Monolayer Of 3-mercaptopropyl Trimethoxysilane Research Articles

Degradation mechanism of protected ultrathin silver films and the effect of the seed layer

In this work, we characterize the oxidation and degradation of protected silver thin films through the Kirkendall effect. We then present a solution to reduce the degradation of silver films exposed to a reactive oxidizing environment. In particular, we study the growth of silver deposited by magnetron sputtering on glass substrates pre-coated with three different underlayers: SiO2, ZnO and a self-assembled monolayer of (3-mercaptopropyl)trimethoxysilane (MPTMS). The films are then covered with a 2-nm barrier titanium film and exposed to reactive oxygen plasma. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy reveal that the degradation process begins with the migration of silver through the top titanium barrier. We quantify the degradation by comparing the atomic content of silver present at the top of the degraded samples. We find that in the case of the ZnO and SiO2, a significantly higher amount of silver migrates through the top barrier and onto the surface, as compared to the MPTMS-treated surface. We attribute this difference to the chemisorption of silver atoms to the MPTMS layer.

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.

Liquid crystal-gold nanoparticle composite-modified indium tin oxide (ITO) substrates and their electrochemical characterisation

ABSTRACTA simple efficient strategy for the simultaneous synthesis and anchoring of liquid crystal (LC)-stabilised gold nanoparticles (NPs) on indium tin oxide (ITO) substrate is described. A monolayer of 3-mercaptopropyltrimethoxy silane (MPS) compound was formed on ITO and quality of the monolayer was assessed using electrochemical techniques namely cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Gold NP preparation was carried out on this monolayer-modified substrate (and on bare ITO), in a single-step reaction, simply by drop-casting a solution containing an appropriate amount of chloroauric acid and a LC compound possessing a terminal amino group, on the MPS monolayer-modified substrate and heating (70degree) for 2-3 min.. The LC compound served as a reducing agent as well as a capping ligand. LC-capped NPs were chemically anchored onto the ITO substrate through bonding to thiol moiety of the MPS. The CV and EIS analysis of the MPS monolayer showed a complete blocking behaviour for the electron transfer across the electrode/electrolyte interface confirming the formation of a high-quality dense compact monolayer. On the other hand, upon immobilisation of LC-gold NP composite on self-assembled monolayer-modified ITO substrates, both CV and impedance studies showed a small current indicating the gold NP-mediated electron transfer, thus confirming the successful immobilisation of NPs.

Immobilization of azurin with retention of its native electrochemical properties at alkylsilane self-assembled monolayer modified indium tin oxide

Indium tin oxide (ITO) is a promising material for developing spectroelectrochemical methods due to its combination of excellent transparency in the visible region and high conductivity over a broad range of potential. However, relatively few examples of immobilization of redox proteins at ITO with retention of the ability to transfer electrons with the underlying material with native characteristics have been reported. In this work, we utilize an alkylsilane functionalized ITO surface as a biocompatible interface for immobilization of the blue copper protein azurin. Adsorption of azurin at ITO as well as ITO coated with self-assembled monolayers of (3-mercaptopropyl)trimethoxysilane (MPTMS) and n-decyltrimethoxysilane (DTMS) was achieved, and immobilized protein probed using protein film electrochemistry. The native redox properties of the protein were perturbed by adsorption directly to ITO or to the MPTMS layer on an ITO surface. However, azurin adsorbed at a DTMS covered ITO surface retained native electrochemical properties (E1/2=122±5mV vs. Ag/AgCl) and could exchange electrons directly with the underlying ITO layer without need for an intervening chemical mediator. These results open new opportunities for immobilizing functional redox proteins at ITO and developing spectroelectrochemical methods for investigating them.

Functionalized diatom silica microparticles for removal of mercury ions

Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH2) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g−1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.

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.

Growth and patterning of pt nanowires on silicon substrates

This paper describes a simple procedure for growing dense films of Pt nanowires directly on silicon substrates by modifying the surface through chemical or physical means. In the former, a self-assembled monolayer of (3-mercaptopropyl)-trimethoxysilane (MPTMS) is applied which can strongly bind Pt(0) nuclei to the surface through Pt S linkages. Once attached, the Pt(0) nuclei can act as catalytic sites for the growth of Pt nanowires along the 〈111〉 direction. Alternately, relief features are physically created on the surface in order to generate nucleation and binding sites for Pt(0) nuclei, due to the higher free energy associated with a rough surface. Additionally, Pt nanowires have been successfully produced in well-defined patterns by scouring grooves on the silicon surface or by photochemically patterning the MPTMS monolayers with a shadow mask. We have also measured the electrochemical properties of these immobilized or patterned Pt nanowires. The results provide an effective route to producing dense films of Pt nanowires with high surface areas for various electrochemical applications.

Preparation and tribological tests of thin fluoroorganic films

Adhesion, friction and consequent wear of sliding surfaces are the basic problems that limit the performance and reliability of microelectromechanical devices. Lubrication of these nano- and microscale contacts is different from traditional lubricants. Self-assembled monolayers (SAMs) chemically bonded to the substrate are considered to be the best solution of lubrication. The majority of these monolayers are hydrophobic providing low friction, adhesion and wear. Chemical vapor deposition was used to grow a fluorosilane film on silicon Si(1 0 0) and a condensed monolayer of 3-mercaptopropyltrimethoxysilane (MPTMS) on Au(1 1 1). The films were characterized by means of a contact angle analyzer for hydrophobicity, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) for identification of thin fluoroorganic monolayers deposited on silica surfaces and condensed monolayer MPTMS. Adhesion and friction measurements were performed using atomic force microscopy (AFM) and compared with measurements performed using a microtribometer operating in millinewton (mN) normal load range. Nanotribological measurements indicated that silica and MPTMS modified by fluorosilanes have the lowest friction coefficient and indicated a decrease friction coefficient with increasing fluoric alkyl chain length.

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.

A Tunnel Current in Self‐Assembled Monolayers of 3‐Mercaptopropyltrimethoxysilane

The current density-voltage (J-V) characteristics of self assembled monolayers of 3-mercaptopropyltrimethoxysilane (MPTMS) chemisorbed on the native oxide surface of p+-doped Si demonstrate the excellent tunnel dielectric behavior of organic monolayers down to 3 carbon atoms. The J-V characteristics of MPTMS SAMs on Si are found to be asymmetric, and the direction of rectification has been found to depend upon the applied voltage range. At voltages 10 carbon atoms) if the chain is chemisorbed at the electrodes. These results extend all previous experiments on such molecular tunnel dielectrics down to 3 carbon atoms. This suggests that these molecular monolayers, having good tunnel behavior (up to 2.5 eV) over a large bias range, can be used as gate dielectric well below the limits of Si-based dielectrics.

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).

Electrochemical evaluation of the corrosion protection of bi-dimensional organic films self-assembled onto brass

Monolayers of (3-mercaptopropyl)trimethoxysilane (MPTS) were grafted from ethanolic solution on electrochemically reduced brass surfaces. In a second step, hydrolysis of the trimethoxysilane functions (–Si(OMe) 3) has been carried out to anchor a second organic layer using either MPTS or (3-heptafluoroisopropoxy)propyltrichlorosilane (HIPS) molecules. XPS, PM-IRRAS and contact angle measurements have been employed to characterize each step of the modified surfaces. The corrosion inhibition properties of the modified surfaces were investigated by cyclic voltammetry (NaOH 0.1 M). Compared to the MPTS monolayer, a significant enhancement of the brass corrosion protection was observed for the bilayers.