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

Synthetic colloidal calcium hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2): CaHap) was treated with pyrophosphoric acid (H(4)P(2)O(7): PP) in acetone and the materials were characterized by XRD, TEM, FTIR, and N(2) and H(2)O adsorption measurements. XRD patterns and morphology of CaHap particles were essentially not changed by the modification. The additional amount of PO(4) of CaHap was increased with an increase of PP concentration and the Ca/P molar ratio of the particles decreased from 1.62 to 0.81. IR results indicated that the isolated surface POH band developed with increasing the PP concentration up to 6.0 mmol dm(-3) by the reaction of isolated surface POH groups of CaHap and pyrophosphoric acids. Above 10.2 mmol dm(-3), a hydrogen-bonding surface POH band appeared at 2913 cm(-1) and enlarged with increasing the PP concentration, while the isolated surface POH band was weakened. The results of N(2) and H(2)O adsorption measurements revealed that the modified particles aggregated compared to the unmodified ones, which would be due to the formation of hydrogen-bonding surface POH groups among the particles.
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PMID:Structure of synthetic calcium hydroxyapatite particles modified with pyrophosphoric acid. 1572 40

The phase transformation of mesostructured titanium phosphate (TiPO) from hexagonal to lamellar structure was observed in a simply hydrothermal treatment, accompanied by drastically morphological changes in the micrometer-sized particles. XRD pattern revealed that different mesostructures were obtained by simply varying hydrothermal temperature or treatment duration. SEM and TEM observations showed the morphological evolution from individual particles to interconnected nanoplatelets. A significant blue shift in UV-vis spectra was observed for lamellar mesostructured material, which may be associated with the different coordinated Ti-sites in the hexagonal and lamellar mesostructures. FT-IR spectra and detailed (31)P MAS NMR studies indicated that additional POH groups were presented in the lamellar structure, which might play a key role in the structural and morphological transformations of mesostructures.
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PMID:Structural and morphological transformations of mesostructured titanium phosphate through hydrothermal treatment. 1788 92

The physicochemical properties of aqueous solutions of novel anionic heterogemini surfactants (POH-n-ODAm) have been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The surfactants are synthesized from oleic acid: the hydrocarbon chain (n=6, 8 and 10) is covalently bound to the terminal carbonyl group and a phosphate headgroup is introduced to the cis double bond of an oleic acid derivative. The static surface tension and fluorescence measurements demonstrate that the critical aggregation concentration (cac) is decreased significantly with increasing hydrocarbon chain length, resulting from the increased hydrophobicity and the increased degree of dissymmetry of the surfactants. As is generally seen for gemini surfactants, the measured cac is much lower than that of the monomeric phosphate-type surfactant reported previously. At concentrations well above the cac, the heterogemini surfactants spontaneously form vesicular assemblies in bulk solution, which is confirmed with DLS and cryo-TEM measurements.
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PMID:Synthesis and aqueous solution properties of novel anionic heterogemini surfactants containing a phosphate headgroup. 1958 36