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

Owing to their unique structure and properties, carbon nanotubes (CNTs) have become the highlight of research since they were discovered. Part of the research interest lies in introducing them into solid state matrix to make them materialized. However, CNTs tend to aggregate in the matrix, which makes it difficult to make homogeneous composites. In order to solve this problem, we first modified the surface of CNTs by chemically bonding them to 3-aminopropyltrie-thoxysilane (NH2 (CH2)3Si(OC2H5)3, APTES) using three-step reactions, and then connected them to silica network by sol-gel technique. In the present paper, CNTs were first treated with HNO3 to get CNTs-COOH, which were then treated with SOCl2 to be transferred to CNTs-COCl, and finally CNTs-COCl reacted with APTES to get CNTs-APTES. After that, CNTs were introduced into silica net work through the individual hydrolysis of CNTs-APTES, tetrathyloxysilane (Si(OC2H5)4, TEOS) and 3-glycidoxy-propltrimethoxysilane (CH2OCHCH2O(CH2)3Si(OCH3)3, GPTMS) as sol-gel precursors, and the copolymerization of their hydrolysis products. FTIR and SEM were used to characterize the composition and microstructure of the obtained samples. (Owing to the connection of CNTs with silica network, little aggregation of CNTs was observed and high-quality CNTs/SiO2 composite gel glass was obtained. A model of CNTs/SiO2 network was also given.
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PMID:[Preparation of surface-modified carbon nanotubes/silica composite gel glass]. 1938 4

A negative-tone sensitive SiO2/TiO2 organic-inorganic hybrid sol-gel material was synthesized and characterized for fabrication of multilevel micro-optical elements by direct electron-beam lithography. The exposure was carried out by an in-house modified electron-beam writing system using LEO SEM-982 with Elphy Quantum exposure beam-blanking control system at 25keV. The hybrid Sol-Gel material demonstrated a superb sensitivity for doses between 0.22microC/cm2 and 0.33microC/cm2.
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PMID:High sensitive SiO2/TiO2 hybrid sol-gel material for fabrication of 3 dimensional continuous surface relief diffractive optical elements by electron-beam lithography. 1943 2

In this paper, a simple synthesis method of small-size (about 50 nm in diameter), high magnetic and fluorescent bi-functional silica composite nanoparticles were developed, in which water-soluble Fe3O4 magnetic nanoparticles (MNs) and CdTe quantum dots (QDs) were directly incorporated into a silica shell by reverse microemulsion method. The high luminescent QDs can be used as luminescent marker, while the high magnetic MNs allow the manipulation of the bi-functional silica composite nanoparticles by external magnetic field. Poly (dimethyldiallyl ammonium chloride) was used to balance the electrostatic repulsion between CdTe QDs and silica intermediates to enhance the fluorescence intensity of MNs-QDs/SiO2 composite nanoparticles. The optical property, magnetic property, size characterization of the bi-functional composite nanoparticles were studied by UV-Vis and PL emission spectra, VSM, TEM, SEM. The stabilities toward time, pH and ionic strength and the effect of MNs on the fluorescence properties of bi-functional silica composite nanoparticles were also studied in detail. By modifying the surface of MNs-QDs/SiO2 composite nanoparticles with amino and methylphosphonate groups, biologically functionalized and monodisperse MNs-QDs/SiO2 composite nanoparticles can be obtained. In this work, bi-functional composite nanoparticles were conjugated with FITC labeled goat anti-rabbit IgG, to generate novel fluorescent-magnetic-biotargeting tri-functional composite nanoparticles, which can be used in a number of biomedical application.
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PMID:The synthesis of magnetic and fluorescent bi-functional silica composite nanoparticles via reverse microemulsion method. 1954 73

In this study, poly(acrylic)/SiO2/EuL3 x 2H2O hybrid thin films were prepared from various acrylic monomers (MMA and EDMA/TMPTA), lanthanide metal complexs (EuL3 x 2H2O, L = pyridine carboxylic acid), and monodispersed colloidal silica with a coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). It was a combination of the sol-gel reaction, thermal polymerization, and spin coating. The EuL3 x 2H2O content in the hybrid thin films was fixed at 0.05 g and silica content was varied from 10 to 50 wt%. TEM results showed that both SiO2 and EuL3 x 2H2O were well dispersed in the hybrid thin films without aggregation. PL spectra showed the unique emission of Eu3+. The addition of SiO2 made the compounds of Eu3+ disperse better and diminished the effect of concentration quenching. UV-Vis spectra and n&k analysis showed that the hybrid thin films had good transparency in visible light. Besides, the refractive index of hybrid thin films could be effectively controlled through the different ratio of SiO2 to EuL3 x 2H2O. TGA and DSC analysis indicated that the temperature of pyrolysis and T(g) increased with the increase in the SiO2 content. The results of SEM, SCMS, and AFM also showed that the hybrid thin films which prepared from the poly-functional acrylate had a flatter surface than those obtained from the single functional acrylate.
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PMID:Hybrid thin films derived from poly(acrylic)/ colloidal silica/lanthanide metal complex. 1991 6

In this study, two types of the polyimide-silica hybrid thin films, 6FDA-ODA/SiO2 (FS0-FS50) and PMDA-ODA/SiO2 (PS0-PS40), with different silica content were synthesized by using the sol-gel method. TGA analysis showed that the thermal decomposition temperatures (T(d)) of FS and PS hybrid films were in the range of 457-505 degrees C and 458-516 degrees C, respectively. The T(d) increased with increasing the silica content. The measurement of contact angle and FTIR indicated that the hydrophilic and hydrolytic abilities were significantly improved when the silica content increased. The contact angle of PS0-PS40 films was in the range of 80.3-51.8 degrees. UV-Vis spectra showed that the cutoff wavelength of prepared hybrid films could be tunable through the silica content. The n&k analysis showed that the refractive index (n) of FS and PS hybrid films were in the range of 1.60-1.49 and 1.76-1.59, respectively, which could be controlled by the silica content. The extinction coefficients (k) are almost zero in the wavelength range of 300-900 nm, indicating the prepared hybrid films have an excellent optical transparency in the UV and visible region. TEM images showed that the particle size of silica in the hybrid thin films could be effectively controlled under sufficient content of coupling agent. Moreover, the results of SEM and AFM showed that the ratios of average roughness to thickness for all the prepared hybrid films were under 1.6%. It demonstrated that the prepared polyimide-silica hybrid thin films have an excellent film formability and planarity.
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PMID:Synthesis and characterization of polyimide/monodispersed colloidal silica hybrid thin films. 1991 20

The crystallization behaviour of hybrid SiO2-TiO2 nanocomposites derived from titanosiloxanes by sol-gel method has been investigated depending on the type of siloxane precursor and the pirolysis temperature. The resulting hybrid titanosiloxanes, crosslinked with trimethylsilil isocyanate (nitrogen-modified) or methyltrietoxisilane (carbon-modified), were pirolyzed in an inert atmosphere in the temperature range between 600 to 1100 degrees C in order to form C-(N)-Si-O-TiO2 nanocomposites. By means of XRD, FTIR, 29Si NMR, SEM, TEM and AFM investigations have been established that the transformation of the nanostructured SiO2-TiO2 hybrid materials into nanocomposites as well as the crystalline size depend on the titanium content and the type of cross-linking agents used in the synthesizes.
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PMID:Crystallization behaviour of nanostructured hybrid SiO2-TiO2 gel glasses to nanocomposites. 2035 46

We investigated the effects of catalyst (Fe)/buffer layer (Al2O3) on the vertical growth multiwalled carbon nanotubes (CNTs) synthesized by thermal chemical vapor deposition. The Fe was deposited onto Al2O3/SiO2/Si wafer by using e-beam evaporator. Ethylene was used as a feeding gas while argon was used as a carrier gas. Hydrogen was also introduced. The catalyst layers were optimized to control the length, diameter, purity, and alignment of CNTs. For the optimized conditions we produced vertically aligned CNTs of about 1 cm in length during 10 h. The effects of catalysts on nanotube characteristics were systematically analyzed using SEM, TEM, and Raman measurement.
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PMID:Effects of catalyst on the super-growth of multi-walled carbon nanotubes. 2035 57

In this study, poly(acrylic)/SiO2/EuL3 x 2H2O hybrid thin films were prepared from various acrylic monomers (MMA and EDMA/TMPTA), lanthanide metal complexes (EuL3 x 2H2O, L = pyridine carboxylic acid), and monodispersed colloidal silica with a coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). It is a combination of the sol-gel reaction, thermal polymerization, and spin coating. The silica content in the hybrid thin films is fixed at 20 wt%, and the EuL3 x 2H2O content is varied from 0.01 g to 0.07 g. FTIR and EA analysis confirms the chemical structure of the prepared EuL3 x 2H2O and poly(acrylic)/SiO2/EuL3 x 2H2O hybrid thin films. UV-Vis spectra and n&k analysis shows that the hybrid thin film has good transparency in visible light. The refractive index of hybrid thin films can be effectively controlled through the EuL3 x 2H2O content. The PL spectra shows that the strongest emission peak occurs at 615 nm and the emission intensity increases to the peak maximum at an EuL3 x 2H2O content of 0.05 g. Both TGA and PL analysis show that the prepared hybrid thin films from the crosslinked acrylic polymer moiety have much better film uniformity, thermal stability, and fluorescence properties. The TEM diagram shows that the MSMA/SiO2/EuL3 x 2H2O particles with a size 15-20 nm are well dispersed in the reaction solution. The SEM diagram shows that the particle distribution in the prepared hybrid thin films is uniform and no phase separation is observed. Finally, AFM analysis indicates that the prepared hybrid thin films have an excellent surface planarity.
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PMID:Preparation of poly(acrylic)/SiO2/EuL3 x 2H2O, hybrid thin films from monodispersed colloidal silica. 2112 99

The Eu(3+) doped TiO2-SiO2 photocatalysts, as a reclaimed visible-light responsive photocatalyst, were prepared by sol-gel method with TEOS, TBT and europium nitrate as precursors, by keeping the molar of TEOS:TBT constant at 1:1 and with different europium doping content. The resulting photocatalysts were characterized by XRD, TEM, SEM, EDX, UV-VIS DRS, FTIR and BET method. Analytical results demonstrated that only anatase phase is present in photocatalysts with high surface areas. The mean size is around 10 nm form TEM, which is consistent with the analytical result according to SEM. It can be seen methyl groups exist in photocatalysts based on analysis of FTIR and EDX. It was found that the resulting Eu(3+) doped photocatalysts exhibit higher photocatalytic activity than undoped photocatalysts and P25 on the degradation of rhodamine B(RhB, 10 mg/l) in water under visible light irradiation (lambda > 410). After irradiation for 3 h, the maximum absorption decreases gradually with irradiation time and absorption band shifts from 554 to 507 nm.
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PMID:Low temperature preparation and visible light induced photocatalytic activity of europium doped hydrophobic anatase TiO2-SiO2 photocatalysts. 2113 5

Hybrid SiO2-TiO2 films are prepared starting from tetraisopropoxy titanate and 3-glycidoxipropyltrimethoxysilane, using the sol-gel process. During the sol synthesis titania clusters grow, conferring to the samples a photocatalytic activity. In this paper we exploit this property for the fabrication of surface-relief gratings. The realized structures are characterized by SEM, AFM and profilometric measurements, while the presence of titania clusters is confirmed by TEM analyses.
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PMID:UV-curable SiO2-TiO2 films for the realization of diffractive optical elements. 2144 26


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