The ability to confine light in small volumes, associated to low background signals, is an important technological
achievement for a number of disciplines such as biology or electronics. In fact, decoupling the source position from the
sample area allows an unprecedented sensitivity which can be exploited in different systems. The most direct
implications are however related to either Surface Enhanced Raman Scattering (SERS) or Tip Enhanced Raman
Scattering (TERS). Furthermore, while the combination with super-hydrophobic patterns can overcome the typical
diffusion limit of sensors, focused surface plasmons decaying into hot electrons can be exploited to study the electronic
properties of the sample by means of a Schottky junction. Within this paper these techniques will be briefly described
and the key role played by both surface and localized plasmons will be highlighted.
Gobind Das, Rosanna La Rocca, Tadepally Lakshmikanth, Francesco Gentile, Rossana Tallerico, Lia Zambetti, James Devitt, Patrizio Candeloro, Francesco De Angelis, Ennio Carbone, Enzo Di Fabrizio
KEYWORDS: FDA class I medical device development, Raman spectroscopy, Molecules, Proteins, Principal component analysis, Molecular spectroscopy, Micro raman spectroscopy, Tumors, Biological research, Deconvolution
Human leukocyte antigen (HLA) class I molecules are formed by three immunoglobulin-like domains (α1, α2, and α3) once folded by peptide and β2-microglobulin show the presence of two α-helix streams and one β-sheet limiting the pocket for the antigenic peptide. The loss of HLA class I expression in tumors and virus-infected cells, on one hand, prevents T cell recognition, while on the other hand, it leads to natural killer (NK) cell mediated cytotoxicity. We propose the possibility of using Raman spectroscopy to measure the relative expression of HLA class I molecules at the single-cell level. Raman spectra are recorded for three cell lines (K562, T2, and T3) and monomers (HLA class I folded, unfolded and peptide+β2-microlobulin refolded) using 830 nm laser line. Our data are consistent with the hypothesis that in the Raman spectra, ranging from 1600 to 1800 cm−1, the intensity variation of cells associated with HLA class I molecules could be measured.
Here we report the design, the fabrication and measurement of a photonic-plasmonic device that is fully compatible
with AFM microscopy and surface enhanced Raman spectroscopy. The physical mechanism exploited is the
adiabatic compression of Surface Plasmon Polaritons which propagate along a silver nanocone generating a very
high electric field at the tip end. A photonic crystal cavity is employed to efficiently couple the external laser
radiation with the nanocone. The reported measurements demonstrate the accumulation of the electric field at the tip
of the nanocone that allow the detection of a few molecules located near the tip end. The estimated Raman
enhancement factor is about 106 with respect to a standard configuration. The present results open a good
perspective for the development of an integrated Raman-AFM microscopy able to perform both topography and
chemical mapping in label free condition with a spatial resolution comparable to the tip end.
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 1012 (theoretically) with respect to the normal
Raman measurements. We estimate the number of Rhodamine6G molecule detected is about 100-150.
This paper reports the fabrication of two reproducible surface enhanced Raman scattering devices using; a) nanoPillar
coupled with PC cavity by means of FIB milling and electron beam induced deposition techniques (Device 1), and b)
plasmonic gold nanoaggregate structures using electro-plating and e-beam lithography techniques (Device 2). Device 1
consists of photonic crystal cavity as an optical source to couple the incident laser with a metallic tapered nanolens.
Exploiting such approach it is possible to overcome the difficulties related to scattering and diffraction phenomena when
visible laser (514 nm) illuminates nanostructures. The nanostructure is covered with HMDS and is selectively removed
leaving HMDS polymer on nanoPillar only. A clear Raman scattering enhancement has been demonstrated for label-free
detection of molecule in sub-wavelength regime. On the other hand, myoglobin protein is deposited on Device 2 using
drop coating deposition method and is estimated that the substrate is able to detect the myoglobin concentration down to
attomole.
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