Papers by Keyword: Tetraethylorthosilicate

Abstract: The combined of superparamagnetic properties (magnetite) and surface characteristics (silica), can produce structures with multiple capacities. The preparation of such magnetite-silica core-shell nanoparticles involves high costs in their execution and longer time. In this work, Fe₃O₄@SiO₂ CSNPs were synthesized in two stages to control their size and the possibility of adjusting their characteristics. First, Fe₃O₄ NPs were synthesized by a green method using carob leaf extract, then coating the magnetite nanoparticles with a silica layer was done by using Tetraethylorthosilicate (TEOS) as a silica precursor. X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscope (AFM), Fourier transform infrared, and vibrating sample magnetometer techniques were used to characterize the magnetite-silica CSNPs. TEM images confirms that Fe₃O₄NPS and Fe₃O₄@SiO₂ CSNPs synthesized had a spherical shape and were within 9 and 17 nm. The average crystallite sizes of the synthesized Fe₃O₄ NPs and Fe₃O₄@SiO₂CSNPs were found to be 17.8 nm and 20 nm. The VSM indicated that the magnetization decreased due to being coated with silica.

Abstract: Synthesis of mesoporous silica from tetraethylorthosilicate (TEOS) by using sodium ricinoleic as a template and 3-aminopropyltrimethoxysilane (APMS) as a co-structure directing agents (CDSA) in a volume variation of acid addition has been carried out. Preparation of mesoporous silica was conducted in HCl 0.1 M at volume variations of 2 ml, 35 ml, 40 ml and 50 ml. In acid conditions, the amine groups of APMS will protonate, which will then interact electrostatically with the carboxylate groups from ricinoleic acid, while the methoxy groups from APMS will condense with the silanol groups from TEOS to form an end product of mesoporous silica. The reaction products were characterized by using X-ray diffractometer (XRD), Fourier transform infra-red spectrometer (FTIR), surface area analyzer (BET), scanning electron microscope (SEM), and transmission electron microscope (TEM). X-ray diffractograms of the products from all of the acid volume variation additions show broadening peaks indicating amorphous materials as a characteristic of mesoporous materials. Infrared spectra show that all of the products have Si-OH and Si-O-Si groups that are characteristics for mesoporous silica. Imaging results from SEM and TEM show morphology and particle size differences in accordance with the differences in volume variation of acid addition. Adsorption/desorption isotherm by using nitrogen at 77 K of the products from the addition of 2 ml of HCl show an isotherm Type II (adsorption on the surface layer) with irregular pore size distribution, whereas from the addition of 30 ml, 35 ml, 40 ml and 50 ml HCl show an isotherm Type IV with a hysteresis loop that is characteristic for mesoporous materials with a regular pore size distribution.

Abstract: The poly(methyl methacrylate)/silica nano-composite made from trimethoxysilyl functionalized poly(methyl methacrylate) and dimethyl diethoxysilane was newly prepared and its apatite-forming ability and mechanical properties were evaluated comparing to poly(methyl methacrylate)/silica nano-composite made from trimethoxysilyl functionalized poly(methyl methacrylate) and tetraethyl orthosilicate. Its apatite-forming ability was similar to that of poly(methyl methacrylate)/silica nano-composite using tetraethyl orthosilicate but its fracture toughness was much improved. Its high fracture toughness might come from the less quantity of siloxane linkages in its structure because dimethyl diethoxysilane had only two ethoxysilane groups while tetraethyl orthosilicate had four ethoxysilane groups. From the results, it can be concluded that it has a possibility to be used as bioactive bone cement.

Abstract: OH groups on hydroxyapatite (HA) and calcium metaphosphate (CMP) were evaluated by grafting tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethyloxysilane (3-APTES) which can bond covalently with OH group of ceramic biomaterials. The prepared HA and CMP disks were soaked in pH 2 and 5 of acidic water and ethanol solution respectively, where pH change of each solution was measured during soaking of samples. After grafting TEOS and 3-APTES on HA and CMP disks, samples were ultrasonically cleaned in distilled water and soaked in pH 5 of ethanol solution, and pH measurement was carried out in the same manner. The pH value of HA and CMP in aqueous solution at pH 2 increased with time continuously, resulting from dissolution of HA and CMP by acidic condition on surface. At pH 5 in aqueous solution, it was the same though the pH increase was smaller. In case of ethanol at pH 5 with HA, though pH value went up slightly, the curve became saturated with time, while there was no change in pH with CMP. After grafting TEOS and 3-APTES, pH values were stabilized with few changes, indicating that there was no direct chemical reaction between the acidic media and the surface of samples due to covalently grafted TEOS and 3-APTES layer. In conclusion, it was confirmed that OH group on the surface of HA was crystallographic and chemical one rather than physically adsorbed one by grafting TEOS or 3-APTES and it will serve an effective binding site for calcium and phosphate ions, or minerals.