Self-assembled Monolayer Of 3-mercaptopropyl Trimethoxysilane Research Articles

Chemically Deposited Sol–Gel Film on Porous TiO2 Nanotube Arrays as an Efficient and Unbreakable Solid-Phase Microextraction Fiber

In the present study, a novel technique was proposed to improve the performance of solid-phase microextraction fibers through the chemical deposition of polydimethylsiloxane/divinylbenzene film on modified TiO2 nanotube arrays substrate. Two different techniques, including the self-assembled monolayer of 3-mercaptopropyl trimethoxysilane and NaOH treatment, were examined to modify the surface of TiO2 nanotube arrays. The morphology of the prepared fibers was studied by scanning electron microscopy. The applicability of the novel fiber was evaluated through the headspace solid-phase microextraction of some polycyclic aromatic hydrocarbons as the model compounds followed by GC–MS determination. Influencing parameters on the extraction efficiency such as extraction time, temperature and salt content were studied and optimized. The thermal stability experiments demonstrated that the novel fiber was stable at 280 °C and reusable for more than 80 times without an obvious decrease in the extraction performance. The proposed method was successfully applied to the determination of PAHs in river water samples with good relative recoveries from 75.8 to 104.5% and the relative standard deviation values for all analytes were below 12%. Finally, the extraction performance of the prepared fiber was compared with those of commercially available fibers and similar previously reported fibers.

Controlled Growth of Gold Nanostars: Effect of Spike Length on SERS Signal Enhancement.

Two different types of gold nanostars (Au NS), namely, short-spiked nanostars (SSNS) and long-spiked nanostars (LSNS), are prepared by using a hexagonal lyotropic liquid-crystalline (LLC) phase as a template. The formation, size and length of spikes or arms of the resultant Au NS are controlled by preparation in either a hexagonal LLC phase or an isotropic phase. These NS are anchored onto indium tin oxide (ITO) electrodes through a self-assembled monolayer of 3-mercaptopropyltrimethoxysilane, which acts as a linker molecule. Structural and morphological characterisations of SSNS- and LSNS-anchored ITO electrodes are performed by means of microscopic and spectroscopic analyses. Further electrochemical techniques, namely, cyclic voltammetry and electrochemical impedance spectroscopy, are also used to confirm the immobilisation of these Au NS on ITO electrodes and to study the electrochemical characteristics. These studies clearly reveal the formation of star-shaped, branched, anisotropic nanostructures of gold during the template preparation method and these Au NS are successfully anchored onto ITO electrodes through a covalent immobilisation strategy. Furthermore, the SERS activity of these Au NS is analysed by using glutathione and crystal violet as analytes and by employing glass and ITO as substrates. It is interesting to note that SSNS show a significant enhancement in SERS signals relative to those of LSNS.

Self-Assembled Monolayer of Mixed Gold and Nickel Nanoparticles

Abstract Forming a monolayer of mixed nickel and gold nanoparticles through self-assembly via simple solution processing constitutes an important step toward inexpensive nanoparticle-based carbon nanofiber growth. In this work, mixed gold and nickel nanoparticles were anchored on the silicon wafer using self-assembled monolayers (SAMs) as a template. SAMs of 3-mercaptopropyl trimethoxysilane (MPTS-SAMs) were formed on silicon wafer, with the exposed thiol functionality providing ligand exchange sites to form the mixed monolayer of nickel and gold nanoparticles via a two-step sequential soaking approach. The densities of the nickel and gold nanoparticles on the surface can be varied by adjusting the soaking sequence.

Nanotribological characteristics of TiO2 films on sulphonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Silane coupling regent [3-mercaptopropyl trimethoxysilane (MPTS)] was prepared on silicon substrate to form two-dimensional self-assembled monolayer (SAM) and the terminal −SH group in the film was in situ oxidised to −SO3H group to endow the film with good chemisorption ability. Thus, TiO2 thin films were deposited on the oxidised MPTS-SAM to form composite thin films, making use of the chemisorption ability of the −SO3H group. Atomic force microscope (AFM) and contact angle measurements were used to characterise TiO2 films. Adhesive force and friction force of TiO2 thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. Results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. In order to study the effect of capillary force, tests were performed in various relative humidity. Results showed that the adhesive force of silicon substrate increases with relative humidity and the adhesive force of TiO2 thin films only increases slightly with relative humidity. Research showed that surfaces with more hydrophobic property revealed the lower adhesive and friction forces.

Fabrication of Micro- and Nano-Scale Gold Patterns on Glass by Transfer Printing

Nano-transfer printing is a soft-lithographic technique which allows the transfer of metal patterns deposited on a polymer stamp to different surfaces. The nano-transfer printing process allows various nanostructures to be formed without using sophisticated methods and expensive equipment. In the present work, we present the formation of gold micro- and nano-structures on a glass surface using a self-assembled monolayer as a transfer agent. A polydimethylsiloxane replica was fabricated from a master chip that has micro- and nano-meter size patterns. A thin gold layer was deposited on the replica stamp and the glass surface was modified with a self-assembled monolayer of 3-mercaptopropyltrimethoxysilane, followed by the transfer of the gold patterns from the polydimethylsiloxane stamp to glass by simple contact printing. The patterns sp obtained were characterized using scanning electron microscopy and optical microscopy.

Nano-tribological characteristics of lanthanum-based thin films on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was prepared on silicon substrate to form two-dimensional Self-Assembled Monolayer (SAM) and the terminal -SH group in the film was in situ oxidized to -SO 3H group to endow the film with good chemisorption ability. Thus, lanthanum-based thin films were deposited on oxidized MPTS-SAM to form rare earth composite thin films (RE thin films), making use of the chemisorption ability of the -SO 3H group. Atomic Force Microscope (AFM). X-ray Photoelectron Spectrometry (XPS), and contact angle measurements were used to characterize the RE thin films. Adhesive force and friction force of the RE thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. The results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. To study the effect of capillary force, tests were performed in various relative humidities. The results showed that the adhesive force of silicon substrate increased with relative humidity and the adhesive force of RE thin films only increased slightly with relative humidity. Research showed that surfaces with higher hydrophobic property reveal lowered adhesive and friction forces.

Preparation and characterization of lanthanum-based thin films on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Silane coupling regent (3-mercaptopropyl trimethoxysilane (MPTS)) is prepared on a single-crystal silicon substrate to form two-dimensional self-assembled monolayer (SAM). The terminal thiol groups (–SH) in the film is oxidized to sulfonic acid groups (–SO3H) in situ to enhance the chemisorption property of the film. Lanthanum-based thin films are deposited on the oxidized MPTS-SAM by means of chemisorption with the –SO3H group. The surface energy, chemical composition, phase transformation and surface morphology of the films are analyzed using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. The results show that MPTS is a self-assembled layer on the substrate and that the terminal –SH groups of the self-assembled MPTS films are closer to the air/silane interface than the silicon atoms. The study also shows that the treatment of SAM with 30% nitric acid (HNO3) at 80 °C in sufficient duration can completely transform the terminal groups in the top-most layer into desirable sulfonate groups. Then the substrates coated with the sulfonated MPTS-SAM were immersed in the RE solution to form lanthanum-based thin films. The experimental results indicate that the lanthanum-based thin films are adsorbed on oxidized MPTS-SAM and that the lanthanum element with different states of oxidation exists in the thin films that are deposited on the surface of self-assembly monolayers. Also, shape analyses of the La3+ XPS peaks reveal that the rare-earth film can react with the substrate by chemical bonding and that some lanthanum molecules are adsorbed on the MPTS-SAM. The above results show that it is the –SO3H group that has good chemisorption trend.

Enhanced CVD of Copper Films on Self-Assembled Monolayers as Ultrathin Diffusion Barriers

Copper films were produced by chemical vapor deposition (CVD) using the precursor Cu(II) bis-hexafluoroacetylacetonate on self-assembled monolayers of 3-mercaptopropyltrimethoxysilane (MPTMS)-modified substrate. X-ray diffraction and X-ray photoelectron spectroscopy results showed that the deposited copper was metal copper. The apparent activation energy of Cu CVD is changed from for the unmodified substrate to for the MPTMS-modified substrate. The growth rate on the MPTMS-modified substrate is approximately 2.2 times as much as on the unmodified one. The results indicate that the Cu CVD on MPTMS-modified substrate is enhanced. Moreover, Cu films which were formed on the oxidized MPTMS-self-assembled monolayer (SAM) surface ( terminated) behaved with higher affinity than those deposited on the MPTMS-SAM surface, a possible reason being that the terminal groups of SAMs accelerate the protonation of ligand hfac and its desorption from the surface.

Fowler–Nordheim tunnelling and electrically stressed breakdown of 3-mercaptopropyltrimethoxysilaneself-assembled monolayers

We report the confirmed occurrence of Fowler–Nordheim (FN) electron tunnelling inp+ Si (SiOx)/self-assembled monolayers of 3-mercaptopropyltrimethoxysilane (MPTMS)/Austructures. The statistically favoured values of the effective mass andenergy barrier heights for electrons are determined to be in the ranges0.15–0.18 me and 1.3–1.5 eV, respectively. The electrically stressed breakdownof the monolayers is observed to take place at very high fields,i.e. 16–50 MV cm−1. Prior to the breakdown, switching of FN currents between different conduction states wasobserved; this is found to be related to a change in the electrical properties of monolayersowing to the creation of field-induced defects.

Mechanical properties and tribological behavior of ZrO2 thin films deposited on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

A silane coupling reagent (3-mercaptopropyl)trimethoxysilane (abridged as MPTS) was self-assembled on a single-crystal Si substrate to form a two-dimensional organic monolayer (MPTS-SAM). The terminal –SH group in the MPTS-SAM film was in-situ oxidized to –SO3H group to endow the film with good chemisorption ability. Then ZrO2 thin films were deposited on the oxidized MPTS-SAM by way of the enhanced hydrolysis of aqueous zirconium sulfate (Zr(SO4)2·4H2O) in the presence of aqueous HCl at 50 °C, making use of the chemisorption ability of the –SO3H group. The thickness of the ZrO2 films was determined with an ellipsometer, while their morphologies and corresponding friction forces were analyzed by means of atomic force microscopy. The hardness and elastic modulus of the ZrO2 thin films were determined on a Nanoindentation II (MET) instrument. The macro-friction and wear behaviors of the ZrO2 films sliding against an AISI-52100 steel ball were examined on a unidirectional friction and wear tester and the worn surface morphologies observed on a scanning electron microscope (SEM). As the results, the as-deposited ZrO2 thin film at a deposition duration of 100 h is about 100 nm thick, it decreases to 48 nm after annealing at 500 °C and further decreases to 45 nm after heating at 800 °C. The as-deposited ZrO2 film is relatively rougher, with the rms to be about 1.0 nm, while the ZrO2 thin films heated at 500 and 800 °C have surface roughness rms of 0.76 nm and 0.68 nm, respectively. The ZrO2 film annealed at 800 °C has a high hardness to elastic modulus (H/E) ratio (0.062) as compared to the as-deposited ZrO2 film and the film annealed at 500 °C. Both the two annealed ZrO2 films show excellent wear-resistance as they slide against AISI-52100 steel at a normal load below 2.0 N, while the one annealed at 800 °C has better wear-resistance. The differences in the friction and wear behaviors of the as-deposited ZrO2 film, the ZrO2 film annealed at 500 °C and that annealed at 800 °C are attributed to their different micro structures and compositions. Since the ZrO2 films was well adhered to the underlying MPTS-SAM, it might find promising application in the surface-protection of single crystal Si and SiC subject to sliding at small normal load in microelectromechanical systems (MEMS).

Preparation, characterization and mechanical properties of Y2O3 thin film deposited on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Abstract Silane coupling reagent (3-mercaptopropyl)trimethoxysilane was self-assembled on a single-crystal Si substrate to form a two-dimensional organic monoalyer (MPTS-SAM) and the terminal –SH group in the film was in-situ oxidized to –SO3H group to endow the film with good chemisorption ability. Thus Y2O3 thin film were deposited on the oxidized MPTS-SAM, by enhanced hydrolysis of yttrium nitrate (Y(NO3)3 · 6H2O) solution in the presence of urea (CO(NH2)2) at 80 °C, making use of the chemisorption ability of the –SO3H group. The thickness and refractive index of the films were determined with an ellipsometer. The morphologies of the films were observed on an atomic force microscope. The adhesion strength and friction behavior of the films on the silicon substrate sliding against a steel ball was examined on a UMT-2MT friction and wear test system. It was found that the Y2O3-600 thin film was well adhered to the substrate with a critical load (Lc) of 2.8 N and had excellent antiwear and friction-reduction performance under a low load of 0.2 N. Thus the Y2O3 film might find promising application in the surface-protection of single crystal Si and SiC in microelectromechanical systems (MEMS).

Preparation and characterization of ZrO 2 thin film on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was prepared on single-crystal Si substrate to form two-dimensional self-assembled monolayer (SAM) and the terminal SH group in the film was in situ oxidized to SO 3H group to endow the film with good chemisorption ability. Thus, ZrO 2 thin film were deposited on the oxidized MPTS-SAM, by enhanced hydrolysis of zirconium sulfate (Zr(SO 4) 2·4H 2O) solution in the presence of HCl at 70 °C, making use of the chemisorption ability of the SO 3H group. The thickness of the films was determined with an ellipsometer, while the chemical feature, phase composition, thermal stability, and morphology of the films were analyzed by means of Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, and atomic force microscopy. As the results, the as-deposited ZrO 2 film was composed of nanocrystalline tetragonal ZrO 2 (t-ZrO 2) and an amorphous basic zirconium sulfate. The annealing of the films at 500 °C led to crystallization to t-ZrO 2, while further heating to 800 °C eliminated S in the film, and the ZrO 2 film consisted of nanocrystalline tetragonal ZrO 2 and monoclinic ZrO 2 in this case. The as-deposited ZrO 2 thin films were compact and crack-free, showing quadratically-looking features which were not observed previously, while the thickness of the ZrO 2 films decreased with increasing annealing temperature. Since the ZrO 2 film was well adhered to the MPTS-SAM, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).