Octyltriethoxysilane Research Articles

Surface modification of silica particles assisted by CO2

This paper reports the synthesis of coating silica particles, in order to design hybrid materials with hydrophobic surface properties. The silica particles were prepared in basic conditions under atmosphere of carbon dioxide (CO2), using tetraethylorthosilicate (TEOS) as a precursor and octyltriethoxysilane (OTES) as a surface modifying agent. It was demonstrated that the contact angles of silica hybrid films could be changed by varying temperature and pressure of CO2. The investigation of the prepared hybrid materials by dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM), respectively, showed that they consisted mainly of particles with a diameter of 100–250nm. Fourier transform infrared (FT-IR) spectra indicate that the interaction between the coupling reagents, at different conditions, is mainly through chemical bonding.

Hydrophobic behaviour of non-fluorinated sol–gel based cotton and polyester fabric coatings

Water repellency was conferred to cotton and polyester fabrics by an hybrid organic–inorganic finishing obtained by hydrolysis and subsequent condensation of octyltriethoxysilane (OTES) under acidic conditions, in combination with melamine based crosslinking agent N, N, N′, N′, N″, N″-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-triamine (MF). The application on textile samples was carried out by padding followed by drying and thermal treatment. Water-resistance properties were determined in terms of the contact angle, water uptake and drop adsorption times, whereas the surface composition of treated fabrics was characterized by attenuated total reflectance Fourier transform infrared analyses. Textile fabrics treated with the hybrid OTES–MF sol exhibited the best water-repellent properties, when compared to those treated with OTES or MF finishing alone. In particular, cotton and polyester samples, treated with a 60 g/L MF solution in a 1:4 MF:OTES molar ratio, showed a water contact angle of 130° and 150°, respectively. The high hydrophobicity of the treated fabrics is supposed to be due to the structural and stereochemical properties of the finishing. The presence of the MF triazine ring seems to favour both the improvement of the outward orientation of the OTES alkyl chains, and the crosslinking of N-methylol groups to form a three-dimensional film around the fibres which increases the surface roughness. The contact angle values and the characteristic IR peaks confirmed the presence of the hybrid coating on cotton fabrics even after multiple washing cycles.

Sensitization of Nanocrystalline TiO2 with Multibranched Organic Dyes and Co(III)/(II) Mediators: Strategies to Improve Charge Collection Efficiency

The photoelectrochemical properties of thiophene-triphenylamine (TTPA) sensitizers (TTPA1–3) used in association with different cobalt based mediators, including kinetically fast shuttles such as [Co(bpy)3]3+/2+ and [Co(phen)3]3+/2+ and sterically hindered couples like [Co(dtb)3]3+/2+ were studied by combining molecular modeling, spectroscopic, and photoelectrochemical techniques. The results indicate that the presence of multiple anchoring points on the dye structure improves its adsorption stability onto TiO2 but induces a pseudoplanar adsorption geometry which is not suited to insulate properly the surface of the semiconductor and of the back contact, against electron recombination; particularly when kinetically fast shuttles are employed. This drawback could be successfully countered by exploiting both a compact blocking underlayer and the chemisorption of octyl triethoxysilane (Si–C8) acting as a molecular barrier onto the TiO2 surface, thus limiting the access of the oxidized mediator to the exposed...

Fabrication of superhydrophobic, antibacterial, and ultraviolet-blocking cotton fabric

Inspired by the superhydrophobic behavior of lotus leaf, a simple coating method was developed which could facilitate bionic creation of superhydrophobic surfaces on cotton textiles with a new functional properties. Silver nanoparticles (AgNPs) with a high deposition density were formed on the surface of cotton fabric through an alkali pre-activation followed by in situ reduction of silver nitrate. The Ag-coated fabric was then reacted with octyltriethoxysilane (OTES) to form a low surface energy layer on the fiber surface. The fabrics were characterized by ultraviolet-visible reflectance spectrophotometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and X-ray diffractometry. Hydrophobicity properties were assessed by contact angle (CA) goniometry and shedding angle (SHA) technique. Antibacterial activity was measured against Staphylococcus aureus and Escherichia coli bacteria, and UV-blocking ability was measured using the AATCC method. SEM images showed the formation of AgNPs which were distributed uniformly on the fibers’ surface with a high coating density. Superhydrophobicity property of the treated fabric was confirmed with the CA of 156° and SHA of 8°. High antibacterial activity was observed without the reduction of inhibition size after coating with the OTES. The fabric also showed excellent UV-blocking with the ultraviolet protection factor of 266.01.

Reducing Leakage Currents in n-Channel Organic Field-Effect Transistors Using Molecular Dipole Monolayers on Nanoscale Oxides

Leakage currents through the gate dielectric of thin film transistors remain a roadblock to the fabrication of organic field-effect transistors (OFETs) on ultrathin dielectrics. We report the first investigation of a self-assembled monolayer (SAM) dipole as an electrostatic barrier to reduce leakage currents in n-channel OFETs fabricated on a minimal, leaky ∼10 nm SiO2 dielectric on highly doped Si. The electric field associated with 1H,1H,2H,2H-perfluoro-octyltriethoxysilane (FOTS) and octyltriethoxysilane (OTS) dipolar chains affixed to the oxide surface of n-Si gave an order of magnitude decrease in gate leakage current and subthreshold leakage and a two order-of-magnitude increase in ON/OFF ratio for a naphthalenetetracarboxylic diimide (NTCDI) transistor. Identically fabricated devices on p-Si showed similarly reduced leakage and improved performance for oxides treated with the larger dipole FOTS monolayer, while OTS devices showed poorer transfer characteristics than those on bare oxide. Comparison of OFETs on both substrates revealed that relative device performance from OTS and FOTS treatments was dictated primarily by the organosilane chain and not the underlying siloxane-substrate bond. This conclusion is supported by the similar threshold voltages (VT) extrapolated for SAM-treated devices, which display positive relative VT shifts for FOTS on either substrate but opposite VT shifts for OTS treatment on n-Si and p-Si. Our results highlight the potential of dipolar SAMs as performance-enhancing layers for marginal quality dielectrics, broadening the material spectrum for low power, ultrathin organic electronics.

Synergistic effect of silane modified nanocomposites for active corrosion protection

Abstract This work presents an effective anticorrosion behavior of a hydrophobic surface on stainless steel 304. The protective coating has been designed by dispersing nanocomposites (cloisite 15A, multiwalled carbon nanotubes and cerium chloride) which act as a corrosion inhibitor. The sol was prepared by using 3-glycidoxypropyltrimethoxysilane (GPTMS), octyltriethoxysilane (OTES) and zirconium (IV) butoxide as precursors. The corrosion resistance of coated stainless steel got improved when nanocomposites were homogeneously embedded in silica sol. The influence of nano-particles on the barrier coatings impedes corrosion. The coatings were analyzed by X-ray diffraction (XRD) to ensure the intercalation and distribution of nanocomposites in layered silicates. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanocomposites modified silica sol. Scanning electron microscopy (SEM) was used to examine the morphology of the modified silane coating. The contact angle measurements ensured the hydrophobic behavior of the coatings. The corrosion behavior was investigated using Electrochemical Impedance Spectroscopy (EIS). This study has led to a better understanding of active anticorrosive coatings with embedded nanocomposites and the factors influencing the anticorrosion performance.

Multi-walled carbon nanotubes coated by multi-layer silica for improving thermal conductivity of polymer composites

Silica has been non-covalently coated on multi-walled carbon nanotubes (MWCNTs) using the sol–gel chemistry, where tetraethoxy silane (TEOS) was used to form an inorganic silica layer immediately next to surface of MWCNTs and octyl triethoxy silane was coated over the TEOS. Transmission electron microscopy (TEM) measurements show that the diameter of MWCNTs increases with increasing the number of coating layer, indicating that the silica has been coated on MWCNTs. Quantitative analysis from thermogravimetric analysis (TG) also indicates that the inorganic and organic silica has been successfully coated on MWCNTs. Further, quantitative analysis found that the amount of silica measured by TG agrees well with the increase of thickness of coated MWCNTs obtained from TEM, indicating that little or no free silica exists in the system. The thermal conductivity of epoxy/MWCNTs composite was studied and the results show that the thermal conductivity of the composite is improved by coating MWCNTs in this manner and increases with increasing the number of coatings.

Prebreakdown current and dc breakdown strength of alumina-filled poly(ethylene-co-butyl acrylate) nanocomposites: Part I - breakdown strength

Dielectric breakdown strength of poly (ethylene-co-butyl acrylate) (EBA) nanocomposites filled with spherical alumina particles was studied as a function of particle coating, moisture content and the effective specific surface area. Two kinds of alumina nanoparticles were used: NA (25 nm in diameter) or ND (45 nm in diameter). The particles were either unmodified or surface-treated with aminopropyltriethoxy silane or octyltriethoxy silane. Two different relative humidities of air were used for conditioning the samples prior to testing: 0 % RH (dry case) and 86 % RH (samples were saturated with moisture). The dielectric breakdown strength measurements were performed with a DC ramp of 1.2 kV/s. Twenty samples were tested for each material formulation - ten of which were tested in dry conditions and ten were tested after conditioning in humid environment. Results were compared to the reference unfilled EBA samples. Applying Weibull analysis to the measured breakdown voltages indicated that the material filled with amino-coated ND particles exhibited the highest breakdown strength under dry conditions. As expected, conditioning materials in a humid environment had a negative impact on breakdown strength. This effect was more pronounced for nanocomposite materials, compared to the unfilled reference material.

OTES modified transparent dip coated silica coatings

The present paper describes the room temperature synthesis of dip coated water repellent silica coatings on glass substrates using octyltriethoxysilane (OTES) as a co-precursor with two-step sol–gel process. Silica sol was prepared by keeping the molar ratio of tetraethylortosilicate (TEOS) precursor, methanol (MeOH) solvent, acidic water (0.001M oxalic acid) and basic water (12M NH4OH) constant at 1:11.03:0.17:0.58 respectively, throughout the experiments and the OTES weight percentage was varied from 0% to 15%. It was found that with an increase in wt% of OTES, the roughness and hydrophobicity of the films increased, however the optical transmission decreased from 93% to 88% in the visible range. The hydrophobic silica films retained their hydrophobicity up to a temperature of 259°C and above this temperature, the films became hydrophilic. The hydrophobic silica thin films were characterized by taking into consideration the surface roughness studies, Fourier transform infrared (FT-IR) spectroscopy, percentage of optical transmission, scanning electron microscopy (SEM), Thermogravimetric-differential thermal analysis (TG-DTA) and contact angle measurements.

Fabrication of hydrophobic and antireflective coatings based on hybrid silica films by sol–gel process

This paper reports the synthesis of hydrophobic and antireflective coatings by sol–gel process at room temperature (25°C), using tetraethylorthosilicate (TEOS) as a precursor and methyltriethoxysilane (MTES), phenyltriethoxysilane (PTES), vinyltriethoxysilane (VTES), and octyltriethoxysilane (OTES) as surface modifying agents. The silica sol was prepared by keeping the molar ratio of TEOS:RTES at 1:1, in acidic conditions with ethanol and 0.1M HCl. All hybrid systems were enriched with titanium(IV) isopropoxide as the cross-linking agent. It was observed that the obtained silica films become hydrophobic with the introduction of the hydrophobic organic group. The higher value of static water contact angle (107±3°) was obtained for the silica film prepared with TEOS+OTES. Under optimal synthesis condition, we obtained antireflection coatings, exhibiting a low reflection in the visible range.

Dielectric properties of alumina-filled poly (ethylene-co-butyl acrylate) nanocomposites Part I - dry studies

The dielectric properties of poly (ethylene-co-butyl acrylate) with 13 wt% of butyl acrylate (EBA) filled with alumina nanoparticles were studied as a function of particle size, particle coating, filler content (2, 6 or 12wt%) and temperature. The particles were either unmodified or surface-treated with either aminopropyltriethoxy silane or octyltriethoxy silane. The complex permittivity was measured with frequencies varying between 1 mHz and up to 1 kHz at different temperatures (25, 45 and 65°C). Measurements were performed in dry conditions. From the dielectric spectroscopy measurements it can be seen that the tan δ for the dry samples is almost independent of the type of the particle coating used. It does, however, depend on the particle size, filler content and temperature.

Hybrid silica coatings on polycarbonate: enhanced properties

Hybrid silica coatings based on 3- glycidoxypropyltriethoxysilane (GPTES), tetraethylorthosilicate (TEOS) and colloidal silica were deposited on polycarbonate (PC) by the sol–gel method, in order to obtain a material with enhanced properties with respect to raw PC (mainly scratch resistance, hydrophobicity and density), and consequently reach increased durability. The necessity of performing a N2-plasma treatment on PC (before coating deposition) was highlighted in order to obtain a good adherence between the coating and the substrate: XPS measurements showed that after treatment, nitrogenous radicals had formed on the PC surface and were able to link covalently with the sol during its deposition. Adherence was also higher when young sols (<8-day-old) were used. Different alkoxysilanes/colloidal silica ratios were tested to optimize the coating resistance: crack resistance of the coatings was found to be greater when the ratio was high. Scratch resistance of raw PC was enhanced as soon as PC was coated, irrespective of the alkoxysilanes/colloidal silica ratio or the sol ageing time. The density of the coatings was assessed by environmental ellipsometric porosimetry and found to be very high. Water contact angle measurements showed that the hydrophobicity of the coatings was inferior to raw PC. The addition in the sol of a small wt% of octyltriethoxysilane (OTES), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FTES) and silicone surface additive (BYK-306) allowed a significant increase in hydrophobicity of the samples.

Evaluation of anti-scratch properties of graphene oxide/polypropylene nanocomposites

Graphene oxide/polypropylene (GO/PP) nanocomposites were fabricated by varying the concentration of GO in the presence of octyltriethoxysilane (OTES) using an internal batch mixer to enhance the anti-scratch properties of pristine PP. Mechanical properties, including hardness, elastic modulus, and fracture toughness, of the prepared GO/PP nanocomposites were analyzed by nanoindentation. As a compatibilizer, OTES increased dispersibility, interfacial interactions, and mechanical interlocking between the GO nanofiller and the PP matrix, improving mechanical strength. A 286% increase in hardness, 127% improvement of elastic modulus and 117% enhancement on fracture toughness are achieved by addition of only 1.0 wt% of GO and OTES. For scratch tests, several GO/PP nanocomposite samples were analyzed according to various scratch parameters. Furthermore, scratch hardness, elastic recovery, and tangential forces acting on the scratch probe were investigated to provide insight into scratch behavior. The outstanding resistance to scratch deformation such as a maximum increase in scratch hardness of 189% was likely due to the excellent mechanical properties of the GO/PP nanocomposites.

Novel composite nanofilm of electropolymerization and self‐assembling on AA5052 surface as anticorrosion coating

AbstractElectropolymerization nanofilm was prepared by cyclic voltammogram with 6N,N‐diallylamino‐1,3,5‐triazine‐2,4‐dithiol monosodium (DAN) on the AA5052 surface in 0.15M NaNO2 at 10°C, then octyl‐triethoxysilane (OTES) film was fabricated on the poly(6N,N‐diallylamino‐1,3,5‐triazine‐2,4‐dithiol) nanofilm (PDA) covered AA5052 surface by self‐assembling method to obtain the composite polymeric nanofilm (C‐PDA/OTES). The composite polymeric nanofilm was characterized by means of FTIR spectra, scanning electron microscope (SEM), contact angle, and potentiodynamic polarization. The results showed that the C‐PDA/OTES covered surface was more homogenous, compact, hydrophobic compared with PDA covered surface and had excellent protection efficiency. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Surface modification of alumina nanofibres for the selective adsorption of alachlor and imazaquin herbicides

The effective removal of pollutants using a thermally and chemically stable substrate that has controllable absorption properties is a goal of water treatment. In this study, the surfaces of thin alumina (γ-Al2O3) nanofibres were modified by the grafting either of two organosilane agents, 3-chloro-propyl-triethoxysilane (CPTES) and octyl-triethoxysilane (OTES). These modified materials were then trialed as absorbents for the removal of two herbicides, alachlor and imazaquin from water. The formation of organic groups during the functionalisation process established super hydrophobic sites on the surfaces of the nanofibres. This super hydrophobic group is a kind of protruding adsorption site which facilitates the intimate contact with the pollutants. OTES grafted substrate were shown to be more selective for alachlor while imazaquin selectivity is shown by the CPTES grafted substrate. Kinetics studies revealed that imazaquin was rapidly adsorbed on CPTES-modified surfaces. However, the adsorption of alachlor by OTES grafted surface was achieved more slowly.

Investigation of novel sol–gel hydrophobic surfaces for desorption electrospray ionization-mass spectrometry analysis

Sol-gel-based materials were synthesized, characterized and finally tested as solid supports for desorption electrospray ionization-mass spectrometry (DESI-MS) analysis of a mixture of compounds of different polarity. Films with thickness in the 2-4 μm range were obtained by a dip-coating process using tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) as sol-gel precursors. Three types of surface with different hydrophobic character were obtained by varying the TEOS/OTES ratio in the sol-gel mixture. Each coating was characterized by atomic force microscopy investigations, gaining insight into homogeneity, smoothness and thickness of the obtained films. To study hydrophobicity of each surface, surface free energy measurements were performed. Different DESI-MS responses were observed when different solvent mixture deposition procedures and solvent spray compositions were investigated. Results were finally compared to those obtained by using commercial polytetrafluoroethylene-coated slides. It was found that surface free energy plays an important role in the desorption/ionization process as a function of the polarity of analytes.

Effect of Concentration on the Photo-Orientation and Relaxation Dynamics of Self-Assembled Monolayers of Mixtures of an Azobenzene-Based Triethoxysilane with Octyltriethoxysilane

Self-assembled monolayers (SAMs) were prepared from solutions with different proportions of a photoactive, azobenzene-based, silanized derivative of disperse red one (dDR1), and octyltriethoxysilane (OTE), a shorter, nonphotoactive molecule. The in-plane photoinduced orientational ordering of the resulting two component monolayers was monitored via precision measurement of in-plane birefringence using a dedicated high-extinction polarimeter. Measurements of contact angle, absorption, and birefringence show that introduction of OTE into the dDR1 deposition solution produces a continuous reduction of the surface density of dDR1 in the SAM, enabling the study of photowriting and relaxation dynamics in monolayers ranging from 100% dDR1 to samples where the dDR1 coverage is about 35%. The orientational dynamics depend strongly on the areal density of dDR1. As the fractional area of dDR1 is reduced, the rates of photowriting, photoerasing, and thermal relaxation increase, and the local orientational confinement of the molecules becomes more heterogeneous.

Hydrolysis-Condensation Kinetics of Different Silane Coupling Agents

The hydrolysis kinetics of 14 alkoxy silane coupling agents were carried out in an ethanol:water 80:20 (w/w) solution under acidic conditions and were monitored by 1H, 13C, and 29Si NMR spectroscopy. Acidic conditions were selected in order to enhance the silanol formation and to slow down the self-condensation between the resulting hydrolysed silanol groups. In situ 29Si NMR spectroscopy allowed the determination of the intermediate species as a function of the reaction time. Thus, the following silane coupling agents were studied: 3-methacryloxypropyl trimethoxy silane (MPMS), 3-mercaptopropyl trimethoxy silane (MRPMS), 3-cyanopropyl triethoxy silane (CPES), triethoxy vinyl silane (VES), trimethoxy (2-phenylethyl) silane (PEMS), octyl triethoxy silane (OES), trimethoxy (7-octen-1-yl) silane (OEMS), 3-aminopropyl triethoxy silane (APES), 3-aminopropyl trimethoxy silane (APMS), 3-(2-aminoethylamino)propyl trimethoxy silane, (DAMS), 3-[2-(2-aminoethylamino)-ethylamino]propyl trimethoxy silane (TAMS), 4-amino-3,3-dibutyl trimethoxy silane (ADBMS), trimethoxy [3-(phenylamino)propyl] silane (PAPMS), and triethoxy-3-(2-imidazolin-1-yl) propyl silane (IZPES). A parameter quantifying the grafting potentiality of each silane coupling agent towards OH-rich solid substrates (such as cellulose) was established as a function of the nature of the alkoxy groups (methoxy or ethoxy), as well as that of the fourth substituent (vinyl, aminopropyl, etc.) of the silane studied.GRAPHICAL ABSTRACT

Diffusion Control of Porous Membrane by Modifying the Nanopore Properties

We have investigated the diffusion of various solvents on nanoporous membranes with various pore size and surface energy. We have modified the size of pore channel and surface energy of porous membrane through grafting different sized alkyl chain on inorganic membranes. Typically, disc type zirconia membranes with pore size of 3 nm and silica ones with 1 nm pore were purchased from Inocermic Co. Ltd. (Germany), and the surface and pore channel was modified by either octyltriethoxysilane (OTS) with chain length approximately 1 nm or pentyltriethoxysilane (PTS) with chain length approximately 0.5 nm. The water contact angles of both OTS and PTS grafted membrane were larger than 100 degrees indicating the hydrophobically modified surface. Contact angles of hydrophilic and hydrophobic solvents were also examined to obtain exact surface energy (gamma(sv)) of grafted membrane, and the values were determined to be 56.3, 45.3, and 42.2 mN/m for ungrafted, PTS- and OTS-grafted membrane, respectively. The solvent diffusion patterns were evaluated by measuring the concentration gradient of small dye molecule, azobenzene. The diffusion coefficients of various solvents were measured on the basis of Fick's diffusion law. It was concluded that the diffusivity is dependent on the pore size for solvent with low surface tension and on the gamma(sv) value for solvent with high surface tension.

Dielectric properties of alumina-filled poly (ethylene-co-butyl acrylate) nanocomposites Part II- wet studies

The influence of moisture on the dielectric properties of different types of poly (ethyleneco- butyl acrylate) filled with alumina nanoparticles was systematically investigated by varying the type of aluminum oxide, particle surface treatment and filler content (2, 6 and 12 wt%). The nanoparticles were either unmodified or surface-treated with either aminopropyl triethoxysilane or octyltriethoxy silane. The complex permittivity was measured with an IDA200 dielectric spectroscopy analyzer at applied voltage of 200 Vpeak with frequencies varying between 1 mHz and 1 kHz. The measurements were performed at 25°C and relative air humidities of 24, 54 and 86%. In order to expand the frequency range the HP 4284A precision LCR meter was used for measuring sample impedance at the frequency range of 100 Hz to 1 MHz. From the frequency dependence of dielectric losses it can be seen that absorbed water plays a significant role in determining the dielectric properties of the nanocomposites. The magnitude of tan δ seems to be determined primarily by the particle size and filler content, while the peak frequency is mostly influenced by the amount of absorbed water and the type of particle coating.