Octadecyltrimethoxysilane Self-assembled Monolayer Research Articles

Time-of-Flight Secondary Ion Mass Spectrometry Analyses of Self-Assembled Monolayers of Octadecyltrimethoxysilane on SiO2 Substrate

The self-assembled monolayers (SAMs) of organosilanes formed on an oxide substrate are thought to have a polymerized –Si–O–Si– network due to the homocondensation of silanols of hydrolyzed silane headgroups, which is the most significant difference in the SAMs of organosilanes in comparison with those of alkanethoils and organophsosphonic acids. In order to explore the interface chemistry of organosilane SAMs, surface-sensitive time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to compare ion fragmentation differences between the SAMs of octadecyltrimethoxysilane (OTMS) formed on a SiO2 substrate and free OTMS molecules, as well as oxide substrate. The ability of ToF-SIMS to verify the hydrolysis of the methoxy groups of OTMS molecules and to assess the polymerized –Si–O–Si– network in their SAMs was demonstrated, which shows that ToF-SIMS provides unique information to help us understand the interface chemistry of OTMS SAMs formed on oxides.

Quantitative Analysis of Scattering Mechanisms in Highly Crystalline CVD MoS2through a Self-Limited Growth Strategy by Interface Engineering

The electrical performance of highly crystalline monolayer MoS2 is remarkably enhanced by a self-limited growth strategy on octadecyltrimethoxysilane self-assembled monolayer modified SiO2 /Si substrates. The scattering mechanisms in low-κ dielectric, including the dominant charged impurities, acoustic deformation potentials, optical deformation potentials), Fröhlich interaction, and the remote interface phonon interaction in dielectrics, are quantitatively analyzed.

Fabrication of free‐standing albumin‐nanosheets having heterosurfaces

Sheet-shaped carriers, having both obverse and reverse surfaces and thus a large contact area for targeting a site, have several advantages over spherical-shaped carriers, which have an extremely small contact area for targeting sites. Here, we proposed a novel method to prepare a free-standing ultrathin and biocompatible nanosheet having heterosurfaces, by a combination of four processes: (1) specific adsorption of recombinant human serum albumin (rHSA) molecules onto a patterned octadecyltrimethoxysilane self-assembled monolayer region (ODS-SAM), (2) preparation of nanosheets of rHSA molecules bearing thiol groups (SH-rHSA) via two-dimensionally disulfide crosslinking, (3) surface modification of the resulting nanosheet, and (4) preparation of the free-standing nanosheet by detachment from the ODS-SAM. The SH-rHSA molecules at pH 5.0 and a concentration of 1 microg/mL were specifically adsorbed on the patterned ODS-SAM regions by hydrophobic interaction, and were two-dimensionally crosslinked in the presence of copper ion as an oxidant. The rHSA-nanosheets were then simply detached from the ODS-SAM by treatment with surfactant. We succeeded in the preparation of rectangular (10 microm x 30 microm) and ultrathin (4.5 +/- 1.0 nm) rHSA-nanosheets on a patterned ODS-SAM, and could also obtain free-standing rHSA-nanosheets having heterosurfaces by surface modification with fluorescent latex beads. Thus, the rHSA-nanosheets having heterosurfaces could be regarded as a new biomaterial for drug carriers, hemostatic reagents, wound dressing for burn injury, and so forth.

Studies on flow behaviors of polymer melts in nanochannels by wetting actions

The flow behavior of polymer melts in nanochannels by wetting actions was investigated by statistical analyses of generated polymer nanofibers' length in nanochannels of nanoporous alumina template using Scanning Electron Microscopy. The polyethylene nanofibers with high aspect ratio are formed after the infiltration of melts into the alumina nanochannels by wetting actions. The wetting of polyethylene melts in nanochannels is a rapid process due to the high surface free energy of inner walls and wetting driven force. Wetting and flow rate of polymer melts in nanochannels are mainly dependent on the wetting temperature, the size of nanochannels and surface properties of nanochannels adjusted by octadecyltrimethoxysilane self-assembled monolayers. High surface free energy and solid–liquid interaction between melts and surface lead to noticeable flow of polymer melts in nanochannels at the wetting stage.

Submicron optical near-field diffraction patterns obtained by irradiation of octadecyltrimethoxysilane self-assembled monolayers with light at 157 nm

Nanostructures less than 200 nm in size are created by the Fresnel diffraction of 157 nm light at the aperture margins of a photomask through proximity irradiation of an octadecyltrimethoxysilane self-assembled monolayer. Photochemical decomposition of the organic monolayer creates complex nanostructure patterns, according to the light intensity distribution at the substrate location. Dimensions and distribution of the nanostructures correlate well with the spatial distribution of the light intensity calculated using the Fresnel equations.

Self‐Assembled Octadecyltrimethoxysilane Monolayers Enabling Selective‐Area Atomic Layer Deposition of Iridium

A preparation method for octadecyltrimethoxysilane (ODS) self‐assembled monolayers (SAMs) that enables the selective‐area ALD of iridium is studied using an ALD process for iridium at 225 °C. ODS SAMs were prepared from the gas phase by two preparation methods: either with exposure to ODS only, or with alternate exposures to ODS and water. SAMs were patterned with a lift‐off process using aluminium as a mask layer.

Assembly of hydrothermally synthesized tin oxide nanocrystals

We have successfully assembled highly crystalline tin oxide nanoparticles, which were synthesized through a simple hydrothermal approach, onto the chemical template of octadecyltrimethoxysilane self-assembled monolayer (OTS-SAM). Tin oxide nanoparticles were synthesized by refluxing ethanol containing 0.1M of tin (IV) chloride pentahydrate at 70°C for 3h, and subsequently hydrothermally treating the resulted precipitates at 200°C for 80h. As a result, we could obtain the highly crystalline tin oxide nanoparticles. The average particle size and its distribution were estimated by high-resolution transmission electron microscopy observation to be about 5.8nm and 27.6%. Area-selective assembly of tin oxide nanoparticles was performed by dipping a few drops of the suspension containing the nanoparticles onto the OTS-SAM template-covered silicon substrates, and then sonicating the substrate covered with the dried suspension in absolute toluene for 10min. The nanoparticles assembled on the methyl-covered regions of the template were easily eliminated from the surface by the sonication, while those on the silanol-covered regions of the template remained tightly adhered to the substrate surface. As confirmed by atomic force microscopy, one-dimensional microarray of tin oxide was achieved on the substrates.

Electron Beam Lithography on Organosilane Self-Assembled Monolayer Resist

We report a result of a feasibility study on the application of an octadecyltrimethoxysilane self-assembled monolayer to a resist film for electron beam lithography. The self-assembled monolayer deposited on a silicon dioxide surface by chemical vapor deposition is resistant to both sulfuric acid and hydrofluoric acid. By immersing the electron-beam-irradiated surface into both acids, we successfully develop microstructural patterns in the self-assembled monolayer. In particular, we show the effectiveness of immersing the substrate into a sulfuric-acid-based solution for the development of the pattern. The relationship between the required dose and the developing time is estimated by measuring the morphology of the developed patterns by atomic force microscopy. The pattern in the self-assembled monolayer can be transferred into both the underlying silicon dioxide layer and the silicon substrate. These results indicate that the organosilane self-assembled monolayer serves as an alternative resist for electron beam lithography.

Reliable Monolayer‐Template Patterning of SnO2 Thin Films from Aqueous Solution and Their Hydrogen‐Sensing Properties

AbstractWe demonstrate a novel lithographic technique utilizing a solvent to fabricate a chemically based semiconductor microdevice from an aqueous solution. According to this technique, SnO2 thin film could be integrated onto predefined sites on a SiO2/Si wafer. A patterned octadecyltrimethoxysilane self‐assembled monolayer (ODS‐SAM) was prepared by vacuum ultraviolet (VUV) irradiation through a photomask to use as a template for the fabrication of a micropatterned SnO2 thin film on the SiO2/Si surface. A Sn‐based thin film was then deposited onto the entire surface of the ODS template from an aqueous solution containing 0.03 mol L–1 of SnCl2·2H2O at 60 °C for 16 h in an ambient atmosphere. The thin film deposited on the methyl‐terminated area of the template was then peeled using an ultrasonic rinse in anhydrous toluene for 30 min, while the film deposited on the silanol area remained intact and undamaged. Rinsing in hydrophilic solvents did not facilitate peeling of the thin film from the methyl‐terminated area. We succeeded by this process in obtaining a high‐resolution, micropatterned Sn‐based thin film on an ODS‐SAM template on Si. The as‐deposited film was composed of fine Sn‐based particles. The sensitivity of this SnO2 thin film to H2 gas increases linearly with improving crystallinity. The effectiveness of anhydrous toluene as a rinse in solution lithography is discussed from the viewpoint of the high hydrophobic affinity between the rinse solvent and the terminal groups in the monolayer template.

Patterning of DNA nanostructures on silicon surface by electron beam lithography of self-assembled monolayer.

Nanoscale patterns of modified oligonucleotides are produced on octadecyltrimethoxysilane self-assembled monolayers at a silicon surface by electron beam lithography. DNA structures with feature sizes of the order of 250 nm were detected by epi-fluorescence microscopy.