Abstract: The possible use of nanopores for single DNA molecules biosensing has been demonstrated, but much remains to do in order to develop advanced engineered devices with enhanced stability, and controlled geometry and surface properties. Here we present morphological and electrical characterization of solid state silicon nitride nanopores fabricated by focused ion beam direct milling and chemically functionalized by probe oligonucleotides, with the final aim of developing a versatile tool for biosensing and gene expression profiling.
Abstract: A sensitive and practical colorimetric test for oxidized carbon nanotubes (CNTs) is described. The assay is based on direct labeling with the commercially available fluorescent dye thionin acetate (THA). This strategy offers the possibility for quantitation of acidic sites in a very fast and easy way.
Abstract: Single-wall carbon nanotubes (SWCNTs) could be promising delivery vehicles for cancer therapy. These carriers are generally introduced intravenously, however, little is known of their interactions with endothelial cells, the cells lining vessels and mediating clearance of nanoparticles. Here we show that SWCNTs of 1 to 5 microm in length, both "pristine" and functionalized by oxidation, had limited toxicity for endothelial cells in vitro as determined by growth, migration morphogenesis, and survival assays. Endothelial cells transiently took up SWCNTs, and several lines of data indicated that they were associated with an enhanced acidic vesicle compartment within the endothelial cells. Our findings of SWCNT interactions with endothelial cells suggest these may be optimal vehicles for targeting the vasculature and potential carriers of anti-angiogenic drugs. The implications on their biological activity must be taken into account when considering the use of these nanoparticles for therapeutic delivery of drugs. FROM THE CLINICAL EDITOR: Interactions of single walled carbon nanotubes (SWCNTs) with endothelial cells following IV administration remains unclear. Functionalized and naïve SWCNTs of 1-5 mm in length had limited toxicity to endothelial cells in vitro. Endothelial cells transiently took up SWCNTs and were associated with an enhanced acidic vesicle compartment within the cells. These findings suggest that SWCNTs may be promising vehicles for targeting the vasculature and potential carriers of anti-angiogenic drugs.
Abstract: Recently, nanopore technology has been introduced for genome analysis. Here we show results related to the possibility of preparing "engineered solid state nanopores". The nanopores were fabricated on a suspended Si3N4 membrane by Focused Ion Beam (FIB) drilling and chemically functionalized in order to covalently bind oligonucleoticles (probes) on their surface. Our data show the stable effect of DNA attachment on the ionic current measured through the nanopore, making it possible to conceive and develop a selective biosensor for gene expression profiling. (c) 2008 Elsevier Ltd. All rights reserved.
Abstract: In the present work a macroporous brushite bone cement for use either as an injected or mouldable paste, or in the shape of preformed grafts, has been investigated. Macropores have been introduced by adding to the powder single crystals of mannitol which worked as a porogen. The size of the crystals was in the range of 250-500microm in diameter, suitable for cell infiltration, with a shape ratio between 3 and 6. From compression tests on cylindrical samples an elastic modulus in the range 2.5-4.2GPa and a compressive strength in the range 17.5-32.6MPa were obtained for a volume fraction of macropores varying between 15 and 0%. Thus the compressive strength exceeded in all tests the maximum value currently attributed to cancellous bone.
Abstract: In recent years there has been a rapid increase in nanotechnology applications to medicine in order to prevent and treat diseases in the human body. The established and future applications have the potential to dramatically change medical science. The present paper will give a few examples that could transform common medical procedures.
Abstract: Point defect formation and stabilization properties, as well as their peculiar spectroscopic characteristics, locally modify the optical properties of insulating materials. Thin layers containing high concentrations of colour centres, hosted in a LiF single crystal and/or a polycrystalline matrix, offer the opportunity to develop innovative light-emitting photonic devices. Control of all the critical parameters should be required on spatial dimension comparable with the optical wavelengths. Recent developments in laser technologies, electron and particles beam methods, and novel photon sources, have opened a wide range of opportunities. An overview of the most significant advances in this field is provided, with particular emphasis on colour-centre LiF-based innovative miniaturised light sources, optical amplifiers and lasers. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Abstract: We present experimental results on simultaneous surface nanostructuring and optical activation of lithium fluoride crystals by 800 eV off-normal Ar+ sputtering. Our data demonstrate that the formation of periodic nanostructures is accompanied by the efficient production of stable electronic defects, optically active in the green and red parts of the visible spectra, thus providing the possibility to conceive and fabricate advanced insulating substrates. (C) 2006 Elsevier B.V. All rights reserved.
Abstract: Metal nano clusters are of great importance in physical and chemical science. One simple method for obtaining metal clusters consists in the deposition of a metal film on an inert substrate followed by annealing at high temperature. After this procedure, the metal film reduces in small clusters, whose morphology depends on the annealing temperature and annealing time. In this work we present a grazing incidence small angle X-ray scattering (GISAXS) study carried out in situ to understand the nucleation and formation of Nimetal clusters. For this purpose uniform Ni metal films, of different thicknesses, were deposited onto an oxidized Si(00 1) substrate, and annealed at different temperatures in the range 400-800 K. Before annealing the samples were characterized by X-ray reflectivity measurements to exactly determine the values of the thickness and of the starting roughness. The GISAXS patterns show a surface roughness increase starting at about 600 K. By increasing the temperature the diffused intensity breaks in two lines around the reflectivity plane, indication of a characteristic length correlation of the roughness. This correlation length is maintained during the metal clusters formation. (C) 2007 Elsevier B.V. All rights reserved.
Abstract: We present results on simultaneous nanostructuring and optical activation of lithium fluoride crystals by 800 eV off-normal Ar+ sputtering at different ion doses. The samples were studied by atomic force microscopy and optical spectroscopy. After ion irradiation smoothening of the initial random roughness is achieved and well-defined self-organized ripple structures appear, having a mean periodicity of 30 nm and a mean height of 3 nm. The simultaneous optical activation of the irradiated samples is due to the stable formation of electronic defects with intense photoluminescence in the visible spectral range.
Abstract: Starting from their discovery in 1991, carbon nanotubes have attracted a great attention, thanks to their peculiar mechanical, electrical and elastic properties that could be used to realize new devices in many different fields. For nanotechnology applications it is very important to be able to control not only shape and position but also alignment and orientation of carbon nanotubes, both during the growth and after it. Here we present preliminary results obtained by depositing carbon nanotubes (CNT) solutions on ion sputtered quartz substrates. Atomic force microscopy (AFM) images allow to study both CNTs positioning on the "ripples" generated by Ar+ sputtering on the SiO2 surface and their radial deformation induced by the "rough" surface. Work is now in progress to optimize the sputtering parameters and solution treatment (purification and functionalization) in order to get single CNTs regularly arranged on a patterned surface. (c) 2004 Elsevier B.V. All rights reserved.
Abstract: We demonstrate that a combination of ion sputtering and soft lithography is an alternative and effective way of nanostructuring soft matter. We create self-organized nanoscale structures on a glass template by irradiating the surface with a defocused, low energy Ar ion beam. Capillary force lithography is then used to transfer the pattern, exploiting the glass transition of polymeric layers. In particular, we demonstrate the pattern transfer of a periodic 150 nm fipple structure onto an organic compound, This new, unconventional combination is then a low-cost strategy that opens the way to a variety of applications in the field of organic-based devices.
Abstract: Planar active waveguides were produced in lithium fluoride crystals by implantation with 1.5 MeV He+ ions at several doses. The colored samples have been characterized by optical absorption, photoluminescence and m-line spectroscopy. By comparing the measured guided-mode effective indices with the ones calculated by means of the Chandler-Lama approach, the depth profile of refractive index was derived, showing that there are two competitive physical mechanisms, associated with different processes of energy deposition along the ion track, responsible for positive and negative modifications of the refractive index in the irradiated volume. (c) 2004 Elsevier B.V. All rights reserved.
Abstract: Various kinds of ionising radiation can be utilised to produce primary F centres (anion vacancies occupied by electrons) and aggregate defects in lithium fluoride (LiF) thin films. The creation of large aggregates of F centres and intrinsic metallic nanometre sized clusters (nano-aggregates) above a critical defect concentration and at irradiation temperatures where the diffusion of single point defects is not negligible has also been reported in LiF crystals. In this work, we present results concerning the stable formation of primary electronic defects (F centres) and lithium nano aggregates in lithium fluoride thin films grown by Xe ion-assisted thermal evaporation. The optical properties of the as grown LiF films are reported as a function of the deposition parameters (ion energy, density of the ion-beam current). The mechanism of the simultaneous formation of F colour centres and lithium nano-clusters is tentatively explained in the framework of low energy knock-on collisions and the thermal spike theory.
Abstract: The advent of scanning near-field optical microscopy (SNOM) has augmented at a microscopic level the usefulness of optical spectroscopy in the region between 300 nm and 10 mum. Two-dimensional imaging of chemical constituents makes this a very attractive and powerful new approach. In this paper we show SNOM results obtained in several geometrical configurations on boron clusters in silicon, Li clusters embedded in a LiF sample and BN growth on silicon. We also show some results on the wavelength dependence of the reflectivity (R) in the near infrared (IR) of biological cells in liquid environment with the observation of the local fluorescence. The SNOM images revealed features that were not present in the corresponding shear-force (SF) images and which were due to localized changes in the bulk properties of the sample. The size of the smallest detected features clearly demonstrated that near-field conditions were reached both in the visible and infrared region. (C) 2004 Elsevier B.V. All rights reserved.
Abstract: Scanning near-field optical microscopy (SNOM) makes it routinely possible to overcome the fundamental diffraction limit of standard (far-field) microscopy. Recently, aperture-based infrared SNOM performed in the spectroscopic mode, using the Vanderbilt University free electron laser, started delivering spatially-resolved information on the distribution of chemical species and on other laterally-fluctuating properties. The practical examples presented here show the great potential of this new technique both in materials science and in life sciences. (C) 2004 Elsevier B.V. All rights reserved.
Abstract: The measured room-temperature absorption spectra of LiF crystals implanted with 1.5 MeV He+ ions at different ion doses are presented. The application of a theoretical model allowed us to give an estimation of the band intensities associated with various kinds of electronic defects and to study their dependence on the ion dose. The model also considers the contribution due to narrometric lithium colloids, whose formation starts in the dose range at which the production of colour centres saturates.
Abstract: We present first results concerning stable formation of primary electronic defects and lithium nanometer sized clusters in LiF thin films grown by ion-assisted thermal deposition. The optical and morphological properties of the as grown LiF films, dependent on the deposition conditions, such as ion-beam energy and ion species (Xe, Ar), are reported. The experimental results show a larger efficiency of low-energy Xe ions in inducing the formation of lithium nano-clusters. To analyse the role of the deposition conditions, a preliminary interpretation of the lithium nano-cluster formation mechanism based on the spherical and/or cylindrical spike thermal model is given. (C) 2003 Elsevier B.V. All rights reserved.
Abstract: The depth refractive index profiles of broadband visible-emitting planar waveguides produced in LiF crystals with 1.5- and 2-MeV He+ ions at different doses have been derived from mode analysis. They show that there are two competitive mechanisms responsible for positive and negative modifications of the refractive index in the irradiated volume associated with different processes of energy deposition of the incident ions, so as to induce a complex coloration profile along the penetration direction, which is strongly dependent on the irradiation dose. (C) 2003 American Institute of Physics.
Abstract: LiF films have been grown on silicon substrate, irradiated with soft x-rays to create fluorescent regular micrometric-spaced arrays based on colour centres, and studied by Scanning Near-field Optical Microscope (SNOM). Strong variations in the local reflectivity have been observed in the infrared region between 6.1 and 9.2 mum and tentatively ascribed to a modulated variation of the refractive index of the coloured zone with respect to that of the uncoloured LiF matrix. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Abstract: Lithium fluoride (LiF) crystals and films treated with ionizing radiation are promising materials to realize light emitting devices in the visible spectral range. We studied the ion dose dependence of the concentration of F-2 and F-3(+) active defects, both absorbing at about 450 nm and separately emitting in the visible range, in He+ implanted LiF crystals. Quantitative information was deduced from transmission measurements by using a specially developed theoretical model to fit them, and was compared with the results obtained from photoluminescence spectra. Their qualitative agreement confirms the validity of our theoretical approach, which provides a simple and versatile tool of investigation of these peculiar active defects. (C) 2003 Elsevier B.V. All rights reserved.
Abstract: LiF films and crystals containing lithium colloids have been studied by scanning near-field optical microscopy (SNOM). Scattering phenomena and possible wave-guided modes have been observed studying the physical mechanism of the interaction between the LiF samples and an external laser source.
Abstract: An elementary derivation is given for the propagator of a particle in an infinitely deep well. The time evolution of the wavefunction is illustrated through some examples, and certain general properties of the propagator are discussed. The connection with the Talbot effect and other phenomena is outlined.
Abstract: The new process of quantum-injection by a single-photon in a pure quantum superposition state into an optical parametric amplifier operating in entangled configuration is adopted to generate an all optical multiphoton Schroedinger-cat state which is largely detectable against the squeezed-vacuum noise. The invariance properties of the OPA interaction hamiltonian show that, under certain conditions, the device may act as a universal quantum cloning machine (UQCM) of the input qubits, Preliminary results here reported show the first experimental realization of such a device based on stimulated emission process in an optical parametric amplifier. (C) 2000 Elsevier Science B.V. All rights reserved.
Abstract: The new process of quantum-injection into an optical parametric amplifier operating in entangled configuration is adopted to amplify into a large dimensionality spin-1/2 Hilbert space the quantum entanglement and superposition properties of the photon-couples generated by parametric down-conversion. The invariance properties of the OPA interaction hamiltonian shaw that, under certain conditions, the device may act as a Universal Quantum Cloning Machine (UQCM) of the input qubits. Preliminary results here reported show the fu;st experimental realization of such a device. The structure of the Wigner function and of the field's correlation functions shows a multiphoton Schrodinger-cat behaviour of the emitted field which is largely detectable against the squeezed-vacuum noise.
Abstract: He+ ions with an energy of 1.5 -2 MeV and doses ranging from 6 x 10(13) to 2.5 X 10(16) ions/cm(2) were used to produce primary and aggregate defects in Lithium Fluoride (LiF) crystals. The optical properties of the implanted samples and their dependence on ion dose were studied by means of optical absorption spectroscopy and Scanning Near-field Optical Microscopy (SNOM). The results show the formation, for high doses, of macrodefects such as lithium intrinsic nano-aggregates that could play an important role in the realisation of non-linear optical waveguides.
Abstract: Planar active waveguides, produced in Lithium Fluoride crystals by implantation with 2 MeV He+ ions at several doses, have been characterized by optical absorption, photoluminescence and m-lines spectroscopy. All the colored samples support several modes, whose analysis allows reconstructing the depth refractive index profiles of the waveguides as a function of dose. Two competitive physical mechanisms, associated with different processes of energy deposition along the ion track, are responsible for positive and negative modifications of the refractive index in the irradiated volume.
