1,720,968 research outputs found
Field Enhancement by Shaping Nanocavities in a Gold Film
No full textThe paper reports on 2D plasmonic crystals composed of
a hexagonal lattice of polymeric nanopillars embedded in
an optically thick gold film on a glass substrate. A tapered
shape of the polymeric pillars is proved to localize the elec-
tric field distribution close to the free surface of the device
and to determine a significant increase in the electric field
intensity particularly when the incident light comes from the
glass side. These effects significantly improve the sample
sensitivity to a refractive index change occurring at the free
surface of the device
Plasmonic resonances in nanostructured gold/polymer surfaces by colloidal lithography
No full textWe investigate nanostructured surfaces consisting of a
hexagonal lattice of polymeric pillars embedded in a gold
matrix. These systems are prepared by a new fabrication
technique based on plasma assisted deposition and colloidal
lithography. A complete characterization of such surfaces is
performed by angle resolved reflectance and transmittance
measurements. Both delocalized and localized plasmonic
modes can be identified: their reciprocal interplay allows to
observe spectral features and to detect refractive index changes
related to one of the sample interfaces by measurements
performed with a light beam incident from the opposite side.
This intriguing behaviour, together with ease of use and low
cost of the deposition procedure, make this kind of nanostructures
particularly interesting in biosensing applications
Interaction among plasmonic resonances in a gold film embedding a two-dimensional array of polymeric nanopillars
No full textNanostructured surfaces have proven to be effective in controlling the electric field distribution and triggering
a series of interesting physical effects. In particular, ordered metallic lattices with a typical size of the same
order of magnitude of the wavelength of the incident radiation exhibit extraordinary transmission and reflection
properties and represent a sensitive tool to exploit surface plasmon resonance for sensing applications. We
investigated, either by experimental structural and optical measurements or by modeling and calculations, samples
consisting of a two-dimensional array of polymeric pillars embedded in a gold film. In particular, we analyzed
the dependence of the plasmonic resonance on the pillar size. We showed that a peculiar interplay among
localized modes and propagating surface plasmon polaritons exists for some selected conditions and affects
the spectral distribution, lifetime, and field configuration of the plasmonic excitations
SPR SENSOR DEVICE WITH NANOSTRUCTURE
No full textA sensor device comprises a dielectric substrate (52); and a metal layer (53) on the substrate (52) with at least one array of cavities (54) therein and adapted to support L- SPR, each of the cavities (54) in the metal layer (53) having an opening (56) and a closed bottom (58) and widening from opening to bottom. A bed of dielectric material (62) is provided over the bottom (58) of each cavity (54) to reduce its apparent depth, the bed surface (62) being functionalized to bind to receptor moieties (64). This sensor device is particularly designed for SPR detection, but can be used in other detection techniques
Multiplexed label-free optical biosensor for medical diagnostics
No full textThis paper describes a new multiplexed label-free biosensor. The detection technology is based on nanostructured gold-polymer surfaces. These surfaces support surface plasmon resonance modes that can be probed by a miniaturized optical setup. The optical characterization of the sensing chip shows the sensitivity and the limit-of-detection to refractive index changes. Moreover, by studying the progressive adhesion of molecular monolayers of polyelectrolytes, the decay of the plasmonic mode electric field above the surface has been reconstructed. A multiplexed label-free biosensing device is then described and characterized in terms of sensitivity, lateral resolution, and sensitivity to a model biological assay. The sensitivity in imaging mode of the device is of the order of 10-6 refractive index units, while the measured lateral resolution is 6.25 μm within a field of view of several tenths of mm2, making the instrument unique in terms of multiplexing capability. Finally, the proof-of-concept application of the technology as a point-of-care diagnostic tool for an inflammatory marker is demonstrated
Plasmonic sensors on 2D ordered structures
No full textColloidal lithography with polystyrene spheres allows for the fabrication of hybrid polymer/metal two-dimensional ordered surfaces. They consist of a hexagonal lattice of plasma-polymerized acrylic acid (ppAA) or poly(methyl methacrylate) (PMMA) pillars embedded in an optically thick gold film deposited on a glass substrate. Such a kind of nanostructured system has been shown to support either propagating Surface Plasmon Polaritons or “Mie-like” localized resonances, and appears to be particularly interesting for sensing applications. Tuning the structural parameters, a strong interaction among delocalized and localized plasmonic modes can be obtained together with a good coupling with light. This opens the way towards an optical biomolecular sensor system in which a modification/adhesion on the free nanostructured surface can be easily detected by a simple, near normal reflectance measurement performed from the substrate side, despite the relatively large gold thickness. The simple configuration allows for a surface plasmon resonance (SPR) imaging configuration and enables the real-time multiplexed detection of several analytes. The sensing performance of the surfaces (sensitivity to refractive index change and to the adhesion of molecular monolayers) has been tested using standard spectroscopic techniques. The electromagnetic field’s spatial distribution within the nanostructures and its intensity enhancement have been numerically calculated by finite difference time domain (FDTD) simulations. The results, including the calculated reflectance spectra, are in good agreement with the experimental data
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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