Search

Abstract In this work, for the first time, a grafting of 3-aminopropyltriethoxysilane (APTES) followed by incorporation of iron nanoparticles (Fe-NPs) was used for the functionalization of graphene oxide (GO). Changes in stability, structural, morphological, thermal and catalytic properties of the resulting GO/APTES/Fe material were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive X-Ray, Fourier transform infrared and UV–visible spectroscopies, zeta potential measurements, X-ray photoelectron spectroscopy and differential scanning calorimetry. The average crystallite size of GO/APTES/Fe was found to decrease significantly after the post treatment, producing slight structure compaction. Iron nanoparticles were immobilized by APTES on the GO sheets, with a particle size around 50 nm. Fe insertion and APTES grafting resulted in high thermal stability of GO. As an application, GO/APTES/Fe exhibited an excellent catalytic activity in the reduction of 4-nitrophenol into 4-aminophenol. The presence of both APTES and small amount of Fe nanoparticles in GO/APTES/Fe induced a significant improvement in catalytic activity. GO/APTES/Fe also showed appreciable recyclability after four repeated uses without noticeable loss in activity. This stability was higher to those of other GO-materials. The results obtained herein open new prospects for Fe-loaded organo-graphene oxide as efficient material in catalysis and industrial applications. Highlights • A novel GO/APTES/Fe as metal-organic-graphene-oxide was prepared firstly. • GO/APTES/Fe exhibited excellent catalytic activity toward the reduction of 4-NP as hazardous pollutant. • Iron nanoparticles were stabilized by APTES within the GO sheets. • The electron transfer between Fe-NPs and GO/APTES contributes to the strong adsorption of negatively-charged reactants. • An excellent new catalyst for the reduction of 4-nitrophenol with recyclability. [ABSTRACT FROM AUTHOR]

Surface functionalization of cellulose nanocrystals (CNCs) is valuable option to tailor properties as well as increase opportunities for their application. In this study, the surface of CNCs was functionalized with 3-aminopropyltriethoxysilane (APTES), without using hazardous solvents and by a direct, simple and straightforward method. APTES was firstly hydrolyzed in water and then adsorbed onto CNC through hydrogen bonds, finally the chain hydrocarbon was covalently linked to the surface of CNC through Si O C bonds which formed via the condensation reaction between hydroxyl and silanol groups. The chemical modification of the CNCs surface was confirmed by ATR-IR and NMR spectroscopy. Experiments conducted by AFM and XRD showed no significant change in the CNC dimensions and crystalline structure as a result of the modification. The EDX and XPS results confirmed the exsistence of APTES onto the CNCs. Silylated CNC exhibited good thermal stability and a greater amount of residual char was formed at 500 °C compared to non-chemically modified CNC. Thus, The silylation of CNCs may offer applications in composite manufacturing, where these nanoparticles have limited dispersibility in hydrophobic polymer matrices, and as nano-adsorbers due to the presence of amino groups attached on the surface. [ABSTRACT FROM AUTHOR]

NaA zeolite membranes were synthesized on top of both disk and tubular porous stainless steel substrates by the secondary growth method. The support seed stage was optimized, considering the seed synthesis conditions and the deposition method. The formation of the NaA zeolite on both the membrane and the residual powder collected at the bottom of the vessel after synthesis was corroborated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed the formation of a film with well-defined crystals with a cubic morphology characteristic of the NaA zeolite. The support modification with 3-aminopropyltriethoxysilane improved the morphology and stability of the NaA zeolite membranes synthesized on top of porous stainless steel substrates. When vacuum was applied only in the last hydrothermal synthesis stage, a smooth zeolite layer was obtained on top of porous stainless steel supports. The single gas (H 2 , N 2 , CO 2 and CH 4 ) and mixture (H 2 /N 2 and H 2 /CH 4 ) perm-selective properties of the tubular membranes were evaluated as a function of temperature and pressure. Separation factors higher than the Knudsen coefficient were obtained in all membranes. The single gas H 2 and CO 2 permeation flux of the membranes increased with temperature indicating a preponderance of the activated diffusion over the Knudsen diffusion. The higher H 2 /CO 2 ideal separation factors were 7.6 and 5.6 for the more selective tubular membranes, at 453 K and 100 kPa. [ABSTRACT FROM AUTHOR]

A two-component waterborne polyurethane (2K-WPU) was obtained by the reaction between a hydroxyl-component waterborne polyurethane and a hydrophilically modified polyisocyanate. A hydroxyl-component waterborne polyurethane with a cross-link structure of Si-O-Si groups was synthesized by means of 3-aminopropyltriethoxysilane (APTES) and trimethylolpropane end-capping concurrently. Mean particle size and viscosity of the hydroxyl-component WPU mini-emulsions were examined by a laser particle analyzer and a Brookfield viscometer. Fourier transform-infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were utilized to analyze the chemical structure of 2K-WPU films. The influence of APTES content on thermal stability, mechanical properties, and solvent resistance of 2K-WPU films was also investigated by thermogravimetric analysis (TGA), a universal testing machine, and an immersion test under three kinds of solvent (ethanol, acetone, and dichloromethane) for 24 h, respectively. The results show that 2K-WPU films containing APTES have excellent thermal stability, tensile strength, and breaking elongation. Additionally, these films possess the strongest resistance to ethanol, as well as resistance to acetone and dichloromethane to a certain extent at the APTES content of 4 wt.%. [ABSTRACT FROM AUTHOR]

The modification of montmorillonite clay mineral (Mt) was performed using the 3-aminopropyltriethoxysilane (γ-APS) silylation agent in different synthesis solutions. The modified products (S-Mt) were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The XRD demonstrated that silane was intercalated in the interlayer space of Mt due to the increase in basal spacing. The basal spacing shown by some S-Mts suggests the presence of a double layer of aminopropyl molecules in the interlayer space of the clay mineral modified in water and in a hydroalcoholic media at both synthesis temperatures (50°C and 80°C). The TGA revealed the presence of peaks in the range of 200°C to 600°C due to the presence of adsorbed silanes, intercalated silanes and silanes chemically bonded between the clay mineral layers and/or the edges. Evidence showed that the presence of water in dispersant is essential for intercalation of the silane in the interlayer space of the Mt such that the S-MMTwater, S-MtE/A(50) e S-MtE/A(80) showed higher amount of silane and higher basal spacing in its structure. Qualitative evidence of the presence of γ-APS in the modified clay minerals was obtained by FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

Designing biointerfaces with enhanced biomolecule binding abilities, along with their distribution and presentation on the surface, largely requires control over underlying surface chemistries. In an effort to correlate experimental parameters to surface properties, ligand distribution and biomolecule binding, the influence of (3-aminopropyl)triethoxysilane (APTES) concentration (1, 2 and 4 vol%) and duration of the silanization reaction (5–60 min) on the number of available - NH2 groups were determined and correlated with the amount of surface bound human immunoglobulin G (HIgG). Surfaces silanized with 2 vol% APTES for 30 min yielded a densely populated silane monolayer (1.0–1.2 nm) where the average molecular orientation was 38 ± 2° with respect to the surface normal. A surface density of - NH2 moieties of ∼1015/cm2 was obtained and was significantly higher compared to other conditions evaluated. The combined data from ellipsometry and atomic force microscopy (AFM) analyses supports our findings. Coupling of HIgG to surfaces silanized with 2 vol% APTES for 30 min yielded ∼1013 IgG/cm2, which was significantly higher than values obtained at 1 vol% APTES for 30 min. The distribution of immobilized HIgG was noted to be dense and uniform on surfaces silanized with 2 vol% APTES when visualized using Nanogold® antibody conjugates. This study highlights the critical role of the experimental parameters that impact the biomolecule immobilization process on functionalized surfaces. [Copyright &y& Elsevier]

Abstract: High temperature inorganic membranes may play an important role in the development of economical processes for pre-combustion and/or post-combustion CO2 capture. The CO2/N2 selectivity of mesoporous silica membranes is enhanced by surface modification using APTS (3-aminopropyl-triethoxy silane). Unmodified silica membranes exhibit Knudsen diffusion behavior for most gases but also have some contribution from surface diffusion of heavier or interacting gases like CO2, CH4, etc. Gas separation experiments were performed on the modified membranes for both pure gas and mixed gases for a range of temperatures and feed gas compositions. Mixed gas separation factors as high as 10 for CO2 over N2 were observed at 393K and CO2 partial pressures of 15kPa; whereas for pure gases (CO2 partial pressure of 303kPa), no separation was seen. The hypothesized transport mechanism is the reaction of CO2 with surface amine groups to form a carbamate species and subsequent surface “hopping” of carbon dioxide. The CO2 binding at ambient conditions is sufficiently strong to greatly inhibit the surface diffusion of CO2, however, as the temperature increases, the CO2 permeance increases and selective transport of CO2 is observed. The permeance of CO2 is highly non-linear, and increases with decreasing CO2 partial pressure in the feed gas. NMR studies performed on the bare support and modified membrane shows the support has been modified by APTS. Pore size analysis on the unmodified and modified silica substrates show that the pore diameter of modified substrates are lower than that of the unmodified substrate indicating that the amine silanes are anchored on the pore walls of the substrate. The NMR measurement for an APTS/silica membrane with adsorbed CO2 shows the presence of a carbamate species and thus supports the hypothesized reaction mechanism or facilitated solid-state CO2 transport. The binding energy for CO2 adsorption is 15.5kcal/mol and activation energy for CO2 diffusion/hopping from one amine group to another of APTS is 7.2kcal/mol as computed using ab initio Density Functional Theory (DFT). [Copyright &y& Elsevier]

Abstract: The grafting reactions between 3-aminopropyltriethoxysilane and Al13-intercalated/Al-pillared montmorillonites thermally pretreated at different temperatures were investigated by using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and nitrogen adsorption–desorption isotherms. The porous structures and the grafting degree of the organosilane modified Al13-intercalated/Al-pillared montmorillonite products are significantly affected by the solvents. The product prepared in anhydrous ethanol has high specific surface area (~160m2 g−1) and larger porous volume (0.134cm3 g−1) but low degree of grafting modification, while the one prepared in cyclohexane has a high loading amount of silane (2.02mmolg−1) but low surface area (7m2 g−1). Thermal treatment affects the grafting process by both reducing the water content in the interlayer space of the pillared montmorillonite and causing the transformation of the interlayer Al compounds from polycations to oxides. The hydrolyzed 3-aminopropyltriethoxysilane is mainly grafted onto the surface of the interlayer Al Keggin ions and/or Al oxides. This study demonstrates the functionalization of pillared clay to form inorganic–organic hybrid material that combines the high porosity of inorganic pillared clay and the lipophilicity of organoclay by adjusting the solvents and the pretreatment conditions, enabling potential applications in adsorption and environmental restoration. [ABSTRACT FROM AUTHOR]

Flexible polyurethane (PU) foams are easily ignitable and show a high burning velocity, mainly due to their high surface area-to-mass ratio and high air permeability. Consequently, flame retardants such as halogenated compounds are applied. However, the use of halogenated flame retardants is not considered beneficial in transport applications, for example, aviation or automobile, in part due to the high smoke generation. Solid nonhalogenated flame retardants, for example, aluminum trihydroxide (ATH), are known as smoke suppressants. The application of ATH in flexible (PU) foam has not yet been reported in the literature. In this study, the application of different types and amounts of ATH and the resulting structure-property relationship in the foam are investigated. The increase in the viscosity of the filled raw materials during the foaming process and the negative effects of the filler on the mechanical properties of the final foam pose particular problems in the application of ATH. To pass the FMVSS 302 test, high amounts of ATH are necessary. To overcome the mentioned drawbacks, ATH particles are functionalized by 3-aminopropyltriethoxysilane under different conditions. The synthesized products were characterized by Fourier transform infrared, energy-dispersive X-ray fluorescence analysis, and 29Si and ¹H solid-state nuclear magnetic resonance spectroscopy. The silane-treated ATH particles show a significant decrease in viscosity of the ATH-polyol system of more than 20% at ATH contents of up to 60 phpp. Values of the rising behavior during foaming and the burning velocity are not affected by this silane treatment. However, the compression test of PU foams with the silane-treated ATH particles show a decrease in compression strength of up to 20% compared to untreated ATH particles in the flexible PU foam. At higher ATH contents, no effect of silanization is observed. [ABSTRACT FROM AUTHOR]

A new series of Cu(II), Ni(II), and Co(II) complexes have been synthesized from 3-formylchromoniminopropylsilatrane (C19H24O5N2Si) (2) and 3-formylchromoniminopropyltriethoxysilane (1). Silatrane ligand (C19H24O5N2Si) (2) has been synthesized by the reaction between 3-aminopropyltriethoxysilane and 3-formylchromone followed by a treatment with triethanolamine. The nature of bonding and the geometry of the complexes have been deduced from elemental analyses, magnetic susceptibility, infrared, electronic, 1H NMR, 13C NMR, and ESR spectral studies. The electronic absorption spectra and magnetic susceptibility measurements of the complexes indicate square planar geometry for Cu(II) and Ni(II) and tetrahedral geometry for Co(II). The redox behavior of copper complexes was studied by cyclic voltammetry. The biological activity of the ligand and metal complexes has been studied on Klebsiella pneumoniae, Staphylococcus aureus, Escherichia Coli, and Bacillus subtilis by the well diffusion method using acetonitrile as solvent. The zone of inhibition values were measured at 37°C for 24 h. Antimicrobial screening tests show better results for the metal complexes than the ligand. [ABSTRACT FROM AUTHOR]

3-aminopropyltriethoxysilane grafted montmorillonites were synthesized with montmorillonite, acid-activated montmorillonites and 3-aminopropyltriethoxysilane in ethanol-water mixture. The resulting products were investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TG). XRD patterns demonstrated that silane was intercalated into the montmorillonite gallery, indicated by increasing basal spacings. These intercalated silanes probably adopt bilayer arrangement models within the montmorillonite and acid-activated montmorilloflites interlayer spaces. TG and DTG curves indicate that acidification results in a decrease of the thermal stability of the resultant montmorillonites. Silane grafting leads to a surface property transformation of montmorillonite from hydrophilicity to lipophilicity and an increase of the thermal stability of the condensed silanes. [ABSTRACT FROM AUTHOR]

Abstract: Amino-functionalized organic films were prepared by self-assembling 3-aminopropyltriethoxysilane (APTES) on silicon wafers in either anhydrous toluene or phosphate-buffered saline (PBS) for varied deposition times. Fourier transform infrared spectroscopy (FTIR) and ellipsometry have shown that the structure and thickness of APTES films are governed by the deposition time and reaction solution. Deposition from an anhydrous toluene solution produces APTES films ranging from 10 to 144 Å in thickness, depending on the reaction time. FTIR spectra indicate that film growth initially proceeds by adsorption of APTES to the silicon surface followed by siloxane condensation, and after an extended period of time APTES molecules accumulate on the underlying APTES film by either covalent or noncovalent interactions. In contrast, spectroscopically indistinguishable APTES films in thickness ranging from 8 to 13 Å were formed when deposition was conducted in aqueous solutions. Measured water contact angles indicate that APTES films deposited in aqueous solutions are more hydrophilic compared to those prepared in toluene solutions. Fluorescence measurements revealed that APTES films prepared in toluene solutions contain more reactive surface amino groups by ca. 3 to 10 times than those prepared in aqueous solutions for the identical reaction time. [Copyright &y& Elsevier]

Abstract: Silane grafted montmorillonites were synthesized by using 3-aminopropyltriethoxysilane and trimethylchlorosilane via two different grafting reaction systems: (a) ethanol–water mixture and (b) vapor of silane. The resulting products were investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA). XRD patterns demonstrate that silane was intercalated into the montmorillonite gallery, as indicated by the increase of the basal spacing. The product prepared by vapor deposition has a larger basal spacing than that obtained from solution, due to the different extent of silane hydrolysis in various grafting systems. TGA curves indicate that the methyl groups penetrate into the siloxane clay are the primary reason for the decrease of the dehydroxylation temperature of the grafted products. 3-Aminopropyltriethoxysilane in the grafted montmorillonite adopts a bilayer arrangement while trimethylchlorosilane adopts a monolayer arrangement within the clay gallery. [Copyright &y& Elsevier]

Abstract: Functionalization of montmorillonite clay has been done using 3-aminopropyltriethoxysilane in the presence of various solvent media. Qualitative evidence of the presence of aminosilane attached to the clay platelets have been identified using Fourier transform infrared spectroscopy (FTIR) and 29Si and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Grafting yield has been calculated using thermogravimetric analysis and total grafting yield increases with the solvent surface energy. X-ray diffraction studies of the silane functionalized montmorillonite clay exhibits two peaks, which may be attributed to intercalation and surface interaction with the broken edge platelets. Functionalized clay has been characterized by surface area measurements to understand the influence of solvents on the surface area of the functionalized clay. [Copyright &y& Elsevier]

Abstract: The grafting reaction between a trifunctional silylating agent and two kinds of 2:1 type layered silicates was studied using FTIR, XRD, TGA, and 29Si CP/MAS NMR. XRD patterns clearly indicate the introduction of 3-aminopropyltriethoxysilane (γ-APS) into the clay interlayer. In the natural montmorillonite, γ-APS adopts a parallel-bilayer arrangement, while it adopts a parallel-monolayer arrangement in the synthetic fluorohectorite. These different silane arrangements have a prominent effect on the mechanism of the condensation reaction within the clay gallery. In natural montmorillonite, the parallel-bilayer arrangement of γ-APS results in bidentate (T2) and tridendate (T3) molecular environments, while the parallel-monolayer arrangement leads to monodentate (T1), as indicated by 29Si CP/MAS NMR spectra. This study demonstrates that the silylation reaction and the interlayer microstructure of the grafting products strongly depend on the original clay materials. [Copyright &y& Elsevier]