1,721,022 research outputs found
Silver nanostructures on porous silicon for multiplexed Surface Enhanced Raman Scattering biosensing platforms
Full text linkSurface Enhanced Raman Scattering (SERS) technique merges an excellent sensitivity and a highly specific label free detection which can be exploited in miniaturized devices with a multiplexed approach. The development of plasmonic nanostructures, aimed to SERS analysis, satisfies therefore the need for point-of-care multianalyte sensing and biosensing platforms, both in the framework of diagnostics and therapy monitoring. In this thesis, SERS active metal-dielectric nanostructures based on silver-coated porous silicon (Ag-pSi) are carefully optimized for biodetection purposes. The thesis is organized in two parts. Basic concepts, necessary to the understanding of the experimental work are provided in the "Background" section, dealing with fundamentals of SERS spectroscopy (Chapter 1), SERS substrates fabrication aimed to biosensing applications (Chapter 2) and the main techniques devoted to the substrates characterization (Chapter 3). On the other side, the "Experimental" part includes the applied materials and methods (Chapter 4) and the presentation and discussion of the experimental results. (Chapters 5-8). In detail, a reliable SERS sensing requires a deep characterization of the optical and SERS response of the substrate providing the Raman enhancement. Theoretical and experimental techniques (FEM simulations and multi-wavelength Raman mapping) are systematically applied to get new insight into the fundamental and applicative SERS properties of Ag-pSi (Chapter 5). Two different approaches for the fabrication of Ag-pSi multianalyte platforms are then presented and discussed. Chapter 6 deals with the in situ synthesis of silver nanoparticles (NPs) patterns synthesized by ink-jet printing. The correlation between the growth parameters, morphology and SERS response is studied in order to optimize the SERS signal efficiency and uniformity of the Ag-pSi printed nanostructures. On the other hand, Chapter 7 concerns with the fabrication of multichamber Ag-pSi-PDMS microfluidic chips, which can be applied as portable SERS multiplexing devices. An all-microfluidic in-flow synthesis of silver NPs is performed, integrating the preparation of the SERS active substrate and the detection step on the same chip. Finally, a biofunctionalization protocol developed for the detection of miRNA222 (a recognized tumor marker) is optimized for the application to the Ag-pSi SERS substrates, assessing their compatibility to bioassays and suggesting the Ag-pSi nanostructures integrated in elastomeric chips as advantageous platforms for miRNA profiling, as well as for several other bioanalytical applications (Chapter 8
New branched flower-like Ag nanostructures for SERS analysis
No full textIn this work, metallic silver flower-like and aerogel-like nanostructures deposited onto hydrophobic dielectric substrates (HF-treated Si and PDMS) showed interesting potentialities as solid SERS substrates aimed to high sensitive molecular detection and quantitation. In detail, the nanostructures were incubated in 4-MBA solutions at 10−2 M – 10−9 M concentrations. The quantitative analysis confirmed a monotonic increase of the SERS signal intensity as a function of the 4-MBA concentration, following a Langmuir model, thus suggesting a chemisorption phenomenon. The best homogeneity and adhesion strength in liquid media of Ag nanostructures to the solid substrates were reached for the flower-like systems and the aerogel-like ones compared to traditional polyhedral nanostructures (taken as reference substrate), thus making them extremely appealing as a solution for the development of SERS-based sensors
Cysteine-mediated synthesis of silver nanonets and their use for surface enhanced Raman scattering (SERS)
No full textHighly-branched plasmonic nanostructures are interesting substrates to be exploited in Surface-
Enhanced Raman Scattering (SERS) detection, as sources of efficient Raman ‘‘hot-spots”. In this study, L-cysteine is proposed as reducing/capping agents for the production of Ag nanonets showing different morphologies by varying the synthesis conditions. Substrates are coupled to PDMS membranes and characterized by Raman spectroscopy using 4-MBA to define their SERS performance. Experimental evidences confirm that only the thinnest structures are able to guarantee significant SERS responses
Determination and qualitative characterization of microplastics in Ocean Arctic waters
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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
Optofluidic chip integrating silvered porous silicon membranes for multianalyte Surface Enhanced Raman Spectroscopy
No full textSurface-enhanced Raman spectroscopy on porous silicon membranes decorated with Ag nanoparticles integrated in elastomeric microfluidic chips
No full textDispositivo microfluidico SERS multicamera integrante membrane di silicio poroso e relativo processo di fabbricazione
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