Octadecyltrichlorosilane Molecules Research Articles

Superhydrophobic magnetic Fe3O4 polyurethane sponges for oil–water separation and oil-spill recovery

The effective and affordable separation of oil and water, a crucial process in the safe handling of environmental disasters such as crude oil spills and recovery of valuable resources, is a highly sought-after yet challenging task. Herein, superhydrophobic PU sponge was fabricated for the fast and cost-effective adsorptive separation of oil and different organic solvents from water. Octadecyltrichlorosilane (OTS)-functionalized Fe3O4@SiO2 core–shell microspheres were dip-coated on the surface of porous materials via a dip-coating process, thereby endowing them with superhydrophobicity. Owing to the hydrophobic interaction between OTS molecules and oil and increased capillary force in the micropores, the resulting superhydrophobic sponge served as a selective oil-sorbent scaffold for absorbing oil from oil–water mixtures, including oil–water suspensions and emulsions. Remarkably, after the recovery of the adsorbed oil via mechanical extrusion, these superhydrophobic materials could be reused multiple times and maintain their oil–water separation efficacy even after 10 oil–water separation cycles.

EFFECT OF AMBIENT RELATIVE HUMIDITY AND SOAKING TIME ON THE FORMATION OF OCTADECYLTRICHLOROSILANE COATINGS ON BOROSILICATE GLASS SUBSTRATES FOR ALKALI-METAL VAPOR CELLS

The most sensitive spin-exchange relaxation-free (SERF) magnetometer generally requires a working temperature greater than 100∘C. To date, octadecyltrichlorosilane (OTS) coating is one of the best candidates for this temperature range. However, the performance and consistency of the OTS coatings within the alkali-metal vapor cells are still poor. In this paper, the formation of OTS coatings on borosilicate glass (BG) substrates was investigated. The effects of ambient relative humidity (RH) on the formation of OTS coatings were examined by atomic force microscopy (AFM) and contact angle measurement. The results showed that 75[Formula: see text] RH can improve the order of the OTS coatings and reduce the root mean square (RMS) roughness of the OTS coatings. Under three different ambient RHs, the soaking time of OTS molecules should be greater than 60[Formula: see text]min to form complete OTS coating.

Fabrication of superhydrophobic surface using one-step chemical treatment

The fabrication techniques of hydrophobic and superhydrophobic surfaces have received attention from many researchers. In this study, the change of water contact angle of the glass surface modified with chlorosilane or trichlorosilane compound was investigated. The microscope glass with water contact angle of 88° and 107° were obtained by treating with trimethylchlorosilane (TMCS) and octadecyltrichlorosilane (OTS), respectively. The chemical resistance of hydrophobic layer was evaluated by immersing the treated samples into an acidic or a basic solution. The result showed that OTS bonded to the glass surface more strongly than TMCS. The superhydrophobic state with the highest contact angle of 154° (sliding angle 17°) could be achieved with the glass microfiber filter by using OTS. The similar phenomenon could not be observed with TMCS because the TMCS-treated glass filter remained completely wetted with all investigated concentrations. The hydrophobic layer on the glass slides was strongly affected by abrasive force while the contact angle value of more than 154° was detected in the treated glass filter after 50 cycles of abrasion test on a sandpaper. The scanning electron microscope (SEM) images had revealed the aggregation of the OTS molecules on the glass filter surface. The chemically-treated filter performed both superhydrophobic and superoleophilic properties. The OTS coating showed strong resistance to the organic solvent. Separation of mixture n-hexane and water was successfully demonstrated using the modified filter.

Superhydrophobic coating on quartz sand filter media for oily wastewater filtration

Deep bed filtration is commonly used to remove oil from oily wastewater. The wettability of the filter media greatly influences the oil removal efficiency. A filter with a strong hydrophobicity and oleophilicity results in a higher oil removal efficiency. To improve the hydrophobicity and oleophilicity, ZnO nanoparticles and octadecyltrichlorosilane (OTS) were coated on quartz sand filter media. SEM, FTIR and XPS were used to study the morphology and chemical composition of the filters, and adsorption capacity and oil removal efficiency experiments were performed to assess the oil removal performance. The results show that the OTS molecules are grafted onto the surface of the quartz sand filter through chemical bonding, and the OTS/ZnO-coated quartz sand filter is superhydrophobic and oleophilic, with a water contact angle of 154.1° and an oil contact angle of 0°. The OTS/ZnO-coated quartz sand filter has very high mechanical stability and acid resistance. The oily wastewater treatment performance is greatly improved after application of the OTS/ZnO coating, and the superhydrophobic quartz sand filter media can potentially be used to filter oily wastewater and achieve high oil removal efficiency.

Surface modification of Norway spruce wood by octadecyltrichlorosilane (OTS) nanosol by dipping and water vapour diffusion properties of the OTS-modified wood

AbstractThe present research deals with a simple dipping method to insert octadecyltrichlorosilane (OTS) into cell walls of spruce wood and to deposit OTS layers on its inner and outer surfaces. Distribution and chemical interactions of OTS with wood polymers has been investigated by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The OTS/n-hexane solution penetrated into wood via capillary forces through ray tracheids and bordered pits and was deposited as OTS organic-inorganic layers on wood cell walls. The hypothesis is supported by the results, according to which the OTS molecules are hydrolysed by the wood moisture and by free OH groups of the cell wall components. The hydrolysed OTS molecules react with the OH groups and elevate the hydrophobicity of wood.

Rubrene on differently treated SiO2/Si substrates: A comparative study by atomic force microscopy, X-ray absorption and photoemission spectroscopies techniques

The performances of organic thin film transistor devices are crucially connected with electronic and structural properties at organic semiconductor/dielectric interfaces. In our studies, Silicon substrates with native SiO2 layer were made hydrophilic according to Radio Corporation of America (RCA) cleaning procedure (RCA treated SiO2, RCA/SiO2) and hydrophobic by following octadecyltrichlorosilane (OTS) modification method (OTS treated SiO2, OTS/SiO2). The surface morphology, molecular orientation and nature of interaction have been studied at rubrene/RCA treated SiO2 and rubrene/OTS treated SiO2 interfaces with increasing thickness of rubrene film from sub-monolayer to multilayer. The angle dependent near edge x-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM) were used to probe the evolution of molecular configuration and surface morphology of rubrene thin films respectively. The nature of interaction was investigated by X-ray photoemission spectroscopy (XPS) techniques. XPS and NEXAFS studies indicate that the rubrene molecules were physically adsorbed onto both substrates. Angle dependent NEXAFS data suggest that OTS molecules were in standing up configuration on SiO2 surface while rubrene molecules were randomly oriented on both RCA and OTS treated SiO2 substrates. On RCA/SiO2 substrate the percentage of rubrene molecules with twisted backbone was higher compared to that on OTS/SiO2 for 20nm thick films. The rubrene films were found to grow with different features onto two studied substrates due to their difference in surface energy. At lower coverage, the grain size was larger and nucleation density was smaller onto hydrophilic RCA/SiO2 surface, compared to hydrophobic OTS/SiO2. Hydrophobation of the dielectric substrate surface tends to hinder the diffusion of rubrene molecules resulting in smaller grains for hydrophobic substrate compared to hydrophilic one.

Octadecyltrichlorosilane Deposition on Mica Surfaces: Insights into the Interface Interaction Mechanism.

Surface functionalization by alkylsilanes has been widely used in many engineering applications. In this work, a systematic investigation was conducted on the deposition behaviors of octadecyltrichlorosilane (OTCS) on freshly cleaved mica surfaces that possess a low density of reactive sites (i.e., silanol groups) by a vapor-deposition method. The deposition of OTCS molecules on mica was found to follow a two-stage process, as monitored by measuring the surface morphology using an atomic force microscope and wettability of the samples obtained at different deposition times. The contact mechanics behaviors and interaction forces of the as-obtained OTCS surfaces were characterized using a surface forces apparatus. The contact mechanics tests demonstrate that the OTCS coatings can significantly reduce the surface adhesion and adhesion hysteresis in air. The force-distance profiles of the OTCS surfaces obtained via a shorter deposition time (e.g., 2, 8 h) in aqueous solutions could be reasonably described by the classical Derjaguin-Landau-Verwey-Overbeek theory. However, for the OTCS surfaces obtained by longer deposition times (e.g., 48 h), hydrophobic interaction and steric interaction play an important role due to the enhanced surface hydrophobicity and roughness. Our results provide useful insights into the physicochemical characteristics of alkylsilane deposition and the surface interaction mechanisms of deposited alkylsilanes at solid-air and solid-water interfaces.

Area-Selective ALD of TiO2 Nanolines with Electron-Beam Lithography

We demonstrate a bottom-up approach to fabricate nanoline structures using self-assembled monolayer (SAM) modified substrates to selectively prevent nucleation during atomic layer deposition (ALD). Low-energy (≤5 kV) electron-beam lithography (EBL) was used to modify the hydrophobic functional groups (−CH3) of octadecyltrichlorosilane (OTS) SAM to hydrophilic species (e.g., −COOH), which allows chemisorption of the titanium isopropoxide (TTIP) and water to initiate titanium oxide (TiO2) nucleation. TiO2 thin films were selectively deposited on the OTS molecules which were properly functionalized or patterned. We systematically investigate the effects of e-beam dose and accelerating voltage on selective TiO2 deposition with nanoline patterns. The results indicate that the former parameter determines the resolution of individual line width, while the latter one is attributed to the minimum pitch dimension of dense line patterns achievable. Using the optimal e-beam parameters, i.e., accelerating voltages of 1–2 kV and a line dose of 10 nC/cm, TiO2 nanolines with a maximum resolution of 30 nm and a minimum pitch of 50 nm were achieved. This study offers a new approach to fabricate close-packed nanopatterns for IC devices without any challenging etching processes.

Ice-phobic behavior of superhydrophobic Al surface undervarious etching conditions

Superhydrophobic Al substrates were fabricated simply by etching pure Al substrates in hot water at 100 °C, followed by hydrophobic coating. The etched/oxidized Al surface layers exhibited spike-like morphologies and superhydrophobicity (corresponding to a water contact angle (CA) of >150°) was induced by surface modification with octadecyltrichlorosilane (OTS). Herein, the ice-repellent behavior of superhydrophobic Al substrates is demonstrated by investigating the CA after applying repeated icing-deicing cycles. The ice-repellent properties were found to be significantly different among apparently similar superhydrophobic surfaces, depending on the Al etching/oxidation and OTS-coating conditions. The loss of hydrophobicity is most likely due to the rupture of Si-O-Al bonds between the OTS molecules and the surface of etched Al, caused by the hydrolysis of these bonds. In freezing delay-time tests, the maximum freezing time of a water droplet was observed on the OTS-coated Al sample with an etching time of 2 h. The Al surface roughness increases with increasing the etching time, then heat is transferred through the water-solid interface area of a water droplet residing on a superhydrophobic surface. Therefore, the larger the surface roughness, the smaller the water-solid contact area, and thus, the larger the amount of entrapped air between water and solid. Therefore, it is very important to find the optimal interfacial bonding conditions between the Al substrate and OTS molecules.

Method for Fabrication of Paper-Based Microfluidic Devices by Alkylsilane Self-Assembling and UV/O3-Patterning

This work presents a novel and facile method for fabricating paper-based microfluidic devices by means of coupling of hydrophobic silane to paper fibers followed by deep UV-lithography. After filter paper being simply immersed in an octadecyltrichlorosilane (OTS) solution in n-hexane for 5 min, the hydrophilic paper became highly hydrophobic (water contact angle of about 125°) due to the hydrophobic OTS molecules were coupled to paper's cellulose fibers. The hydrophobized paper was then exposed to deep UV-lights through a quartz mask that had the pattern of the to-be-prepared channel network. Thus, the UV-exposed regions turned highly hydrophilic whereas the masked regions remained highly hydrophobic, generating hydrophilic channels, reservoirs and reaction zones that were well-defined by the hydrophobic regions. The resolution for hydrophilic channels was 233 ± 30 μm and that for between-channel hydrophobic barrier was 137 ± 21 μm. Contact angle measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform-infrared (ATR-FT-IR) spectroscopy were employed to characterize the surface chemistry of the OTS-coated and UV/O(3)-treated paper, and the related mechanism was discussed. Colorimetric assays of nitrite are demonstrated with the developed paper-based microfluidic devices.

Fabrication of superhydrophobic spherical-like α-FeOOH films on the wood surface by a hydrothermal method

The superhydrophobic spherical-like α-FeOOH films on the wood surface was obtained from ferric sulfate and urea by a hydrothermal reaction process followed by a self-assembly of Octadecyltrichlorosilane (OTS) monolayer. The microstructure, chemical state and composition of the products were observed by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Energy disperse X-ray analysis (EDX). The hydrophobic property of the treated samples was described by static water contact angles (CAs) and sliding water contact angles (SA) measurement. The stability under ambient condition and durability for corrosive liquid of the surperhydrophobic samples were also investigated in this paper. An analytical characterization revealed that the spherical-like α-FeOOH films with micro–nano structure uniformly deposited on the wood surface and OTS molecules combined with α-FeOOH films. The water contact angle of the as-prepared samples reached as high as 158° and the sliding angle was about 4°. The prepared superhydrophobic wood surface still maintained the superhydrophobic property when stored under ambient condition for 3 months or immersed in a sodium hydroxide solution of pH 12 and a hydrochloric acid solution of pH 2 for 2h at room temperature.

Selective Adsorption of Organosilane Molecules Along Step Edges of Atomically Flattened Si(111) Surfaces

We investigate the selective adsorption of organosilane molecules (3-aminopropyltriethoxysilane (APTES) and octadecyltrichlorosilane (OTS)) at the step edges of a flattened Si(111) surface by atomic force microscopy. The flattened Si(111) surface is formed by dipping a vicinal Si(111) wafer into ultralow-dissolved-oxygen water after treatment with HF. The selective adsorption of these organosilanes is achieved only when the Si(111) sample is pretreated with a Cu-containing solution to form Cu wires along the step edges of the Si(111) surface. This is probably due to the simultaneous formation of one-dimensional Si oxide covered with hydroxyl (OH) groups underneath Cu wires during the electroless reduction of Cu ions in water. At the step edges, APTES and OTS molecules are adsorbed as disperse clusters and as rows of bumps, respectively. The reason for this difference is still unclear, but a key factor is probably the control of the moisture content in the environment. The step edges, which are functionalized by organosilane molecules with various terminations such as -NH2 and -CH3, are expected to be utilized in novel nanoscale devices and processes.

Preparation and micro-mechanical studies of polysiloxane-containing dual-layer film on Au surface

A novel polysiloxane-containing self-assembled dual-layer film was grafted onto Au surface with a simple three-step method. Firstly, (3-mercaptopropyl)trimethoxysilane (MPTMS) molecules were self-assembled on Au surfaces through S–Au bond followed by hydrolysis and condensation, then the octadecyltrichlorosilane molecules were attached to the resultant hydroxyl terminated surface via the Si–O–Si bonds. The structure and morphology of the film were characterized by means of contact angle measurement, ellipsometry, attenuated total reflectance Fourier transformed infrared spectra, and atomic force microscopy. The resistant ability of charge transfer in the film forming process was detected by electrochemical techniques. Using force–volume technique, we investigated how the different surface chemical groups influence the surface adhesion properties. The nano-friction properties of the as-prepared films were investigated by frictional force microscopy. The results indicated that the dual-layer film fabricated via the hydrolyzation of MPTMS underlayer had significantly less friction. Moreover, compared to the self-assembled monolayer of octadecane thiol, the resultant dual-layer film showed much less wear. This improvement was mainly ascribed to the existence of the network of lateral cross-linked polysiloxane layer within the film which can enhance the stability of the film.

Structural Effect on Formation of Alkylsilane Self-Assembled Monolayers on Indium Tin Oxide Surface

The effects of immersion time and the number of chlorine attached to silane atom on the formation of self-assembled monolayers (SAMs) on indium tin oxide (ITO) surface were examined by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Among octadecyltrichlorosilane (OTS), octadecyldichloromethylsilane (ODDMS), and octadecyldimethylchlorosilane (ODMS), OTS SAMs on ITO surface formed after 1 h deposition at room temperature have a high contact angle value of 86° compared to ODDMS and ODMS SAMs with 45° and 31°, reflecting that OTS on ITO surface would form a high-quality SAMs with a hydrophobic surface. STM imaging revealed that the surface structure of OTS SAMs on ITO surface was markedly different from that of bare ITO surface resulting from the the adsorption of OTS molecules. In addition, XPS measurements showed that the formation of OTS SAMs is strongly driven by the chemical reactions between the Si atoms and the hydroxyl group of ITO surface during self-assembly.

Effect of Reaction Temperature on Growth of Organosilane Self-Assembled Monolayers

The effect of reaction temperature on the self-organization and growth mechanism of octadecyltrichlorosilane (OTS) self-assembled monolayers (SAM) was investigated by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXD) measurement, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). OTS SAM was prepared by a liquid phase method and chemical vapor deposition. In the liquid phase method, OTS SAM was prepared in the temperature range from 5 to 40 °C. In the reaction temperature range from 5 to 30 °C, OTS molecules formed domain structures early in the growth process and grew two-dimensionally on SiO2 substrates. In addition, the crystalline peaks of GIXD measurements indicated that OTS SAM prepared at lower temperatures (5–30 °C) grew in the crystalline state. Thus, “self-organization” occurred under these conditions. However, OTS SAM prepared at 40 °C showed an amorphous structure. XPS and FT-IR spectra showed that the SiO2 peak increased while reaction temperature decreased. These results indicated that the formation of a siloxane bond between OTS molecules was important for the self-organization of the OTS monolayer. In addition, FT-IR measurement indicated that the packing density of the OTS monolayer prepared at lower temperatures was higher than that prepared at higher temperatures by chemical vapor deposition.

Effects of Humidity and Solution Age on Growth of Organosilane Self-Assembled Monolayers

The effect of humidity on the self-organization and growth mechanism of octadecyltrichlorosilane (OTS) monolayers was investigated using an atomic force microscope (AFM), grazing incidence X-ray diffraction (GIXD), and Fourier transform IR spectroscopy (FT-IR). OTS self-assembled monolayers (SAMs) were prepared under humidity ranging from 5 to 80%. Under humidity ranging from 15 to 80%, OTS molecules produced domain structures early in the growth process that grew two-dimensionally on SiO2 substrates. Also, the crystalline peaks of the obtained from the GIXD measurement indicated that OTS-SAMs prepared under high humidity (15–80%) had grown in a crystalline state. Thus, “self-organization” occurred under these conditions. However, OTS-SAMs prepared under 5% humidity were in an amorphous structure. OTS-SAMs prepared at high humidity were denser than those prepared at low humidity. The domain size early in the growth process increased in proportion to the solution age. This shows that the reaction rate is governed by the hydrolysis of organosilane. On the other hand, solution age has no great influence on the density of the OTS-SAMs under conditions of more than 50% humidity.

Control of Chemical States on Locally Anode-Oxidized Si Surfaces

We have demonstrated that chemical states on the anode-oxidized Si surfaces prepared by atomic force microscopy (AFM) can be controlled by selecting the appropriate applied voltage for the oxidation. The frictional force on the oxidized surface formed at relatively low voltages (4.5–9 V) was large, whereas that at relatively high voltages (9–10 V) was small. This is due to a difference in the hydrophilicity of the surfaces. Octadecyltrichlorosilane (OTS) films were formed only on the oxidized surface prepared at the low voltages. Since OTS molecules require OH groups to form a film, the hydrophilicity originates from OH group termination of the surfaces. Therefore, the oxide surface is terminated with OH groups when the applied voltage is relatively low. When the applied voltage is relatively high, it is speculated that the oxide surface is covered with Si–O–Si groups instead of OH groups.

Construction of the homogeneously mixed SAM composed of octyltriethoxysilane and octadecyltrichlorosilane by taking advantage of the molecular steric restriction

By taking advantage of the steric restriction offered by the C8TES molecules, a homogeneously mixed self-assembled monolayer (SAM) composed of octyltriethoxysilane (C8TES) and octadecyltrichlorosilane (OTS) was constructed by means of the stepwise method on Si(1 0 0) substrate. The kinetic formation processes of the pure and mixed SAMs were investigated by the advancing contact angle measurements, and the topographies of the sample surfaces were characterized by AFM. The experimental results showed that by coadsorption method, it was impossible to construct the mixed SAMs for C8TES and OTS system, since the difference of the chemical activities between C8TES and OTS molecules could not be simply balanced through the tailoring of the concentration ratios in the coadsorption solutions. However, by taking advantage of the steric restriction caused by the three ethoxyl groups on the heads of C8TES molecule as well as the difference of the chemical activities between C8TES and OTS molecules, it was possible to construct both the homogeneously and phase-separated mixed C8TES/OTS SAMs by means of the stepwise method. The molecular steric analysis and AFM scanning experiments by AFM cantilever probes with different spring constants also indicated that, the structure inside the pure C8TES SAM should be in a loose and unassembled state, which resulted in an ultra-low surface contact angle, ∼20°, on the C8TES SAM surface.

Fabricating tunable nanoparticle density gradients with the contact printing based approach

Recently, the generation of spatial gradient nanoparticle assemblies has attracted much attention. Such assemblies can be intriguing templates for building novel molecular architectures, and be employed as a combinatorial tool for quick determination of interaction selectivity for nanoparticles. In this communication, we report on convenient contact printing based techniques for generating lateral gradients containing nanoparticles with tunable geometry, scale and steepness. In the first method, octadecyltrichlorosilane (OTS) gradient surfaces were generated via the contact printing approach, and then spaces un-occupied by OTS molecules were back-filled with an amine-terminated silane, which allows the grafting of nanoparticles that were surface functionalized with carboxylic acid. By varying the size and geometry of the stamp, different geometrical gradients were generated. In addition, by changing the stamping procedures, either well-defined stepwise gradients or continuous gradients can be achieved. Furthermore, the contact printing based technique can be utilized in combination with diffusion of the aminosilane molecules to directly create its gradient, and consequently a nanoparticle density gradient.

Molecular dynamics study of optimal packing structure of OTS self-assembled monolayers on SiO 2 surfaces

Optimal packing structure of Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) adsorbed on a SiO 2 (1 0 0) surface with a Si substrate was studied performing molecular dynamics (MD) computational simulations. Molecular substitution, substitution pattern and molecular orientation of the OTS molecules on the SiO 2 (1 0 0) are the main factors studied in order to determine the optimal packing structure taking into account energetic balance. We have used the optimal packing structure to study other properties usually used to characterize SAMs as molecular and system tilt angles, film thickness and gauche defects. These properties and monolayer stability were studied performing MD simulations in a temperature range from 100 to 600 K and we found that results obtained agree with those from experimental measurements. We found that OTS films are stable up to 500 K. The optimal structure obtained could be used in further MD simulations studies in order to determine tribological properties of OTS–SiO 2 systems.