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1.
P. Kölsch I. Pitsch D. Schultze D. Heidemann D. Hoebbel 《Journal of Thermal Analysis and Calorimetry》1994,41(4):789-806
Four organosilicate polymers synthesized by addition of vinyl- and H-substituted double four-ring silicic acid derivatives were characterized using DSC and simultaneous TG-DTA measurements. Thermooxidative decomposition proceeds in several steps: Oxidation of (Si?H) groups, oxidation of (Si?CH2?CH2?Si) bridges, and oxidation of (Si?CH3) groups, with formation of new (Si?O?Si) bonds.29Si-NMR-spectroscopic measurements confirm this interpretation. Thermoanlytical methods of investigation proved useful to characterize these organosilicate polymers. 相似文献
2.
Synthesis, Constitution and Properties of Cage-like Vinyl- and Allylsilylated Silicic Acids By silyation of tetramethylammonium silicate [N(CH3)4]8Si8O20 · 69 H2O with vinyldimethylchlorosilane ( I ) and divinyltetramethyldisiloxane, respectively, or allyldimethylchlorosilane there were synthesized the crystalline silicic esters [CH2?CH(CH3)2Si]8Si8O20 and[CH2?CH? CH2(CH3)2Si]8Si8O20. By means of gas chromatography, mass spectrometry, 1H and 29Si NMR the two compounds were identified to be cage-like double four-ring(D4R)-silicic esters containing eight vinyldimethylsilyl- or allyldimethylsilyl groups, Silylation with a mixture of I and trimethylchlorosilane yields in dependence on the ratio of silanes vinyldimethylsilyltrimethylsilyl D4R silicic esters with average numbers of unsaturated groups < 8. 相似文献
3.
Miewon Jung 《Journal of Sol-Gel Science and Technology》2000,19(1-3):563-568
The systematic modifications of silica matrix as a function of modified Ti-alkoxide contents (Au nanocrystals doped TiO2/SiO2 mixed oxide thin films) have been investigated by the sol-gel process. A structural analysis on the various steps of the hydrolysis-condensation process as well as solid powder is determined by IR, UV-Visible, and 29Si NMR spectroscopy. 29Si MAS spectra are characterized by broad lines for the three types of sites. Different distributions (Q
2, Q
3, and Q
4 units) observed in the TiO2/SiO2 (1 : 3) sample. Proper control of the process condition, modifying the Ti alkoxide as a less reactive precursor, improves the increase the amount of Ti–O–Si bonding in the silica network of TiO2/SiO2 mixed oxide matrices and the distribution of metal oxides. This method can be used for the preparation of homogeneous metal and metal-metal alloy nanocrystals deposition from mixed oxide thin films. 相似文献
4.
Inorganic sulfate- and organic dodecylbenzenesulfonate (DBS)-intercalated zinc-iron layered double hydroxides (LDHs) materials were prepared by one-step coprecipitation method from a mixed salt solutions containing Zn(II), Fe(II) and Fe(III) salts. The as-prepared samples have been characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption, scanning electron microscopy (SEM), inductively coupled plasma emission spectroscopy (ICP), and Mössbauer spectroscopy (MS). The XRD analyses demonstrate the typical LDH-like layered structural characteristics of both products. The room temperature MS results reveal the characteristics of both the Fe(II) and Fe(III) species for SO42−-containing product, while only the Fe(III) characteristic for DBS-containing one. The combination characterization results and Rietveld analysis illustrate that the SO42−-containing product possesses the Green Rust two (GR2)-like crystal structure with an approximate chemical composition of [Zn0.435·FeII0.094·FeIII0.470·(OH)2]·(SO42−)0.235·1.0H2O, while the DBS-containing one exhibits the common LDH compound-like structure. The contact angle measurement indicates the evident hydrophobic properties of DBS-containing nanocomposite, compared with SO42−-containing product, due to the modification of the internal and external surface of LDHs by the organic hydrophobic chain of DBS. 相似文献
5.
On the Anion Constitutions of Tetrabutylammonium Silicates and their Aqueous Solutions The anion distribution of tetra-n-butylammonium-(TBA)-silicate solutions with molar TBA/SiO2 ratios between 0.6 and 4 and silica concentrations between 0.1 M and 2.2 M has been investigated by trimethylsilylation and 29Si NMR techniques. In contrast to concentrated tetramethylammonium- and tetraethylammonium silicate solutions in TBA silicate solutions a preference of double ring silicate anions does not occur. In TBA silicate solutions a broad distribution of silicate anions consisting of monomeric, oligomeric chain and ring, as well as polymeric silicate anions has been observed. Crystalline TBA silicates with TBA/SiO2 ratios of 0.78 to 1 contain mainly double five-ring silicate anions Si10O2510? whereas for TBA/SiO2 ratios higher than 1.4 the double three-ring anion Si6O156? predominates. A recently prepared TBA silicate with low TBA content (TBA/SiO2 = 0.23) has been found to consist of double four-ring silicate anions with 6 SiOH groups per double four-ring. 相似文献
6.
Kanji Tsuru Yasushi Aburatani Takeshi Yabuta Satoshi Hayakawa Chikara Ohtsuki Akiyoshi Osaka 《Journal of Sol-Gel Science and Technology》2001,21(1-2):89-96
Organically modified silicates containing calcium ion have a potential to bond to bone via an apatite layer deposited on their surfaces in the body environment. In this study, we examined the relationship between apatite deposition and the microstructure of the organically modified silicates synthesized from tetraethoxysilane (TEOS) and poly (dimethylsiloxane) (PDMS) with a different amount of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and hydrochloric acid (HCl). Apatite deposition was evaluated in vitro using a simulated body fluid (Kokubo solution). Copolymerization was confirmed between TEOS and PDMS even if PDMS free from —SiOH termination are used as one of the starting materials. The porosity and Ca content incorporated in the structure depended on the amount of HCl, whereas analysis of 29Si MAS NMR spectra indicates that it caused few effects on the local structure around Si atoms. Apatite-forming ability is enhanced by optimal amounts of HCl and Ca (NO3)2·4H2O. The difference in apatite-forming ability among the hybrid gels was attributed to both Ca(II) contents in the structure and aggregation states of the Si—OH groups. Better bioactivity of the hybrid gels is achieved by the release of Ca(II) ions trapped in structure at gelation and the formation of hydrated silica rich in Si—OH. 相似文献
7.
F. Sediri F. Touati N. Etteyeb N. Gharbi 《Journal of Sol-Gel Science and Technology》2003,26(1-3):425-430
The polymethylhydrosiloxane (PMHS) modified by bifunctional organic compounds (diamines), offer the possibility of producing organic-inorganic hybrid materials. These materials present excellent opto-electronic properties and find numerous applications such as the manufacture of electroluminescent diodes and ion or radiation sensors.This work shows that monolithic and transparent hybrid gels were obtained by reaction at room temperature of PMHS with diamines in tetrahydrofuran, using hexachloroplatinic acid (H2PtCl6·6H2O) as catalyst. The products have been characterized by infrared and 29Si MAS-NMR spectroscopy. The results show that the diamines have reacted with the PMHS leading to the monolithic and transparent gels in which both organic-inorganic —Si—(H)N—(CH2)
n
—N(H)—Si— bridges are formed (n = 3, 4 and 6). The thermal analysis of the xerogels was determined by TGA and DTA. The structure and texture of the obtained materials, were studied by Chemical Analysis and the Brunauer-Emmett-Teller (BET) method. 相似文献
8.
In order to unambiguously assign the 29Si-NMR chemical shifts of polydisilahydrocarbons containing structural units -CH2Si1(R1R2)Si2(R1R2)CHPh-, where R1=R2=Me or Ph, a model polymer viz., poly(tetramethyldisilyleneethylene) was synthesised through the dechlorination of 1,2-bis(chlorodimethylsilyl)ethane using potassium in toluene. The 29Si-NMR spectrum of this polymer shows only one resonance peak at δ=−15.1 ppm due to Si atoms in the structural units, -CH2Si(Me)2Si(Me)2CH2- which unambiguously reveals that the chemical shift in the up field region of polydisilahydrocarbons containing structural units -CH2Si1(R1R2)Si2(R1R2)CH(Ph)- is due to Si1, i.e., silicon attached to -CH2- and accordingly, the chemical shift in the down field region is due to Si2, i.e., silicon attached to -CH(Ph)-. 相似文献
9.
New hybrid organic-inorganic gels have been obtained by reaction of 1,4-butanediol, on tetramethoxysilane Si(OMe)4 dissolved in CCl4. This reaction does not require water and leads to the formation of polymeric transparent materials.Infrared, 29Si and 13C NMR spectroscopy shows that interchange reactions between OMe groups of alkoxide and -O-(CH2)4-O of 1,4-butanediol occurred, leading to the monolithic transparent gels in which both organic (Si-O-(CH2)4-O-Si) and inorganic (Si-O-Si) bridges are formed. 相似文献
10.
Channel-like and cage-like mesoporous silicas, SBA-15 (P6mm symmetry group) and SBA-16 (Im3m symmetry group), were modified by introducing single ureidopropyl surface groups, mixed ureidopropyl and mercaptopropyl surface
groups, and single bis(propyl)disulfide bridging groups. These hexagonal and cubic organosilicas were prepared under acidic
conditions via co-condensation of tetraethyl orthosilicate (TEOS) and proper organosilanes using poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) amphiphilic block copolymer templates, P123 (EO20PO70EO20) and F127 (EO106PO70EO106). The modified SBA-15 and SBA-16 materials were synthesized by varying the molar ratio of organosilane to TEOS in the initial
synthesis gel. The removal of polymeric templates, P123 and F127, was performed with ethanol/hydrochloric acid solution. In
the case of SBA-15 the P123 template was fully extracted, whereas this extraction process was less efficient for the removal
of F127 template from the SBA-16-type organosilicas; in the latter case a small residue of F127 was retained. The adsorption
and structural properties of the resulting materials were studied by nitrogen adsorption-desorption isotherms at −196∘C (surface area, pore size distribution, pore volumes), powder X-Ray diffraction, CHNS elemental analysis and high-resolution
thermogravimetry. The structural ordering, the BET specific surface area, pore volume and pore size decreased for both channel-like
and cage-like mesoporous organosilicas with increasing concentration of incorporated organic groups. 相似文献
11.
Taoufik Hellali Fathi Touati Ahmed Hichem Hamzaoui 《Phosphorus, sulfur, and silicon and the related elements》2016,191(8):1092-1100
New hybrid organic–inorganic materials have been obtained by the reaction of tetraethylorthosilicate (TEOS) with bi-functional heterocyclic molecules in ethanol using HCl as a catalyst at room temperature. This reaction has led to the formation of colored and transparent gels. The characterization of xerogels has been carried by infrared, 29Si and 13C CP MAS-NMR, DTA–TGA, scanning electron microscopy, Brunauer–Emmet–Teller method (BET), and DRX. The obtained results show that organic molecules react with TEOS leading to gels, in which Si–N, Si–O, and Si–S bridges are formed. According to N2-physisorption results, isotherms seem to have a similar sit, and classified as type IV according to the International Union of Pure and Applied Chemistry, synthesized X1, X2, and X4 are mesoporous solids but X3 is microporous. The BET surface area of these materials is important. It varied from 47 to 302 m2g?1. The optic and magnetic properties of hybrids are also studied by Ultraviolet–visible spectroscopy and résonance para-électronique. The obtained results show that all materials are semiconductors, and X2, X3, and X4 are paramagnetic but X1 is diamagnetic. 相似文献
12.
Denis L. Guerra Victor L. Leidens Claudio Airoldi 《Journal of solid state chemistry》2010,183(5):1141-166
The compound N1-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of 29Si and 13C. The well-defined peaks obtained in the 13C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k2 values 16.0 and 25.1 mmol g−1 min−1 ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations. 相似文献
13.
Kawahara K Hagiwara Y Kuroda K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13188-13196
A spherosilicate dendrimer ( DMS‐1 ) with closely spaced reaction sites (Si? H groups) on the dendrimer surface has been synthesized by stepwise silylation of double‐four‐ring silicate with chlorotriethoxysilane (ClSi(OEt)3) and subsequently with chlorodimethylsilane (ClSiHMe2). DMS‐1 consists of a maximum of 40 Si atoms in the interior frameworks and 24 reactive Si? H groups on the surface. Because DMS‐1 is spherical and about 1.5 nm in diameter, it can be regarded as the smallest well‐defined silica‐based nanoparticle. DMS‐1 also forms molecular crystals and is soluble in typical organic solvents. A molecularly ordered silica‐based hybrid can be prepared by heating a cast film of DMS‐1 at 180 °C for 5 days. The surface of DMS‐1 can be modified by hydrosilylation with 1‐hexadecene, triethoxyvinylsilane, and allylic‐terminated tetraethylene glycol monomethyl ether. More than 20 Si? H groups out of 24 react with these reagents. The solubilities of the products depend on the modification. DMS‐1 is not only a building block for nanohybrids, but also the smallest and most precisely designed siloxane‐based nanoparticle. 相似文献
14.
An electrochemiluminescence (ECL) sensor based on Ru(bpy)32+-graphene-Nafion composite film was developed. The graphene sheet was produced by chemical conversion of graphite, and was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. The introduction of conductive graphene into Nafion not only greatly facilitates the electron transfer of Ru(bpy)32+, but also dramatically improves the long-term stability of the sensor by inhibiting the migration of Ru(bpy)32+ into the electrochemically inactive hydrophobic region of Nafion. The ECL sensor gives a good linear range over 1 × 10−7 to 1 × 10−4 M with a detection limit of 50 nM towards the determination of tripropylamine (TPA), comparable to that obtained by Nafion-CNT. The ECL sensor keeps over 80% and 85% activity towards 0.1 mM TPA after being stored in air and in 0.1 M pH 7.5 phosphate buffer solution (PBS) for a month, respectively. The long-term stability of the modified electrode is better than electrodes modified with Nafion, Nafion-silica, Nafion-titania, or sol-gel films containing Ru(bpy)32+. Furthermore, the ECL sensor was successfully applied to the selective and sensitive determination of oxalate in urine samples. 相似文献
15.
Laurence Crouzet Dominique Leclercq Pierre Hubert Mutin André Vioux 《Journal of Sol-Gel Science and Technology》2003,26(1-3):335-338
Organosilsesquioxane-metal oxide hybrid materials prepared by the Sol-Gel process are mainly heterogeneous. In this paper we report the preparation of methylsilsesquioxane-titanium oxide, and methylsilsesquioxane-aluminium oxide hybrid materials by a nonhydrolytic sol-gel process involving the etherolysis-condensation of a mixture of methyltrichlorosilane and metal chloride. The Si/M ration in the xerogels were very closed to the one of the starting solutions. 29Si MAS NMR study has revealed that the methylsilsesquioxane-titanium oxide xerogel was heterogeneous at the atomic level. The spectrum of the hybrid containing aluminium, has shown beside a peak at –66 ppm corresponding to MeSi(OSi)3 environment, another peak at –47 ppm which was ascribed to MeSi(OAl)3 environment. The presence of only these two sites might be due to their stability. 相似文献
16.
Investigation on the Silicate Constitution in Trimethyl- and Triethyl-2-hydroxyethyl-ammoniumsilicate Solutions In trimethyl-2-hydroxyethyl-ammoniumsilicate solutions with molar N:Si ratios of 1:1 to 2:1 only double four-ring silicate anions are observed. In triethyl-2-hydroxyethyl-ammoniumsilicate solutions with the same molar N:Si changing quantities of double three-ring and double four-ring silicate anions are detectable. There is a range of SiO2 concentrations, where these two silicate anion constitutions dominate among all the SiO2 existing in the solutions. Increased quantities of alkali hydroxides effect the decomposition of double ring silicates, the decomposing effect of sodium and potassium hydroxide differing in their strength. 相似文献
17.
Michael A. Beckett Martin P. Rugen-Hankey K. Sukumar Varma 《Journal of Sol-Gel Science and Technology》2006,39(2):95-101
The reaction of metaborate esters (RO)3B3O3 [R = Me, Et, ClCH2CH2–, Cl3CCH2–, ClCH2CH2CH2–, (ClCH2)2CH–] with Si(OR)4 (R = Me, Et), either neat or in dry propan-2-one or dry THF at room temperature, led to gels which when dried and heated
in air for 20 mins at 600°C afforded borosilicate glasses in high ceramic yields. The dried gels and glasses were characterized
by elemental analysis, TGA, IR, and powder XRD, and solid-state MAS 29Si and 11B NMR. The gelling reaction was investigated by solution 11B and 29Si NMR. These NMR studies indicated B–O–Si reaction intermediates and a mechanism involving alkoxy exchange and various condensation/elimination
reactions of the borosilicate esters have been proposed. 相似文献
18.
Zhang Zhengping Gorman B.P. Dong Hanjiang Orozco-Teran Rosa A. Mueller D.W. Reidy R.F. 《Journal of Sol-Gel Science and Technology》2003,28(2):159-165
Dimethyldiethoxysilane (DMDES) appears to be a very promising modifier to introduce functional groups to a silicate network. The polymerization and cyclization of DMDES under acid-catalyzed conditions (DMDES : Ethanol : water : HCl = 1:4:4:3.68 × 10–4 in molar ratio) were investigated by high resolution liquid 29Si nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometry (FTIR). Time-dependent NMR and FTIR data illustrate that monomers of (CH3)2Si(OC2H5)2, (CH3)2Si(OC2H5)(OH), and (CH3)2Si(OH)2 reach meta-equilibrium in less than 4 minutes. 3-membered rings ((CH3)2SiO)3 appear about half an hour later and 4-membered rings ((CH3)2SiO)4 an hour later, which continue to be formed over 24 hours. The relative concentrations of monomers, linear structures and cyclic structures suggest a modified model for the kinetics of cyclization, where 4-membered rings are formed by dimer-dimer interactions, as opposed to monomer-trimer interactions previously proposed. 相似文献
19.
Isao Hasegawa 《Journal of Sol-Gel Science and Technology》1994,2(1-3):127-130
29Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O–)4/2 and CH3Si(O–)3/2 units, (CH3)
n
Si8O
20 – n
/(8 – n) –
(n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that 29Si NMR peaks due to Si(OSi)3(O–) units shift to lower frequencies by replacement of the adjacent Si(O–)4/2 units by CH3Si(O–)3/2 units, in other words, with increasing m value in Si[OSi(O–)3]3 – m
[OSi(CH3) (O–)2]
m
(O–) (m=0–2). Peaks from CH3
Si(OSi)3 units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH3Si(O–)3/2 units in the cubic octameric siloxane framework of (CH3)
n
Si8O
20 – n
/(8 – n) –
(n=2, 3), for both of which three isomers are present, have been estimated. 相似文献
20.
采用5-((4-吡啶基)甲氧基)-异烟酸(H2PLIA)、1,3,5-三(1-咪唑基)-苯(TIB)合成了金属有机骨架[Cd(PLIA)(TIB)]n (MOF-1),MOF-1是具有理想一维孔道的二维结构化合物,其一维孔道由柔性三角形PLIA2-配体和刚性三角形TIB配体间隔形成。利用MOF-1 易掺杂的优势,采用后修饰合成策略制备了Tb@MOF-1。对MOF-1 和Tb@MOF-1 进行了基本表征及荧光探针性能研究。2种探针材料具有相同的结构。MOF-1和Tb@MOF-1分别对水溶液中的Cr2O72-和S2O82-离子具有较强荧光识别能力,均有响应时间快,稳定性、选择性、灵敏度高的特点。研究了MOF-1和Tb@MOF-1对Cr2O72-和S2O82-的荧光识别机理,其不同可能与Tb3+离子掺杂有关。 相似文献