Andrea Toma

Plasmon based biosensor for distinguishing different peptides mutation states

Periodic and reproducible gold nanocuboids with various matrix dimensions and with different inter-particle gaps were fabricated by means of top-down technique. Rhodamine 6G was used as a probe molecule to optimize the design and the fabrication of the cuboid nanostructures. The electric field distribution for the nanocuboids with varying matrix dimensions/inter-particle gap was also investigated. These SERS devices were employed as biosensors through the investigation of both myoglobin and wild/mutated peptides. The results demonstrate the probing and the screening of wild/mutated BRCA1 peptides, thus opening a path for the fabrication of simple and cheap SERS device capable of early detection of several diseases.

Plasmon resonance tuning in metal nanostars for surface enhanced Raman scattering

We report the fabrication of Au nanostar arrays by means of electron beam lithography, in which the plasmon resonance energy can be tuned via the nanostar size from the visible into the near-infrared region. The spectral response of the nanostar arrays was investigated by optical extinction (transmittance) experiments, and their surface enhanced Raman scattering performance has been tested at two different excitation wavelengths, 633 nm and 830 nm, using chemisorbed Cresyl violet molecules as analyte. The experimental results are supported by numerical simulations of the spatial and spectral electric field enhancement.

Terahertz Dipole Nanoantenna Arrays: Resonance Characteristics

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 (∼1–2xa0THz) 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.

Interplay between electric and magnetic effect in adiabatic polaritonic systems

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.

Nanoparticles and Nanostructures for Biophotonic Applications

The aim of this chapter is to expound on the theoretical analysis and experimental assessment of NanoParticles (NPs) for imaging, early detection and therapeutic applications. NPs are extremely small particulates with dimensions ranging from few micrometers down to few tens of nanometers. Their characteristics, including size, shape, physical and chemical properties, can be tailored during the fabrication/synthesis process and, on account of these, they would feature certain aspects that may be exploited for applications ranging from drug delivery to the enhancement of the local electric field, and thus the detection of few molecules. In particular, intravascularly injectable NPs (that are sometimes called nanovectors or nanocarriers) are probably the major class of nanotechnological devices of interest for use in cancer or, in general, for the treatment of diseases. On the other hand, aggregates of metallic NPs, either of silver or gold, represent extremely efficient SERS (Surface Enhanced Raman Scattering) substrates. In the following, after a brief description of NPs as a whole, a number of different applications will be discussed.

Metal Structures as Advanced Materials in Nanotechnology

‘Metal structures as advanced materials in nanotechnology’ is a collection of fabrication and characterization techniques which involve metallic materials for the realization of advanced micro- and nanostructured devices.

3D plasmonic nanostructures as building blocks for ultrasensitive Raman spectroscopy

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.

Terahertz Resonant Dipole Nanoantennas

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.