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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dehydroxylated MCM-41 and SBA-15 surfaces were modified by the grafting of two different titanocene complexes ([Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] and [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)]) to give new materials, which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, MAS-NMR spectroscopy, thermogravimetry, SEM, and TEM. The toxicity of the resulting materials toward human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, such as peripheral blood mononuclear cells PBMC has been studied. Estimation of the number of particles per gram of material led to the calculation of Q(50) values for these samples, which is the number of particles required to inhibit normal cell growth by 50%. In addition, M(50) values (quantity of material needed to inhibit normal cell growth by 50%) of the studied surfaces is also reported. Nonfunctionalized MCM-41 and SBA-15 did not show notable antiproliferative activity, whereas functionalization of these materials with different titanocene based anticancer drugs led to very promising antitumoral activity. The best Q(50) values correspond to titanocene functionalized MCM-41 surfaces (MCM-41/[Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] (1) and MCM-41/[Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (2)) with Q(50) values between 3.8+/-0.6x10(8) and 24.5+/-3.0x10(8) particles. Titanocene functionalized SBA-15 surfaces (SBA-15/[Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] (3) and SBA-15/[Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (4)) gave higher Q(50) values, showing lower activity from 73.2+/-9.9x10(8) to 362+/-7x10(8) particles. The best response of the studied materials in terms of M(50) values was observed against Fem-x (309+/-42 microg for 4) and K562 (338+/-18 microg for 2), whereas moderate activities were observed in HeLa cells (from 508+/-63 microg of 2 to 912+/-10 microg of 1). In addition, the analyzed surfaces presented only marginal activity against unstimulated and stimulated PBMC, showing a slight selectivity on human cancer cells. Comparison of the in vitro cytotoxicity in solution of the titanocene complexes [Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] and [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] and the corresponding titanocene functionalized materials is also described.
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PMID:A new generation of anticancer drugs: mesoporous materials modified with titanocene complexes. 1937 Jul 42

Mn-MCM-41 was synthesized in various (Si/Mn = 25, 50, 75 and 100) ratios, using manganese acetate as source for manganese by hydrothermal method and was calcined at 550 degrees C for 6 hrs. The physico-chemical characterizations of Mn-MCM-41 showed the formation of hexagonally arranged mesopores with high surface area. The calcined Mn-MCM-41 was used as catalytic templates for the growth of large amount of carbon nanotubes. Acetylene was used as carbon source and nitrogen as carrier gas for the formation of carbon nanotubes by chemical vapor deposition method. The effect of temperature was carried out 750, 800, 850 and 900 degrees C, at a flow rate of 40 ml/min of acetylene precursor. The SEM, TEM and XRD confirmed the formation of large amount of carbon nanotubes.
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PMID:Synthesis and characterization of Mn-MCM-41--its catalytic activity for the synthesis of carbon nanotubes. 1992 63

The effect of cationic template on the adsorption of chromium (VI), furfural and copperphthalocyanine-3,4',4'',4'''-tetrasulfonic acid tetrasodium salt (CuPc) in MCM-41 and MCM-48 mesoporous materials was investigated in this work. We used cetyltrimethylammonium bromide (CTAB) as the cationic template and sodiummetasilicate (for MCM-41) and tetraethyl-orthosilicon (for MCM-48) as the silica source for the synthesis of mesoporous materials. The properties of synthesized samples were characterized with XRD-low angle, SEM, N(2) adsorption-desorption and TG-DT analysis. The extent of adsorption was investigated as a function of solution pH, shaking speed, contact time, analyte concentration, reaction temperature and supporting electrolyte (sodium chloride) concentration. Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data. The as-synthesized mesoporous samples showed very high adsorption capacity for the analytes and adsorption uptakes were rapid on the adsorbents reaching equilibrium in less than 2 h. The materials without surfactant did not show significant affinity for the analytes.
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PMID:Fast and efficient mesoporous adsorbents for the separation of toxic compounds from aqueous media. 2002 25

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 novel rich heteroatom-containing (15 wt.%) composite molecular sieves M(1)-MFI/M(2)-MCM-41 have been prepared from the ionic complex [(C(4)H(9))(4)N](2)(+)[M(1)(EDTA)](2-) and [C(16)H(33)(CH(3))(3)N](2)(+)[M(2)(EDTA)](2-) as the organic templates, which could effectively introduce a large amount of heteroatoms into the framework of molecular sieves. The products were characterized by XRD, XRF, SEM, HRTEM, N(2) adsorption-desorption, H(2)-TPR, FT-IR, TG and DSC techniques. The catalytic performances of the composite materials were investigated by means of residual oil hydrocracking. Characterization results showed that the composite materials simultaneously possessed a typical orthogonal MFI phase and a hexagonal MCM-41 phase and the two phases were composite rather than the physical mixture. H(2)-TPR data indicated all of the heteroatoms were incorporated by isomorphous substitution of silicon in framework. N(2) adsorption-desorption analysis exhibited that these samples possessed regular and stable structure with high specific surface area and large pore diameters of 550-620 m(2) g(-1), 3.5 nm and 5.5 nm, respectively. M(1)-MFI/M(2)-MCM-41 presented excellent activities in hydrocracking of residual oil, which were superior to the pure materials of MFI/MCM-41.
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PMID:Synthesis and characterization of composite molecular sieves M1-MFI/M2-MCM-41(M1, M2=Ni, Co) with high heteroatom content and their catalytic properties for hydrocracking of residual oil. 2022 67

Surface modification offers a great opportunity to adjust both the pore diameter and surface properties of MCM-41 type organic-inorganic hybrid materials which result in materials of improved hydrothermal and mechanical stability. Therefore, MCM-41 silica, surface modified with organic ligands, are promising systems with engineered properties and attractive for advanced applications. In the present study, after optimization of the reaction conditions highly ordered MCM-41 silica spheres with uniform mesopores were prepared by the pseudomorphic transformation route. The effect of functionality and alkyl chain length of the alkyl ligands during surface modification was probed by using butyl and octylsilanes with two different functionalities. Due to steric hindrance, the longer chains are assumed to bind only on the outer silica surface and near the entrance of the pores, while the shorter chains are also able to bind to the interior mesopore walls. The resulting materials were comprehensively characterized before and after surface modification using nitrogen sorption techniques, XRD, SEM, solid-state NMR spectroscopy and FTIR spectroscopy. From chromatographic test measurements it was found that the separation power primarily depends on surface coverage and alkyl chain length. On the basis of the present data, surface modified mesoporous silica of MCM-41 type are very promising candidates for future chromatographic applications.
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PMID:Synthesis and surface modification of mesoporous mcm-41 silica materials. 2035 13

Spherical-like Pt-MCM-41 meso-materials, including Pt-MCM-41, Pt-Al-MCM-41, and Pt-La-MCM-41, as well as MCM-41, were synthesized by a "one-step" approach with orthosilicate (TEOS) as silica source and cetyltrimethylammonium bromide (CTAB) as a template in the presence of suitable H(2)SO(4) (or HCl) at 0 degrees C. The samples were characterized by XRD, N(2) sorption, FTIR, SEM, TEM, ICP-AES, and XPS techniques. The results show that the metallic cations (such as Al(3+) and La(3+)) were hard to be incorporated into the synthesized samples under strong acidic conditions. However, H(2)PtCl(6) can be introduced almost 100% in the as-synthesized Pt-containing meso-materials, and H(2)PtCl(6) in the samples can be decomposed mostly into metallic Pt accompanied by part Pt(2)Si and few Pt oxides during the calcination at 550 degrees C to remove the template. In the catalytic hydrogenation of nitrobenzene, the calcined Pt-MCM-41 meso-materials, like the corresponding reduced samples, exhibit high catalytic activities with an excellent selectivity to aniline, which are much better than those of the reduced Pt/MCM-41 prepared by the incipient wetness method.
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PMID:Synthesis of spherical-like Pt-MCM-41 meso-materials with high catalytic performance for hydrogenation of nitrobenzene. 2038 12

Fe-MCM-41 with varying Si/Fe ratios (20, 50, 70 and 90) were prepared by using cetyltrimethylammoniumbromide (CTAB) as the structure-directing agent (SDA), tetraethylorthosilicate (TEOS) as the silica source and ethanol as co-surfactant in alkaline medium. The characterization was done by SEM; UV-vis diffused reflectance and FT-IR. Adsorption of copper solutions with varying parameters such as concentration, temperature and pH were performed over Fe-MCM-41 samples. The experimental data fitted well to the Langmuir and Freundlich adsorption isotherm. Fe-MCM-41 having Si/Fe ratio (90) showed highest copper adsorption capacity at pH 5.5, Cu(2+) concentration of 59.6 ppm and temperature 323 K. Fe-MCM-41(90)-Cu(59.6) was tested as a catalyst for oxidation of adamantane using hydrogen peroxide as the oxidant. The GC analyses revealed significant conversion of 32.5% and selectivity of 54% towards formation of 1-adamantanol.
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PMID:Adsorption of Cu2+ on spherical Fe-MCM-41 and its application for oxidation of adamantane. 2039 42

Novel mesoporous silica nanoparticles of peculiar shapes were synthesized, from which hierarchically porous silica coatings were fabricated on glass substrates via layer-by-layer (LbL) assembly, followed by calcination. These porous silica coatings were highly transparent and superhydrophilic. The maximum transmittance reached as high as 94%, whereas that of the glass substrate is 91%. The time for a droplet to spread lower than 5 degrees decreased to as short as 0.25 s. After the coating surface was treated with a low surface energy material, the surface became superhydrophobic (water contract angle >150 degrees) with a very low sliding angle of <1 degree. Compared with MCM-41-type mesoporous silica nanoparticles, the coatings fabricated using the novel mesoporous silica nanoparticles possess much better self-cleaning property. We used scanning (SEM) and transmission (TEM) electron microscopy to observe the morphology and structure of nanoparticles and surfaces. Transmission spectra and their change with time were characterized by UV-vis spectrophotometer. We studied the surface wettability by a contact angle/interface system. The influence of mesopores on the transmittance and wetting properties of coatings was discussed on the basis of experimental observations.
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PMID:Self-cleaning antireflective coatings assembled from peculiar mesoporous silica nanoparticles. 2069

In this work, we report the fabrication and characterization of silver nanoelectrode ensembles (Ag-NEEs) on a glassy carbon electrode. For this purpose, Ag nanoparticles (NPs) were anchored to the mercaptopropyl functionalized MCM-41 type silica spheres utilizing the chemisorption property of Ag NPs by -SH groups. The successful anchoring of Ag NPs into the silica matrix is characterized by several techniques including UV-vis diffuse reflectance and X-ray powder diffraction methods. The surface morphology of the Ag-NEEs was assessed by scanning and transmission electron microscopy (SEM and TEM respectively). Further, nitrite (NO(2)(-)) is electrocatalytically oxidized at Ag-NEEs, which leads to a sensitive determination of NO(2)(-). The fabrication, characterization, and efficient sensing of NO(2)(-) at the Ag-NEEs are presented.
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PMID:Electrochemical determination of nitrite using silver nanoparticles modified electrode. 2071 23


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