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Porous Silicon Surface (porous + silicon_surface)
Selected AbstractsPorous silicon surfaces for metabonomics: Detection and identification of nucleotides without matrix interferencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007D. Gómez Abstract In present work, porous silicon surfaces (PSS) have been developed for time of flight mass spectrometric experiments (TOF-MS) in the monitoring of nucleotides, commonly found as metabolites in the cell. The mass range of the studied molecules (, 400 amu) is common to several important messengers and other metabolites. Different porosified surfaces have been developed by means of electrochemical etching and different degree of porosity and pore size achieved as function of silicon dopant concentration, silicon resistivity, current density and the presence or absence of illumination along the process. As main conclusion, it can be said that an interesting commercial nucleotide (Cyclic adenosine monophosphate, c-AMP) has been detected on low concentrations (,hundreds of femtomols) for some of the fabricated porous surfaces. Taking into account that these concentrations are similar to the ones found in real samples, this result opens the possibility to the fabrication of DIOS (Desorption Ionization On Silicon) chips for the detection of nucleotides in biological fluids. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Possible model of protein nucleation and crystallization on porous siliconPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005S. Stolyarova Abstract The problem of macromolecular nucleation and crystallization on porous silicon surface is investigated theoretically. The fractality of the porous silicon layer is exploited. It is shown that the effective surface density of adsorbed particles on a fractal self-similar surface significantly exceeds that on a flat surface. The resulting local supersaturation explains enhanced nucleation phenomena associated with porous silicon. In addition, the self-affine fractal surface exhibits quasi-periodicity that can facilitate long-range ordering of the nucleated molecules, i.e. the crystallization process. Moreover, small elastic constants of porous silicon are favorable for the surface periodicity tuning to different lattice parameters of growing crystals. The anomalous large scaling range (from silicon interatomic distance up to 100 nm) is favorable for the crystallization of wide range of big macromolecules such as proteins. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] EPR and photoluminescence diagnostics of singlet oxygen generation on porous silicon surfacePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2009E. A. Konstantinova Abstract Electron paramagnetic resonance and photoluminescence spectroscopy are used to investigate photosensitized generation of singlet oxygen in the porous silicon layers. The singlet oxygen concentration in the samples was estimated at various oxygen pressures. The time of energy transfer from excitons confined in Si nanocrystals to adsorbed O2 molecules on silicon nanocrystal surface and photosensitization efficiency are found to depend on the porosity of the samples. The singlet oxygen generation efficiency increases strongly for porous silicon with high (>80%) porosity. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Physical adsorption vs. chemical binding of undecylenic acid on porous silicon surface: a comparative study of differently functionalized materialsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2009E. Pastor Abstract To imply miscibility to porous silicon (PSi) used for biomedical purposes a number of functionalization methods are employed. In order to distinguish between a non-specific surfactant-like interaction (physical sorption) and chemical binding of unsaturated chemicals (undecylenic acid, UD) to H-terminated PSi surface we studied the two differently treated materials. Differential scanning calorimetry (DSC) and thermogravimetry (TGA), BET and FTIR measurements were performed with the PSi powder samples (n+ doped). Changes in surface area, weight loss, calorific effect and chemical composition that accompanied the thermal treatment have shown that the physisorbed UD molecules undergo a chemical process (binding) with the Si-Hx surface groups at about 150 °C in both, N2 inert atmosphere and in a synthetic air, oxidative atmosphere. Controlled conversion of physically sorbed molecules to the chemically attached ones is discussed with respect to methods of surface modification of PSi materials for increasing their biocompatibility. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Peculiarities of ozone adsorption on a porous silicon surface at low temperaturePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007V. B. Pikulev Abstract Interaction between ozone molecules and silicon nanocrystallites in porous silicon (por-Si) results in effective luminescence similar to optically excited emission but the mechanism still is not quite understood. To study the process the kinetics of both adsorption and oxidation of highly porous silicon surface under exposure to ozone (16O3 and 18O3) at low temperatures were measured using FTIR- and luminescence spectroscopy. It is shown that ozone chemisorption on por-Si surface takes place yet at liquid oxygen temperature. The oxide coat formed instantly after ozone admission inhibits further oxidation and results in the predominance of ozone physisorption. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of iodine molecule adsorption on electronic properties of porous silicon studied by FTIR and EPR spectroscopyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007L. A. Osminkina Abstract The infrared absorption and electron paramagnetic resonance spectroscopy are used for studying the effect of adsorption of iodine (I2) molecules, strong acceptors of electrons, on the electronic properties of silicon nanocrystals in micro- and mesoporous silicon layers with different types of doping impurities. It is found that the concentration of free charge carries (holes) in silicon nanocrystals, obtained by electrochemical etching of p-type and n-type silicon wafers, sharply increases in the presence of I2 molecules. At the same time the decrease of the dangling silicon bonds (Pb -centers) concentration is observed. A microscopic model proposed for explaining this effects presumes the formation of donor-acceptor pairs (Pb1+ -I2,), and shallow acceptor states on the porous silicon surface which, together with the initial dopant and surface defect states, specify the charge carrier type and concentration in the silicon nanocrystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hybrid metal/silicon nanocomposite systems and their catalytic activityPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2009Sergej Polisski Abstract In this work we studied the reduction of metal salts and their mixtures on extended hydrogen-terminated porous silicon surfaces. For these experiments we employed salts of Au, Ag, Pt and their mixtures. We show that the size and shape of resulting metal and metal alloy nanoparticles depends on the pore morphology. This has been confirmed by transmission electron microscopy measurements and plasmon resonance experiments. Finally we demonstrate catalytic activity of formed Pt nanoparticles in PSi matrix via monitoring the conversion of carbon monoxide. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Porous silicon surfaces for metabonomics: Detection and identification of nucleotides without matrix interferencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007D. Gómez Abstract In present work, porous silicon surfaces (PSS) have been developed for time of flight mass spectrometric experiments (TOF-MS) in the monitoring of nucleotides, commonly found as metabolites in the cell. The mass range of the studied molecules (, 400 amu) is common to several important messengers and other metabolites. Different porosified surfaces have been developed by means of electrochemical etching and different degree of porosity and pore size achieved as function of silicon dopant concentration, silicon resistivity, current density and the presence or absence of illumination along the process. As main conclusion, it can be said that an interesting commercial nucleotide (Cyclic adenosine monophosphate, c-AMP) has been detected on low concentrations (,hundreds of femtomols) for some of the fabricated porous surfaces. Taking into account that these concentrations are similar to the ones found in real samples, this result opens the possibility to the fabrication of DIOS (Desorption Ionization On Silicon) chips for the detection of nucleotides in biological fluids. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||