Search results for "silicon"
showing 10 items of 1391 documents
Enzyme-responsive intracellular-controlled release using silica mesoporous nanoparticles capped with ε-poly-L-lysine.
2014
The synthesis and characterization of two new capped silica mesoporous nanoparticles for controlled delivery purposes are described. Capped hybrid systems consist of MCM-41 nanoparticles functionalized on the outer surface with polymer epsilon-poly-L-lysine by two different anchoring strategies. In both cases, nanoparticles were loaded with model dye molecule [Ru(bipy)(3)](2+). An anchoring strategy involved the random formation of urea bonds by the treatment of propyl isocyanate-functionalized MCM-41 nanoparticles with the lysine amino groups located on the epsilon-poly-L-lysine backbone (solid Ru-rLys-S1). The second strategy involved a specific attachment through the carboxyl terminus of…
Apposition of silica lamellae during growth of spicules in the demosponge Suberites domuncula: Biological/biochemical studies and chemical/biomimetic…
2006
Recently it has been discovered that the formation of the siliceous spicules of Demospongiae proceeds enzymatically (via silicatein) and occurs matrix guided (on galectin strings). In addition, it could be demonstrated that silicatein, if immobilized onto inorganic surfaces, provides the template for the synthesis of biosilica. In order to understand the formation of spicules in the intact organism, detailed studies with primmorphs from Suberites domuncula have been performed. The demosponge spicules are formed from several silica lamellae which are concentrically arranged around the axial canal, harboring the axial filament composed of silicatein. Now we show that the appositional growth o…
High Fluorescence of Thioflavin T Confined in Mesoporous Silica Xerogels
2013
Trapping of organic molecules and dyes within nanoporous matrices is of great interest for the potential creation of new materials with tailored features and, thus, different possible applications ranging from nanomedicine to material science. The understanding of the physical basis of entrapment and the spectral properties of the guest molecules within the host matrix is an essential prerequisite for the design and control of the properties of these materials. In this work, we show that a mesoporous silica xerogel can efficiently trap the dye thioflavin T (ThT, a molecule used as a marker of amyloid fibrils and with potential drug benefits), sequestering it from an aqueous solution and pro…
Novel silicon microparticles to improve sunlight stability of raw polypropylene
2015
Oxidation of polyolefins by ultraviolet/visible irradiation is a significant limitation for their use in several technological applications. The use of high-tech additives such as silicon microparticles becomes a compositing strategy that can improve the performance of these materials at long-term service conditions. Silicon particles were added to non-additivated raw polypropylene (PP) prepared by hot melt extrusion and subjected to accelerated sunlight irradiation tests. The stability of thermal properties, mechanical performance and thermal decomposition behaviour of composites was evaluated by differential scanning calorimetry, dynamic mechanical thermal analysis and thermogravimetry. T…
Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water
2016
Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a sub-nanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO2 and amorphous fully oxidized SiO2, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescen…
Boron doping of silicon rich carbides: Electrical properties
2013
Boron doped multilayers based on silicon carbide/silicon rich carbide, aimed at the formation of silicon nanodots for photovoltaic applications, are studied. X-ray diffraction confirms the formation of crystallized Si and 3C-SiC nanodomains. Fourier Transform Infrared spectroscopy indicates the occurrence of remarkable interdiffusion between adjacent layers. However, the investigated material retains memory of the initial dopant distribution. Electrical measurements suggest the presence of an unintentional dopant impurity in the intrinsic SiC matrix. The overall volume concentration of nanodots is determined by optical simulation and is shown not to contribute to lateral conduction. Remarka…
Determination of molecular stopping cross section of 12C, 16O, 28Si, 35Cl, 58Ni, 79Br, and 127I in silicon nitride
2015
Abstract Silicon nitride is a technologically important material in a range of applications due to a combination of important properties. Ion beam analysis techniques, and in particular, heavy ion elastic recoil detection analysis can be used to determine the stoichiometry of silicon nitride films, which often deviates from the ideal Si3N4, as well as the content of impurities such as hydrogen, even in the presence of other materials or in a matrix containing heavier elements. Accurate quantification of IBA results depends on the basic data used in the data analysis. Quantitative depth profiling relies on the knowledge of the stopping power cross sections of the materials studied for the io…
Advanced fragmentation stage of oxide coating on polymer substrate under biaxial tension
2005
Crack patterns of 100-nm-thick silicon oxide coating on polypropylene film subjected to equibiaxial stress loading are studied experimentally. The loading is achieved by means of a bulging cell mounted under an optical microscope with stepwise pressurization of film specimens. The evolution of the coating fragment area distribution at relatively high strains is modeled using Weibull statistics to describe the coating strength. The fragment area distribution at an advanced fragmentation stage is shown to scale with the average fragment area, the latter being a power function of the applied biaxial strain.
Sputtered SiOxNy thin films: improving optical efficiency of liquid crystal diffuser elements in multi-focal near-to-eye display architecture
2021
In this work we present reactive sputtered SiOxNy films with a variable refractive index as a convienent solution for contrast improvement of liquid crystal diffuser multi stacks in near-to-eye AR/VR displays. The focus concerns minimization of light reflections between internal structures, in particular ITO, by optimizing internal layers through tailored properties of thin film coatings, as well as subsequent laser patterning of thin film stack. Inorganic thin films have been deposited on glass by physical vapor deposition. Corresponding refractive index, thickness, uniformity and dielectric characteristics and other electro-optical properties have been measured and their impact on the res…
Polarization Insensitive Wavelength Conversion in a Low-Birefringence SiGe Waveguide
2016
We report the first demonstration of a single-pass dual-orthogonal-pump four-wave mixing-based wavelength conversion scheme in a silicon-based waveguide. The silicon germanium waveguide used was designed to exhibit strong TE/TM mode similarity across a broad wavelength range as well as a large nonlinear coefficient. A polarization-dependent loss of just 0.42 dB was measured, and the conversion of 40-Gb/s differential phase-shift keying signals was demonstrated with 1.5-dB power penalty at a bit error ratio of $10^{-9}$ .