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Angelini M, Manobianco E, Pellacani P, Floris F, Marabelli F. Refractive Index Dependence of Fluorescence Enhancement in a Nanostructured Plasmonic Grating. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1289. [PMID: 36770293 PMCID: PMC9920896 DOI: 10.3390/ma16031289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 06/18/2023]
Abstract
Plasmonic gratings are attracting huge interest in the context of realizing sensors based on surface-enhanced fluorescence. The grating features control the plasmonic modes and consequently have a strong effect on the fluorescence response. Within this framework, we focused on the use of a buffer solution flowing across the grating active surface to mimic a real measurement. The refractive index of the surrounding medium is therefore altered, with a consequent modification of the resonance conditions. The result is a shift in the spectral features of the fluorescence emission accompanied by a reshaping of the fluorescence emission in terms of spectral weight and direction.
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Affiliation(s)
| | | | - Paola Pellacani
- Plasmore S.r.l, Via Vittorio Emanuele II 4, 27100 Pavia, Italy
| | - Francesco Floris
- Department of Physics, University of Pavia, Via Bassi 6, 27100 Pavia, Italy
| | - Franco Marabelli
- Department of Physics, University of Pavia, Via Bassi 6, 27100 Pavia, Italy
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Zagaglia L, Demontis V, Rossella F, Floris F. Particle swarm optimization of GaAs-AlGaAS nanowire photonic crystals as two-dimensional diffraction gratings for light trapping. NANO EXPRESS 2022. [DOI: 10.1088/2632-959x/ac61ec] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Abstract
Semiconductor nanowire ordered arrays represent a class of bi-dimensional photonic crystals that can be engineered to obtain functional metamaterials. Here is proposed a novel approach, based on a particle swarm optimization algorithm, for using such a photonic crystal concept to design a semiconductor nanowire-based two-dimensional diffraction grating able to guarantee an in-plane coupling for light trapping. The method takes into account the experimental constraints associated to the bottom-up growth of nanowire arrays, by processing as input dataset all relevant geometrical and morphological features of the array, and returns as output the optimised set of parameters according to the desired electromagnetic functionality of the metamaterial. A case of study based on an array of tapered GaAs-AlGaAs core-shell nanowire heterostructures is discussed.
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Zagaglia L, Demontis V, Rossella F, Floris F. Semiconductor nanowire arrays for optical sensing: a numerical insight on the impact of array periodicity and density. NANOTECHNOLOGY 2021; 32:335502. [PMID: 33971637 DOI: 10.1088/1361-6528/abff8b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 05/10/2021] [Indexed: 06/12/2023]
Abstract
Recent advances in the nanofabrication and modeling of metasurfaces have shown the potential of these systems in providing unprecedented control over light-matter interactions at the nanoscale, enabling immediate and tangible improvement of features and specifications of photonic devices that are becoming always more crucial in enhancing everyday life quality. In this work, we theoretically demonstrate that metasurfaces made of periodic and non-periodic deterministic assemblies of vertically aligned semiconductor nanowires can be engineered to display a tailored effective optical response and provide a suitable route to realize advanced systems with controlled photonic properties particularly interesting for sensing applications. The metasurfaces investigated in this paper correspond to nanowire arrays that can be experimentally realized exploiting nanolithography and bottom-up nanowire growth methods: the combination of these techniques allow to finely control the position and the physical properties of each individual nanowire in complex arrays. By resorting to numerical simulations, we address the near- and far-field behavior of a nanowire ensemble and we show that the controlled design and arrangement of the nanowires on the substrate may introduce unprecedented oscillations of light reflectance, yielding a metasurface which displays an electromagnetic behavior with great potential for sensing. Finite-difference time-domain numerical simulations are carried out to tailor the nanostructure parameters and systematically engineer the optical response in the VIS-NIR spectral range. By exploiting our computational-methods we set-up a complete procedure to design and test metasurfaces able to behave as functional sensors. These results are especially encouraging in the perspective of developing arrays of epitaxially grown semiconductor nanowires, where the suggested design can be easily implemented during the nanostructure growth, opening the way to fully engineered nanowire-based optical metamaterials.
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Affiliation(s)
- Luca Zagaglia
- Tyndall National Institute, University College Cork, Cork, Ireland
| | - Valeria Demontis
- NEST Laboratory, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Pisa, Italy
| | - Francesco Rossella
- NEST Laboratory, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Pisa, Italy
| | - Francesco Floris
- Tyndall National Institute, University College Cork, Cork, Ireland
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Oggianu M, Figus C, Ashoka-Sahadevan S, Monni N, Marongiu D, Saba M, Mura A, Bongiovanni G, Caltagirone C, Lippolis V, Cannas C, Cadoni E, Mercuri ML, Quochi F. Silicon-based fluorescent platforms for copper(ii) detection in water. RSC Adv 2021; 11:15557-15564. [PMID: 35481193 PMCID: PMC9029085 DOI: 10.1039/d1ra02695j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 04/19/2021] [Indexed: 12/23/2022] Open
Abstract
The potential of silicon-based fluorescent platforms for the detection of trace toxic metal ions was investigated in an aqueous environment. To this aim, silicon chips were first functionalized with amino groups, and fluorescein organic dyes, used as sensing molecules, were then covalently linked to the surface via formation of thiourea groups. The obtained hybrid heterostructures exhibited high sensitivity and selectivity towards copper(ii), a limit of detection compatible with the recommended upper limits for copper in drinking water, and good reversibility using a standard metal–chelating agent. The fluorophore–analyte interaction mechanism at the basis of the reported fluorescence quenching, as well as the potential of performance improvement, were also studied. The herein presented sensing architecture allows, in principle, tailoring of the selectivity towards other metal ions by proper fluorophore selection, and provides a favorable outlook for integration of fluorescent chemosensors with silicon photonics technology. Covalent linkage of fluorescein to silanized silicon chips yields solid-state platforms for detection of copper(ii) in water. This architecture represents a step forward towards the fabrication of sensors for remote water analysis applications.![]()
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Laser writing of nanostructured silicon arrays for the SERS detection of biomolecules with inhibited oxidation. Colloids Surf B Biointerfaces 2019; 174:174-180. [PMID: 30453136 DOI: 10.1016/j.colsurfb.2018.11.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 10/17/2018] [Accepted: 11/05/2018] [Indexed: 12/17/2022]
Abstract
The present work reports the processing of laser irradiated Si arrays (LISi) and underlines their surface enhanced Raman scattering (SERS) functionality. A nanostructured Si/SiOx surface forms providing additional fluidic and photoprotective properties. Because of their optical and surface characteristics, the arrays exhibit a SERS analytical enhancing factor of 500, without any noble metals such as gold or silver. Micro-Raman maps allowed studying LISi properties, identifying maximum amplification in nanostructured areas characterized by the presence of 7 nm Si nanocrystals. These structures are confined by a SiOx layer as illustrated by XPS valence band measurements. The highly hydrophilic LISi areas allow a pre-concentration of target molecules prior to SERS analysis. A relevant application of LISi was found in the detection of apomorphine (APO), a drug used for the treatment of Parkinson's disease. In contrast with what is obtained by using gold SERS substrates, LISi allows the detection of APO with no sign of oxidation. This invites for the use of the Si/SiOx SERS detection in future systems for the personalized delivery of APO.
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Self-Assembled InAs Nanowires as Optical Reflectors. NANOMATERIALS 2017; 7:nano7110400. [PMID: 29160860 PMCID: PMC5707617 DOI: 10.3390/nano7110400] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/11/2017] [Accepted: 11/16/2017] [Indexed: 11/16/2022]
Abstract
Subwavelength nanostructured surfaces are realized with self-assembled vertically-aligned InAs nanowires, and their functionalities as optical reflectors are investigated. In our system, polarization-resolved specular reflectance displays strong modulations as a function of incident photon energy and angle. An effective-medium model allows one to rationalize the experimental findings in the long wavelength regime, whereas numerical simulations fully reproduce the experimental outcomes in the entire frequency range. The impact of the refractive index of the medium surrounding the nanostructure assembly on the reflectance was estimated. In view of the present results, sensing schemes compatible with microfluidic technologies and routes to innovative nanowire-based optical elements are discussed.
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Bruzas I, Unser S, Yazdi S, Ringe E, Sagle L. Ultrasensitive Plasmonic Platform for Label-Free Detection of Membrane-Associated Species. Anal Chem 2016; 88:7968-74. [PMID: 27436204 DOI: 10.1021/acs.analchem.6b00801] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lipid membranes and membrane proteins are important biosensing targets, motivating the development of label-free methods with improved sensitivity. Silica-coated metal nanoparticles allow these systems to be combined with supported lipid bilayers for sensing membrane proteins through localized surface plasmon resonance (LSPR). However, the small sensing volume of LSPR makes the thickness of the silica layer critical for performance. Here, we develop a simple, inexpensive, and rapid sol-gel method for preparing thin conformal, continuous silica films and demonstrate its applicability using gold nanodisk arrays with LSPRs in the near-infrared range. Silica layers as thin as ∼5 nm are observed using cross-sectional scanning transmission electron microscopy. The loss in sensitivity due to the thin silica coating was found to be only 16%, and the biosensing capabilities of the substrates were assessed through the binding of cholera toxin B to GM1 lipids. This sensor platform should prove useful in the rapid, multiplexed detection and screening of membrane-associated biological targets.
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Affiliation(s)
- Ian Bruzas
- Department of Chemistry, College of Arts and Sciences, University of Cincinnati , 301 West Clifton Court, Cincinnati, Ohio 45221-0172, United States
| | - Sarah Unser
- Department of Chemistry, College of Arts and Sciences, University of Cincinnati , 301 West Clifton Court, Cincinnati, Ohio 45221-0172, United States
| | - Sadegh Yazdi
- Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, MS-325, Houston, Texas 77005, United States
| | - Emilie Ringe
- Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, MS-325, Houston, Texas 77005, United States
| | - Laura Sagle
- Department of Chemistry, College of Arts and Sciences, University of Cincinnati , 301 West Clifton Court, Cincinnati, Ohio 45221-0172, United States
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Figus C, Patrini M, Floris F, Fornasari L, Pellacani P, Marchesini G, Valsesia A, Artizzu F, Marongiu D, Saba M, Marabelli F, Mura A, Bongiovanni G, Quochi F. Synergic combination of the sol-gel method with dip coating for plasmonic devices. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:500-507. [PMID: 25821692 PMCID: PMC4362208 DOI: 10.3762/bjnano.6.52] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 01/22/2015] [Indexed: 06/04/2023]
Abstract
Biosensing technologies based on plasmonic nanostructures have recently attracted significant attention due to their small dimensions, low-cost and high sensitivity but are often limited in terms of affinity, selectivity and stability. Consequently, several methods have been employed to functionalize plasmonic surfaces used for detection in order to increase their stability. Herein, a plasmonic surface was modified through a controlled, silica platform, which enables the improvement of the plasmonic-based sensor functionality. The key processing parameters that allow for the fine-tuning of the silica layer thickness on the plasmonic structure were studied. Control of the silica coating thickness was achieved through a combined approach involving sol-gel and dip-coating techniques. The silica films were characterized using spectroscopic ellipsometry, contact angle measurements, atomic force microscopy and dispersive spectroscopy. The effect of the use of silica layers on the optical properties of the plasmonic structures was evaluated. The obtained results show that the silica coating enables surface protection of the plasmonic structures, preserving their stability for an extended time and inducing a suitable reduction of the regeneration time of the chip.
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Affiliation(s)
- Cristiana Figus
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
| | - Maddalena Patrini
- University of Pavia, Department of Physics, Via Agostino Bassi 6, 27100 Pavia, Italy
| | - Francesco Floris
- University of Pavia, Department of Physics, Via Agostino Bassi 6, 27100 Pavia, Italy
| | - Lucia Fornasari
- University of Pavia, Department of Physics, Via Agostino Bassi 6, 27100 Pavia, Italy
| | | | | | | | - Flavia Artizzu
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
- University of Cagliari, Department of Chemistry and Geology, S.P. Monserrato-Sestu Km 0.700, 09042 Monserrato, Cagliari, Italy
| | - Daniela Marongiu
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
| | - Michele Saba
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
| | - Franco Marabelli
- University of Pavia, Department of Physics, Via Agostino Bassi 6, 27100 Pavia, Italy
| | - Andrea Mura
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
| | - Giovanni Bongiovanni
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
| | - Francesco Quochi
- University of Cagliari, Department of Physics, S.P. Monserrato-Sestu Km 0.7, 09042 Monserrato, Italy
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