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

A novel and easy synthesis pathway of small SnO2 nanoparticles is reported. The method consists of the spontaneous hydrolysis of SnCl4 x 5H2O in dimethyl sulfoxide (DMSO), containing 3% water, at room temperature. The structure of the SnO2 nanocrystals corresponds to that of the cassiterite phase, as shown by powder X-ray diffraction and HR-TEM. The UV-visible electronic absorption and emission spectra of the SnO2 colloids are discussed. The reactions of NO(g) and SO2(g) with ZnO (wurtzite phase) and SnO2 nanocolloids are studied. The interaction of NO with ZnO nanoparticles generates the dissolution of the particles and it is quite probable that NO3(-1), NOs(-2), N2O and N2 are formed; while its contact with SO2 probably yields SO4(-2), SO3(-2) and also the dissolution of the particles is observed. When these gases are reacted with SnO2, then NO3(-1), NO2(-1), SO3(-2) and SO4(-2), were respectively obtained.
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PMID:Direct interaction of colloidal nanostructured ZnO and SnO2 with NO and SO2. 1920 11

The synthesis and characterization of colloidal mesoporous silica (CMS) functionalized with vinyl-, benzyl-, phenyl-, cyano-, mercapto-, aminopropyl- or dihydroimidazole moieties is reported. Uniform mesoporous particles ranging in size from 40 to 150 nm are generated in a co-condensation process of tetraethylorthosilicate (TEOS) and organotriethoxysilanes (RTES) in alkaline aqueous media containing triethanolamine (TEA) in combination with cetyltrimethylammonium chloride (CTACl) serving as a structure-directing agent. The materials are obtained as colloidal suspensions featuring long-term stability after template removal by ion exchange with an ethanolic solution of ammonium nitrate or HCl. The spherical particles exhibit a wormlike pore system with defined pore sizes and high surface areas. Samples are analyzed by a number of techniques including TEM, SEM, DLS, TGA, Raman, and cross-polarized (29)Si-MAS NMR spectroscopy, as well as nitrogen sorption measurements. We demonstrate that co-condensation and grafting methods result in similar changes in the nitrogen adsorption behavior, indicating a successful internal lining of the pores with functional groups through both procedures.
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PMID:Colloidal suspensions of functionalized mesoporous silica nanoparticles. 1920 12

Stable pseudo-boehmite sol was obtained by adding HNO3 as peptizing agent and adjusting pH to be 2.0. TEM result shows that the AlOOH colloidal particle size is about 60 nm. Field emission transmission electron microscope (FETEM) result shows that pseudo-boehmite colloidal particle is composed of 8 nm scaled AlOOH nanocrystals. The interaction of Eu3+ ions and colloidal AlOOH nanoparticle was investigated. The adsorption of Eu3+ ions on the surface of AlOOH nanocrystal was attributed to the chemical adsorption caused by electrostatic attraction. The photoluminescence characters of Eu3+ in AlOOH/Eu(NO3)3 composite sol system were investigated. The 529 nm emission intensity of Eu3+, I592, decreased with the increase in the molar ratio of AlOOH and Eu3+, RBoe/Re. The adsorption ratio (denoted R) and the adsorption density (denoted D) of Eu3+ ions on AlOOH colloidal particle surface was calculated from I592. The results show that the values of R and D increase with increasing RBoe/Re.
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PMID:[Fluorescence studies of Eu ions adsorption on pseudo-boehmite colloidal particle surface]. 1938 34

Utilization of single-walled carbon nanotubes (SWNTs) in high-end applications hinges on separating metallic (met-) from semiconducting (sem-) SWNTs. Surfactant amines, like octadecylamine (ODA) have proven instrumental for the selective extraction of sem-SWNTs from tetrahydrofuran (THF) nanotube suspensions. The chemical shift differences along the tail of an asymmetric, diacetylenic surfactant amine were used to probe the molecular dynamics in the presence and absence of nanotubes via NMR. The results suggest that the surfactant amine head is firmly immobilized onto the nanotube surface together with acidic water, while the aliphatic tail progressively gains larger mobility as it gets farther from the SWNT. X-ray and high-resolution TEM studies indicate that the sem-enriched sample is populated mainly by small nanotube bundles containing ca. three SWNTs. Molecular simulations in conjunction with previously determined HNO(3)/H(2)SO(4) oxidation depths for met- and sem-SWNTs indicate that the strong pinning of the amine surfactants on the sem-enriched SWNTs bundles is a result of a well-ordered arrangement of nitrate/amine salts separated with a monomolecular layer of H(2)O. Such continuous 2D arrangement of nitrate/amine salts shields the local environment adjacent to sem-enriched SWNTs bundles and maintains an acidic pH that preserves nanotube oxidation (i.e., SWNT(n+)). This, in turn, results in strong interactions with charge-balancing NO(3)(-) counterions that through their association with neutralized surfactant amines provide effective THF dispersion and consequent sem enrichment.
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PMID:Enrichment mechanism of semiconducting single-walled carbon nanotubes by surfactant amines. 1939 91

Nanocrystalline HoCrO4 powder was synthesized by a combustion technique using glycine and citric acid as the fuels in different oxidant-to-fuel ratios. Fuel-deficient glycine-nitrate combustion reaction resulted in zircon type HoCrO4 free from HoCrO3 phase. The crystallite size for the phase pure product after calcination at 575 degrees C in oxygen atmosphere was found to be 34 nm by X-ray line broadening. The TEM observations showed highly porous structure. Magnetic measurements reveal the ferromagnetic nature of HoCrO4 nano particles with Tc = 18 K. The compound shows high remanence of 30.4 emu x g(-1) and low coercivity of -0.0343 T.
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PMID:Nanocrystalline HoCrO4: facile synthesis and magnetic properties. 1944 41

Yellowish (Fe, N)-doped nanocrystalline TiO2 powders have been prepared using TiOSO4, CO(NH2)2, Fe(NO3)3.9H2O and CN3H5.HCl as precursors by hydrothermal method. The as-synthesized powders were anatase in phase and the grain size was about 10 nm according to the TEM photos. The ratio of Fe/Ti is 2.2 at% and N/O is 0.8 at% respectively. TiO2 powders were mixed with organic silicon and acrylic syrup to test their antibacterial performance by the colony counting method. The results show that the sterilization ratio of E. coli by the heat-treated (Fe, N)-doped nanocrystalline TiO2 powders is reached up to 94.5% while that of the powders without any heat treatment is 91.1% by 8 hours-400 lux-Visible-light irradiation with humidity of 55% RH.
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PMID:Preparation of (Fe, N)-doped TiO2 powders and their antibacterial activities under visible light irradiation. 1944 63

Hollow mesoporous carbon spheres with magnetic cores are directly replicated from hollow mesoporous aluminosilicate spheres with hematite cores by a simple incipient-wetness impregnation technique. The amount of magnetic cores and the saturation magnetization value can be easily tuned by changing the concentration of iron nitrate solution used in the synthesis procedure. As-prepared hollow mesoporous carbon spheres with magnetic cores are used as separable bilirubin adsorbents and show very good adsorptive properties. The characteristics of as-prepared composites are examined by XRD, N(2) sorption, TEM, vibrating-sample magnetometry, and UV/Vis spectroscopy.
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PMID:Hollow mesoporous carbon spheres with magnetic cores and their performance as separable bilirubin adsorbents. 1958 33

In this work, we report the preparation of the Sm2O3 nanoparticle precursors (Sm(OH)3) via a simple W/O microemulsion process, in which microemulsions of cetyltrimethylammonium bromide (CTAB)/alkanol/1-octane/Sm(NO3)3 aqueous solution were added into sodium hydroxide (NaOH) aqueous solutions. The Sm2O3 nanoparticles were then prepared by calcining the precursors at 900 degrees C. Particularly, DeltaG(c-->i), which is the change in standard Gibbs free energy for transferring cosurfactant from the continuous phase to the microemulsion interface and can be used to estimate the thermodynamic properties of microemulsions, was determined using the dilution method. The effects of alkanol carbon chain length (1-pentanol, 1-hexanol, 1-heptanol and 1-octanol) and the reaction temperatures (298, 308, 318 and 328 K) on both DeltaG(c-->i) and Sm2O3 nanoparticle size have been investigated. Specifically, the Sm2O3 nanoparticle size, when calcined at 900 degrees C, was found to be mainly controlled by DeltaG(c-->i), and was thereby affected by the thermodynamic properties of microemulsions. The obtained products were characterized by DSC-TGA, XRD, TEM and UV-Vis. The results showed that DeltaG(c-->i) decreased with the increase in both the length of alkanol carbon chain and the reaction temperature, and the average size of Sm2O3 nanoparticles decreased as DeltaG(c-->i) decreased. The effect of microemulsion thermodynamic properties on Sm2O3 nanoparticle size reported here can provide some insights in controllable preparation of other rare earth oxide nanoparticles via the microemulsion route.
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PMID:Effect of the thermodynamic properties of W/O microemulsions on samarium oxide nanoparticle size. 1974 Apr 77

Cryo-TEM, SAXS, and light microscopy techniques were used to probe the morphology and kinetics of silver stearate self-assembly and crystallization from the reaction of silver nitrate with lithium stearate. Unlike the reaction of sodium stearate with silver nitrate, which proceeds via micelle aggregation, the lithium stearate forms vesicles that drastically change the reaction kinetics of the silver stearate nucleation and self-assembly process. In addition, even with excess silver nitrate present, only about 80% of the lithium stearate can be converted to silver stearate. The presence of the residual lithium stearate inhibits the silver stearate crystal growth process. Consequently, no silver stearate micelle aggregates of any significant size form, unlike the system utilizing sodium stearate. Instead, significantly smaller silver stearate crystals result from lithium stearate compared to the silver stearate crystals from sodium stearate and provide an opportunity to further control silver stearate self-assembly and crystal growth.
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PMID:Cation-controlled crystal growth of silver stearate: cryo-TEM investigation of lithium vs sodium stearate. 2001 6

Three nanobiocomposites (PRAg31, PRAg11, and PRAg13; the numbers indicate the weight ratios of poly(o-methoxyaniline) (POMA) and ribonucleic acid (RNA), respectively), produced from the same amount of POMA (P) and silver nitrate (AgNO(3)) with differing proportions of RNA (R) are prepared by aging the aqueous solutions of the mixture for 3 weeks at 30 degrees C. The scanning and transmission electron microscopy (SEM and TEM) indicate Ag nanoparticle formation on the hybrid fiber surface and in the PRAg31 system the hybrid fibrils become coated with metallic Ag, the phenomenon being termed as "nanojacketting". The circular dichroism (CD) spectra indicate a small distortion of RNA conformation from A helix toward B helix. FTIR and UV-vis spectra suggest that POMA (emeraldine base, EB) being doped by Ag(+) become oxidized to its pernigraniline base (PB) form and reduce Ag(+) to metallic Ag. The Ag nanoparticles thus produced become stabilized on the fibril surface by co-ordination through nitrogen atoms of POMA (PB) chains. The much slower red shift of pi band to polaron band transition peak in PRAg31 than that of the other two nanobiocomposites is indicative of difficulty in conformational transitions of POMA chain in the "nanojacketted" hybrid fibrils. The dc-conductivity values of the nanobiocomposites are two orders higher than that of the pure POMA-RNA hybrids. The PRAg31 system exhibits rectification property in the I-V characteristic curves and a probable explanation based on the feasibility of p-n junction formation arising from the transfer of lone pair of electrons of nitrogen of POMA (p-type) to the Ag nanoparticles (n-type) has been offered.
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PMID:RNA-poly(o-methoxyaniline) hybrid templated growth of silver nanoparticles and nanojacketing: physical and electronic properties. 2002 Jul 56


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