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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Water-soluble triblock copolymers consisting of hydrophobic-hydrophilic-dye segments were synthesized by ring-opening metathesis polymerization (ROMP) of norbornadiene monomers, copper-catalyzed click reaction, osmium-catalyzed dihydroxylation, and the following transformations. These polymers in aqueous conditions could form spherical assemblies, whose diameters were 50-60 nm by TEM measurement. From in vivo optical imaging experiments, the spherical assemblies of these copolymers could be efficiently accumulated in tumor cells. In addition, the spherical assemblies of water-soluble polymers accumulated in a tumor cell over two weeks.
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PMID:Ring-opening metathesis polymerization-based synthesis of ICG-containing amphiphilic triblock copolymers for in vivo tumor imaging. 1919 62

An Al(86)Mn(3)Be(11) alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be(4)AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. The composition of the Be(4)AlMn slightly deviated from the stoichiometric composition, whereas the composition of the i-phase was approximately Al(52)Mn(18)Be(30), containing an appreciable amount of Be. The average composition of the hexagonal phase was Al(66)Mn(21)Be(13). Deep etching and particle extraction provided a deep insight into the three-dimensional morphology of the i-phase and the hexagonal phase, whereas Be(4)AlMn was slightly attacked by the etchant. The i-phase was present predominantly in the form of dendrites and a rodlike eutectic phase. The hexagonal phase was primarily in the form of hexagonal platelets, whereas Be(4)AlMn was rather irregular in shape. The morphology of the i-phase can be explained by predominant growth in 3-fold directions and the lowest energy of the 5-fold planes, leading to the faceting and adopting a pentagonal dodecahedron shape. The brightnesses of phases in the backscattered electron images were rationalized by determining their backscattering coefficients. TEM investigation showed considerable phason strain in the i-phase, and the polycrystalline nature of the Be(4)AlMn phase.
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PMID:Characterization of cast Al86Mn3Be11 alloy. 1925 Apr 57

Adsorption of nickel, copper, zinc and cadmium from aqueous solutions on carbon nanotubes oxidized with concentrated nitric acid was carried out in single, binary, ternary and quaternary systems. TEM and adsorption of nitrogen were used to determine texture and structural parameters, respectively. The surface chemistry was evaluated using the pH at the point of zero charge, FTIR spectroscopy and XPS analysis. The experimental results showed that all isotherms for Cu(2+)(aq) fit to Langmuir model in each system. On the other hand, the isotherms for Ni(2+)(aq), Cd(2+)(aq) and Zn(2+)(aq) in multi-component systems reveal the effect of competition for adsorption sites seen as a decrease in the amount adsorbed. The uptakes at the equilibrium concentration of 0-0.04 mmol L(-1) in single system and 0-0.15 mmol L(-1) in binary system are in the order Cu(2+)(aq)>Ni(2+)(aq)>Cd(2+)(aq)>Zn(2+)(aq) while for the ternary and quaternary, the order is Cu(2+)(aq)>Cd(2+)(aq)>Zn(2+)(aq)>Ni(2+)(aq). The results indicate that the mechanism of adsorption is governed by the surface features, ion exchange process and electrochemical potential. The latter plays a significant role in multi-component adsorption where redox reactions, not only on the adsorbent surface but also between the adsorbates, are likely to occur.
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PMID:Investigation of factors affecting adsorption of transition metals on oxidized carbon nanotubes. 1926 2

N,N-Dialkylcarbamato complexes of copper(II), [Cu(O(2)CNR(2))(2)] (R = All = allyl, C(3)H(5); iPr, CH(CH(3))(2)) were prepared with the aim of functionalizing silica and nanostructured silica-zirconia matrices. The mixed matrices for the grafting reactions were prepared by copolymerizing MAPTMS (methacryloxypropyltrimethoxysilane), the precursor for the silica matrix, with the zirconium tetranuclear derivative [Zr(4)O(2)(OMc)(12)] (OMc = methacrylate), the precursor for the zirconia nanoparticles. Suspension of the silica and silica-zirconia matrices in a solution of the copper dialkylcarbamate led to the functionalization of the respective substrates. The composition, microstructure, morphology, and physicochemical nature of the copper species grafted on the matrices were investigated by FTIR, X-ray photoelectron spectroscopy (XPS), EPR, X-ray absorption spectroscopy (XAS), XRD, TEM, and dinitrogen adsorption. The effect of selected experimental parameters (the nature of the copper precursor and of the matrix, grafting time, thermal treatment) on the grafting reaction was investigated. The Cu/Si ratio is increased by increasing the grafting time and the ZrO(2)-SiO(2) matrix is more reactive to attack by the carbamato complexes than either prepared or commercial SiO(2). After functionalization of the matrix, thermal treatment yielded nanostructured copper(II) oxide clusters, average diameter 12-15 nm, uniformly supported on the silica and on the silica-zirconia matrices.
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PMID:Nanostructured copper oxide on silica-zirconia mixed oxides by chemical implantation. 1930 78

A new mass spectrometry surface imaging method is presented in which ion-sputtered neutrals are postionized by wavelength-tunable vacuum ultraviolet (VUV) light from a synchrotron source. Mass spectra and signal counts of the photoionized neutrals from GaAs (100) and Au are compared to those of the secondary ions. While clusters larger than dimers are more efficiently detected as secondary ions, certain species, such as As(2), Au, and Au(2), are more efficiently detected through the neutral channel. Continuously tuning the photon wavelength allows photoionization efficiency (PIE) curves to be obtained for sputtered As(m) (m = 1,2) and Au(n) (n = 1-4). From the observed ionization thresholds, sputtered neutral As and Au show no clear evidence of electronic excitation, while neutral clusters have photoionization onsets shifted to lower energies by approximately 0.3 eV. These shifts are attributed to unresolved vibrational and rotational excitations. High-spatial resolution chemical imaging with synchrotron VUV postionization is demonstrated at two different photon energies using a copper TEM grid embedded in indium. The resulting images are used to illustrate the use of tunable VUV light for verifying mass peak assignments by exploiting the unique wavelength-dependent PIE of each sputtered neutral species. This capability is valuable for identifying compounds when imaging chemically complex systems with mass spectrometry-based techniques.
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PMID:Imaging with mass spectrometry: a secondary ion and VUV-photoionization study of ion-sputtered atoms and clusters from GaAs and Au. 1937 Nov 12

Fe(3)O(4) magnetic nanoparticles with different particle sizes were synthesized using two methods, i.e., a co-precipitation process and a polyol process, respectively. The atomic pair distribution analyses from the high-energy X-ray scattering data and TEM observations show that the two kinds of nanoparticles have different sizes and structural distortions. An average particle size of 6-8 nm with a narrow size distribution was observed for the nanoparticles prepared with the co-precipitation method. Magnetic measurements show that those particles are in ferromagnetic state with a saturation magnetization of 74.3 emu g(-1). For the particles synthesized with the polyol process, a mean diameter of 18-35 nm was observed with a saturation magnetization of 78.2 emu g(-1). Although both kinds of nanoparticles are well crystallized, an obviously higher structural distortion is evidenced for the co-precipitation processed nanoparticles. The synthesized Fe(3)O(4) particles with different mean particle size were used for treating the wastewater contaminated with the metal ions, such as Ni(II), Cu(II), Cd(II) and Cr(VI). It is found that the adsorption capacity of Fe(3)O(4) particles increased with decreasing the particle size or increasing the surface area. While the particle size was decreased to 8 nm, the Fe(3)O(4) particles can absorb almost all of the above-mentioned metal ions in the contaminated water with the adsorption capacity of 34.93 mg/g, which is approximately 7 times higher than that using the coarse particles. We attribute the extremely high adsorption capacity to the highly-distorted surface.
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PMID:Tailoring size and structural distortion of Fe3O4 nanoparticles for the purification of contaminated water. 1941 49

This study used ionotropic crosslinking to synthesize chitosan-tripolyphosphate chelating resin beads, which are used to fabricate zero-valent copper-chitosan nanocomposites. The copper nanoparticles were dispersed on chitosan-tripolyphosphate beads, and were thus able to maintain appropriate dispersion and stability, which greatly improves their applicability. The fabrication process contains two steps: using chitosan-tripolyphosphate beads to adsorb Cu(II) ions, followed by chemical reduction to reduce Cu(II) ions to zero-valent copper. This study explored the adsorption of synthesized chitosan-tripolyphosphate beads to Cu(II) ions, and used SEM/EDS, XPS, and TEM to examine the properties of zero-valent copper-chitosan nanocomposites. The results showed that, the adsorption behavior of hexavalent chromium from aqueous solution onto fabricated nanocomposites has better adsorption capacity than that of the chitosan-tripolyphosphate beads.
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PMID:Synthesis of zero-valent copper-chitosan nanocomposites and their application for treatment of hexavalent chromium. 1941 51

PLGA nanoparticles were prepared via a modified W/O/W emulsion solvent diffusion process, in which all formulation components were fully biocompatible and biodegradable. Different independent processing parameters were systematically studied. Nanoparticles were characterized by DLS (particle size, polydispersity, zeta-potential) and TEM/AFM (surface morphology). An optimized formulation was used to encapsulate copper complexes of cyclen and DOTA as potential PET imaging agents. Results showed that the predominant formulation factors appeared to be the lactide-to-glycolide (L:G) ratio of PLGA, the nature of the diffusion phase, and the presence of hydroxyl ions in the first-emulsion aqueous phase. By regulating those 3 parameters, PLGA nanoparticles were prepared with very good preparation yields (>95%), a size less than 200 nm and a polydispersity index less than 0.1. TEM pictures showed nanoparticles with a narrow size distribution, a spherical shape and a smooth surface. The optimized formulation allowed to encapsulate Cu-cyclen and Cu-DOTA complexes with an encapsulation efficiency between 20% and 25%.
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PMID:Development and physicochemical characterization of copper complexes-loaded PLGA nanoparticles. 1942 98

Azide moiety-functionalized gold nanoparticles were conjugated with acetylene functionalized single-walled carbon nanotubes by employing copper-catalyzed Huisgen's [3+2] dipolar cycloaddition 'click chemistry' reaction. Evidences of conjunction were observed by TEM, EDX and Raman images.
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PMID:Assembly of gold nanoparticles on single-walled carbon nanotubes by using click chemistry. 1945 1

Modified goethite samples were prepared with Mg(II) content varying in the range of 0-1.36%. A typical TEM of Mg(II) doped sample showed needle shaped goethite particles having 10-30 nm width and 100-400 nm length. Sorption studies of cations namely Pb(II), Cu(II), Cd(II), Zn(II) and Fe(III) were conducted onto the Mg(II) doped modified goethite surface. Goethite doping with 0.18 M Mg (GMg(2)) showed better sorption capacity for Pb(II), Cu(II) and Cd(II). Therefore, the effect of contact time, solution pH, sorbate and sorbent concentrations on the sorption of various metal ions was studied on this sample in batch experiments. The time data fitted to pseudo-second-order kinetics for all the metal ions. Sorption on GMg(2) sample for the metal ions increased with the increase in pH from 2 to 4. The isothermic data showed good fit to both Langmuir and Freundlich isotherms except for Cd(II) which followed only the later model. The sorption capacities with respect to Pb(II), Cd(II), Zn(II), Cu(II) and Fe(III) were found to be 87.7, 153.25, 86.25, 33.4 and 72.5mg/g respectively. The results of sorption studies on GMg(2) from binary and ternary solutions have also been presented. The XRD patterns of metal ion loaded GMg(2) samples confirmed that metal ion adsorption resulted in shifting of d-values/altering of relative intensity (RI) of major planes of goethite.
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PMID:Synthesis of Mg(II) doped goethite and its cation sorption behaviour. 1958 Oct 48


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