Tetraethoxysilane In Presence Research Articles

Synthesis of Tetraethoxysilane-Reacted Hydroxyapatite Nanoparticles and Their Stabilization in Phosphate-Buffered Saline.

Hydroxyapatite (HA) particle, which is an inorganic component of biological hard tissues, is being applied as a bioceramic for biotechnology and medicine fields. However, early bone formation is difficult in the implantation of well-known stoichiometric HA into our body. To solve this problem, it is important to control the shapes and chemical compositions of the physicochemical properties of HA to be functionalized as the state similar to the biogenic bone. In this study, the physicochemical properties of the HA particles synthesized in the presence of tetraethoxysilane (TEOS) (SiHA particles) were evaluated and investigated. In particular, the surface layers of the SiHA particles were successfully controlled by adding silicate and carbonate ions in the synthetic, which would be involved in the bone formation process, and their elusive reaction behavior with phosphate-buffered saline (PBS) was also evaluated. The results showed that the ions in the SiHA particles increased with the increase in the added TEOS concentration, and the silica oligomer was also formed on the surfaces. The ions were present not only in the HA structures but also on the surface layers, indicating the formation of the non-apatitic layer containing the hydrated phosphate and calcium ions. The change in state of the particles with the immersion in PBS was evaluated, the carbonate ions eluted from the surface layer into PBS, and the free water component in the hydration layer increased with the immersion time in PBS. Therefore, we successfully synthesized the HA particles containing silicate and carbonate ions, suggesting the important state of the surface layer consisting of the characteristic non-apatitic layers. It was found that the ions in the surface layers can react with PBS and leach out, weakening the interaction of hydrated water molecules on the particle surfaces to increase the free water component in the surface layer.

Polyacrylonitrile Fibers with a Gradient Silica Distribution as Precursors of Carbon-Silicon-Carbide Fibers.

This study presents preparing and characterization of polyacrylonitrile (PAN) fibers containing various content of tetraethoxysilane (TEOS) incorporated via mutual spinning solution or emulsion using wet and mechanotropic spinning methods. It was shown that the presence of TEOS in dopes does not affect their rheological properties. The coagulation kinetics of complex PAN solution was investigated by optical methods on the solution drop. It was shown that during the interdiffusion process phase separation occurs and TEOS droplets form and move in the middle of the dope's drop. Mechanotropic spinning induces the TEOS droplets to move to the fiber periphery. The morphology and structure of the fibers obtained were investigated by scanning and transmission electron microscopy, as well as X-ray diffraction methods. It was shown that during fiber spinning stages the transformation of the TEOS drops into solid silica particles takes place as a result of hydrolytic polycondensation. This process can be characterized as the sol-gel synthesis. The formation of nano-sized (3-30 nm) silica particles proceeds without particles aggregation, but in a mode of the distribution gradient along the fiber cross-section leading to the accumulation of the silica particles either in the fiber center (wet spinning) or in the fiber periphery (mechanotropic spinning). The prepared composite fibers were carbonized and according to XRD analysis of carbon fibers, the clear peaks corresponding to SiC were observed. These findings indicate the useful role of TEOS as a precursor agent for both, silica in PAN fibers and silicon carbide in carbon fibers that has potential applications in some advanced materials with high thermal properties.

Fabrication and investigation of gold (III) ion-imprinted functionalized silica particles.

Au (III) ion-imprinted mesoporous silica particles (Au-Si-Py) was manufactured by the condensation reaction of (3-Aminopropyl)triethoxysilane (AT)and 2-pyridinecarboxaldehyde (Py). The obtained AT-Py Schiff base ligand was then coordinate with the template gold ions and the polymerizable gold-complex was allowed to gel in presence of tetraethoxysilane (TEOS) and then the coordinated gold ions were leached out of the obtained silica matrix using acidified thiourea solution. During the synthetic steps, the obtained materials were investigated utilizing advanced instrumental and spectral methods. Moreover, the morphological structure of both Au (III) ions imprinted Au-Si-Py and non-imprinted NI-Si-Py silica particles were visualized using scanning electron microscope (SEM). Various adsorption experiments had been carried out using both Au-Si-Py and NI-Si-Py to examine their potential for selective extraction of gold ions under different conditions.

A Novel Mesoporous Carbon as Potential Conductive Additive for a Li-Ion Battery Cathode

A new mesoporous carbon (MC) is obtained from pyrolysis of resorcinol/formaldehyde resin, polymerized in the presence of tetraethoxysilane and Pluronic F108, followed by pyrolysis at 800 °C and silica removal. The reaction mixture in a molar ratio of 1F108/60resorcinol/292 formaldehyde/16900 H2O/50 tetraethoxysilane heated at 67 °C produces MC nanoparticles (200 nm average size) exhibiting 3D bimodal mesopores (3.9 and 8.2 nm), 1198 m2/g surface area, 1.8 cm3/g pore volume, and important graphitic character for use as a conductive material. Composites LiFePO4/carbon prepared with MC or commercial Super P, by the slurry method, were tested as coin Li-ion battery (LiB) cathodes. Super P (40 nm average particle size) exhibits better graphitic character, but lower porosity than MC. LiFePO4/MC shows better specific capacity (161 mAhg−1) than LiFePO4/Super P (126 mAhg−1), with a retention capacity (RC) after cycling at C/10 of 81%. Both composites with MC and Super P show well-distributed particles. According to impedance analysis, MC mesoporosity improves the charge transfer kinetics (CTK) more than Super P, producing a cathode with higher efficiency, although lithium ions’ diffusion decreases because larger MC particles form longer diffusion paths. Owing to the good specific capacity of the LiB cathode prepared with MC, research looking into improving its retention capacity should be a focus.

Synthesis of novel hard mesoporous carbons and their applications as anodes for Li and Na ion batteries

Mesoporous-microporous carbons, were obtained from the pyrolysis of resol polymerized in the presence of tetraethoxysilane (TEOS) and the triblock copolymer PEO140-PPO39-PEO140 (F108). Carbons Cx-y (x = TEOS/F108 M ratio; y = synthesis temperature) exhibit interconnected porosity measured by N2 adsorption with high BET area and micro-mesoporous volume. According to this information and that obtained by Raman, XRD and CO2 adsorption, the carbons are described as hard carbons.As conductive additive-free anodes for Li- ion coin cells (LIBs), the carbons Cx-y present high initial specific capacity, being the highest for C70-100 (670 mAh/g) with high capacity retention: 500 mAh/g at 27 mA/g, 68 cycles and rate capability: 100 mAh/g at 1365 mA/g, 56 cycles. The C70-100 improved efficiency is attributed to the highest mesoporosity and lowest non-graphitizing hard carbon nature and surface activity.As anodes for Na-ion batteries (NIBs), these carbons present higher first discharge capacities ∼ 780-420 mAh/g and initial capacity, ∼192-109 mAh/g, than graphite. C90-150 with the lowest irreversible capacity is promising anode for NIBs. This result is due to its higher hard carbon nature and surface activity than C70-100 and lower porosity than C70-100 and C90-100, allowing more stability in carbon-sodium intercalation and less electrolyte decomposition, respectively.

Synthesis of cellulose-L-tyrosine-SiO2/ZrO2 hybrid nanocomposites by sol-gel process and its potential

Cellulose is an excellent natural biopolymer that can be modified to organic-inorganic hybrid nanocomposites by connecting nanomaterials to hydroxyl structure to improve the thermal, morphological, optical and biological properties. Based on the unique properties of oxide materials, we selected SiO2 and ZrO2, which has a large bandgap and a high dielectric constant. To modify the cellulose structure, we used an in-situ sol-gel process to form a cellulose-L-tyrosine (CE-L-tyr) and further synthesized hybrid cellulose-L-tyrosine-SiO2/ZrO2 nanocomposite materials by γ-aminopropyl triethoxysilane (γ-APTES) as coupling agent in the presence of tetraethoxysilane (TEOS) and zirconium isopropoxide. The cellulose-L-tyrosine-SiO2/ZrO2 hybrid nanocomposites were characterized by FTIR, XPS, XRD, UV, TGA, DSC, SEM, EDX and TEM measurements. The different analysis results show the optical transparency, thermal stability, and control morphology of hybrid nanocomposites. From antimicrobial test, CE-L-tyr-SiO2/ZrO2 hybrid nanocomposites exhibit stronger activity against Bacillus cereus and E. coli than that Lactobacillus and Pseudomonas aeruginosa.

Preparation and thermal stability of initiator fragments end-capped oligomers/silica nanocomposites

A variety of initiator fragments end-capped oligomers [X ∼ (M)n ∼ X; M = N, N-dimethylacrylamide (DMAA), acrylic acid (ACA), N-(1,1-dimethyl-3-oxobutyl)acrylamide (DOBAA), and acryloylmorpholine (ACMO); X = initiator fragments] were synthesized by oligomerization of the corresponding monomers catalyzed by the radical initiators such as ammonium persulfate (APS), 2,2′-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) (VA-086), and azobisisobutyronitrile (AIBN). These initiator fragments end-capped oligomers were found to cause a gelation toward not only water but also traditional organic media such as methanol, 2-propanol, propylene carbonate, 1,2-dichloroethane, and tetrahydrofuran. These obtained oligomers were applied to the nanocomposite reactions with silica nanoparticles in the presence of tetraethoxysilane (TEOS) under alkaline conditions to provide the corresponding oligomers/silica nanocomposites. In these nanocomposites, X ∼ (M)n ∼ X/SiO2 nanocomposites, which were prepared by using APS as an initiator, were found to afford the clear weight loss in proportion to the contents of the oligomers in the composites after calcination at 800 °C. However, interestingly, X ∼ (M)n ∼ X/SiO2 nanocomposites, which were prepared by using VA-086 and AIBN, afforded no weight loss corresponding to the contents of the oligomers in the composites even after calcination at 800 °C.

Covalently cross-linked pyridinium based AEMs with aromatic pendant groups for acid recovery via diffusion dialysis

In this study, the pyridinium anion exchange precursor was prepared by alkylation of 4-bromomethyl benzoic acid to pyridine and then the corresponding covalently cross-linked pyridinium based AEMs were obtained by esterification reaction through the prepared pyridinium salt and polyvinyl alcohol (PVA) as a base material in presence of tetraethoxysilane (TEOS) as a crosslinker. The prepared anion exchange membranes are characterized by FTIR, SEM, TGA and DMA. Td values are in the range of 322–335 °C. The tensile strength (TS) ranges from 43.74 to 47.23 MPa and elongation at break (Eb) in the range of 262.59–474.44%. The acid dialysis coefficients (UH) are in the range of 1.28–1.88 × 10−2 m/h, greater than the well known commercial membrane DF-120 (9 × 10−3 m/h). The membrane containing 40 wt% of PVA has the highest separation factor (S) of 71.35. Note that the DD tests have been evaluated according to the membrane structure and its composition.

A sol-gel based molecular imprint incorporating carbon dots for fluorometric determination of nicotinic acid

We are introducing functionalized carbon dots (C-dots) coated with a shell of molecularly imprinted sol-gel as a new tool in molecular imprint-based detection. Specifically, an imprint recognizing nicotinic acid (NA) was prepared in two steps. The first involves pyrolytic decomposition of citric acid in the presence of aminopropyltriethoxysilane to yield triethoxysilyl-modified C-dots with a typical size of 2.8 ± 1.1 nm. These are then polycondensed in the presence of tetraethoxysilane and NA at room temperature to give spherical silica nanoparticles (SiNPs) with a typical size of ~300 nm and containing C-dots and NA in the silica matrix. NA was then removed by extraction. The resulting SiNPs are well permeable to NA, photostable, display strong blue luminescence and can bind NA fairly selectively. The fluorometric detection scheme is based on the finding that increasing concentrations of NA quench the fluorescence of the C-dots in the SiNPs. NA can be determined by this method in the 0.5 to 10.5 μM concentration range, with a 12.6 nM detection limit. The composite was successfully utilized as a fluorescent probe for the determination of NA in spiked human urine samples. The method is believed to have a wider scope in being applicable to other analytes that are capable of quenching the fluorescence of C-dots.

Imidazolium functionalized anion exchange membrane blended with PVA for acid recovery via diffusion dialysis process

Anion exchange silica precursor (AESP) was prepared by alkylation of 3-chloropropyltriethoxysilane (CPTS) to 1-methyl imidazole and then the corresponding anion exchange membranes were obtained through sol–gel process of AESP with polyvinyl alcohol (PVA) in the presence of tetraethoxysilane (TEOS). The obtained anion-exchange membranes showed water uptakes (WU) in the range of 44.11–118.86% and ion-exchange capacities (IEC) of 1.34–1.86mmol/g. The presence of alkoxy-silane groups influenced the membrane properties as they exhibited moderate thermal stability and excellent mechanical properties. When applied for acid recovery through diffusion dialysis process, the membranes exhibited excellent acid flux. The H+ dialysis coefficients (UH) are in the range of 1.87–4.83×10−2m/h greater than commercial membrane DF-120 (9×10−3m/h). The obtained separation factors (S) 12.72–52.5 are also greater than that of commercial membrane DF-120 (18.5). Hence, the results of this study suggest that the imidazolium functionalized AEMs can be potentially applied in diffusion dialysis process for acid recovery.

Design of new lanthanide pH switches based on a cross-linked poly(vinyl alcohol)/tetraethoxysilane hybrid matrix

The design and synthesis of cross-linked siloxane and polymeric matrices incorporated with terbium or europium complexes have been studied. The preparation of hybrid hosts demonstrated that poly(vinyl alcohol) in the presence of tetraethoxysilane with various concentrations gave different mechanical stabilities and water solubilities. The as-derived films exhibited excellent photophysical properties of lanthanides with large Stokes shifts, narrow emissions, and high color purity. It has been found that the luminescent materials were dramatically quenched over the assayed pH ranges (pH 7 to 1 and pH 7 to 14). These optical probes could be recycled for ten times by changing the aqueous media. The novel inorganic-organic responsive films that can be switched on or off based on pH values will find potential application in biological analysis.

Supported and Non-Supported Ruthenium(II)/Phosphine/[3-(2-Aminoethyl)aminopropyl]trimethoxysilane Complexes and Their Activities in the Chemoselective Hydrogenation of trans-4-Phenyl-3-butene-2-al

Syntheses of four new ruthenium(II) complexes of the [RuCl2(P)2(N)2] type using 2-(diphenylphosphino)ethyl methyl ether (P~O) as ether-phosphine and triphenylphosphine (PPh3) as monodentate phosphine ligands in the presence of [3-(2-aminoethyl)aminopropyl]trimethoxysilane as diamine co-ligand are presented for the first time. The reactions were conducted at room temperature and under an inert atmosphere. Due to the presence of the trimethoxysilane group in the backbone of complexes 1 and 2 they were subjected to an immobilization process using the sol-gel technique in the presence of tetraethoxysilane as cross-linker. The structural behavior of the phosphine ligands in the desired complexes during synthesis were monitored by 31P{1H}-NMR. Desired complexes were deduced from elemental analyses, Infrared, FAB-MS and 1H-, 13C- and 31P-NMR spectroscopy, xerogels X1 and X2 were subjected to solid state, 13C-, 29Si- and 31P-NMR spectroscopy, Infrared and EXAF. These complexes served as hydrogenation catalysts in homogenous and heterogeneous phases, and chemoselective hydrogenation of the carbonyl function group in trans-4-phenyl-3-butene-2-al was successfully carried out under mild basic conditions.

Preparation of A Novel Type of Fluorescein Isothiocyanate-Doped Fluorescent Silica Nanoparticle and Its Application as pH Probe

Abstract In this study, a novel type of core-shell fluorescein isothiocyanate (FITC)-doped fluorescent silica nanoparticle was synthesized and used as an intracellular pH sensor. First, a silane reagent of 3-aminopropyl-trimethoxysilane (APTMS) was used to synthesize a novel precursor FITC-APTMS. Then, FITC-APTMS/SiO2 (FAS) nanoparticles were obtained using water-in-oil (W/O) microemulsion technique in the presence of tetraethoxysilane (TEOS). Characterizations by transmission electron microscopy (TEM) and fluorescence spectroscopy show that the nanoparticles are spherical, monodisperse, and uniform in size with the diameters being (150 ± 15) nm. They are also highly fluorescent and highly photostable. When the nanoparticles were dispersed in aqueous solution under ultrasonic treatment for 6 h, no obvious dye leaking was observed. It was found that the fluorescence of the nanoparticles was pH sensitive, and the pH response range was 3.6–9.7, with a linear range of pH 6.0–9.0. The FAS nanoparticles could be phagocytosed by murine neural stem cell and thus could be applied to detect intracellular pH value of single cell.

IrO 2–SiO 2 binary oxide films: Preparation, physiochemical characterization and their electrochemical properties

Mixed IrO 2–SiO 2 oxide films were prepared on titanium substrate by the thermo-decomposition of hexachloroiridate (H 2IrCl 6) and tetraethoxysilane (TEOS) mixed precursors in organic solvents. The solution chemistry and thermal decomposition kinetics of the mixed precursors were investigated by ultra violet/visible (UV/vis) spectroscopy and thermogravimetry (TGA) and differential thermal analysis (DTA), respectively. The physiochemical characterization of the resulting materials was conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. It is shown from the UV/vis spectra that the electronic absorption intensity of IrCl 6 2− complexes in the precursors decreases in the presence of TEOS, indicating the interaction between these two components. Thermal analysis shows the decomposition reaction of H 2IrCl 6 is inhibited by TEOS in the low temperature range, but the further oxidation reaction at high temperatures of formed intermediates is independent of the presence of silane component. Physical measurements show a restriction effect of silica on the crystallization and crystal growth processes of IrO 2, leading to the formation of finer oxide particles and the porous morphology of the binary oxide films. The porous composite films exhibit high apparent electrocatalytic activity toward the oxygen evolution reaction. In addition, the long-term stability of Ti-supported IrO 2 electrodes is found to apparently improve with appropriate amount of SiO 2 incorporation, as tested under galvanostatic electrolysis.

Synthesis and characterization of thermoluminescent glass-ceramics Li 2O–Al 2O 3–SiO 2:CeO 2

Vitroceramic powders of Li 2O–Al 2O 3–SiO 2 systems (LAS), doped with 1% (LAS:1Ce) and 10% (LAS:10Ce) molar of cerianite (CeO 2) were synthesized by means of the gelification technique of metal formates of aluminum and lithium, in the presence of tetraethoxy silane and CeO 2. The gels obtained were dried (120 °C, 2.5 h), calcined (480 °C, 5 h) and sinterized (1250 °C, 30 min). The sinterized samples were characterized by X-ray difraction (XRD), scanning electron microscopy (SEM) and microchemical analysis (EDS). There is evidence for a mixture of two phases of 64% β-spodumene (Li 2O–Al 2O 3–4SiO 2) and 36% β-eucryptite (Li 2O–Al 2O 3–2SiO 2). The LAS:1Ce system was enriched in aluminum, the LAS:10Ce system showed areas of heterogeneous composition; some regions with a shortage of CeO 2, while others zones with cerium cumulus. From the microscopy images it was found that CeO 2 acts as a densificant agent in LAS system, favoring the sintering in the host. The chemical route and the sintering processes utilized allow the production of samples exhibiting an acceptable linear correlation between total thermoluminescent emission intensity and the irradiation dose when the CeO 2 concentration is low (less than 1%), opening the possibility of using this kind of glass-ceramic in dosimetry.

A carbon-silica composite material based on powdered cellulose: Synthesis and properties

A procedure was developed for preparing a carbon-silica composite by thermolysis of powdered cellulose in the presence of tetraethoxysilane. The resulting composite was studied in model processes of trimethylhydroquinone oxidation and hydrogen peroxide decomposition.

PVC–Silica Sol-gel Hybrids: Effect of Interphase Bonding by Aminopropyltrimethoxysilane on Thermal and Mechanical Properties

Two types of hybrid materials from Poly(vinyl chloride) (PVC) using different amounts of silica have been prepared by the sol-gel technique. The hybrids without inter-phase bonding were prepared by the in-situ generation of silica network from tetraethoxysilane (TEOS) in the PVC matrix. The inter-phase bonding in the hybrid material was achieved by the reaction of aminopropyltrimethoxysilane (APTMOS) with the PVC chain and then carrying out sol-gel process in presence of TEOS. Morphology of the silica particles produced in-situ in the hybrid films was studied by Scanning Electron Microscopy. The inter-phase bonding considerably reduced the silica particle size making their distribution more uniform in the matrix as compared to the unbonded hybrids. Dynamical mechanical thermal analysis was carried out to measure the glass transition temperature from the maxima of tan δ curves. The storage modulus and the glass transition temperature of the resulting hybrids were found to increase whereas the thermal coefficient of expansion was considerably reduced with the inclusion of aminosilane in the sol-gel hybrids.

Mesostructured Silica Films with Metal Oxide Doped Pore Walls

ABSTRACTIn this work, novel approaches towards mixed metal oxide mesostructured films by a combination of evaporation-induced self-assembly and sol-gel processing of deliberately designed precursor molecules (from single source precursors to metal-surfactant complexes) are reported. The focus lies on Ti-oxide doped silica films with in a wide range variable Ti to Si ratios. The ligand-assisted templating based on metal-coordinated surfactants allows a selective positioning of the metal species in the silica wall which is advantageous for many catalytic applications. For the synthesis of these metal doped silica films, a non-ionic polyether-based surfactant (Brij56) was simultaneously used as the structure-directing agent and ligand for the respective metal-alkoxide, such as titanium isopropoxide. These metal-coordinated surfactants were mixed with a prehydrolyzed silica-solution based on tetraethoxysilane and ethanol and spin- or dip coated. In the second approach, a single source precursor for network formation based on 3-acetyl-6-trimethoxysilylhexane-2-one that was coordinated to titanium isopropoxide was synthesized. This precursor was either used as network forming agent in the presence of tetraethoxysilane and a surfactant (Brij56) or in combination with the metal-coordinated surfactant to broaden the accessible range of the Si:Ti ratios. The final films were characterized by XRD, XPS, nitrogen porosimetry and TEM.

Surface properties of fluorinated hybrid coatings

AbstractA commercial perfluoropolyether containing alkoxysilane functionalities was employed to prepare organic–inorganic hybrid coatings by using the sol‐gel process in the presence of tetraethoxysilane. Contact angle analysis revealed a strong hydrophobic and oleophobic character of the coatings almost independently from the molecular weight of the starting fluorinated oligomer. Surface tension values were in the range of 14–16 mN/m, suggesting a preferential segregation of fluorinated segments onto the surface of the coating. Atomic force microscopy showed the presence very smooth surfaces permitting to neglect the contribution of the surface roughness to wettability. Friction coefficient values were markedly lower with respect to the value of uncoated glass substrate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1483–1488, 2006

Poly(ethylene glycol) electrolyte gels prepared by condensation reaction

Poly(ethylene glycol) electrolyte gels were prepared by condensation reaction in the presence of tetraethoxysilane. Differential scanning calorimetry and X-ray diffraction spectroscopy were used to investigate the thermal transition behavior and crystalline structure of polymer gels prepared. Both formation of crosslinks and incorporation of salts or plasticizers reduced the development of crystalline structure of poly(ethylene glycol)s. Cyclic voltammetric and ion-conducting behaviors of polymer gels were analyzed using potentiostat and impedance spectroscopy, and those were also considerably affected by the crosslinking density of polymers and the concentration of electrolyte salt or plasticizers incorporated. Poly(ethylene glycol) gels possessing certain levels of electrolyte salt and plasticizer were expected to have applications of solid electrolytes for lithium polymer secondary batteries. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 948–956, 2002