silicon and silicon-monoxide

Nanometer wide silicon filaments embedded in an amorphous silicon oxide matrix are grown at low temperatures over a large area. The optical and electrical properties of these mixed-phase nanomaterials can be tuned independently, allowing for advanced light management in high efficiency thin-film silicon solar cells and for band-gap tuning via quantum confinement in third-generation photovoltaics.

Topics: Light; Luminescence; Nanostructures; Oxides; Silicon; Silicon Compounds; Solar Energy

The article reports on the selective adhesion of Bacillus cereus spores on patterned and heterogeneously wetted superhydrophobic silicon nanowires surfaces. Superhydrophilic patterns on superhydrophobic silicon nanowire (SiNW) surfaces were prepared by a standard optical lithography technique. Exposure of the patterned surface to a suspension of B. cereus spores in water led to their specific adsorption in superhydrophobic areas. Comparable results were obtained on a patterned hydrophobic/hydrophilic flat silicon (Si) surface even though a higher concentration of spores was observed on the hydrophobic areas, as compared to the superhydrophobic regions of the SiNW substrate. The surfaces were characterized using scanning electron microscopy (SEM), fluorescence spectroscopy, and contact angle measurements.

Topics: Bacillus cereus; Bacterial Adhesion; Hydrophobic and Hydrophilic Interactions; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Movement; Nanowires; Oxides; Silanes; Silicon; Silicon Compounds; Spores, Bacterial; Surface Properties; Water

Materials with chemical micropatterned surface have broad applications in many fields. In this article, we report a simple one-step UV lithography method to activate inert hydrocarbon monolayers for spontaneous formation of water and covalently immobilized protein micropatterns on the surface. Two types of hydrocarbon monolayers including octadecyltrichlorosilane (OTS) on silicon oxide and 1-hexadecene on hydrogen-terminated silicon were studied. It was found that after UV modifications, water can form micropatterns spontaneously on both surfaces. Furthermore, when protein solutions were used, covalently immobilized protein micropatterns can be formed. Our XPS results and controlled reducing experiments showed that UV exposure transformed inert monolayers into active surfaces with aldehyde groups, which are responsible for the covalent immobilization of proteins. The method reported herein can be applied under ambient conditions without having a high vacuum system. It can also be extended to pattern other biomolecules bearing amine groups.

Topics: Animals; Humans; Hydrocarbons; Immobilized Proteins; Oxides; Silanes; Silicon; Silicon Compounds; Ultraviolet Rays

The first gas-phase infrared spectra of silicon monoxide cations (SiO)(n)(+), n = 3-5, using multiple photon dissociation in the 550-1250 cm(-1) frequency range, are reported. All clusters studied here fragment via loss of a neutral SiO unit. The experimental spectra are compared to simulated linear absorption spectra from calculated low energy isomers for each cluster. This analysis indicates that a "ring" isomer is the primary contributor to the (SiO)(3)(+) spectrum, that the (SiO)(4)(+) spectrum results from two close-lying bicyclic ring isomers, and that the (SiO)(5)(+) spectrum is from a bicyclic ring with a central, fourfold-coordinated Si atom. Experiment and theory indicate that the energies and energetic orderings of (SiO)(n)(+) isomers differ from those for neutral (SiO)(n) clusters.

Topics: Adsorption; Algorithms; Cations; Isomerism; Nanoparticles; Oxides; Photons; Silicon; Silicon Compounds; Spectrophotometry, Infrared

The modification of silicon oxide with poly(ethylene glycol) to effectively eliminate protein adsorption has proven to be technically challenging. In this paper, we demonstrate that surface-initiated atom transfer radical polymerization (SI-ATRP) of oligo(ethylene glycol) methyl methacrylate (OEGMA) successfully produces polymer coatings on silicon oxide that have excellent protein resistance in a biological milieu. The level of serum adsorption on these coatings is below the detection limit of ellipsometry. We also demonstrate a new soft lithography method via which SI-ATRP is integrated with microcontact printing to create micropatterns of poly(OEGMA) on glass that can spatially direct the adsorption of proteins on the bare regions of the substrate. This ensemble of methods will be useful in screening biological interactions where nonspecific binding must be suppressed to discern low probability binding events from a complex mixture and to pattern anchorage-dependent cells on glass and silicon oxide.

Topics: Adsorption; Cell Adhesion; Chemistry, Physical; Light; Microscopy; Microscopy, Phase-Contrast; Models, Chemical; Oxides; Polyethylene Glycols; Polymers; Silanes; Silicon; Silicon Compounds; Silicon Dioxide; Spectrometry, X-Ray Emission; Surface Properties

Room temperature photoluminescence (PL) with a peak at 1.54 microns was observed from silicon oxide, silicon-rich silicon oxide, silicon nitride and silicon-rich silicon nitride films, all doped with Er and grown by the magnetron sputtering technique. To determine the optimum annealing temperature for the 1.54 microns PL, these films were annealed in the range of 600-1,100 degrees C with an interval of 100 degrees C. Among these four types of films annealed at an identical temperature, the intensity of 1.54 microns PL peak of the Er-doped silicon-rich silicon oxide film was always the strongest one, which arrived at a maximum in 800 degrees C annealing. A 1.38 microns PL band was also observed in each of these four types of films, and which in the silicon-rich silicon oxide or silicon-rich silicon nitride films was found to be correlated with the 1.54 microns PL band in intensity.

Topics: Chemical Phenomena; Chemistry, Physical; Erbium; Luminescence; Nanotechnology; Oxides; Silicon; Silicon Compounds; Temperature