Advanced optical materials or interfaces are gaining attention for diagnostic applications. Howev... more Advanced optical materials or interfaces are gaining attention for diagnostic applications. However, the achievement of large device interface as well as facile surface functionalization largely impairs their wide use. The present work is aimed to address different innovative aspects related to the fabrication of large area 3D plasmonic arrays, their direct and easy functionalization with capture elements and their spectroscopic verifications through enhanced Raman and enhanced fluorescence techniques. In detail we have investigated the effect of Au-based nanoCones array, fabricated by means of direct nanoimprint technique over large area (mm2), on protein capturing and on the enhancement in optical signal. A selective functionalization of gold surfaces was proposed by using a peptide (AuPi3) previously selected by phage display. In this regard, two different sequences, labeled with fluorescein and biotin, were chemisorbed on metallic surfaces. The presence of Au nanoCones array con...
ABSTRACT The fabrication of complex 3D plasmonic nanostructures opens new scenarios towards the r... more ABSTRACT The fabrication of complex 3D plasmonic nanostructures opens new scenarios towards the realization of high electric field confinement and enhancement. We exploit the unique properties of these nanostructures for performing Raman spectroscopy in the single/few molecules detection limit.
Micro and nano-patterned devices were fabricated which disclose the possibility of concentrating,... more Micro and nano-patterned devices were fabricated which disclose the possibility of concentrating, localizing, detecting and thus analyzing with unprecedented accuracy few molecules (at the limit a single molecule) of biological and medical interest. Important applications are envisioned where proteins poorly concentrated in blood are detected thus (early) revealing the appearance of diseases.
In our body, cells are continuously exposed to physical forces that can regulate different cell f... more In our body, cells are continuously exposed to physical forces that can regulate different cell functions such as cell proliferation, differentiation and death. In this work, we employed two different strategies to mechanically stress cancer cells. The cancer and healthy cell populations were treated either with mechanical stress delivered by a micropump (fabricated by deep X-ray nanolithography) or by ultrasound wave stimuli. A specific down-regulation of Major Histocompatibility Complex (MHC) class I molecules expression on cancer cell membrane compared to different kinds of healthy cells (fibroblasts, macrophages, dendritic and lymphocyte cells) was observed, stimulating the cells with forces in the range of nano-newton, and pressures between 1 and 10 bar (1 bar5100.000 Pascal), depending on the devices used. Moreover, Raman spectroscopy analysis, after mechanical treatment, in the range between 700-1800 cm 21 , indicated a relative concentration variation of MHC class I. PCA analysis was also performed to distinguish control and stressed cells within different cell lines. These mechanical induced phenotypic changes increase the tumor immunogenicity, as revealed by the related increased susceptibility to Natural Killer (NK) cells cytotoxic recognition.
Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II, 2009
This paper reports on the fabrication of reproducible surface enhanced Raman scattering (SERS) de... more This paper reports on the fabrication of reproducible surface enhanced Raman scattering (SERS) device based on nanoPillar coupled with PC cavity by means of FIB milling and electron beam induced deposition techniques (Device 1): In addition to this device, another SERS device using e-beam lithography and electroless metal deposition techniques (Device 2) is fabricated in order to have planar geometry particularly useful for future nanoarray architectures SERS device. Various measurements have been performed for the monolayer of different materials showing extremely promising SERS based device. It is revealed that the Rhodamine6G is clearly evidenced in Raman 2D mapping spectrum, showing a very high enhancement in SERS signal in the order of 10 12 (theoretically) with respect to the normal Raman measurements. We estimate the number of Rhodamine6G molecule detected is about 100-150.
Latin America Optics and Photonics Conference, 2012
Abstract We investigate the resonance characteristics of terahertz nanoantenna arrays, both numer... more Abstract We investigate the resonance characteristics of terahertz nanoantenna arrays, both numerically and experimentally. We demonstrate their tunability and their significant field enhancement properties, which can find several applications in terahertz spectroscopy and nonlinear optics.
Resonant dipole nanoantennas promise to considerably improve the capabilities of terahertz spectr... more Resonant dipole nanoantennas promise to considerably improve the capabilities of terahertz spectroscopy, offering the possibility of increasing its sensitivity through local field enhancement, while in principle allowing unprecedented spatial resolutions, well below the diffraction limit. Here, we investigate the resonance properties of ordered arrays of terahertz dipole nanoantennas, both experimentally and through numerical simulations. We demonstrate the tunability of this type of structures, in a range (∼1-2 THz) that is particularly interesting and accessible by means of standard zinc telluride sources. We additionally study the near-field resonance properties of the arrays, finding that the resonance shift observed between near-field and far-field spectra is predominantly ascribable to ohmic damping.
Polymer pyrolysis to nanoceramics is employed for the production of photo-luminescent thin film s... more Polymer pyrolysis to nanoceramics is employed for the production of photo-luminescent thin film samples, consisting of Si-nanocrystals dispersed in silica matrix. Thin films were deposited on Si wafer by spin-coating technique from a triethoxysilane-derived sol-gel solution. This is a fast process and a low cost technique. Samples were annealed at different temperatures between 600°C and 1300°C, under N 2 gas atmosphere. Structural evolution and luminescence from Si-ncs vs. temperature were investigated by FT-IR absorption spectroscopy and photo-luminescence. Absorption spectrum of As-Prep sample shows several vibrational bands due to Si-H, C-H x , and Si-O-Si structural units, without any appreciable luminescence. Silica phase segregation and intense PL (790 nm) due to Si-ncs were observed on annealing at T N 1000°C.
Mg–Ni multilayers and Ni-rich Mg thin films were deposited by electron gun and pulsed laser depos... more Mg–Ni multilayers and Ni-rich Mg thin films were deposited by electron gun and pulsed laser deposition, respectively. Samples were submitted to thermal treatment in deuterium or hydrogen atmosphere at 423K and ∼105Pa pressure to promote the metal to hydride phase transition.The H chemical bonding in the multilayer samples, after annealing in H2 atmosphere, was examined by Fourier transform infrared spectroscopy:
We report on the possibility of realizing adiabatic compression of polaritonic wave on a metallic... more We report on the possibility of realizing adiabatic compression of polaritonic wave on a metallic conical nano-structure through an oscillating electric potential (quasi dynamic regime). By comparing this result with an electromagnetic wave excitation, we were able to relate the classical lighting-rod effect to adiabatic compression. Furthermore, we show that while the magnetic contribution plays a marginal role in the formation of adiabatic compression, it provides a blue shift in the spectral region. In particular, magnetic permeability can be used as a free parameter for tuning the polaritonic resonances. The peculiar form of adiabatic compression is instead dictated by both the source and the metal permittivity. The analysis is performed by starting from a simple electrostatic system to end with the complete electromagnetic one through intermediate situations such as the quasi-electrostatic and quasi-dynamic regimes. Each configuration is defined by a particular set of equations which allows to clearly determine the individual role played by the electric and magnetic contribution in the generation of adiabatic compression. We notice that these findings can be applied for the realization of a THz nano-metric generator.
1 Disordered solid phases, containing appreciable amounts of hydrogen ions, are grown at the surf... more 1 Disordered solid phases, containing appreciable amounts of hydrogen ions, are grown at the surface of rhenium oxide crystals, because of the high reactivity of this compound with ambient moisture. To investigate such phenomena, a comparative study is performed on ground powder and thermally evaporated or sputtered films using x-ray diffraction and micro-Raman spectroscopy. Two types of solid phases were found in the films: H x ReO 3 distorted perovskite structures, based on corner-sharing ReO 6 octahedra as in the bulk crystals, and ordered HReO 4 crystalline structures, based on tetrahedral perrhenate ions. The complex impedance measurements on ReO 3 films support the hypothesis of mobile hydrogen ions in such defective films. Moreover, this relevant protonic conductivity allows the application of these films as active layers inserted into asymmetric nematic liquid-crystalline cells to rectify the electro-optical response of such devices, with performances quite similar to previously studied oxides such as WO 3 .
ABSTRACT In this paper we report the fabrication and characterization of a plasmonic device for l... more ABSTRACT In this paper we report the fabrication and characterization of a plasmonic device for label-free detection of few molecules in sub-wavelength regime by means of Raman scattering. The device is based on the coupling between a gold nanocone and a photonic crystal cavity, that is able to excite surface plasmon polaritons (SPPs) at the base on the cone. During the propagation toward the tip of the cone, the SPPs experiment and adiabatic compression that allow the accumulation of a very high electric field at the tip end. Raman enhancement factor of more than five order of magnitude is reported for a tip with a radius of curvature of about 10 nm. The present results open up future perspective on single molecule detection even in combination with AFM measurements.
In this work we report, for the first time to our knowledge, the possibility to fabricate various... more In this work we report, for the first time to our knowledge, the possibility to fabricate various structures, with good optical proprieties, on the top of optical fibers, using the two-photon lithography (TPL) technique. We show the convenience of this approach to quickly create generic 3D shapes using a single set-up by contrast to past shape-dependent methods. A set of different structures are fabricated and characterized to demonstrate the versatility of this approach and their high optical quality.
This paper reports on the fabrication and characterization of a novel device for surface enhanced... more This paper reports on the fabrication and characterization of a novel device for surface enhanced Raman scattering, fabricated using focused ion beam milling and electron beam induced deposition. The device exploits a photonic crystal cavity as an optical source to couple the incident laser with a metallic tapered nanolenses. The collected Raman measurements show that exploiting such approach is possible to overcome the difficulties related to scattering and diffraction phenomena occurring when visible laser illuminates nanostructures. A clear Raman scattering enhancement has been demonstrated for label-free detection of molecule in sub-wavelength regime.
Materials Science in Semiconductor Processing, 2004
Low-dielectric constant SiOC:H films were prepared by plasma enhanced chemical vapour deposition ... more Low-dielectric constant SiOC:H films were prepared by plasma enhanced chemical vapour deposition (PECVD) from trimethyl-silane (H-Si-(CH 3 ) 3 ) and ozone (O 3 ) gas mixture. The samples were preliminarily annealed at 400 1C in N 2 atmosphere and then in N 2 +He plasma. Afterwards, they were treated in vacuum at some fixed temperatures in the range between 400 and 900 1C. Structural investigations of the annealed films were carried out by means of vibrational spectroscopy techniques. FT-IR spectrum of a preliminarily treated sample shows absorption bands due to stretching modes of structural groups like Si-CH 3 at $1270 cm À1 , Si-O-Si at 1034 cm À1 and C-H x in the region between 2800 and 3000 cm À1 . No significant spectral change was observed in the absorption spectra of samples annealed up to 600 1C, indicating that the preliminarily treated film retains a substantial structural stability up to this temperature. Above 600 1C, absorption spectra show a strong quenching of H-related peaks while the band due to Si-O-Si anti-symmetric stretching mode shifts towards higher energy, approaching the value observed for thermally grown SiO 2 . Raman spectra of samples treated at temperatures TX500 1C exhibit both D and G bands typical of sp 2 -hybridised carbon, due to the formation of C-C bonds within the film which is accompanying the release of hydrogen. The intensity of D and G bands becomes more pronounced in samples annealed at higher temperatures, thus suggesting a progressive precipitation of carbon within the oxide matrix. r
Advanced optical materials or interfaces are gaining attention for diagnostic applications. Howev... more Advanced optical materials or interfaces are gaining attention for diagnostic applications. However, the achievement of large device interface as well as facile surface functionalization largely impairs their wide use. The present work is aimed to address different innovative aspects related to the fabrication of large area 3D plasmonic arrays, their direct and easy functionalization with capture elements and their spectroscopic verifications through enhanced Raman and enhanced fluorescence techniques. In detail we have investigated the effect of Au-based nanoCones array, fabricated by means of direct nanoimprint technique over large area (mm2), on protein capturing and on the enhancement in optical signal. A selective functionalization of gold surfaces was proposed by using a peptide (AuPi3) previously selected by phage display. In this regard, two different sequences, labeled with fluorescein and biotin, were chemisorbed on metallic surfaces. The presence of Au nanoCones array con...
ABSTRACT The fabrication of complex 3D plasmonic nanostructures opens new scenarios towards the r... more ABSTRACT The fabrication of complex 3D plasmonic nanostructures opens new scenarios towards the realization of high electric field confinement and enhancement. We exploit the unique properties of these nanostructures for performing Raman spectroscopy in the single/few molecules detection limit.
Micro and nano-patterned devices were fabricated which disclose the possibility of concentrating,... more Micro and nano-patterned devices were fabricated which disclose the possibility of concentrating, localizing, detecting and thus analyzing with unprecedented accuracy few molecules (at the limit a single molecule) of biological and medical interest. Important applications are envisioned where proteins poorly concentrated in blood are detected thus (early) revealing the appearance of diseases.
In our body, cells are continuously exposed to physical forces that can regulate different cell f... more In our body, cells are continuously exposed to physical forces that can regulate different cell functions such as cell proliferation, differentiation and death. In this work, we employed two different strategies to mechanically stress cancer cells. The cancer and healthy cell populations were treated either with mechanical stress delivered by a micropump (fabricated by deep X-ray nanolithography) or by ultrasound wave stimuli. A specific down-regulation of Major Histocompatibility Complex (MHC) class I molecules expression on cancer cell membrane compared to different kinds of healthy cells (fibroblasts, macrophages, dendritic and lymphocyte cells) was observed, stimulating the cells with forces in the range of nano-newton, and pressures between 1 and 10 bar (1 bar5100.000 Pascal), depending on the devices used. Moreover, Raman spectroscopy analysis, after mechanical treatment, in the range between 700-1800 cm 21 , indicated a relative concentration variation of MHC class I. PCA analysis was also performed to distinguish control and stressed cells within different cell lines. These mechanical induced phenotypic changes increase the tumor immunogenicity, as revealed by the related increased susceptibility to Natural Killer (NK) cells cytotoxic recognition.
Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II, 2009
This paper reports on the fabrication of reproducible surface enhanced Raman scattering (SERS) de... more This paper reports on the fabrication of reproducible surface enhanced Raman scattering (SERS) device based on nanoPillar coupled with PC cavity by means of FIB milling and electron beam induced deposition techniques (Device 1): In addition to this device, another SERS device using e-beam lithography and electroless metal deposition techniques (Device 2) is fabricated in order to have planar geometry particularly useful for future nanoarray architectures SERS device. Various measurements have been performed for the monolayer of different materials showing extremely promising SERS based device. It is revealed that the Rhodamine6G is clearly evidenced in Raman 2D mapping spectrum, showing a very high enhancement in SERS signal in the order of 10 12 (theoretically) with respect to the normal Raman measurements. We estimate the number of Rhodamine6G molecule detected is about 100-150.
Latin America Optics and Photonics Conference, 2012
Abstract We investigate the resonance characteristics of terahertz nanoantenna arrays, both numer... more Abstract We investigate the resonance characteristics of terahertz nanoantenna arrays, both numerically and experimentally. We demonstrate their tunability and their significant field enhancement properties, which can find several applications in terahertz spectroscopy and nonlinear optics.
Resonant dipole nanoantennas promise to considerably improve the capabilities of terahertz spectr... more Resonant dipole nanoantennas promise to considerably improve the capabilities of terahertz spectroscopy, offering the possibility of increasing its sensitivity through local field enhancement, while in principle allowing unprecedented spatial resolutions, well below the diffraction limit. Here, we investigate the resonance properties of ordered arrays of terahertz dipole nanoantennas, both experimentally and through numerical simulations. We demonstrate the tunability of this type of structures, in a range (∼1-2 THz) that is particularly interesting and accessible by means of standard zinc telluride sources. We additionally study the near-field resonance properties of the arrays, finding that the resonance shift observed between near-field and far-field spectra is predominantly ascribable to ohmic damping.
Polymer pyrolysis to nanoceramics is employed for the production of photo-luminescent thin film s... more Polymer pyrolysis to nanoceramics is employed for the production of photo-luminescent thin film samples, consisting of Si-nanocrystals dispersed in silica matrix. Thin films were deposited on Si wafer by spin-coating technique from a triethoxysilane-derived sol-gel solution. This is a fast process and a low cost technique. Samples were annealed at different temperatures between 600°C and 1300°C, under N 2 gas atmosphere. Structural evolution and luminescence from Si-ncs vs. temperature were investigated by FT-IR absorption spectroscopy and photo-luminescence. Absorption spectrum of As-Prep sample shows several vibrational bands due to Si-H, C-H x , and Si-O-Si structural units, without any appreciable luminescence. Silica phase segregation and intense PL (790 nm) due to Si-ncs were observed on annealing at T N 1000°C.
Mg–Ni multilayers and Ni-rich Mg thin films were deposited by electron gun and pulsed laser depos... more Mg–Ni multilayers and Ni-rich Mg thin films were deposited by electron gun and pulsed laser deposition, respectively. Samples were submitted to thermal treatment in deuterium or hydrogen atmosphere at 423K and ∼105Pa pressure to promote the metal to hydride phase transition.The H chemical bonding in the multilayer samples, after annealing in H2 atmosphere, was examined by Fourier transform infrared spectroscopy:
We report on the possibility of realizing adiabatic compression of polaritonic wave on a metallic... more We report on the possibility of realizing adiabatic compression of polaritonic wave on a metallic conical nano-structure through an oscillating electric potential (quasi dynamic regime). By comparing this result with an electromagnetic wave excitation, we were able to relate the classical lighting-rod effect to adiabatic compression. Furthermore, we show that while the magnetic contribution plays a marginal role in the formation of adiabatic compression, it provides a blue shift in the spectral region. In particular, magnetic permeability can be used as a free parameter for tuning the polaritonic resonances. The peculiar form of adiabatic compression is instead dictated by both the source and the metal permittivity. The analysis is performed by starting from a simple electrostatic system to end with the complete electromagnetic one through intermediate situations such as the quasi-electrostatic and quasi-dynamic regimes. Each configuration is defined by a particular set of equations which allows to clearly determine the individual role played by the electric and magnetic contribution in the generation of adiabatic compression. We notice that these findings can be applied for the realization of a THz nano-metric generator.
1 Disordered solid phases, containing appreciable amounts of hydrogen ions, are grown at the surf... more 1 Disordered solid phases, containing appreciable amounts of hydrogen ions, are grown at the surface of rhenium oxide crystals, because of the high reactivity of this compound with ambient moisture. To investigate such phenomena, a comparative study is performed on ground powder and thermally evaporated or sputtered films using x-ray diffraction and micro-Raman spectroscopy. Two types of solid phases were found in the films: H x ReO 3 distorted perovskite structures, based on corner-sharing ReO 6 octahedra as in the bulk crystals, and ordered HReO 4 crystalline structures, based on tetrahedral perrhenate ions. The complex impedance measurements on ReO 3 films support the hypothesis of mobile hydrogen ions in such defective films. Moreover, this relevant protonic conductivity allows the application of these films as active layers inserted into asymmetric nematic liquid-crystalline cells to rectify the electro-optical response of such devices, with performances quite similar to previously studied oxides such as WO 3 .
ABSTRACT In this paper we report the fabrication and characterization of a plasmonic device for l... more ABSTRACT In this paper we report the fabrication and characterization of a plasmonic device for label-free detection of few molecules in sub-wavelength regime by means of Raman scattering. The device is based on the coupling between a gold nanocone and a photonic crystal cavity, that is able to excite surface plasmon polaritons (SPPs) at the base on the cone. During the propagation toward the tip of the cone, the SPPs experiment and adiabatic compression that allow the accumulation of a very high electric field at the tip end. Raman enhancement factor of more than five order of magnitude is reported for a tip with a radius of curvature of about 10 nm. The present results open up future perspective on single molecule detection even in combination with AFM measurements.
In this work we report, for the first time to our knowledge, the possibility to fabricate various... more In this work we report, for the first time to our knowledge, the possibility to fabricate various structures, with good optical proprieties, on the top of optical fibers, using the two-photon lithography (TPL) technique. We show the convenience of this approach to quickly create generic 3D shapes using a single set-up by contrast to past shape-dependent methods. A set of different structures are fabricated and characterized to demonstrate the versatility of this approach and their high optical quality.
This paper reports on the fabrication and characterization of a novel device for surface enhanced... more This paper reports on the fabrication and characterization of a novel device for surface enhanced Raman scattering, fabricated using focused ion beam milling and electron beam induced deposition. The device exploits a photonic crystal cavity as an optical source to couple the incident laser with a metallic tapered nanolenses. The collected Raman measurements show that exploiting such approach is possible to overcome the difficulties related to scattering and diffraction phenomena occurring when visible laser illuminates nanostructures. A clear Raman scattering enhancement has been demonstrated for label-free detection of molecule in sub-wavelength regime.
Materials Science in Semiconductor Processing, 2004
Low-dielectric constant SiOC:H films were prepared by plasma enhanced chemical vapour deposition ... more Low-dielectric constant SiOC:H films were prepared by plasma enhanced chemical vapour deposition (PECVD) from trimethyl-silane (H-Si-(CH 3 ) 3 ) and ozone (O 3 ) gas mixture. The samples were preliminarily annealed at 400 1C in N 2 atmosphere and then in N 2 +He plasma. Afterwards, they were treated in vacuum at some fixed temperatures in the range between 400 and 900 1C. Structural investigations of the annealed films were carried out by means of vibrational spectroscopy techniques. FT-IR spectrum of a preliminarily treated sample shows absorption bands due to stretching modes of structural groups like Si-CH 3 at $1270 cm À1 , Si-O-Si at 1034 cm À1 and C-H x in the region between 2800 and 3000 cm À1 . No significant spectral change was observed in the absorption spectra of samples annealed up to 600 1C, indicating that the preliminarily treated film retains a substantial structural stability up to this temperature. Above 600 1C, absorption spectra show a strong quenching of H-related peaks while the band due to Si-O-Si anti-symmetric stretching mode shifts towards higher energy, approaching the value observed for thermally grown SiO 2 . Raman spectra of samples treated at temperatures TX500 1C exhibit both D and G bands typical of sp 2 -hybridised carbon, due to the formation of C-C bonds within the film which is accompanying the release of hydrogen. The intensity of D and G bands becomes more pronounced in samples annealed at higher temperatures, thus suggesting a progressive precipitation of carbon within the oxide matrix. r
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Papers by Gobind Das