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

The copper-tellurolate cluster [(Cu(6)(TePh)(6)(PPh(2)Et)(5)] has been loaded into the pores of MCM-41 by solid-state impregnation techniques. It was found that the best loading conditions are 110 degrees C and 10(-)(3) Torr static vacuum. The resulting material was analyzed by powder X-ray diffraction (PXRD), nitrogen adsorption isotherms, thermogravimetric analysis (TGA), (31)P CP MAS NMR spectroscopy, and TEM. It was observed that loading is accompanied by loss of the phosphine shell, with retention of the copper-tellurium core. Condensation of the impregnated material may proceed thermally or photochemically. Thermal condensation results in the formation of Cu(2)Te nanoparticles as demonstrated by PXRD, and TEM data suggests that the process has taken place inside the pores of MCM-41. Photochemical condensation yields larger metal-chalcogen clusters in the pores as suggested by the result of UV-vis diffuse reflectance spectroscopy and TEM measurements.
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PMID:Preparation, characterization, and condensation of copper tellurolate clusters in the pores of periodic mesoporous silica MCM-41. 1470 65

A novel adsorbent, aminated and protonated mesoporous alumina, was prepared and employed for the removal of copper from aqueous solution at concentrations between 5 and 30 mg/l, in batch equilibrium experiments, in order to determine its adsorption properties. The removal of copper by the adsorbents increases with increasing adsorbent dosages. The adsorption mechanism is assumed to be an ion exchange between copper and the hydrogen ions present on the surface of the mesoporous alumina. The adsorbent was characterized by XRD, TEM, SEM, and BET methods. The sorption data have been analyzed and fitted to linearized adsorption isotherm of the Freundlich, Langmuir, and Redlich-Peterson models. The batch sorption kinetics have been tested for first-order, pseudo-first-order, and pseudo-second-order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results also showed that the intraparticle diffusion of Cu(II) on the mesoporous catalyst was the main rate-limiting step.
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PMID:Removal of copper from aqueous solution by aminated and protonated mesoporous aluminas: kinetics and equilibrium. 1521 57

Nanofiber formation of dipeptide-based bolaamphiphiles, bis (N-alpha-amide--valyl--valine) 1,n-alkane dicarboxylate (n=6, 8, 10, and 12) in water was analyzed by TEM, SEM, IR, and XRD. The bolaamphiphiles proved to be coordinated to divalent transition-metal cations, such as Co2+, Ni2+, Cu2+, and Zn2+, giving precipitates, colloidal dispersions (loose hydrogels), and hydrogels upon self-assembly at 23 or 70 degrees C. Longer oligomethylene chains and strong interaction between the metal cations and the carboxylate anions are responsible for the hydrogel formation. Energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (EF-SEM) images revealed that the colloidal dispersions and the hydrogels consist of a large number of nanofibers with widths of 15-20 nm and lengths of several micrometers. FT-IR and powder XRD measurement supported the existence of a beta-sheet structure-based nanofibers complexing with metal cations.
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PMID:Metal-complexed nanofiber formation in water from dicarboxylic valylvaline bolaamphiphiles. 1508 73

The Sonogashira reaction proceeds at ambient temperature (30 degrees C) in acetone or room-temperature ionic liquid, 1,3-di-n-butylimidazolium tetrafluoroborate ([bbim]BF4), as solvent under ultrasound irradiation to give enhanced reaction rates, excellent chemoselectivity, and high yields in the absence of a copper cocatalyst and a phosphine ligand. TEM analysis showed the formation of stable, crystalline, and polydispersed Pd(0) nanoparticles as catalyst for the reaction.
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PMID:Copper- and ligand-free Sonogashira reaction catalyzed by Pd(0) nanoparticles at ambient conditions under ultrasound irradiation. 1593 33

The well-mixed copper-nickel nanoparticles were prepared when the molar ratio of Cu2+ to Ni2+ was 1:1 by simultaneous reduction of CuSO4 and NiCl2 with hydrazine in the microemulsion of SDS/n-butanol/n-heptane/water at 70 degrees C, and was characterized by TEM, ED, TGA, EDS, and XRD. ED analysis and XRD patterns suggest the formation of the homogeneous alloy structure in the bimetallic nanoparticles. Average size of the sample calculated from the full width at medium height of peak 111 in the XRD patterns using Scherrer formula is 5.53 nm. TEM photographs show a narrow distribution of Cu-Ni nanoparticles that essentially are monodispersed and the mean diameter is 12 nm. The results indicate that the composition and size of alloy nanoparticles depend on the mole ratio of H2O to SDS, the method of addition of Cu2+ and Ni2+, and the mole ratio of Cu2+ and Ni2+ in the initial precursor solution.
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PMID:Preparation of Cu-Ni alloy nanocrystallites in water-in-oil microemulsions. 1606 Dec 44

A type of anhydrous electrorheological (ER) material of copper phthalocyanine (CuPC)-doped mesoporous TiO2 was synthesized by in situ micelle-assisted incorporation CuPC during mesoporous TiO2 synthesis. TEM, XRD and the nitrogen adsorption-desorption isotherms demonstrated that the material had mesoporous structure and an anatase framework. The ER behavior of the suspensions of CuPC-doped mesoporous TiO2 in silicone oil with the different volume fractions was investigated under an applied electric field. It is found that the suspensions showed visible electrorheological behavior which were compared with that of pure TiO2. The dopants of CuPC molecules within the mesochannel of TiO2 mesoporous sieve improved the conductivity of the particles and produced a proper conductivity of approximately 10(-7) S m(-1). Dielectric spectra of the ER fluid were measured to examine the peak of epsilon'' should appear in the frequency range of 10(2)-10(5) Hz and have a large Deltaepsilon' in this frequency range. Therefore, the both properties may make a conjunct effect on electrorheological behavior.
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PMID:Electrorheological behavior of copper phthalocyanine-doped mesoporous TiO2 suspensions. 1664 40

Porphyrins bearing four urea-linked dodecyl groups (3a) or four urea-linked triethoxysilylpropyl groups (3TEOS) at their peripheral positions were synthesized. 3a tends to assemble into a sheetlike two-dimensional structure due to the predominant hydrogen-bonding interaction among the urea groups and acts as a moderate gelator of organic solvents. On the other hand, its Cu(II) compelx (3a.Cu) tends to assemble into a fibrous one-dimensional structure due to the predominant porphyrin-porphyrin pi-pi stacking interaction and acts as an excellent gelator of many organic solvents. 3TEOS and 3TEOS.Cu, which also act as gelators, afforded similar superstructures as those of 3a and 3a.Cu, respectively, and as evidenced by SEM and TEM observations and XRD measurements, the original superstructures could be precisely immobilized by in situ sol-gel polycondensation of the triethoxysilyl groups. The TEM images of 3a gels and 3TEOS gels after sol-gel polycondensation showed a fine striped structure, the periodical distance of which was either 2 or 4 nm. X-ray crystallographic analysis of a single crystal obtained from a reference porphyrin bearing four urea-linked butyl groups revealed that there are two different porphyrin-stacked columns in the crystal and both the 2 nm distance and the 4 nm distance can appear, depending on the observation tilting angle. The hybrid gel prepared from 3TEOS.Cu by sol-gel polycondensation showed unique physicochemical properties such as a high sol-gel phase-transition temperature (>160 degrees C), sufficient elasticity, high mechanical strength, etc. Thus, the present study has established new concepts for molecular design of porphyrin-based gelators on the basis of cooperative and/or competitive actions of hydrogen-bonding and pi-pi stacking interactions and for immobilization of their superstructures leading to development of new functional organic/inorganic hybrid materials.
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PMID:Porphyrin gels reinforced by sol-gel reaction via the organogel phase. 1620 18

The effects of cations on the absorption spectra of silver sols have been investigated by the UV-vis spectrometry and TEM. Experiments showed that injection of certain amounts of transition metal cations into silver sols resulted not only in the aggregation of silver nanoparticles but also in the appearance of a new band centered near 510 nm in the absorption spectra of silver sols. However, the new band was not observed in the presence of alkaline earth metal cations or the Mv2+ cations. The peak position of the new band depends on the nature as well as the concentration of metal cations used. Comparing the peak positions of the new bands, it was found that the new band induced by the injection of Cr3+ was red-shifted with respect to those induced by Cu2+, Zn2+, or the Cd2+ cations. It is reasonable that this band near 510 nm should be attributed to the coeffects of the adsorption of metal cations onto the surfaces of silver nanoparticles and the aggregation of silver nanoparticles.
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PMID:Adsorption of cations onto the surfaces of silver nanoparticles. 1625 71

Room-temperature synthesis of Pd nanoparticles protected by polyvinylpyrrolidone (PVP) has been successfully achieved by merely adding sodium hydroxide (NaOH) acting as accelerator for the reduction of Pd(II) in ethylene glycol (EG) without any externally added reducing agent. The Pd particle sizes were controlled in the range from 8.6 to 2.4 nm by changing the concentration of NaOH from 0 to 3.2x10(-1) M. The particle formation was monitored by UV-vis spectroscopy and the microstructure of Pd nanoparticles was analyzed by TEM and XRD. The product of adding NaOH in EG was characterized by FTIR and a -CHO group which possesses reductive ability was identified. In addition, the prepared Pd nanoparticle could serve as an effective activator for electroless copper deposition (ECD) on epoxy substrate, which is an essential process in the printed circuit board (PCB) industry. In contrast to existing commercial activators, the new activator shows superior stability and excellent performance for ECD.
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PMID:Chemical preparation of Pd nanoparticles in room temperature ethylene glycol system and its application to electroless copper deposition. 1628 74

beta-FeOOH particles were prepared by aging aqueous FeCl3 solutions containing Ti(IV), Cr(III), and Cu(II) at room temperature for 360 days. The structures of the formed particles were investigated by various techniques including TEM, XRD, XAFS, and adsorption of N2 and H2O. Ti(IV) markedly impeded the crystallization and particle growth of beta-FeOOH by coprecipitation with Fe(III) and disturbing the short-range structure of beta-FeOOH particles. In the presence of a large amount of Ti(IV), it was pronounced that the hydrolysis of Ti(IV) impeded beta-FeOOH formation by reducing the solution pH, whereas Cr(III) and Cu(II), which were hardly involved in the products, gave rise to no noticeable effects on the formation of beta-FeOOH particles. The knowledge obtained in this study can be available for interpretation of the anti-corroding function of Ti alloyed with steels in a Cl- -containing environment.
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PMID:Structures of beta-FeOOH particles formed in the presence of Ti(IV), Cr(III), and Cu(II) ions. 1629 Jun 36


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