Octadecyltrichlorosilane Solution Research Articles

A comprehensive study of the effects of different factors on anti-relaxation properties of octadecyltrichlorosilane-coated rubidium vapor cells

Anti-relaxation coatings play an important role in enhancing the polarization lifetime of polarized alkali-metal atoms. In this study, octadecyltrichlorosilane (OTS) was coated in spherical rubidium vapor cells fabricated using borosilicate glass with two stems as anti-relaxation coatings. An orthogonal experiment method was employed to obtain the optimal conditions. The results showed that OTS concentration is the dominant factor in the number of bounces, followed by the soaking time and molar ratio/(H2O:OTS). The optimal parameters were 6 mM of OTS, 6:1 of molar ratio/(H2O:OTS), and 80 min of soaking time. The number of bounces can be up to 200. Atomic force microscope images showed that the number and coverage ratio of clusters on the anti-relaxation coating fabricated by the optimized parameters are significantly less than the number and coverage ratio of clusters formed by other conditions. This means that the clusters in the coatings significantly affect the anti-relaxation performance. In addition, five OTS-coated cells were fabricated by A3B3C5 combination. However, the variability from cell to cell using the exact same preparation procedure can be up to 43.6%. The variability may be caused by the different aging times of the OTS solution. Because only one beaker of OTS solution was prepared, the OTS solution was pumped into the cells in sequence, not at the same time.

Photochemically Produced Superhydrophobic Silane@polystyrene‐Coated Polypropylene Fibrous Network for Oil/Water Separation

Cost-effective separation of oil and immiscible organic contaminants from water has become an urgent challenge to protect aquatic and human life from devastating effects. Therefore, it has become imperative to develop super-selective materials for efficiently separating oil from water. In this work, a superhydrophobic surface has been formed that consists of a silane@polystyrene-coated polypropylene fibrous network (silane@PS-PPF) for efficient separation of accidentally spilled oil from water. The superhydrophobic PPFs were designed by a simple, cost-effective two-step process that includes photochemically controlled polymerization of styrene and subsequent dip coating in octadecyltrichlorosilane solution. The hydrophobic surface (CA=129°±4°) of the PS coated PPF after treating with silane was turned into a superhydrophobic body (CA=161°±2°). The achieved silane@PS-PPF fibrous network selectively allowed the fast permeation of the oils and non-polar organic liquids by altogether rejecting water during operation. The separation efficiency for various oils from the contaminated water was 96 to 99%, with a high flux in the range of 7606±312 L m-2 h-1 to 9870±151 L m-2 h-1 . Apart from being used as a filter, the silane@PS-PPF was also used as an oil absorber and has shown an absorption capacity in the range of 1185 to 1535% for various oils. We anticipate that the developed silane@PS-PPF, due to its facile synthetic route, cost-effectiveness, and high performance, can be effectively used in oily wastewater treatment and clean-up of large oil spills from water.

Functionalization of electropolished titanium surfaces with silane-based self-assembled monolayers and their application in drug delivery

This work reports a novel and reproducible route for the successful modification of the surface of titanium (Ti) with self-assembled monolayers (SAMs). By electropolishing the surface of Ti, suitable physical/chemical surface properties were obtained for adequate growth of OctadecylTrichloroSilane (OTS) based SAM. Optimum conditions to achieve a well-organized and densely packed OTS film were also determined by monitoring the effect of different parameters including time, concentration, and temperature for OTS adsorption. The optimum conditions for the formation of an OTS–SAM were found to be upon immersion of the electropolished Ti substrate in a 10mM OTS solution at 10°C for 24h. Furthermore, multiple growth regimes for the formation of OTS–SAM on electropolished Ti surface were observed. The kinetics for the self-assembly were fast at the beginning of OTS adsorption, but rapidly slowed down after 10h of immersion, i.e. during the densification process of the film at the surface of Ti. In addition, the growth behavior was found to be random as opposed to the island growth behavior usually observed with OTS at the surface of silica. The successful implementation of OTS–SAM was further investigated through the immobilization and delivery of a model drug and the OTS monolayer showed clear abilities in drug delivery with an initial burst release up to 5days followed by a sustained release up to 26days.

Organic field-effect transistor with octadecyltrichlorosilane (OTS) self-assembled monolayers on gate oxide: effect of OTS quality

The effect of OTS (octadecyltrichlorosilane) Self-Assembled Monolayer (SAM) grafted on SiO2 gate dielectric of pentacene-based OFETs (organic field-effect transistors) is investigated. A significant improvement of the charge mobility (μ), up to 0.74 cm2/V s, is reached thanks to OTS treatment. However, in spite of improved performances, several drawbacks, such as an increase in mobility dispersion, substantial hysteresis in IDS-VG characteristics and high threshold voltages (VT), are observed. Changing solvent and deposition method turns out to have no significant effect on the mobility dispersion. A more accurate approach on the evolution of the mobility and the threshold voltage dispersion with OTS storage time highlights the effect of the OTS solution aging. Even if no difference is evidenced in the surface energy and roughness of the OTS layer, electrical characteristics exhibit considerable deterioration with OTS solution storage time. Using an “aged” OTS solution, opened under air, kept under argon and distilled before use, results in an increase of the IDS-VG hysteresis as well as in VT and in mobility dispersion. In comparison, fresh-OTS-based OFETs present a very low hysteresis, a threshold voltage close to 0 and a much lower mobility dispersion. It is demonstrated that aged OTS solutions contain impurities that are not removed by distillation process, which leads to a less densely packed layer causing interfacial charge traps thus deteriorated performances.

Development of hydrogel microstructures on single-walled carbon nanotube films

In this study, the development of polyethylene glycol (PEG) hydrogel microstructures led to the micropatterning of single-walled carbon nanotube (SWCNT) films. Polyethylene glycol was patterned in a process analogous to photolithography in order to manufacture high-density arrays of micrometer-scale hydrogel wells on SWCNT film surfaces. These microwells were composed of hydrophobic SWCNT films surrounded by hydrophilic PEG hydrogel walls. Effects of PEG hydrogel microstructures on the micropatterning of SWCNT films were systematically investigated under different substrates prepared with 3-(trichlorosilyl)propyl methacrylate or octadecyltrichlorosilane solution. A characterization of protein adsorption and an electrochemiluminescence (ECL) reaction were performed to evaluate the biocompatible and electrical efficiency of the patterned SWCNT films in various applications. The proteins selectively adhered to the SWCNT surface inside the microwells, while adherent proteins were absent from the hydrogel walls. In the ECL reaction, the SWCNT films patterned with PEG hydrogel exhibited good, stable ECL behavior, a sign that patterned SWCNT films can be used as flexible and transparent electrodes.

Low-operating-voltage polymer thin-film transistors based on poly(3-hexylthiophene)

Polymer-based thin film transistors (PTFTs) with poly(3-hexylthiophene) (P3HT) as semiconducting active layers are successfully fabricated on silicon substrates in air which are used as gate electrods. HfTiO film deposited by RF sputtering method is used as gate insulators,and gold metal is used as source and drain electrodes. The HfTiO surface is modified by using octadecyltrichlorosilane solution in the fabrication process. Experimental results indicate that the PTFTs show good saturation behaviors at low drive voltages (-2 cm2/V ·s. The frequency-dependence and hysteresis effect are observed in the C-V measurements for the metal-polymer-oxide-silicon (MPOS) capacitors,and discussed in detail to understand their physical mechanism.

Variable‐Focus Liquid Microlenses and Microlens Arrays Actuated by Thermoresponsive Hydrogels

Traditional optical systems utilize mechanical parts (e.g., gears, motors, and drivers) to allow adjustable focusing and magnification. Emerging variable-focus microlenses have exhibited the potential to miniaturize and advance optical systems without the need for mechanical parts, impacting significantly on a multitude of fields, such as cameras, biomedical instruments, and lab-on-a-chip systems. A variety of variable-focus liquid microlenses have been demonstrated based on different mechanisms, including reorientation of liquid crystals, electrowetting of a liquid droplet, and mechanical actuation of polymeric materials. These microlens technologies rely on external controls and power supplies; for example, additional electric fields are necessary to drive both electrowetting liquid microlenses and liquid-crystal microlenses, and external actuation devices are required to control the pressure in flexible polymer microlenses. The requirement for additional discrete components increases the complexity and makes integration, especially in lab-on-a-chip applications, challenging. We are interested in taking advantage of smart materials to realize variable-focus liquid microlenses without requiring external controls and power supplies. Responsive hydrogels are smart materials that undergo significant and reversible volume change in response to environmental stimuli by absorbing and releasing water through the network interstitials of the hydrogels. The ability to convert chemical energy directly into mechanical work means that the hydrogels can function as sensors, actuators, and power sources in specific conditions (e.g., the human body) where most external controls and power supplies are limited or difficult to obtain. By taking advantage of responsive hydrogels, we previously reported an innovative approach for realizing smart-liquid microlenses responsive to environmental changes. The liquid microlens extends the concept of pinned liquid/liquid interfaces to apertures to form a liquid microlens. A hydrogel ring located within a microfluidic channel responds to an environmental change by expanding and contracting, which regulates the shape of a water/oil interface (i.e., a liquid microlens), thus, tuning the focal length of the microlens. In this paper, we demonstrate thermoresponsive variable-focus cylindrical microlenses and spherical microlens arrays formed using liquid/liquid interfaces. Thermoresponsive reversible N-isopropylacrylamide (NIPAAm) hydrogels were employed; unconstrained NIPAAm hydrogels swell by as much as a factor of ten when the temperature decreases from above to below the hydrogel’s lower critical solution temperature (LCST). First, arbitrary shapes of microlenses (e.g., cylindrical and spherical) can be realized by patterning apertures that have corresponding shapes (e.g., rectangular and circular, respectively). This benefits the implementation of various microlenses with different shapes, among which variable-focus cylindrical lenses are of strong interest for a multitude of optical applications such as stretching an image, focusing light into a slit, and correcting low-order aberration. Second, we extended single variable-focus spherical microlenses to microlens arrays, allowing the devices not only to have wide-angle observation and parallel optical signal acquisition, but also to implement combinatorial interrogation of complicated environments in microfluidics by individually regulating the focal lengths of the microlens elements. In a typical variable-focus cylindrical microlens (Fig. 1a), a rectangular window was photopatterned in a 250 lm thick polymer slip to form an aperture. The sidewall of the aperture was treated to be hydrophilic (water contact angle of 29°) through an oxygen plasma treatment; the top-side surface of the aperture was rendered hydrophobic (water contact angle of 118°) by coating it with an octadecyltrichlorosilane solution. Thus, a hydrophobic/hydrophilic contact line coincided at the boundary between the sidewall and top-side surface of the aperture. A thermoresponsive NIPAAm hydrogel (LCST = 32 °C) ring was photopatterned in a 750 lm deep microfluidic channel. When the hydrogel ring was filled with deionized water through the aperture, a water meniscus emerged from the rectangular aperture, and the peripheral boundary of the meniscus was pinned stably at the hydrophobic/hydrophilic contact line. Mineral oil was stored within a C O M M U N IC A IO N

Preparation of Submicron-Structured Alkylsiloxane Monolayers Using Prepatterned Silicon Substrates by Laser Direct Writing

A new constructive method for the preparation of laterally structured alkylsiloxane monolayers is demonstrated. Laser direct writing has been used to create oxide patterns on H-terminated Si(100) samples under ambient conditions. Depending on the laser power and the writing speed, oxide structures with a lateral resolution below 500 nm are prepared routinely. The patterned samples are suitable as temporary templates for the preparation of laterally structured octadecylsiloxane monolayers. Prior to immersion in an octadecyltrichlorosilane solution, however, hydration of the samples in water is essential to facilitate a selective coating of the oxidized areas. After coating, atomic force microscopy reveals the formation of octadecylsiloxane islands exclusively on top of the oxide lines.

Site-selective deposition and micropatterning of tantalum oxide thin films using a monolayer

We developed a novel process to fabricate a micropattern of tantalum oxide thin film on a patterned self-assembled monolayer (SAM) using the gradual hydrolysis reaction of tantalum ethoxide. SAM of octadecyltrichloro-silane (OTS) was prepared on a Si substrate from an OTS solution. The OTS-SAM was irradiated with UV light through a photomask to form methyl group and silanol group patterns on a substrate. The patterned OTS-SAM was then immersed in a tantalum ethoxide solution to selectively deposit thin films on silanol group regions. Site-selective deposition of amorphous tantalum compound was realized and a micropattern of the thin films was successfully fabricated at room temperature. The thin film was characterized to have the composition, Ta 2O 5·4H 2O (Ta 2O(OH) 8) by XRD, XPS, FT-IR and TG-DTA. The amorphous thin film transformed into crystalline Ta 2O 5 after annealing at 800 °C for 2 h in air. The feature edge acuity of the micropattern remained unchanged by the annealing and thus a micropattern of Ta 2O 5 thin film was successfully fabricated.

Differentiation of field-induced and native oxide using selective formation of self-assembled monolayer

The formation process of an alkylsiloxane self-assembled monolayer (SAM) on silicon oxide produced under various conditions was investigated. The growth rate of octadecyltrichlorosilane (OTS) SAM was dependent on the moisture level in the oxidation system. Area-selective oxidation of a silicon substrate with a native oxide layer was carried out under controlled humidity conditions by the field induced oxidation (FIO) technique using an atomic force microscope with a conductive cantilever. The silicon substrate partly FIO oxidized under dry nitrogen was immersed into the OTS solution, and the contact angle and topographic image showed that the OTS layer was formed only on the native oxide. In contrast, when the FIO was performed under a humidity of 88%, OTS SAM was formed both on FIO and native oxides. These results indicate that SAM formation on silicon oxides can be locally suppressed by FIO in a dry environment. Using this technique, we could fabricate an OTS SAM line structure as narrow as 22 nm.

Neutron reflection study of bovine beta-casein adsorbed on OTS self-assembled monolayers.

Specular neutron reflection has been used to determine the structure and composition of bovine beta-casein adsorbed on a solid surface from an aqueous phosphate-buffered solution at pH 7. The protein was adsorbed on a hydrophobic monolayer self-assembled from deuterated octadecyltrichlorosilane solution on a silicon (111) surface. A two-layer structure formed consisting of one dense layer of thickness 23 +/- 1 angstroms and a surface coverage of 1.9 milligrams per square meter adjacent to the surface and an external layer protruding into the solution of thickness 35 +/- 1 angstroms and 12 percent protein volume fraction. The structure of the (beta-casein) layer is explained in terms of the charge distribution in the protein.