Gobind Das | Istituto Italiano di Tecnologia / Italian Institute of Technology (original) (raw)

Papers by Gobind Das

ACS applied materials & interfaces, Jan 24, 2015

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...

Materials Science and Engineering: A, 2007

Encyclopedia of Nanotechnology, 2012

CLEO: 2014, 2014

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.

The Delivery of Nanoparticles, 2012

Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II, 2009

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.

Plasmonics, 2012

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.

Renewable Energy, 2008

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:

Optics Express, 2013

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.

Molecular Crystals and Liquid Crystals, 2007

Microelectronic Engineering, 2010

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.