Presence Of 3-aminopropyltriethoxysilane Research Articles

The Role of Adsorption in the Photocatalytic Decomposition of Dyes on APTES-Modified TiO2 Nanomaterials

This work investigated for the first time the role of adsorption in the photocatalytic degradation of methylene blue and Orange II dyes in the presence of 3-aminopropyltriethoxysilane (APTES)-modified TiO2 nanomaterials. It has been demonstrated that the decrease in adsorption has a detrimental effect on photocatalytic activity. APTES/TiO2 photocatalysts were successfully prepared by solvothermal modification of TiO2 in a pressure autoclave, followed by heat treatment in an inert gas atmosphere at the temperature range from 300 °C to 900 °C. It was observed that functionalization of TiO2 via APTES effectively suppressed the anatase-to-rutile phase transformation, as well as the growth of crystallites size during calcination, and reduction of specific surface area (APTES modification inhibits sintering of crystallites). The noted alterations in the adsorption properties, observed after the calcination, were generally related to changes in the surface characteristics, mainly surface charges expressed by the zeta potential. Positively charged surface enhances adsorption of anionic dye (Orange II), while negatively charged surface was better for adsorption of cationic dye (methylene blue). The adsorption process substantially affects the efficiency of the photocatalytic oxidation of both dyes. The methylene blue decomposition proceeded according to the pseudo-first and pseudo-second-order kinetic models, while the degradation of Orange II followed the zero, pseudo-first, and pseudo-second order kinetic models.

Sensitive and Selective Determination of 2,4,6-Trichlorophenol Using a Molecularly Imprinted Polymer Based on Zinc Oxide Quantum Dots

ABSTRACTNovel core-shell molecularly imprinted polymers were prepared based on zinc oxide quantum dots for the determination of 2,4,6-trichlorophenol by fluorescence. Principally, ZnO quantum dots and 2,4,6-trichlorophenol were chosen as the core substrate and the template molecule, respectively. The specific recognition sites for 2,4,6-trichlorophenol were obtained during the polymerization process in presence of 3-aminopropyltriethoxysilane and tetraethylorthosilicate. Molecularly imprinted ZnO quantum dots were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy and the optical properties were evaluated by spectrofluorometry. Under the optimal conditions, molecularly imprinted ZnO quantum dots were successfully applied to the sensitive determination and selective recognition of 2,4,6-trichlorophenol in water. A linear relationship was obtained to cover the concentration range of 0–160 µmol L−1 with a correlation coefficient of 0.9931 calculated by the Stern–Volmer equation. The products were used for the determination of 2,4,6-trichlorophenol in the water from local rural areas and the results strongly supported that the molecularly imprinted ZnO quantum dots were suitable for the determination of 2,4,6-trichlorophenol in real examples.

Enhanced antioxidation and microwave absorbing properties of SiO2-coated flaky carbonyl iron particles

SiO2 was successfully coated on the surface of flaky carbonyl iron particles using a chemical bath deposition method in the presence of 3-aminopropyl triethoxysilane (APTES). The morphologies, composition, valence states of elements, as well asantioxidation and electromagnetic properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and microwave network analyzer. TG curve shows the obvious weight gain of carbonyl iron was deferred to 360°C after SiO2-coated, which can be ascribed to the exits of SiO2 overlayer. Compared with the raw carbonyl iron, SiO2-coated sample shows good wave absorption performance due to its impedance matching. The electromagnetic properties of raw and SiO2-coated carbonyl iron particles were characterized in X band before and after heat treatment at 250°C for 10h. It was established that SiO2-coated carbonyl iron demonstrate good thermal stability, indicating SiO2-coating is useful in the usage of microwave absorbers operating at temperature up to 250°C.

Synthesis, characterization and magnetorheological study of 3-aminopropyltriethoxysilane-modified Fe3O4 nanoparticles

In this study, monodisperse Fe3O4 nanoparticles were synthesized successfully using a sonochemical method in the presence of 3-aminopropyltriethoxysilane (APTES). The morphology, microstructure and magnetic properties of the bare Fe3O4 and APTES-coated Fe3O4 were investigated in detail by TEM, XRD, FTIR and SQUID. It was found that APTES-coated Fe3O4 showed relatively good dispersion with a narrow size distribution of 8.4 ± 2.1 nm diameter. The functionalization of Fe3O4 was proved to be covalent linking between Fe3O4 and APTES. The field-dependent magnetization curve indicated superparamagnetic behavior of Fe3O4-APTES with a saturation magnetization (Ms) of 70.5 emu g−1 at room temperature. A magnetorheological (MR) fluid was prepared using the obtained Fe3O4-APTES nanoparticles with 25 wt% particles, and its MR properties were tested using a Physica MCR301 rheometer fitted with an MRmodule. The results showed that the as-prepared APTES-coated Fe3O4 nanoparticle-based MR fluid exhibited typical MR effects, with increasing viscosity, shear stress and yield stress depending on the applied magnetic field strength.

Nitroxide-Mediated Radical Polymerization of Styrene Initiated from the Surface of Titanium Oxide Nanoparticles

Titanium dioxide (TiO 2 ) nanoparticles, with an average size of about 45 nm, were encapsulated by polystyrene using in situ nitroxide mediated radical polymerization in the presence of 3-aminopropyl triethoxy silane as a coupling agent and 2, 2, 6, 6-tetramethylpiperidinyl-1-oxy as a initiator. First, the initiator for nitroxide mediated radical polymerization was covalently bonded onto the surface of Titanium dioxide nanoparticles through our novel method. For this purpose, the surface of TiO 2 nanoparticle was treated with 3-aminopropyl triethoxy silane, a silane coupling agent, and then these functionalized nanoparticles was reacted with ± -chloro phenyl acetyl chloride. The chlorine groups were converted to nitroxide mediated groups by coupling with 1-hydroxy-2, 2, 6, 6-tetramethyl piperidine. These modified TiO 2 nanoparticles were then dispersed in styrene monomers to carry out the in situ free radical polymerization.

Effect of nanosilica on the dielectric properties and thermal stability of polyimide/SiO2 nanohybrid

New polyimide–silica (PI–SiO2) nanohybrids were prepared by the reaction of bis(5-amino-1-naphthoxy) diphenylsilane (5-APS) with commercially available 4,4’-(Hexafluoroisopropylidene) diphthalic anhydride (6-FDA) in the presence of 3-aminopropyl triethoxysilane as a coupling agent and tetraethylorthosilicate (TEOS) as precursor of inorganic network. Hybrid thin films with 5–50 wt.% silica content were synthesized. The prepared PI–SiO2 films were characterized by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The morphology and crystallinity of these hybrid systems were investigated by transmission electron microscopy and XRD analysis. Thermal properties of the nanohybrids were evaluated by thermogravimetric analysis and dynamic mechanical thermal analysis techniques. The optical constants (n and k) and dielectric parameters ( and ) were calculated from IR reflection spectra by employing the Kramers–Kronig dispersion relations. Under proper condition, the silica particle size was in the range of 50–70 nm for the prepared hybrids. The results showed that presence of silica severely modified the properties of samples.

Preparation and Characterization of Novel Polyimide/SiO2 Nano-hybrid Films by In Situ Polymerization

A silicon-based aromatic polyimide (PI) containing pendent aryl rings was synthesized by solution polycondensation of a silicon-containing diamine with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride. Its nano-hybrids with different colloidal SiO2 concentrations were synthesized by in situ polymerization. The reactions were carried out in presence of 3-aminopropyltriethoxysilane as a coupling agent. The inclusion of the coupling agent in the polymer chain and its co-condensation with SiO2 nanoparticles afforded a silica network that was interconnected chemically with the PI matrix. The chemical structure of the hybrid materials was analyzed by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The morphology of the hybrid films and the surface roughness were characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The results indicated that nanometer-scale inorganic particles were homogeneously dispersed throughout the PI matrix with 50–70 nm size range. The best results and favorable miscibility between polymer and silica phases in the nano-hybrids were obtained when up to 40 wt% nanoparticles were introduced into the backbone of PI matrix.

N<sub>2</sub>O Direct Decomposition over Hierarchical FeZSM-5 Catalysts

Hierarchical FeZSM-5 microspheres were prepared in the presence of 3-aminopropyltriethoxysilane (APTES) in the synthesis system. The structure and morphology of the synthesized zeolites have been characterized by XRD, SEM, and N2 adsorption techniques. The hierarchical FeZSM-5 shows a much better catalytic performance in the direct decomposition of N2O, compared to FeZSM-5 synthesized without APTES.

Surface properties and structure of organofluorosilicon polymers based on organotrialkoxysilanes RFOCH2Si(ORF)3

The hydrolysis of trifunctional alkoxysilanes RFOCH2 Si(ORF)3, where RF = CH2CF3, CH2CF2CF3, CH2CF2CF2CF3, or CH2CF2CF2CF2CF3, during the action of atmospheric moisture in the presence of 3-aminopropyltriethoxysilane under mild conditions yields new ladderlike polysiloxanes. Their structure is studied via 1H NMR spectroscopy, GPC, TGA, and AFM. Polymer coatings prepared on their basis are found to be low-energy and hydrophobic. The total surface energy and polarity of the surface of polysiloxane films decrease, while their hydrophobicity increases with lengthening of the fluoroorganic substituent at the silicon atom.

Structure of Silica Xerogels Synthesized with Organoalkoxysilane Co-reactants Hints at Multiple Phase Separation

The microstructure of hybrid silica xerogels synthesized by the base-catalyzed polymerization of tetraethoxysilane (TEOS) in ethanol in the presence of 3-aminopropyltriethoxysilane (AES) and of 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) as co-reactants, and dried in subcritical conditions, is analyzed. A thorough structural characterization of the samples is performed combining nitrogen adsorption, small-angle X-ray scattering (SAXS), and transmission electron microscopy coupled with digital image analysis. The use of these methods shows that, for both co-reactants, the xerogels are made of macropores supported by filaments, with each filament being formed of smaller structures. The quantitative impact of the additive on each structural level is assessed. The data are compared with a previous time-resolved SAXS study conducted during the formation of the gels (J. Phys. Chem. B 2004, 108, 8983-8991). The results are analyzed in the framework of a double phase separation model.

Cu 2+-perchlorophthalocyanine immobilized MCM-41: catalyst for oxidation of alkenes

The immobilization of copperperchlorophthalocyanine (CuCl 16Pc) complex in the channels of HSi-MCM-41 molecular sieves has been carried out by (i) post-synthesis in the presence of 3-aminopropyltriethoxysilane (3-APTES) and (ii) impregnation in the absence of 3-APTES. The resulting host–guest samples were characterized by XRD, MAS-NMR, nitrogen adsorption, IR and cyclic voltammetry. Each sample showed an IR band at 1390 cm −1 suggesting the presence of CuCl 16Pc complex in the channels of HSi-MCM-41. The results of the alkene epoxidation in presence of (i) TBHP and (ii) O 2/isobutyraldehyde are compared. The oxo–metal and acyl peroxy radical species that formed predominantly using isobutyraldehyde give a high yield of epoxide, as compared to the reaction using TBHP as the oxidant.

Effects of hygrothermal aging and a silane coupling agent on the tensile properties of injection molded short glass fiber reinforced poly(butylene terephthalate) composites

The hygrothermal and mechanical properties of injection molded poly(butylene terephthalate) (PBT) composites containing 10, 20 and 30 wt.% short glass fiber (SGF) has been investigated. The kinetics of moisture absorption was investigated by immersion of PBT and SGF–PBT specimens in water at three different temperatures, i.e. 60°C, 80°C and 100°C. A single free-phase model of diffusion, which assumed Fickian diffusion and utilized Fick's second law of diffusion was used in analysing the data. A good agreement was observed between the experimental and theoretical values. The equilibrium moisture content, M m and the apparent diffusivity, D, were found to be dependent on the volume fraction of the fibers. DSC measurements revealed that the thermal behavior, viz. the melting point and the degree of crystallinity of PBT and SGF–PBT composites were affected by hygrothermal aging process. This was attributed to the changes in the microstructure of PBT due to its interactions with water molecules. Hygrothermal aging reduced the tensile properties of PBT, the effect of which is strongly dependant on factors such as water immersion temperatures, volume fractions of fibers and also the chemical treatment of SGF. The presence of 3-aminopropyltriethoxysilane (3-APE) coupling agent has improved the retention of tensile properties of SGF–PBT composites, especially under adverse hygrothermal condition. Failure modes of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope (SEM) are discussed.

Synthesis and characterization of poly(methyl acrylate-co-itaconic anhydride)/TiO2 hybrid materials via sol-gel process

In the presence of 3-aminopropyltriethoxysilane (APTES), the transparent and yellowish poly(methyl acrylate-co-itaconic anhydride)/TiO2 [P(MA-co-Itn)/TiO2] hybrid materials were prepared from the copolymer of methyl acrylate and itaconic anhydride [P(MA-co-Itn)] and tetrabutyl titanate (TBT) via a sol–gel process. At first, the triethoxysilane groups were incorporated into the copolymer P(MA-co-Itn) as pendant side chains by the aminolytic reaction between the itaconic anhydride units of the copolymer and the amino group of 3-aminopropyltriethoxysilane (APTES), and then the covalent bonds between the organic and inorganic phases were introduced by the hydrolysis and polycondensation of the triethoxysilane groups on the copolymer with TBT. FTIR analysis proved the existence of the covalent bonds. The influences of APTES on glass transition and morphology of the hybrid materials was studied by differential scanning calorimetry, scanning electron microscope, and atomic force microscope. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1763–1768, 2000

Effect of 3-aminopropyltriethoxysilane on properties of poly(butyl acrylate-co-maleic anhydride)/silica hybrid materials

The transparent poly(butyl acrylate-co-maleic anhydride)/silica [P(BA-co-MAn)/SiO2] has been successfully prepared from butyl acrylate-maleic anhydride copolymer P(BA-co-MAn) and tetraethoxysilane (TEOS) in the presence of 3-aminopropyltriethoxysilane (APTES) by an in situ sol–gel process. Triethoxysilyl group can be readily incorporated into P(BA-co-MAn) as pendant side chains by the aminolysis of maleic anhydride unit of copolymer with APTES, and then organic polymer/silica hybrid materials with covalent bonds between two phases can be formed via the hydrolytic polycondensation of triethoxysilyl group-functionalized polymer with TEOS. It was found that the amount of APTES could dramatically affect the gel time of sol–gel system, the sol fraction of resultant hybrid materials, and the thermal properties of hybrid materials obtained. The decomposition temperature of hybrid materials and the final residual weight of thermogravimetry of hybrid both increase with the increasing of APTES. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the morphology of hybrid materials prepared in the presence of APTES was a co-continual phase structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 419–424, 1999