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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An N-alky-beta-Ala-L: -Phe derivative, N'-octadecyl-N ( alpha )-[(N-acryloyl)-beta-alanyl]-L: -phenylalanineamide (1), with a polymerizable head group has been synthesized and telomerized with the silane coupling agent 3-mercaptopropyltrimethoxysilane (MPS). SEM and DSC observations indicated that both 1 and its telomer (T-1) could self-assemble into fibrillar forms with highly ordered structures in organic media such as benzene through complementary hydrogen bonding between the amide moieties. T-1 was grafted onto porous silica gels through the terminal trimethoxysilyl group and then packed into a stainless steel column. RP-HPLC results for polycyclic aromatic hydrocarbons (PAHs) demonstrated that significantly higher molecular shape recognition could be achieved by silica-supported T-1 (Sil-T-1). In this paper, the mechanism of the selectivity enhancement in HPLC by Sil-T-1 is discussed on the basis of comparing with the corresponding L: -Phe derivative N'-octadecyl-N ( alpha )-(acryloyl)-L: -phenylalanineamide (2) without beta -Ala and the stationary phase (Sil-T-2) obtained from it. The HPLC column materials Sil-T-1 and Sil-T-2 were characterized by DSC, TGA, DRIFT-IR, and (13)C and (29)Si CP-MAS NMR spectroscopic measurements.
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PMID:Synthesis and assessment of molecular recognizability by RP-HPLC of an N-alkyl-beta-Ala-L: -Phe-derived organic phase with self-assembling ability. 1879 58

Manganese-containing nanoscale metal-organic frameworks (NMOFs) with controllable morphologies were synthesized using reverse-phase microemulsion techniques at room temperature and a surfactant-assisted procedure at 120 degrees C with microwave heating. The nanoparticles were characterized using a variety of methods including SEM, TEM, TGA, PXRD, and ICP-MS. Although the nanoparticles gave a modest longitudinal relaxivity (r1) on a per Mn basis, they provided an efficient vehicle for the delivery of large doses of Mn2+ ions which exhibited very high in vitro and in vivo r1 values and afforded excellent MR contrast enhancement. The particle surface was also modified with a silica shell to allow covalent attachment of a cyclic RGD peptide and an organic fluorophore. The cell-targeting molecules on the Mn NMOFs enhanced their delivery to cancer cells to allow for target-specific MR imaging in vitro. The MR contrast enhancement was also demonstrated in vivo using a mouse model. Such core-shell hybrid nanostructures provide an ideal platform for targeted delivery of other imaging and therapeutic agents to diseased tissues.
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PMID:Manganese-based nanoscale metal-organic frameworks for magnetic resonance imaging. 1884 56

Dextrin, which is widely used throughout many industries for their functional properties, was selected for studying the influences of gamma irradiation on its viscosity, physicochemical properties and dextrin granule structure. The formation of radicals during irradiation process of dextrin in air condition was investigated by electron spin resonance (ESR) showing the influence of irradiation and storage parameters on the nature and concentration of the free radicals. Two major radicals or groups of radicals are observed. The radicals show g-values varying among g=2.0102+/-0.0002 and g=2.0126+/-0.0006. Irradiation was observed to induce increases in the intensity of single. The material left behind after irradiation treatment was characterized using thermal analysis, TGA and DSC. A structural analysis was made using SEM and X-ray diffraction to investigate whether the partial hydrolysis had any influence on the granular structure and the crystallinity of the dextrin. The results show that dextrin undergoes oxidative degradation under the influence of gamma radiation.
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PMID:Controlling degradation of low-molecular-weight natural polymer "dextrin" using gamma irradiation. 1899 9

The effect caused by dehydration and rehydration of the synthetic Na-magadiite was investigated by TGA, XRD, SEM, and (29)Si NMR. Thermal analysis of Na-magadiite presented two well-defined loss mass stages between 20 and 150 degrees C and another between 270 and 310 degrees C, both related to the removal of interlayer water. The swelling behavior of Na-magadiite was studied by thermal dehydration data obtained at 150 and 300 degrees C, and respective rehydration by water addition. X-ray patterns showed that the dehydration of Na-magadiite at 150 and 300 degrees C provoked the basal spacing decrease. The XRD also showed that only the material treated at 150 degrees C returned to the original structure with the rehydration. (29)Si NMR spectra showed that after rehydration, the Q(3)/Q(4) relationship presented the same value for Na-magadiite treated at 150 degrees C. However, this Q(3)/Q(4) value decreased when the treatment was done at 300 degrees C. Kinetic studies of thermal decomposition showed that the dehydration of magadiite is based on a phase boundary-controlled reaction, caused by contracting areas. The exfoliation of lamellas with thermal treatment can explain this behavior, as observed in SEM images.
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PMID:Effect of thermal dehydration and rehydration on Na-magadiite structure. 1902 25

Despite considerable progress in the field of metal nanoparticles synthesis, major challenges remain in many practical applications of nanoparticles which require their immobilization on solid substrates, presenting additional difficulty in separation and processing. Here, transparent nanoporous cellulose gel obtained from aqueous alkali hydroxide-urea solution was examined as supporting medium for noble metal nanoparticles. Silver, gold, and platinum nanoparticles were synthesized in the gel by hydrothermal reduction by cellulose or by added reductant. Both methods gave nanoparticles embedded with high dispersion in cellulose gels. Supercritical CO2 drying of the metal-carrying gel gave corresponding aerogels with high transmittance, porosity, surface area, moderate thermal stability, and good mechanical strength. The cellulose and metal-cellulose gels were characterized by UV/vis spectroscopy, optical microscopy, SEM, TEM, XRD, nitrogen physisorption, TGA, and tensile testing, systematically.
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PMID:Nanoporous cellulose as metal nanoparticles support. 1905 96

Two dioctadecyl L-glutamic acid derivatives with amide and ester type bondings have been synthesized and immobilized from 3-aminopropyltrimethoxysilane (APS) grafted silica (Sil-APS) to be used in reversed-phase high-performance liquid chromatography (RP-HPLC). Subsequent studies showed that dioctadecyl-L-glutamide derivative (GLN) can self-assemble into highly ordered structures by forming three-dimensional fibrillar aggregates as observed in scanning and transmission electron microscopes (SEM and TEM). Variable temperature (1)H NMR and FT-IR spectra of organogel revealed that the special aggregation morphology shown by GLN was stabilized by inter and or intra molecular hydrogen bonding among amide moieties. However, such ordered aggregated or self-assembled structures were not observed for the dioctadecyl-L-glutamate (GLU) derivative. The stationary phases Sil-GLN and Sil-GLU were characterized by DRIFT, elemental analysis, TGA, and (13)C and (29)Si CP-MAS NMR spectroscopic measurements. The chromatographic selectivity for both stationary phases was evaluated from the retention studies of different size and shape polycyclic aromatic hydrocarbons (PAHs). The chromatographic experiment for PAHs and geometrical isomers in RP-HPLC showed that Sil-GLN demonstrated extremely enhanced selectivity than Sil-GLU. The higher selectivity attributed by Sil-GLN has been brought by multiple pi-pi interactions among the pi-electrons of the grafted organic phase and pi-electrons of the guest PAHs molecules. Thermodynamic studies for linear and nonlinear PAHs revealed that the retention behavior does not change over a temperature range from 10 to 60 degrees C for both stationary phases.
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PMID:Evaluation of selectivity for L-glutamide-derived highly ordered assemblies in reversed-phase high-performance liquid chromatography. 1906 17

An organic-inorganic hybrid poly-o-toluidine Th(IV) phosphate was chemically synthesized by mixing ortho-tolidine into the gel of Th(IV) phosphate in different mixing volume ratios, concentration of inorganic reactant with a fixed mixing volume ratios of organic polymer. The physico-chemical characterization was carried out by elemental analysis, TEM, SEM, XRD, FTIR and simultaneous TGA-DTA studies. The ion-exchange capacity, chemical stability, effect of eluant concentration, elution behavior and pH titration studies were also carried out to understand the ion-exchange capabilities. The distribution studies revealed that the cation-exchange material is highly selective for Hg(2+), which is an important environmental pollutant. Due to selective nature of the cation-exchanger ion-selective membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The analytical utility of this electrode was established by employing it as an indicator electrode in electrometric titrations.
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PMID:Preparation and characterization of a new organic-inorganic nano-composite poly-o-toluidine Th(IV) phosphate: Its analytical applications as cation-exchanger and in making ion-selective electrode. 1907 75

NiFeCO(3) hydrotalcites with Ni/Fe molar ratio of 3 were synthesized by co-precipitation method at constant pH, followed by hydrothermal treatment at various temperatures 85-180 degrees C for 3-360h. The obtained materials were characterized by XRD analysis, FT-IR spectroscopy, SEM and TEM microscopy, TGA and BET techniques. The resulting materials were found to be similar to the hydrotalcite with a well-defined hexagonal morphology of crystallites. The hydrothermal treatment and aging time increases the platelet sizes and decreases the surface area. XRD analysis showed the formation of sharper and intense peaks, which might indicate the larger crystallites size of LDH as well as higher crystallinity. Furthermore, textural studies revealed influence of aging time and temperature on the properties of the crystalline phase. The prolonged time tends to form additional products, identified as NiFe(2)O(4) spinel and NiO nickel oxide. The effect of hydrothermal treatment temperature on the kinetics of dye removal has been explored. It was found that the percentage color removal increases with increasing hydrothermal treatment temperature up to 140 degrees C and aging time up to 4 days. Furthermore, the color removal decreases with increasing hydrothermal treatment temperature up to 140-180 degrees C and prolonged aging time.
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PMID:Nickel-iron layered double hydroxide (LDH): textural properties upon hydrothermal treatments and application on dye sorption. 1915 31

A comparison of different purification procedures for single walled carbon nanotubes (SWCNTs) synthesized by laser-vapourization has been presented. The methods involved gas-phase oxidation by calcination, liquid-phase oxidation by H2O2, hydrothermal treatment and acid refluxing in HCI. Sample purity is documented with Raman spectroscopy, Transmission electron microscopy, Scanning electron microscopy and thermogravimetric analysis. Multi-spot analyses were done to check the homogeneity of the purified samples. Different purification processes produced SWCNT material with purity in the range of 48-78%. Raman and TEM results suggested that prolonged calcination results in selective etching of larger diameter nanotubes. SEM and TGA analyses showed increase in density of SWCNTs with better oxidation resistance after purification.
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PMID:Purification of laser synthesized SWCNTs by different methods: a comparative study. 1919 41

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


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