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

Elaboration of mesoporous titanium oxide film supporting silver nanoparticles is described. Mesoporous titanium oxide films are characterized by TEM analysis. Titania films are infiltrated with a silver salt solution and chemical reduction treatments are performed using either a NaBH(4) or a formaldehyde solution. Infiltrated films are then characterized by TEM, SEM, AFM, UV-visible spectroscopy, X-ray diffraction, and Rutherford Backscattering Spectrometry (RBS). The utilization of a mesoporous titania substrate allows to control the nanoparticle size and the interparticle distance. RBS experiments provide the evidence that NaBH(4) treatment induces a strong accumulation of silver nanoparticles in the subsurface of the layer, while formaldehyde treatment induces the formation of silver nanoparticles embedded into almost the whole depth of the titania film. Large silver nanocrystals are also formed at the film surface whatever the reducer used. A broad visible absorption band related to the surface plasmon resonance (SPR) is obtained in both cases and is strongly red-shifted compared to the SPR obtained for silver nanoparticles inside a silica matrix. Moreover, irradiation with visible light causes the photooxidation of silver nanoparticles by titania and a complete discoloration of the material. The photooxidation is related to a drastic decrease in the silver nanoparticle size and is found to be reversible, particularly in the case of the material obtained by the formaldehyde reduction.
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PMID:Chemical growth and photochromism of silver nanoparticles into a mesoporous titania template. 2006 16

Silver nanoparticles doped on titanium oxide (TiO(2)) were produced by laser-liquid interaction of silver nitrate (AgNO(3)) in isopropanol. Characteristics of Ag/TiO(2) (Ag doped TiO(2)) nanoparticles produced by the methods presented in this article were investigated by XRD, TEM, SEM, EDX, and UV-Vis. From the UV-Vis measurements, the absorption of visible light of the Ag/TiO(2) photocatalysts was improved (additional absorption at longer wavelength in visible light region) obviously. The photocatalytic efficiency of Ag/TiO(2) was tested by the degradation of methylene blue (MB) in aqueous solution. A maximum of 82.3% MB degradation is achieved by 2.0 wt% Ag/TiO(2) photocatalyst under 2 h illumination with a halogen lamp.
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PMID:Laser-induced silver nanoparticles on titanium oxide for photocatalytic degradation of methylene blue. 2008 59

Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.
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PMID:Biomimetic whisker-shaped apatite coating of titanium powder. 2009 1

The reaction of [Ti(eta(5)-C(5)H(5))(2)Cl(2)] (1), with 3-mercaptopropyltrimethoxysilane or 3-mercaptopropyltriethoxysilane in the presence of triethylamine leads to the formation of the thiolate complexes [Ti(eta(5)-C(5)H(5))(2){SCH(2)CH(2)CH(2)Si(OMe)(3)}(2)] (2) and [Ti(eta(5)-C(5)H(5))(2){SCH(2)CH(2)CH(2)Si(OEt)(3)}(2)] (3), respectively. Complexes 2 and 3 have been characterized by traditional methods, in addition, structural studies based on DFT calculations are reported. 1-3 have been grafted onto dehydroxylated MCM-41 to give the novel materials MCM-41/[Ti(eta(5)-C(5)H(5))(2)Cl(2)] (S1), MCM-41/[Ti(eta(5)-C(5)H(5))(2){SCH(2)CH(2)CH(2)Si(OMe)(3)}(2)] (S2) and MCM-41/[Ti(eta(5)-C(5)H(5))(2){SCH(2)CH(2)CH(2)Si(OEt)(3)}(2)] (S3) which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, multinuclear MAS NMR spectroscopy, thermogravimetry, UV spectroscopy, SEM and TEM. Materials S2 and S3 present much higher values of Ti wt% (ca. 3%) than S1 (ca. 1%), indicating the higher functionalization rate induced by the substitution of the chloro ligands by the thiolato ligands in the starting titanocene derivatives. The cytotoxicity of the non-functionalized MCM-41 and S1-S3 toward human cancer cell lines such as adenocarcinoma HeLa, human myelogenous leukemia K562 and human malignant melanoma Fem-x has been studied. In addition the cytotoxicity of these materials on normal immunocompetent cells such as stimulated (PBMC+PHA) and non-stimulated (PBMC-PHA) peripheral blood mononuclear cells have been also studied. M(50) values (quantity of material needed to inhibit normal cell survival by 50%) of the studied surfaces show that non-functionalized MCM-41 was not active against any of the studied cells, while the functionalized surfaces S1-S3 were active against all the tested human cancer cells. The cytotoxic activity of surfaces S2 and S3 were very similar, however, S1 showed lower cytotoxic activity. This phenomenon indicates that the cytotoxicity of the titanocene-functionalized materials strongly depends on the titanium content.
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PMID:Improvement of cytotoxicity of titanocene-functionalized mesoporous materials by the increase of the titanium content. 2017 53

The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders. Sol-gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats. The kinetics of the drug release depend on: (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates. The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir. The titanium n-butoxide/water ratio was systematically varied during the sol-gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements. The particle agglomerate size and porosity were found to depend on the amount of water used in the sol-gel reaction.
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PMID:The effect of water on particle size, porosity and the rate of drug release from implanted titania reservoirs. 2018 18

Monodisperse mesoporous anatase titania beads with high surface areas and tunable pore size and grain diameter have been prepared through a combined sol-gel and solvothermal process in the presence of hexadecylamine (HDA) as a structure-directing agent. The monodispersity of the resultant titania beads, along with the spherical shape, can be controlled by varying the amount of structure-directing agent involved in the sol-gel process. The diameter of the titania beads is tunable from approximately 320 to 1150 nm by altering the hydrolysis and condensation rates of the titanium alkoxide. The crystallite size, specific surface area (from 89 to 120 m(2)/g), and pore size distribution (from 14 to 23 nm) of the resultant materials can be varied through a mild solvothermal treatment in the presence of varied amounts of ammonia. On the basis of the results of small-angle XRD, high-resolution SEM/TEM, and gas sorption characterization, a mechanism for the formation of the monodisperse precursor beads has been proposed to illustrate the role of HDA in determining the morphology and monodispersity during the sol-gel synthesis. The approach presented in this study demonstrates that simultaneous control of the physical properties, including specific surface area, mesoporosity, crystallinity, morphology, and monodispersity, of the titania materials can be achieved by a facile sol-gel synthesis and solvothermal process.
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PMID:Synthesis of monodisperse mesoporous titania beads with controllable diameter, high surface areas, and variable pore diameters (14-23 nm). 2020 15

TiO2-based nanopowders are elaborated by flame spray synthesis, FSS from organic precursors of titanium and chromium with the Cr content changing from 0 to 15 at.%. Well-crystallized nanopowders with high specific surface area SSA reaching 107 m2/g for undoped TiO2 and 177 m2/g for TiO2 + 15 at.% Cr are obtained. Thin films are deposited by rf reactive sputtering from metallic Ti and Ti-Cr targets in Ar + O2 flow controlled atmosphere. The adjustable area of Cr/Ti allows to obtain up to 16 at.% Cr in TiO2 thin films. X-ray diffraction, transmission electron spectroscopy, TEM, atomic force microscopy, AFM and optical spectrophotometry over the ultraviolet UV and visible VIS range of the light spectrum have been performed in order to characterize the nanomaterials. The particle size of nanopowders is within the range of 5-42 nm. Anatase is the predominating polymorphic form while the amount of rutile increases with Cr content to reach of about 25 wt.% at 15 at.% Cr. The post-deposition annealing of thin films in air at temperatures from 770 K to 1280 K modifies the phase composition, leads to irreversible transformation from anatase to rutile and affects the surface roughness. Structural and optical properties of TiO2-based nanopowders and thin films are compared. The effect of grain size and the level of chromium doping on the band gap E(g) is discussed. Photocatalytic activity of the nanopowders is tested for degradation of methylene blue, MB.
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PMID:TiO2-based nanopowders and thin films for photocatalytical applications. 2035 53

This paper aims to characterize the photoelectrochemical properties of the visible-light enabling titanium dioxide (TiO2) film electrodes prepared by codoping nitrogen (N) and a presputtered carbon film (C-film) onto indium tin oxide (ITO) glass substrates using a direct current (DC) magnetron sputtering technique. To improve its photoelectrochemical properties, different amount of C-doping sources, 2 h and 4 h C-film, are chose to prepare the N/C-codoped TiO2 film electrodes. Under visible-light (420 < lambda < 610 nm) illumination, a remarkable photocurrent density of 22 microA/cm2 is obtained for the N/C-TiO2 film electrode prepared with a 4 h C-film (NC(4)-T) at an applied potential of +1.2 V versus SCE. Under ultraviolet (lambda approximately 365 nm) illumination, the NC(4)-T film electrode also exhibits the highest photocurrent density of 0.23 mA/cm2 among all samples tested. A more negative flat band potential of NC(4)-T film electrode is attributed to the synergistic effect of N/C codoping. The XRD spectrum of the NC(4)-T film electrode shows mainly the well-crystallized anatase TiO2 phase and an extremely intense (211) plane. Thus, photoelectrochemical activity of the NC(4)-T film electrode can be ascribed to the well-crystallized columnar crystals with pores at its grain boundary, open surface morphology, which are revealed by SEM and TEM images, and a more negative flat band potential. The visible-light induced activity is mostly enhanced as a result of the synergistic effects of N/C-codoping into the TiO2 crystals. A potential application to photocatalytic splitting of water for hydrogen evolution using solar light is practically possible.
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PMID:Photoelectrochemical properties of N/C-codoped TiO2 film electrodes prepared by reactive DC magnetron sputtering. 2035 56

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

Dispersed titanium dioxide in polymer nanofibers were prepared by sol-gel processing and electrospinning techniques using titanium isopropoxide (TiP)/polyvinylpyrrolidone (PVP) solution. The prepared titanium dioxide nanofibers were characterized by FE-SEM, TEM, XRD, and FT-IR. Pure titanium dioxide nanofibers were obtained from calcination of inorganic-organic composite fiber. The diameter of titanium oxide nanofibers were in the range of 70 nm to 150 nm. Prepared titanium dioxide nanofibers show rough surface and rather small diameter compare with TiP/PVP composite nanofibers. After calcined at 500 degrees C, TiO2 nanofibers convert into anatase and rutile mixed phased from amorphous structure. Calcination of these composite fibers above 600 degrees C resulted in pure rutile TiO2 nanofibers.
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PMID:Characterization and morphology of prepared titanium dioxide nanofibers by electrospinning. 2035 66


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