3-glycidoxypropyl Trimethoxysilane Research Articles

Mechanical Properties and Fracture Behavior of Dual-Curable Epoxyacrylate Composites Filled with Different Functionalized Silica Particles

To investigate the interfacial effect on properties of epoxyacrylate-silica composites, sub-micron silica particles were synthesized by sol-gel reaction in an ammonia/ethanol solution and their surfaces were endowed with different functional groups by reaction with several silanes including 3-methacryloxypropyl trimethoxysilane (MPTMS), vinyl trimethoxysilane (VTMS), 3-glycidoxypropyl trimethoxysilane (GPTMS) and 3-aminopropyl trimethoxysilane (APTMS). Except the APTMS-modified silica particles due to its severe aggregation, the modified silica particles with size ranging from 150∼250 nm were then added to the pre-synthesized difunctional epoxyacrylate resin at a concentration of 15 phr, in addition to the photo- and thermo-curing agents. Tensile mechanical properties and the fracture toughness were all increased by adding the silica particles into the epoxyacrylate. Particularly, the composite filled with the MPTMS-modified silica particles (EA-MPS15) had the best performance. The reason is that the vinyl double bond of the MPTMS on the surface of the silica particles could took part in the curing reaction of the epoxyacrylate, thus providing strong interfacial chemical bonding between the silica particles and the polymer matrix and also improving the dispersion of the silica particles. The increase of fracture toughness was due to the crack deflection and particle-matrix debonding as evidenced by SEM pictures on the fracture surface.

Exploring GPTMS reactivity against simple nucleophiles: chemistry beyond hybrid materials fabrication

Hybrid materials with interpenetrating networks of silica and degradable polymers have the potential to outperform current biomaterials as their mechanical properties and degradation rates can be tightly controlled. GPTMS is one of the most widely used precursors for sol–gel hybrid fabrication. It can be used as the silica precursor or as a coupling agent to create hybrids with covalent bonds between the silica and organic components. Understanding its reactivity with nucleophilic groups on organic molecules in aqueous conditions is of key importance to hybrid synthesis. NMR spectrometry assisted by mass spectrometry was successfully used for the investigation of the reaction system of (3-glycidoxypropyl)trimethoxysilane (GPTMS) in the presence of different simple nucleophiles. Inorganic condensation and silica network formation is accelerated in the presence of propylamine; propanoic acid gives nucleophilic attack on the epoxy ring; propanol and propanthiol do not seem to participate in the reaction.

Antimicrobial Surfaces Using Covalently Bound Polyallylamine

We investigated the antimicrobial properties of the cationic polymer polyallylamine (PA) when covalently bonded to glass. The objective was to obtain a robust attachment, yet still allow extension of the polymer chain into solution to enable interaction with the bacteria. The PA film displayed strong antimicrobial activity against Staphylococcus epidermidis , Staphylococcus aureus , and Pseudomonas aeruginosa , which includes both Gram-positive and Gram-negative bacteria. Glass surfaces were prepared by a straightforward two-step procedure of first functionalizing with epoxide groups using 3-glycidoxypropyltrimethoxy silane (GOPTS) and then exposing to PA so that the PA could bind via reaction of a fraction of its amine groups. The surfaces were characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy to verify the presence of the polymer on the surface, zeta potential measurements to estimate the surface charge of the films, and atomic force microscopy to determine the extension of the polymer chains into solution. Antimicrobial properties of these coatings were evaluated by spraying aqueous suspensions of bacteria on the functionalized glass slides, incubating them under agar, and counting the number of surviving cell colonies.

Development of bio-based F-SBA-15 reinforced epoxy nanocomposites for low-k dielectric applications

The present work focuses on the utilization of renewable biomaterial as reinforcement for the development of nanocomposites for high-performance low- k microelectronic applications. In the present work, rice husk ash (RHA) was chemically treated and processed to obtain two-dimensional mesoporous silica (SBA-15), which was functionalized using 3-glycidoxypropyl trimethoxy silane through sonication process. The surface functionalized SBA-15 (F-SBA-15) with varying weight percentages (1, 3, and 5 wt%) was incorporated into the epoxy resin. The resulting F-SBA-15-reinforced epoxy composites were characterized by Fourier transform infrared spectroscopy, x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and impedance analyzer. Among the composite samples with varying loadings, the dielectric behavior of 5 wt% F-SBA-15-loaded composite sample possesses the lowest value of dielectric constant, that is, 2.14 at 1 MHz frequency when compared with that of other samples. Further, the thermal stability was also enhanced to an appreciable extent, when compared with that of the samples with lower F-SBA-15 loadings.

AFM, CLSM and EIS characterization of the immobilization of antibodies on indium–tin oxide electrode and their capture of Legionella pneumophila

The microscopic surface molecular structures and properties of monoclonal anti-Legionella pneumophila antibodies on an indium-tin oxide (ITO) electrode surface were studied to elaborate an electrochemical immunosensor for Legionella pneumophila detection. A monoclonal anti-Legionella pneumophila antibody (MAb) has been immobilized onto an ITO electrode via covalent chemical bonds between antibodies amino-group and the ring of (3-Glycidoxypropyl) trimethoxysilane (GPTMS). The functionalization of the immunosensor was characterized by atomic force microscopy (AFM), water contact angle measurement, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN)₆](3-/4-) as a redox probe. Specific binding of Legionella pneumophila sgp 1 cells onto the antibody-modified ITO electrode was shown by confocal laser scanning microscopy (CLSM) imaging and EIS. AFM images evidenced the dense and relatively homogeneous morphology on the ITO surface. The formation of the complex epoxysilane-antibodies acting as barriers for the electron transfer between the electrode surface and the redox species in the solution induced a significant increase in the charge transfer resistance (Rct) compared to all the electric elements. A linear relationship between the change in charge transfer resistance (ΔRct=Rct after immunoreactions - Rct control) and the logarithmic concentration value of L. pneumophila was observed in the range of 5 × 10(1)-5 × 10(4) CFU mL(-1) with a limit of detection 5 × 10(1)CFU mL(-1). The present study has demonstrated the successful deposition of an anti-L. pneumophila antibodies on an indium-tin oxide surface, opening its subsequent use as immuno-captor for the specific detection of L. pneumophila in environmental samples.

Activity improvement of xylylenediamine as a base catalyst by incorporation in SBA-15 mesoporous material

Meta- and para-xylylenediamine (mXD and pXD, totally XD) were incorporated on SBA-15, MCM-41, and amorphous silica supports using 3-glycidoxypropyltrimethoxy silane (GP) as a connecting material. The amounts and states of GP and XD incorporated in silica supports were examined by thermogravimetry, X-ray diffraction, N2 adsorption, SEM, and FT-IR. The catalytic activities of XD catalysts incorporated on the supports were investigated in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. The maximum amount of GP incorporated in SBA-15 was 0.73mmol/g, and that of mXD was 0.38mmol/g on GP(0.73)-SBA, indicating that one mXD molecule was combined with two GP molecules. The incorporation of mXD on the silica supports through GP enhanced the catalytic activity of mXD in the condensation from TOF=0.0072s−1 on liquid-state mXD to 0.0258s−1 on mXD(0.38)-GP(0.73)-SBA. The improvement of the catalytic activities of XD by the incorporation was explained by the increase of the basicity according to the conversion of primary amine to secondary amine. The effects of the size and shape of pores on the catalytic performance of the XD catalysts incorporated in the silica supports in the condensation are discussed.

Wear behavior of light-cured resin composites with bimodal silica nanostructures as fillers

To enhance wear behavior of resin composites, bimodal silica nanostructures including silica nanoparticles and silica nanoclusters were prepared and proposed as fillers. The silica nanoclusters, a combination of individually dispersed silica nanoparticles and their agglomerations, with size distribution of 0.07–2.70μm, were fabricated by the coupling reaction between amino and epoxy functionalized silica nanoparticles, which were obtained by the surface modification of silica nanoparticles (~70nm) using 3-aminopropyl triethoxysilane (APTES) and 3-glycidoxypropyl trimethoxysilane (GPS) as coupling agents, respectively. Silica nanoparticles and nanoclusters were then silanized with 3-methacryloxypropyl trimethoxysilane (γ-MPS) to prepare composites by mixing with bisphenol A glycerolate dimethacrylate (Bis-GMA) and tri (ethylene glycol) dimethacrylate (TEGDMA). Experimental composites with various filler compositions were prepared and their wear behaviors were assessed in this work. The results suggested that composites with increasing addition of silica nanoparticles in co-fillers possessed lower wear volume and smoother worn surface. Particularly, the composite 53:17 with the optimum weight ratio of silica nanoparticles and silica nanoclusters presented the excellent wear behavior with respect to that of the commercial Esthet-X, although the smallest wear volume was achieved by Z350 XT. The introduction of bimodal silica nanostructures as fillers might provide a new sight for the design of resin composites with significantly improved wear resistance.

Effect of clay surface modification and organoclay purity on microstructure and thermal properties of poly(l-lactic acid)/vermiculite nanocomposites

Vermiculite (VMT) was successfully modified by cationic exchange of hexadecyltrimethyl ammonium ions, covalent grafting of glycidoxypropyl trimethoxy silane, and combining grafting and intercalation. The complete removal of excess surfactant from VMT resulted in a change in the interlayer structure and higher thermal stability of the organoclay mineral. The organosilane grafted on the clay mineral edges improved the thermal stability of the organoclay mineral. The organoclay minerals were melt compounded with poly(l-lactic acid) (PLLA), and the effect of the nanofiller concentration, type of modification and organoclay mineral purity on the nanostructure and thermal properties of nanocomposites was investigated. The removal of excess surfactant and organosilane functionalization enhanced the dispersion level of the organoclay mineral. PLLA degradation that occurred during nanocomposite processing depended on the clay mineral concentration, the extent of clean surface and the clay mineral dispersion state. The removal of excess surfactant and organosilane functionalization improved the thermal stability of nanocomposites.

Synthesis of polypyrrole-magnetite/silane coatings on steel and assessment of anticorrosive properties

This work presents a detailed study of the synthesis of polypyrrole-magnetite/silane coatings (PPy-Fe3O4/GPTMS-TEOS-γ-APS) and their anticorrosion properties. The use of a bilayer system is proposed consisting of a PPy-Fe3O4 internal conductive coating (active coating), obtained electrochemically, and an outer coating or insulating barrier consisting of silanes (passive coating). This latter is composed by Tetraethoxysilane (TEOS), glycidoxypropyltrimethoxysilane (GPTMS) and γ-aminopropyl-silane (γ-APS). The GPTMS-TEOS-γ-APS hybrid was obtained by the sol-gel method and applied by the dip coating technique. The anticorrosive properties of the PPy-Fe3O4/GPTMS-TEOS-γ-APS bilayer coating applied on carbon and stainless steel substrate were assessed by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The electrochemical characterization has shown that the anodic polarization of the substrate by the conductive polymer was beneficial for the carbon steel substrate whereas it induced pitting corrosion to stainless steel. It was also demonstrated that the addition of Fe3O4 to the PPy matrix slows down its reduction rate increasing its stability and that the presence of a barrier top-coat (like a silane film) is fundamental to preserve the effective anticorrosion performance of the PPy-Fe3O4 composite coating for long term exposure.

Effect of thermal treatment on mechanical and tribological properties of hybrid coatings deposited by sol–gel route on stainless steel

This paper deals with the effect of thermal treatment on the mechanical and tribological properties of an organic–inorganic hybrid coating deposited on stainless steel 430. Organic–inorganic coating derived from glycidoxypropyltrimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(OsBu)3 were prepared via sol–gel route and deposited by dip-coating process with various thicknesses. A preliminary thermal analysis (DTA, TGA) of xerogel obtained by hydrolysis and condensation reaction of sols, highlighted three characteristic domains of temperature (110–200°C, 250–300°C, 400–500°C). When thermal treatments were applied to the coated stainless steel in these temperature domains, the tribological behavior (wear and friction) underwent strong changes, analyzed from linear ball/plane tribometry. The tribological tests showed a lower friction coefficient and wear after thermal treatment at a temperature in the domain 250–300°C. In order to explain this phenomenon, xerogel structure was studied from XRD and Raman spectroscopy and correlated to the mechanical and adhesive properties and to the tribological behavior.

Improving the adhesion between a aqueous PU and a polyamide fibre with silane

Glycidoxypropyltrimethoxysilane (GPS) and γ-aminopropyltrimethoxysilane (APS) were used to modify the surface chemistry of polyamide fibre. The surface chemistry was characterised using X-ray photoelectron spectroscopy. The silanol functional group was designed to be introduced on the surface of polyamide fibre to increase its chemical activity by N-alkylation of GPS and hydrolysis of APS, and to improve the poor interfacial adhesion between a polyamide 66 fibre and an aqueous polyurethane polymer adhesive. The microbond test was used to measure the interfacial shear strength between the waterborne PU adhesive and the polyamide fibre. It has been found that APS hydrolysis and GPS-alkylated fibre surface can be used to improve the interfacial adhesion of polyamide fibre to PU. The IFSS can be improved by N-alkylation of GPS from 5.0 to 8.4 MPa. After water immersion at 50 °C for 48 h, then drying, the IFSS increased to 8.8 MPa due to the plasticisation of PU in water. Better interfacial adhesion was also observed by the hydrolysis of APS, but not significantly improved by this method due to the relatively weak hydrogen bond at the interface between APS and polyamide fibre.

Adhesion improvement of UV-curable ink using silane coupling agent onto glass substrate

In order to enhance the adhesions of the UV-curable inks onto glass substrate, the silane coupling agents were added into the mixture of monomer and oligomer. The monomer, containing high functionality or surface tension could lead to a high cross-link density of the polymeric network and low adhesions of UV-curable inks. With the amount of ethyoxyls of ethoxylated trimethylolpropane triacrylate increasing, adhesions of the oligomers were improved. As the monomer concentration increased, the adhesion ability of UV-curable ink onto glass was decreased. The adhesion ability of UV-curable inks onto glass was increased via adding silane coupling agents. When the concentration of the silane coupling agents was more than 12%, the adhesion ability of UV-curable inks onto glass was decreased. Silane coupling agents (3-methacryloxypropyl) trimethoxy silane (KH570) and (3-aminopropyl) triethoxy silane (KH550) were more effective than (3-glycidoxypropyl) trimethoxy silane (KH560) in the inks under the same concentration. Video microscope and scraper fineness test revealed that the pigment particles declined with the increase of grinding times, whereas the adhesions of UV-curable inks were enhanced.

Ex situ IR and Raman spectroscopy as a tool for studying the anticorrosion processes in (3-glycidoxypropyl)trimethoxysilane-based sol–gel coatings

Ex situ IR reflection–absorption (IR RA) and Raman spectroscopic measurements were performed on sol–gel anticorrosion coatings to take advantage of the complementarity of the two vibrational techniques. The coatings were prepared on the basis of (3-glycidoxypropyl)trimethoxysilane, (3-aminopropyl)trimethoxysilane and amino-heptaisooctyl-functionalised polyhedral oligomeric silsesquioxane and their protective efficiency evaluated in terms of the hydrophobic poly(dimethylsiloxane) (PDMS) content. The results of IR absorbance and rheology measurements of sols showed that coatings should be deposited 30min after the addition of acetic acid sol–gel catalyst and thermally treated at 150°C. The surface energy values of coatings decreased with increasing amounts of PDMS chains, from 29.6 to 22.6mJ/m2. Potentiodynamic polarisation revealed that the concentration of PDMS chains in coatings should be optimised to depict the lowest corrosion current density, of the order of magnitude 10−9A/cm2. Extensive ex situ IR RA studies of the degradation of coatings during polarisation indicated that breakage of siloxane bonds occurred through the formation of lower cyclosiloxanes and hydration, while conformational changes of methylene groups were noted in coatings without PDMS chains. Ex situ confocal Raman images of coatings with PDMS recorded after anodic polarisation mainly revealed bands of PDMS chains of decreasing intensity, while no signal was found in areas of pitting corrosion. The stretching ν(Si–O–Si) mode of the condensed network around 476cm−1 could not support the formation of lower cyclosiloxanes, since it overlapped with the 496cm−1 siloxane mode of PDMS chains.

Synthesis of novel chitosan–silica/CpG oligodeoxynucleotide nanohybrids with enhanced delivery efficiency

Chitosan–silica/CpG oligodeoxynucleotide (ODN) nanohybrids were synthesized to stimulate Toll-like receptor 9-mediated induction of interleukin-6 (IL-6). The chitosan–silica hybrid was first synthesized from a mixture of chitosan and 3-glycidoxypropyl trimethoxysilane under acidic conditions via a sol–gel process, and then used to condense CpG ODN2006x3-PD to yield chitosan–silica/CpG ODN nanohybrids. Scanning electron microscopy and atomic force microscopy showed that the chitosan–silica/CpG ODN nanohybrids had an elliptic shape with a diameter of 100–200nm. After soaking in HAc–NaAc buffer solution (pH5.5), the nanohybrids exhibited sustained release of CpG ODN. When the nanohybrids were separately exposed to 293XL-hTLR9 cells and peripheral blood mononuclear cells, no significant toxicity was observed. An immunochemical assay for cellular uptake revealed that the nanohybrids were taken up by the cells and located in endolysosomes. An enzyme-linked immunosorbent assay for cytokines indicated that the nanohybrids effectively stimulated the induction of IL-6. Chitosan–silica/CpG ODN nanohybrids underwent cellular uptake and enhanced induction of IL-6 to a greater degree than conventional chitosan/CpG ODN nanocomplexes, indicating that they have an enhanced delivery efficiency.

Shear Strength of Single Lap Joint Aluminium-Thermoplastic Natural Rubber (Al-TPNR) Laminated Composite

In this work, we studied the effect of surface treatment on the aluminium surface and a coupling agent to improve adhesion between aluminium with organic polymer. Thermoplastic natural rubber (TPNR) matrix was prepared by melt blending of natural rubber (NR), liquid natural rubber (LNR) compatibilizer, linear low density polyethylene (LLDPE) and polyethylene grafted maleic anhydride (PE-g-MAH). The PEgMAH concentration used was varied from 0% – 25%. In addition, the aluminium surface was pre-treated with 3-glycidoxy propyl trimethoxy silane (3-GPS) to enhance the mechanical properties of laminated composite. It was found that the shear strength of single lap joint Al-TPNR laminated composite showing an increasing trend as a function of PE-g-MAH contents for the 3-GPS surface treated aluminium. Moreover, the scanning electron microscope (SEM) revealed that the strength improvement was associated with the chemical state of the compound involved.

Development of fluorescent nanoparticle-labeled lateral flow assay for the detection of nucleic acids

The rapid, specific and sensitive detection of nucleic acids is of utmost importance for the identification of infectious agents, diagnosis and treatment of genetic diseases, and the detection of pathogens related to human health and safety. Here we report the development of a simple and sensitive nucleic acid sequence-based and Ru(bpy)3 (2+)-doped silica nanoparticle-labeled lateral flow assay which achieves low limit of detection by using fluorescencent nanoparticles. The detection of the synthetic nucleic acid sequences representative of Trypanosoma mRNA, the causative agent for African sleeping sickness, was utilized to demonstrate this assay. The 30nm spherical Ru(bpy)3 (2+)-doped silica nanoparticles were prepared in aqueous medium by a novel method recently reported. The nanoparticles were modified by 3-glycidoxypropyl trimethoxysilane in order to conjugate to amine-capped oligonucleotide reporter probes. The fluorescent intensities of the fluorescent assays were quantified on a mictrotiter plate reader using a custom holder. The experimental results showed that the lateral flow fluorescent assay developed was more sensitive compared with the traditional colloidal gold test strips. The limit of detection for the fluorescent lateral flow assay developed is approximately 0.066fmols as compared to approximately 15fmols for the colloidal gold. The limit of detection can further be reduced about one order of magnitude when "dipstick" format was used.

Poly(l-lactic acid)/organically modified vermiculite nanocomposites prepared by melt compounding: Effect of clay modification on microstructure and thermal properties

In this work, vermiculite (VMT) was successfully modified by organic cation intercalation (oleyl bis(2-hydroxyethyl) methyl ammonium), silane grafting (glycidoxypropyl trimethoxy silane), and combining silane grafting and alkylammonium cation intercalation. The organically modified VMTs were melt compounded with poly(l-lactic acid) (PLLA), and the effect of the nanofiller concentration and type of modification of the VMT on the nanostructure and thermal properties of the PLLA/organo-VMT nanocomposites was investigated. The effect of the melt processing conditions used in the preparation of nanocomposites on the molecular weights of the polymer matrix was determined by gel permeation chromatography (GPC). The structure of the intercalated surfactant in the modified clays was characterized by X-ray diffraction (XRD) analysis. The morphology of the nanocomposites was examined by XRD and transmission and scanning electron microscopy (TEM, SEM). The thermal behavior of the clays and nanocomposites was analyzed by differential scanning calorimetry (DSC) and thermogravimetry (TGA), and microscale pyrolysis combustion calorimetry (PCFC) was used to measure the flammability of the nanocomposites. GPC analysis showed that the molecular weights of native and unfilled extruded PLLA were similar, while the incorporation of organo-VMTs resulted in a reduction of the PLLA molecular weights. XRD and TEM investigations showed that exfoliation predominantly occurred in 2wt% nanocomposites, whereas intercalated structures together with exfoliated clays were observed with high contents of organoclays. The double modification of the clay resulted in a higher level of exfoliation, attributed to the enhanced interactions between the end groups of the PLLA and the clay containing the epoxy groups. DSC analysis showed that the glass transition and cold crystallization temperatures of nanocomposites were slightly lower than those of neat PLLA. The crystallization enthalpies increased with the addition of organo-VMTs. However, the crystallinity of the PLLA was unaffected by the addition of clays, only the crystal size and perfection were affected. The nanocomposites prepared with 2wt% of organoclays displayed increased thermal stability. The flammability test revealed that no significant reduction of fire hazards was caused by the presence of organo-VMTs.

Sol–gel incorporation of silica nanofillers for tuning the anti-corrosion protection of acrylate-based coatings

The aim of the present work is to synthesize through sol–gel approach new hybrid polymeric nanocomposites to be used as coating materials. An acrylic-based polymer was prepared by free-radical copolymerization of two monomers widely used for coatings, namely 2-ethylhexylacrylate (EHA) and glycidyl methacrylate (GMA) bearing epoxy moieties, in which silica nanoparticles were incorporated by in situ acid hydrolysis and subsequent condensation of tetraethoxysilane (TEOS). Glycidoxypropyl trimethoxysilane (GPTS) was used as coupling agent to fine-tune the compatibility between organic and inorganic phases. The morphology, mechanical properties and corrosion resistance of thin films applied on aluminum alloys were optimized by varying the content of silica nanoparticles whose properties were strongly affected by the TEOS/GPTS ratios. Performances of the obtained hybrid materials were scrutinized by atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS). Thus it was evidenced that an optimum amount of silica nanoparticles with a precise morphology and composition in term of TEOS/GPTS ratio is needed to maintain good coating barrier properties. Outstanding anti-corrosion protection was reached by using optimized hybrid films.

Indium-tin-oxide thin film transistor biosensors for label-free detection of avian influenza virus H5N1

As continuous outbreak of avian influenza (AI) has become a threat to human health, economic development and social stability, it is urgently necessary to detect the highly pathogenic avian influenza H5N1 virus quickly. In this study, we fabricated indium-tin-oxide thin-film transistors (ITO TFTs) on a glass substrate for the detecting of AI H5N1. The ITO TFT is fabricated by a one-shadow-mask process in which a channel layer can be simultaneously self-assembled between ITO source/drain electrodes during magnetron sputtering deposition. Monoclonal anti-H5N1 antibodies specific for AI H5N1 virus were covalently immobilized on the ITO channel by (3-glycidoxypropyl)trimethoxysilane. The introduction of target AI H5N1 virus affected the electronic properties of the ITO TFT, which caused a change in the resultant threshold voltage (VT) and field-effect mobility. The changes of ID–VG curves were consistent with an n-type field effect transistor behavior affected by nearby negatively charged AI H5N1 viruses. The transistor based sensor demonstrated high selectivity and stability for AI H5N1 virus sensing. The sensor showed linear response to AI H5N1 in the concentrations range from 5×10−9gmL−1 to 5×10−6gmL−1 with a detection limit of 0.8×10−10gmL−1. Moreover, the ITO TFT biosensors can be repeatedly used through the washing processes. With its excellent electric properties and the potential for mass commercial production, ITO TFTs can be promising candidates for the development of label-free biosensors.

Influence of Reaction Conditions on the Grafting Pattern of 3-Glycidoxypropyl trimethoxysilane on Montmorillonite

Surface modification of montmorillonite (MMT) with 3-glycidoxypropyl trimethoxysilane (3GTO) in mild methanol/water mixture has been investigated in detail. The influence of reaction conditions (including silane concentration in feed, reaction time and reaction temperature) on the grafting amount and yield of silane, and further on the grafting pattern of silanes was studied by thermogravimetric analysis, elemental analysis, X-ray diffraction (XRD) and BET. Higher silane concentration, longer reaction time and higher reaction temperature are all benefit to higher grafting amount. When the grafting reaction was performed with 3 mmol/g silane concentration, at <TEX>$90^{\circ}C$</TEX> for 24 h, the grafted amount and yield of silane reached 1.4443 mmol/g and 30%, respectively. Based on the XRD and BET data analysis, a speculation that the grafting pattern of silanes was concentration dependence was proposed.