Characterization of the carbon thus obtained was performed by N2 adsorption isotherms (BET surface area), temperature programmed desorption (TPD), temperature programmed oxidation (TPO), X-ray diffraction, Raman spectrometry, and electron microscopy SEM and TEM. The carbon obtained possesses high crystallinity and poor surface chemistry. The crystallinity is enhanced when using Mg as textural promoter and in the presence of copper. SEM and TEM examinations show that the fibers have fishbone structure and they grow generally from one nickel particle (tip growing) although there are some bidirectional growing. Copper-doping lead to the formation of thicker filaments and promotes the formation of bamboo-like structures. Catalyst particles higher than 100 nm do not promote the formation of nanofibers and the carbon deposits as uniform coatings.
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PMID:Characterization of carbon nanofibers grown over Ni and Ni-cu catalysts. 1991 25

Synthetic heteroaggregate particle gels are a relatively unexplored area of colloidal science. In our previous work pH-triggered formation of heteroaggregate gels prepared from mixed pigment/polystyrene (PS) dispersions were investigated [Hui et al., J. Colloid Interface Sci. 324 (2008) 110]. The pigment was beta-copper phthalocyanine (beta-CuPc). In this study that work is extended by investigating the structure of the heteroaggregates formed at room temperature in greater detail and also studying the temperature-triggered gel breakdown that occurs upon moderate heating for the first time. In this work the heteroaggregate structures were studied using TEM, atomic force microscopy (AFM) and also SEM. AFM showed the mesoscale structure to consist of highly branched space-filling heteroaggregates. They are proposed to be the building blocks of the heteroaggregate gels. TEM data supported our previous suggestion that the pigment particles act as a crosslink centre within the heteroaggregate gels. SEM images showed evidence for softening and partial coalescence of the aggregates at elevated temperatures which helped to explain the temperature-triggered gel breakdown that occurred upon heating. The temperature-triggered gel breakdown was directly correlated with the glass transition temperature of the PS particles. A study of the maximum storage modulus, G', achieved just prior to gel breakdown, revealed a maximum at a volume fraction of pigment of 0.033. The data from the study are used to propose a conceptual model for the temperature-triggered breakdown of the pigment/PS heteroaggregate gels.
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PMID:A study of structure and temperature-triggered breakdown of particle gels prepared by pH-triggered heteroaggregation. 1994 22

We report a two-step process for the growth/patterning of Ni honeycomb nanostructures on various substrates, such as carbon paper, carbon nanotubes (CNTs), silicon wafers, and copper grids, via the combination of a sputter-coating/patterning technique and a replacement reaction solution method. The morphology, crystallinity, and chemical composition of the honeycombs were analyzed by SEM, TEM, high-resolution TEM, and EDX. These honeycombs are composed of numerous nanocells, several tens of nanometers in diameter and with cell wall thickness of approximately 10 nm, randomly connecting to each other. The growth process of honeycomb nanostructures has been systematically studied. Interestingly, the diameter and wall thickness of the cells could be easily tuned by simply adjusting the experimental parameters, such as the concentrations and cations of metal salts. Additionally, this simple method has been successfully extended to synthesize Co nanostructures with well-controlled morphologies, which indicates the great potential of this strategy in the synthesis of other metal nanostructures on various desired substrates. These metal-substrate composites, especially with desired patterns, are expected to be ideal candidates for wide application in modern electronic and optoelectronic devices, sensors, fuel cells, and energy storage systems.
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PMID:Controlled growth/patterning of Ni nanohoneycombs on various desired substrates. 2003 86

Immobilized Saccharomyces cerevisiae on the surface of chitosan-coated magnetic nanoparticles (SICCM) was applied as a new magnetic adsorbent for the adsorption of Cu(II) from aqueous solution. The prepared magnetic adsorbent was characterized by TEM, XRD and FTIR. TEM images indicated that S. cerevisiae was immobilized on the surface of chitosan-coated magnetic nanoparticles (CCM) successfully, and conglobation was not observed. The XRD pictures suggested that the Fe(3)O(4) nanoparticles were pure Fe(3)O(4) with a spinel structure and that the immobilizing process did not result in the phase change of Fe(3)O(4). Factors that influence the adsorption of Cu(II) were investigated, which included the initial pH of Cu(II) solution, initial concentration of Cu(II) solution and contact time. The optimum pH for Cu(II) absorption was 4.5. The highest removal efficiency of 96.8% was reached when the initial Cu(II) concentration was 60 mg L(-1), and the adsorption capacity was increased with the increase of initial concentration of Cu(II). In particular, SICCM was highly efficient for the fast adsorption of Cu(II) within the first 10 min, and adsorption equilibrium could be achieved in 1h. Equilibrium studies show that the data of Cu(II) adsorption follow the Langmuir model. The maximum adsorption capacity for Cu(II) was estimated to be 144.9 mg g(-1) with a Langmuir adsorption equilibrium constant of 0.0719 L mg(-1) at 301 K.
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PMID:Biosorption of copper(II) by immobilizing Saccharomyces cerevisiae on the surface of chitosan-coated magnetic nanoparticles from aqueous solution. 2006 Feb 11

Screening of different sources of Pd/C shows reagents of highly variable nanoparticle sizes and oxidation states of the metal. Typically, catalysts with higher surface area are viewed as likely to be the more reactive. In this paper a new form of Pd/C, "UC Pd" is described that is shown to contain larger nanoparticles yet it is the most reactive catalyst of those sold commercially for Sonogashira coupling reactions. UC Pd functions efficiently in the absence of a copper co-catalyst, under very mild and "green" conditions using inexpensive 95% EtOH at 50 degrees C. It is also the only form of Pd/C that can be recycled. In side-by-side reactions with several commercially available forms of Pd/C, none compete successfully with UC Pd under standardized conditions. Physical data obtained from extensive surface analysis using TEM, XRD, XPS, and CO-TPD measurements lead to an explanation behind the unique reactivity of this new recyclable form of Pd/C.
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PMID:UC Pd: a new form of Pd/C for Sonogashira couplings. 2014 Sep 14

In this study three types of scanning electron microscopes were used for the size determination of spermatozoa of sterlet Acipenser ruthenus - high vacuum scanning electron microscope (SEM, JEOL 6300), environmental scanning electron microscope (ESEM, Quanta 200 FEG), field emission scanning electron microscope (FESEM, JEOL 7401F) with cryoattachment Alto 2500 (Gatan) and transmission electron microscope (TEM, JEOL 1010). The use of particular microscopes was tied with different specimen preparation techniques. The aim of this study was to evaluate to what degree the type of used electron microscope can influence the size of different parts of spermatozoa. For high vacuum SEM the specimen was prepared using two slightly different procedures. After chemical fixation with 2.5% glutaraldehyde in 0.1M phosphate buffer and post-fixation by 1% osmium tetroxide, the specimen was dehydrated by acetone series and dried either by critical point method or by means of t-butylalcohol. For ESEM fresh, unfixed material was used, which was dropped on microscopic copper grids. In FESEM working in cryo-mode the specimen was observed in a frozen state. Ultrathin sections from chemically fixed and Epon embedded specimens were prepared for TEM observation. Distinct parts of sterlet spermatozoa were measured in each microscope and the data obtained was statistically processed. Results confirmed that the classical chemical procedure of specimen preparation for SEM including critical point drying method led to a significant contraction of all measured values, which could deviate up to 30% in comparison with values measured on the fresh chemically untreated specimen in ESEM. Surprisingly sperm dimensions determinated on ultrathin sections by TEM are comparable with values obtained in ESEM or FESEM.
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PMID:Size determination of Acipenser ruthenus spermatozoa in different types of electron microscopy. 2022 81

The preparation of ligand-functionalised copper(II) hydroxide (Cu(OH)(2)) particles and their conjugation with hydrophobic CdSeS quantum dots (QDs) is reported. The photoluminescence of the QDs is efficiently quenched upon their conjugation with the functionalised Cu(OH)(2) particles. Cu(OH)(2) was functionalised with 2,2'-dipyridyl (2,2-bipy) and n-octanoic acid (OcA), by adsorption of the desired ligand to Cu(OH)(2) suspended in solvent. The resulting functionalised Cu(OH)(2) substrates were characterised using infrared, UV-visible diffuse reflectance, and X-ray photoelectron spectroscopic techniques, TEM imaging, and micro- and thermogravimetric analysis. The spectral data indicated that both 2,2-bipy and OcA coordinated to Cu(OH)(2) in a bidentate manner. The functionalised Cu(OH)(2) substrates were introduced to suspensions of hydrophobic CdSeS QDs, and the resulting QD-functionalised Cu(OH)(2) conjugates were also characterised using spectroscopic and electron microscopy techniques. UV-visible diffuse reflectance spectroscopy indicated the extension of the optical absorption of the Cu(OH)(2) to longer wavelengths upon conjugate formation.
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PMID:Ligand-functionalised copper(II) hydroxide for quantum dot photoluminescence quenching. 2035 Jul 26

Formation of Au-Ag-Cu ternary alloy nanoparticles (NPs) is difficult mainly because the system Cu/Ag is immiscible. We present a new synthetic technique to generate such ternary alloy NPs in silica film matrix employing a three-layer (3L) coating design. In this methodology three successive coating layers were deposited on silica glass substrates from separately prepared Cu-, Au- and Ag-ion incorporated inorganic-organic hybrid silica sols by dipping method. The Au layer is kept in the middle because it is miscible with both the Ag and Cu. The 3L film assembly was subjected to UV- and heat-treatment at 450-750 degrees C in H2-N2 atmosphere. UV-treatment generates small Au and Ag NPs in the respective layers and Cu remains as Cu2+; subsequent heat-treatment in H2-N2 induces the formation of ternary alloy NPs by the interlayer diffusion of nanometals. The final heat-treated film (750 degrees C/H2-N2) shows single and sharp plasmon band centered at 480 nm in the UV-visible spectrum indicating the formation of alloy (solid solution) NPs. GIXRD study shows one set of diffraction peaks which are shifted towards higher angle with respect to the Au or Ag diffraction peaks. FESEM, GIXRD, HRTEM, and SAED analyses reveal that the alloy has a composition close to (Au + Ag)0.88Cu0.12. The EDS analyses using the nano probe attached with TEM confirm the presence of Au, Ag and Cu in all the alloy NPs.
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PMID:Cu-Au-Ag alloy nanoparticles incorporated silica films using a new three-layer deposition technique. 2035 17

We report the anisotropic shape evolution of colloidal copper nanocrystals (Cu NCs) in nonionic microemulsion media by adopting tetraethylammonium hydroxide as a reactant and capping agent in water phase. Relatively large-size Cu NCs were synthesized to confine the growth of Cu NCs below 100 nm. TEM images showed the triangular and hexagonal morphologies of Cu NCs ranging over 55-70 nm after 28 h, while they showed the spherical NCs dominantly under higher concentration of a reducing agent. The surface plasmon resonance (SPR) absorption band of anisotropic Cu NCs was centered at 571 nm with signal enhancement over time. The formation kinetics revealed that the gradual conversion of the Cu seeds into larger NCs during 28 h at room temperature. The NCs were characterized to be Cu rather than CuO or Cu2O by electron diffraction patterns, exhibiting relevant d-spacing figures consistent with the bulk Cu crystal.
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PMID:Anisotropic shape evolution of large-size Cu nanocrystals prepared in nonionic microemulsion media. 2035 67


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