Amounts Of 3-aminopropyltriethoxysilane Research Articles

CO2-Switchable Emulsification and Demulsification of Pickering Emulsion Stabilized by Zirconium-Based Metal–Organic Frameworks

Stimuli-responsive Pickering emulsions have aroused considerable amounts of attention recently because of their potential for on-demand demulsification. Metal–organic frameworks (MOFs) are promising emulsifiers for the construction of Pickering emulsions due to their ultrahigh specific surface area, tunable porosity, and designable structures. However, CO2-responsive zirconium-based MOF-stabilized Pickering emulsions have been rarely reported up to now. Herein, a new series of amine-functionalized UiO-66-O-APTES were developed via the covalent post-modification of UiO-66-OH with different amounts of (3-aminopropyl)triethoxysilane (APTES) and were then applied to construct CO2-switchable Pickering emulsions. It was shown that UiO-66-O-APTES could emulsify toluene and water well to form an emulsion even at the content of 0.1 wt %. Significantly, the Pickering emulsion could be reversibly demulsified and re-emulsified by alternate CO2 and N2 bubbling under constant pressure. Mechanism results revealed that the CO2-switchable phase transition based on the formation of hydrophilic ammonium salts resulting from the reaction of APTES with CO2, which lowered the wettability of particles, reduced emulsion stability, and resulted in emulsion breaking. After CO2 was removed, the Pickering emulsion could be rebuilt by the reverse reaction. By using this strategy, a controllable and highly effective CuI-catalyzed cycloaddition reaction has been achieved, and the coupling of efficient condensation, product separation, and recovery of MOF catalysts has been demonstrated to give rise to a sustainable reaction process.

Enhanced Performance of Polylactide Film via Simultaneous Biaxial Stretching and Silane Coupling Agent as a Thermal Shrinkable Film

Biaxial stretching technique has been known to improve the toughness of polylactide (PLA) film. Furthermore, blending with an additive is another way to control the mechanical properties of the product. The integrated effect of simultaneous biaxial stretching and blending with silane coupling agent on the properties of PLA film is examined in this study. The PLA pellets are melt compounded with various amounts of 3-aminopropyltriethoxy silane (APS). Then, the films are prepared by cast film extrusion and simultaneous biaxial stretching process with a stretching speed of 75 mm s–1. The relationships among the crystallinity, tensile properties, and thermal shrinkage of the prepared films are investigated. The crystallinity of PLA is significantly induced in the film by the stretching technique. An increase in the additive content also facilitates the polymeric crystallinity. The elongation at the break of the biaxially stretched film increases with the additive content, which corresponds with the PLA crystallinity. Compared to the pristine PLA film, the addition of 1% APS improves tensile strength in a transverse direction of the film about 10 times. The thermal shrinkage of the obtained films was evaluated to assess their applications as heat-shrinkable films. The prepared films show a thermal shrinkage of 45%, which are comparable to that of a commercial shrink film.

Graphene oxide incorporated polystyrene electrospun nanofibers for immunosensing of CD36 as a marker of diabetic plasma

Electrospun nanofibers (ESNF) offer us a chance to obtain nanoscale building blocks by adding the desired modification agent to the polymer solution. Here, nanocomposite-based electrospun nanofibers designed for the recognition surface of the developed immunosensor were used for the first time in the determination of CD36. Firstly, graphene oxide (GO) was synthesized from graphite powder (GR), and GO sheets were silanized with different amounts of (3-Aminopropyl)triethoxysilane (APTES). Synthesized GO-APTES nanocomposite and polystyrene (PS) solution were mixed in different ratios to obtain uniform nanofibers without beads. As a result of the amino groups obtained on the surface of the nanofibers, the surface was made ready for covalent immobilization of the Anti-CD36 antibody. The nanofibers obtained under the optimum conditions determined were deposited on the surface of the screen-printed carbon electrode (SPCE) by the electrospinning technique. Then, Anti-CD36 was immobilized on the PS/GO-APTES modified SPCE through covalent bonding and used to prepare the biofunctional surface for the usage of bioelectrochemistry of CD36. The optimum Anti-CD36 concentration decided to be used in experiments was determined as 10 µg/mL. The linear detection range of CD36 was from 0.5 to 20 ng/mL, and the detection limit was 0.999 ng/mL. Finally, the developed PS/GO-APTES/Anti-CD36 immunosensor was used for the determination of CD36 in artificial blood serum without any interference effect.

Adsorption of organic pollutants by amine functionalized mesoporous silica in aqueous solution. Effects of pH, ionic strength and some consequences of APTES stability

A mesoporous silica with MCM-41 type pore array was synthesized by hydrothermal method and then was functionalized with known amounts of 3-aminopropyltriethoxysilane (APTES) in order to study the selective adsorption towards several species/pollutants. Antibiotics doxycycline hydrochloride (DC) and norfloxacin (NFX), the dye methyl orange(MO) and the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) were used as adsorbates. The adsorption has been studied under different batch experimental conditions such as contact time, pH and ionic strength. The modification with APTES produced a decrease in the surface area of the solid and reversed the surface charge although did not change appreciably the mosoporosity and shape of the particles. This change in the charge strongly increased the adsorption of species that behave as anions in aqueous solution such as 2,4-D and MO. On the contrary, for species with several polar groups and charge-development the effect was very low and only detectable at specific pH. Electrostatic attractions between the protonated amine-end groups of APTES-SiO2 and the negative functional groups of 2,4-D and MO were the main responsible of the adsorption process. Partial hydrolysis of the supported coupling agent to regenerate silanol groups played an important role in decreasing the adsorption capacity of polar species and in the reuse capacity for adsorbing anionic species, i.e., the performance decreased up to 75% after four cycles of successive adsorption-desorption. Finding new methodology or functionalization agents to improve the silica surface reactivity should be the main goal of the researchers in the future. This work perhaps contributes with such perspectives.

Hybrid adsorbents of tannin and APTES (3-aminopropyltriethoxysilane) and their application for the highly efficient removal of acid red 1 dye from aqueous solutions

Hybrid adsorbents were prepared by reacting tannin with different amounts of 3-aminopropyltriethoxysilane (APTES). The materials were characterized by SEM, TEM, FTIR, CHN, N2 adsorption/desorption isotherms and vapor sorption (water and n-heptane adsorptions–for determination of the hydrophobicity-hydrophilicity ratio). The modified materials were utilized as adsorbents for the removal of Acid Red 1 (AR-1) dye from aqueous solutions. The N2 isotherm results showed low porosities of the modified materials, however they presented high efficient adsorption of AR-1 dye. To find a proof of hybridization between tannin and APTES, the materials were characterized by Diffuse Reflectance Ultraviolet-Visible Absorption (DRUV) spectroscopy. The results indicate that the electronic structure of the final materials was changed, and was related to a hybrid formation between tannin and APTES.For the adsorption experiments, the best experimental conditions were reached at pH 2.0, contact time of 8h and at 50°C. The equilibrium and kinetics adsorption data were well represented by the Liu isotherm and the General order kinetic models, respectively. The maximum adsorption capacity of 418.3mgg−1 was obtained at 50°C for a tannin-APTES material at ratio 1:1 (Tan-Ap-1.0). Based on experimental data it was found that electrostatic interactions and hydrogen bonds between adsorbent and AR-1 dye played the most important role in the adsorption process.Effect of temperature and thermodynamic studies revealed that the adsorption processes of AR-1 onto tannin materials are dependent on temperature and are exothermic and spontaneous. With regards to the applicability of the adsorbents for treating simulated effluents, they showed an excellent outcome confirming their high-efficiency for dye adsorption.

Novel Multifunctional Mesoporous Microsphere with High Surface Area for Removal of Zinc Ion from Aqueous Solution: Preparation and Characterization

Amino-functionalized magnetic mesoporous microsphere has been successfully synthesized through a two-step coating process of silica on a magnetic core (Fe3O4). In the synthesis process, cetyltrimethyl ammoniumbromide (CTAB) was used as a structure-directing agent and it was removed by combination of solvent extraction and calcination modified processes. In this method, mesoporous silica shell with higher surface area was formed which could facilitate the loading of much more amino groups and the capacity to adsorb more heavy metal ions such as Zn2+ was provided. Different amounts of 3-aminopropyl triethoxysilane (APTES) were examined in order to obtain an optimum amount of amino groups which can be grafted on Fe3O4/SiO2/meso-SiO2 microsphere. The resultant multifunctional microsphere was characterized by field emission scanning electron microscope, transmission electron microscope, FTIR spectrophotometer, X-ray diffraction, vibration sample magnetometer, thermogravimetric analysis, nitrogen adsorption–desorption and particle size analyzer. Comparing to functionalized amino group on traditional magnetic mesoporous silica, the as-prepared microsphere not only exhibited higher specific surface area (617.31 m2 g−1) but also demonstrated higher adsorption capacity for Zn(II) (270.2703 mg g−1 at 25 °C). Important of all, the adsorbent was simply removed from sample solution by magnetic field and it was regenerated by acid treatment. Synthetic route of Fe3O4/SiO2/meso-SiO2–NH2 and its use for Zn(II) ions removal.

Sustainable composite materials based on ethylene-vinylacetate copolymer and organo-modified silica

AbstractSilica nanoparticles (SNPs) were modified by different amounts of 3-aminopropyltriethoxysilane (APTES). Nanocomposites based on ethylene vinyl acetate copolymer (EVA) and modified SNP (m-SNP) were prepared by the melt mixing method. They were characterized by Haake torque measurement, differential scanning calorimetry (DSC), horizontal burning test, scanning electron microscopy. Accelerated weather testing of the nanocomposites was performed according to ASTM D4329 (cycle A) for 168 h. The Haake torque indicates that the relative melt viscosity of EVA/m-SNPs is slightly higher than that of EVA/SNP nanocomposites. The DSC and burning test results show that m-SNPs decrease crystallinity degree and flammability of EVA. After accelerated weather testing, the relative amount of C=O groups in EVA/m-SNP nanocomposites is lower than that in EVA/SNP nanocomposites. Micro crack of EVA/m-SNP nanocomposite is smaller than that of EVA/SNP nanocomposite. In our study, the EVA/m-SNP nanocomposites with good tensile properties, flame and weather resistance can be used as sustainable materials in some technique fields.

Surface functionalized TiO2 supported Pd catalysts for solvent-free selective oxidation of benzyl alcohol

Pd catalysts supported on TiO2 functionalized with various amounts of 3-aminopropyltriethoxysilane (APTES) were prepared using a post-synthesis grafting method combined with electroless deposition of Pd. As revealed by the Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results, monolayer APTES grafting was obtained using 0.005mmol APTES on 1.5g TiO2 support. Excess amounts of APTES resulted in both multilayer and reversed attachment, which NH2 attached to the TiO2 surface rather than giving free NH2 termination. The catalytic activity in the solvent-free selective oxidation of benzyl alcohol was correlated well with the highest amount of Pd deposited as well as the formation of small and uniform Pd nanoclusters with narrow particle size distribution (average diameter 3.4nm) on the 1%Pd/TiO2-0.005APTES. Increasing of surface basicity via the hydrolysis of amino groups (NH2) is suggested to enhance the dehydrogenation of benzyl alcohol, and as a consequence the selectivity toward benzaldehyde increased for all the APTES-modified TiO2 supported Pd catalysts. In addition, the combination of metallic Pd0 and PdOx (Pd2+/Pd4+) species gave high catalytic activity in the benzyl alcohol oxidation, emphasizing that the reduction of PdOx species by the adsorbed benzyl alcohol is an essential step to form highly active metallic Pd0 sites.

Preparation, characterization and luminescent properties of dense nano‐silica hybrids loaded with 1,8‐naphthalic anhydride

Novel luminescent dense nano-silica hybrid materials (DNSS) modified with different amounts of (3-aminopropyl)triethoxysilane (APTES) and 1,8-naphthalic anhydride (NA) were successfully synthesized via two steps combined with post-grafting methods. Powder X-ray diffraction (XRD), N2-sorption analysis, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), photoluminescence (PL) spectroscopy and elemental analysis, as well as time-resolved decays were employed to characterize the resultant hybrid materials. The results revealed that luminescent organic molecules had been successfully loaded onto the amine-modified surface of nano-silica spheres. In addition, their fluorescence intensity and characteristic peak of emission spectra changed with increasing amount of APTES and NA additive. In particular, the characteristic peak showed a red shift from 390 to 450 nm, however, this was inconsistent with results calculated on the basis of the elemental analysis data, most probably because of the dispersion behaviors of NA molecules from the aggregating to the monolayer state. These observations demonstrated the existence of a quantum confinement effectiveness of NA-DNSS samples, and therefore a possible mechanism was put forward.

Controlled drug release on amine functionalized spherical MCM-41

MCM-41 silica with spherical morphology and small particle sizes (100nm) was synthesized and modified by post-synthesis method with different amounts of 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, was carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N2 physisorption, elemental analysis, thermal analysis and FT-IR spectroscopy. A new method was developed for the quantitative determination of amino groups in surface modified mesoporous materials by the ninhydrin reaction. Good correlation was found between the amino content of the MCM-41 materials determined by the ninhydrin method and their ibuprofen adsorption capacity. Amino modification resulted in high degree of ibuprofen loading and slow release rate in comparison to the parent non-modified MCM-41.

Adsorption and protection of plasmid DNA on mesoporous silica nanoparticles modified with various amounts of organosilane

Ordered MCM-41-type mesoporous silica nanoparticles (MSNs) with pore size of 2.6nm were synthesized and were further modified with various amounts of 3-aminopropyltriethoxysilane (APTES), respectively, by a direct co-condensation method. These amine functionalized mesoporous silica nanoparticles (Am-MSNs) were employed to complex with plasmid DNA (pDNA) to study their adsorption and protection capacities. The results demonstrate the MSNs functionalized with aminopropyl groups present advanced adsorption capacities for pDNA immobilization. And Am-MSNs with high APTES amount lead to high amount of pDNA adsorption. Further investigation of pDNA protection shows that Am-MSNs with moderate APTES amount could completely protect pDNA from enzymatic degradation, while those with smaller and/or higher amount of APTES could partially provide protection of pDNA.

Synthesis of chalcones catalyzed by aminopropylated silica sol–gel under solvent-free conditions

Aminopropylated nanosilica was prepared by a simple sol–gel process from tetraethyl orthosilicate (TEOS) and then it was functionalized with different amounts of 3-aminopropyltriethoxysilane (APS) under toluene reflux. The prepared solids were characterized by means of XRD, FT-IR, TGA–DTA, SEM–EDS, and TEM. Their textural properties were determined by adsorption–desorption isotherms of N 2 at 77 K. It was proved that the amount of APS used in the preparation process had a great influence on the physicochemical properties of the hybrid organic–inorganic solid materials. The materials were used as catalyst in the Claisen–Schmidt preparation of chalcones for the reaction of substituted acetophenones and benzaldehydes under solvent-free conditions. The result showed that the presence of a high amount of aminopropyl groups was important for a very good performance of the catalyst in the substrate conversion. Also, the influence of different groups in the aromatic ring of acetophenones and benzaldehydes was investigated. In all cases, coproduct formation was not observed; the catalysts were recovered and can be recycled twice without appreciable loss of reactivity.