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1.
Georgi E. Chernev Bisserka I. Samuneva Petar R. Djambaski Isabel M. M. Salvado Helena V. Fernandes 《Central European Journal of Chemistry》2006,4(1):81-91
In this work we present experimental results about the formation, properties and structure of sol — gel silica based biocomposite
containing Calcium alginate as an organic compound. Two different types of silicon precursors have been used in the synthesis:
tetramethylortosilicate (TMOS) and ethyltrimethoxysilane (ETMS). The samples have been prepared at room temperature. The hybrids
have been synthesized by replacing different quantitis of the inorganic precursor with alginate. The structure of the obtained
hybrid materials has been studied by XRD, IR Spectroscopy, EDS, BET and AFM. The results proved that all samples are amorphous
possessing a surface area from 70 to 290 m2/g. It has also been established by FT IR spectra that the hybrids containing TMOS display Van der Walls and Hydrogen bonding
or electrostatic interactions between the organic and inorganic components. Strong chemical bonds between the inorganic and
organic components in the samples with ETMS are present. A self-organized nanostructure has been observed by AFM. In the obtained
hybrids the nanobuilding blocks average in size at about 8–14 nm for the particles. 相似文献
2.
I. M. Miranda Salvado F. M. A. Margaça J. Teixeira 《Journal of Sol-Gel Science and Technology》1994,2(1-3):289-294
Silica-titania gels, prepared in acidic conditions, with contents of TiO2 up to 6 mol%, have been studied by small angle neutron scattering (SANS) as wet gel with increasing aging times. In all samples, small primary particles have been found with a diameter of about 3 nm. At the gel point, cylindrical clusters, ca. 10 nm long, were observed as well. These grow with aging time, becoming branched. The cluster-cluster diffusion limited aggregation model is found to be consistent with the SANS results. The growth process is independent of the TiO2 content. It is mainly influenced by the ratio of the aging time to the gelation time. 相似文献
3.
Georgi E. Chernev Borislava V. Borisova Lyudmila V. Kabaivanova Isabel M. Salvado 《Central European Journal of Chemistry》2010,8(4):870-876
This work reports the sol-gel synthesis of silica hybrids. We determined the effect of the type and quantity of silica precursors
and organic compounds on the resulting structure, surface area, nanostructure design and size, and potential applications.
The structure of the synthesized hybrids was analyzed using FT-IR, XRD, BET-Analysis, SEM, and AFM. We demonstrate the immovilization
of whole living thermophilic bacterial cells with cyanocompound degradation activity in the synthesized silica hybrid biomaterials
by entrapment, chemical binding, and adsorption. 相似文献
4.
Georgi Chernev Nadezhda Rangelova Petar Djambazki Sanchi Nenkova Isabel Salvado Maria Fernandes Aiying Wu Lyudmila Kabaivanova 《Journal of Sol-Gel Science and Technology》2011,58(3):619-624
The purpose of the present work is the sol–gel synthesis, structure characterization and potential application of hybrid biomaterials
based on silica precursor (MTES) and natural polymers such as gelatin or pectin. The structure formation in the biomaterials
was investigated by XRD, FTIR, BET and AFM. The results showed that all studied hybrid biomaterials have an amorphous structure.
The FT-IR spectra of the obtained materials with MTES showed chemical bonds at 2,975, 1,255, 880 and 690 cm−1 due to the presence of Si–O–R (CH3 and C2H5) and Si–C bonds. In the samples synthesized with TEOS the inorganic and organic components interact by hydrogen bonding,
Van der Waals or electrostatic forces. Surface area of investigated samples decreases with increasing of the natural polymers
content. The structure evolution was studied by AFM and roughness analysis. Depending on the chemical composition a different
design and size of particles and their aggregates on the surface structure were established. The hybrid biomaterials were
used for immobilization of bacterial cells and applied in the biodegradation of the toxic compound 4-chlorobutyronitrile,
possible constituent of waste water effluents in a laboratory glass bioreactor. Optimization of the process at different temperatures
was carried out. 相似文献
5.
Nadezhda Rangelova Lachezar Radev Sanchi Nenkova Isabel M. Miranda Salvado Maria H. Vas Fernandes Michael Herzog 《Central European Journal of Chemistry》2011,9(1):112-118
Methylcellulose (MC) / SiO2 organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized
by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content.
相似文献
6.
A. Caputo P. Hernandez M. Kekic J. López-Pavón J. Salvado 《The European Physical Journal C - Particles and Fields》2017,77(4):258
Future experiments such as SHiP and high-intensity \(e^+ e^-\) colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below \(M_Z\). We show that the measurement of the mixing to electrons and muons of one such state could establish the existence of CP violating phases in the neutrino mixing matrix, in the context of low-scale seesaw models. We quantify in the minimal model the CP reach of these future experiments, and demonstrate that CP violating phases in the mixing matrix could be established at 5\(\sigma \) CL in a very significant fraction of parameter space. 相似文献
7.
J.J.H. Lancastre N. Fernandes F.M.A. Margaça I.M. Miranda Salvado L.M. Ferreira A.N. Falcão M.H. Casimiro 《Radiation Physics and Chemistry》2012,81(9):1336-1340
Polydimethylsiloxane-silicate based hybrid materials have recognized properties (high flexibility, low elastic modulus or high mechanical strength) for which there are a large number of applications in development, such as for the bioapplications field. The hybrids addressed in the present study were prepared by gamma irradiation of a mixture of polydimethylsiloxane (PDMS) with tetraethylorthosilicate (TEOS) and zirconium propoxide (PrZr) without addition of any solvent or other product. The materials are homogeneous, transparent, monolithic and flexible. The structure dependence on the PrZr content is addressed. A combination of X-ray diffraction (XRD) and Infrared Spectroscopy (IR) was used. The results reveal that the polymer in the hybrids prepared with PrZr, in a content≤5 wt%, shows a structure similar to that in the irradiated pure polymer sample. In these samples the presence of ordered polymer regions is clearly found. For samples prepared with higher content of Zr almost no ordered polymer regions are observed. The addition of PrZr plays an important role on polymer conformation in these hybrid materials. 相似文献
8.
Mendonça A.M.R. Ferreira J.M.F. Salvado I.M. Miranda 《Journal of Sol-Gel Science and Technology》1998,13(1-3):201-205
Ceramic composite gels in the mullite-alumina system (with mullite phase contents ranging from 20 to 100 wt%) were prepared by sol-gel in acid media and using a water/alkoxide molar ratio of 4. Powders were uniaxially pressed to obtain discs.The effect of heat treatment on the materials was followed by thermal analysis and X-ray diffraction (XRD). The crystalline phases formed from the gels were dependent upon the sample composition and the heat treatment temperature. For samples with composition close to the stoichiometric mullite composition the crystallization of mullite was observed after heat treatment at temperatures 900°C, and corundum appeared at higher temperatures. For samples with higher alumina contents mullite formation together with the spinel phase was observed at the lower heat treatment temperatures, while mullite, silimanite, corundum, and other transient phases of alumina were also detected at higher temperatures. The densities and microstructures of materials sintered at 1400°C were studied. Densification of the samples was low due to the agglomeration of the powders, as confirmed by scanning electron microscopy. 相似文献
9.
Aiying Wu Isabel M. Miranda Salvado Paula M. Vilarinho João L. Baptista Armando J.D. Silvestre 《Journal of Sol-Gel Science and Technology》2000,19(1-3):671-676
Lead zirconate titanate (PZT) thin films were prepared by the sol-gel process using acetic acid and 1,2-propanediol as solvents. Acetone was used as final solvent and in this way a stable stock sol (for more than 12 months) was obtained. The PZT sols prepared were reproducible and suitable for the preparation of PZT thin films. To study the sol structure evolution gas chromatography mass spectrum (GC-MS) and Fourier-transform-infrared (FT-IR) spectra were recorded and analyzed on each step of the synthesis. The rheological behavior and the stability of the stock sol were checked using a rheometer. It is observed that the addition of acetone leads to a very stable stock sol. The preliminary investigation of the electric properties of the obtained PZT thin films showed that the crystallized films deposited from a fresh prepared sol and a 12 months aged sol exhibit similar ferroelectric properties and comparable to those reported in the literature. 相似文献
10.
Lachezar Radev Maria Helena V. Fernandes Isabel Miranda Salvado Daniela Kovacheva 《Central European Journal of Chemistry》2009,7(4):721-730
In this work we present our experimental results on synthesis, structure evolution and in vitro bioactivity assessment of new gelatin/silicocarnotite hybrid materials. The hybrids were obtained by diluting gelatin (G)
and silicocarnotite (S) ceramic powder with G:S ratios of 75:25 and 25:75 wt.% in hot (40°C) water. The hybrids were characterized
using XRD, FTIR, SEM/EDS and XPS. FTIR depicts that the “red shift” of amide I and COO− could be attributed to the fact that the gelatin prefers to chelate Ca2+ from S. The growth of calcium phosphates on the surface of the hybrids synthesized and then immersed in 1.5 SBF for 3 days
was studied by using of FTIR, XRD and SEM/EDS. According to FTIR results, after an immersion of 3 days, A and B-type CO3HA can be observed on the surface. XRD results indicate the presence of hydroxyapatite with well defined crystallinity. SEM/EDS
of the precipitated layers show the presence of CO3HA and amorphous calcium phosphate on the surface of samples with different G/S content when immersed in 1.5 SBF. XPS of the
G/S hybrid with 25:75 wt.% proved the presence of Ca-deficient hydroxyapatite after an in vitro test for 3 days. 相似文献