Antonio Sasso - Academia.edu (original) (raw)

Papers by Antonio Sasso

Nanophotonics, May 23, 2024

International Journal of Molecular Sciences

Surface-enhanced Raman scattering (SERS) is of growing interest for a wide range of applications,... more Surface-enhanced Raman scattering (SERS) is of growing interest for a wide range of applications, especially for biomedical analysis, thanks to its sensitivity, specificity, and multiplexing capabilities. A crucial role for successful applications of SERS is played by the development of reproducible, efficient, and facile procedures for the fabrication of metal nanostructures (SERS substrates). Even more challenging is to extend the fabrication techniques of plasmonic nano-textures to atomic force microscope (AFM) probes to carry out tip-enhanced Raman spectroscopy (TERS) experiments, in which spatial resolution below the diffraction limit is added to the peculiarities of SERS. In this short review, we describe recent studies performed by our group during the last ten years in which novel nanofabrication techniques have been successfully applied to SERS and TERS experiments for studying bio-systems and molecular species of environmental interest.

Scientific Reports

We investigate a quasi-2D suspension of Brownian particles in an optical speckle field produced b... more We investigate a quasi-2D suspension of Brownian particles in an optical speckle field produced by holographic manipulation of a laser wavefront. This system was developed to study, in a systematic and controllable way, a distinctive instance of diffusion, called Fickian yet Non Gaussian diffusion (FnGD), observed, during the last decade, for colloidal particles in a variety of complex and biological fluids. Our setup generates an optical speckle field that behaves like a disordered set of optical traps. First, we describe the experimental setup and the dynamics of the particles, focusing on mean square displacements, displacement distributions and kurtosis. Then, we present Brownian Dynamics simulations of point-like particles in a complex energy landscape, mimicking that generated by the optical speckle field. We show that our simulations can capture the salient features of the experimental results, including the emergence of FnGD, also covering times longer than the ones so far a...

Frontiers in Bioengineering and Biotechnology, 2022

Two-dimensional nanomaterials, such as MoS2 nanosheets, have been attracting increasing attention... more Two-dimensional nanomaterials, such as MoS2 nanosheets, have been attracting increasing attention in cancer diagnosis and treatment, thanks to their peculiar physical and chemical properties. Although the mechanisms which regulate the interaction between these nanomaterials and cells are not yet completely understood, many studies have proved their efficient use in the photothermal treatment of cancer, and the response to MoS2 nanosheets at the single-cell level is less investigated. Clearly, this information can help in shedding light on the subtle cellular mechanisms ruling the interaction of this 2D material with cells and, eventually, to its cytotoxicity. In this study, we use confocal micro-Raman spectroscopy to reconstruct the thermal map of single cells targeted with MoS2 under continuous laser irradiation. The experiment is performed by analyzing the water O-H stretching band around 3,400 cm−1 whose tetrahedral structure is sensitive to the molecular environment and temperat...

Journal of Colloid and Interface Science, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Scientific Reports, 2019

A correction to this article has been published and is linked from the HTML and PDF versions of t... more A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Crystals, 2016

We numerically investigate the electromagnetic field localization in a two-dimensional photonic q... more We numerically investigate the electromagnetic field localization in a two-dimensional photonic quasicrystal generated with a holographic tiling. We demonstrate that light confinement can be induced into an air mirrorless cavity by the inherent symmetry of the spatial distribution of the dielectric scatterers forming the side walls of the open cavity. Furthermore, the propagation direction can be controlled by suitable designs of the structure. This opens up new avenues for designing photonic materials and devices.

Journal of biophotonics, May 15, 2016

Conjunctival microvilli are microscopic cellular membrane protrusions on apical epithelial cells,... more Conjunctival microvilli are microscopic cellular membrane protrusions on apical epithelial cells, which increase the surface area available for tear adherence. Pathological alterations of microvilli structure affect the tear film stability and, conversely, dysfunctions of tear film composition can lead to a suffering epithelium (dry-eye syndrome). In this work we propose the use of micro-Raman analysis to reveal conjunctival microvilli abnormalities. Samples were obtained by impression cytology from patients by different stage of dry-eye syndrome. Our experimental outcomes demonstrate that Raman analysis, combined with the use of Principal Component Analysis, is able to detect different stages of microvilli reduction. Globally, these results hold promise for the use of Raman analysis for an objective, effective, non-invasive and potentially also in-vivo analysis of the conjunctiva in all the cases of microvilli-related ocular pathologies.

Physical Chemistry Chemical Physics, 2015

The self-assembling of gold nanoparticles directed by the phase separation of poly(styrene)-b-pol... more The self-assembling of gold nanoparticles directed by the phase separation of poly(styrene)-b-poly(methylmethacrylate) produces a homogeneous and isotropic nanostructure with excellent SERS spatial reproducibility.

ACS Nano, 2014

Tip-enhanced Raman Scattering (TERS) has recently emerged as a powerful spectroscopic technique c... more Tip-enhanced Raman Scattering (TERS) has recently emerged as a powerful spectroscopic technique capable of providing subdiffraction morphological and chemical information on samples. In this work, we apply TERS spectroscopy for surface analysis of the Bacillus subtilis spore, a very attractive biosystem for a wide range of applications regulated by the spore surface properties. The observed spectra reflect the complex and heterogeneous environment explored by the plasmonic tip, therefore exhibiting significant point-to-point variations at the nanoscale. Herein, we demonstrate that TERS data processing via principal component analysis allows handling such spectral changes, thus enabling an unbiased correlative imaging based on TERS. Our experimental outcomes suggest a denser arrangement of both proteins and carbohydrates on specific spore surface regions simultaneously revealed by AFM phase imaging. Successful TERS analysis of spores&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; surface is useful for bacterial surface-display systems and drug delivery applications.

Optics Communications, 1986

Ill this paper we study the influence of tile transverse spatial distribution of the laser beana ... more Ill this paper we study the influence of tile transverse spatial distribution of the laser beana on the estinaatc of tile photoionization cross section for the specific case of two-step photoionization (TSP1) of benzene. In particular, we discuss the sensitivity of the inferred cross section on the nlultimode transverse operation of the dye laser oscillator.

La Rivista del Nuovo Cimento, 1989

The two-photon excitation and three-photon ionization of atomic cesium is investigated over the 6... more The two-photon excitation and three-photon ionization of atomic cesium is investigated over the 6550-6950-A wavelength region with a tunable-dye-laser source having a 0.06-0.0S-A. linewidth and a space-charge ionization detector sensitive to a few iona per second. An online data-acquisition computer provides significant signal-to-noise recovery. The resulting dispersion curve for photoionization is interpreted in terms of the two-photon transitions from the ground 628&y2 level to resonant n D and n 8 intermediate states, and represents, to the authors'knowledge, the first such two-photon absorption spectrum of Cs. Transitions from n =9 to 13 have been recorded for the 6 Qy2n Dg(2 3/2 series and from n =11 to 14 for the 62+g2n 2@F2 series.

Optics Communications, 1998

In this work we report on a Doppler-free investigation of the argon atom using saturation spectro... more In this work we report on a Doppler-free investigation of the argon atom using saturation spectroscopy. As laser source we used a narrow-band semiconductor diode laser emitting in the near infrared. Isotope shifts in the transitions 4s[3/2]o–4p[3/2] (1s5–2p7 in Paschen notation) at 772.59 nm and 4s′[1/2]o–4p′[3/2] (1s3–2p2) at 772.64 nm were investigated in enriched samples with the three stable isotopes

Journal of Molecular Spectroscopy, 2004

In this paper we present the main results concerning lineshape analysis on ν1 and ν3 water vapor ... more In this paper we present the main results concerning lineshape analysis on ν1 and ν3 water vapor lines in the region around 3μm. Narrow-bandwidth radiation used in this experiment was produced by difference-frequency generation in a periodically poled crystal between two near-infrared solid state lasers. We have investigated pressure broadening and shift for five H2O absorption lines induced by collisions

Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1992

We measured isotope shifts and hyperfine structure of visible transitions of stable strontium iso... more We measured isotope shifts and hyperfine structure of visible transitions of stable strontium isotopes by means of Doppler-free saturated absorption spectroscopy. In particular, we investigated transitions between excited states where the upper level involves two excited electrons. We report hyperfine coupling constants for the levels 5p4d 1D2, 5p4d 3F2, 5s4d 3D 1, 5s6s 3S~, 5s5p 3p1 and, for some of the studied transitions, we separate the specific mass and volume contribution to the isotope shifts.

In the biomedicine field, scientists act as detectives working hard to unravel the mysteries surr... more In the biomedicine field, scientists act as detectives working hard to unravel the mysteries surrounding cells. To this end, Raman spectroscopy has revealed itself particularly useful, providing information concerning both the chemical composition and the structural conformation of the investigated samples. If compared to many other techniques devoted to the identification of microorganisms (as for instance fluorescence spectroscopy), Raman spectroscopy presents the relevant advantage of providing sharp peaks correlated to vibrational modes of the investigated sample. Moreover, it is a noninvasive technique, not requiring the addition of chemical agents or labels for a sample identification. Therefore, Raman spectra behave as the fingerprints of the analyzed sample. Hence, the Raman spectroscopy technique represents a powerful tool to detect cellular transformations in real time, contributing to elucidate many biochemical processes even in living cells. However, the analytical capab...

Physical Review A, 1991

Saturation spectroscopy, velocity-selective atomic orientation, and velocity-selective alignment ... more Saturation spectroscopy, velocity-selective atomic orientation, and velocity-selective alignment have been applied to a high-resolution investigation of the 3s'S2-3p'P& 2 3 transitions at 777 nm of atomic oxygen. Pure Lorentzian lineshapes were obtained, which allowed an accurate measurement of the radiative linewidth. Using an isotopically enriched sample, isotope shifts and hyperfine structure were resolved and measured.

Physical Review Letters, 1990

By exploiting a narrow-linewidth diode-laser source we measure the hyperflne structure of the S2 ... more By exploiting a narrow-linewidth diode-laser source we measure the hyperflne structure of the S2 state of "O. Nuclear parameters can be calculated from the measured hyperfine structure. Recorded collision-free linewidths allow an estimate of the lifetime of the levels involved in a new scheme proposed for the cooling of atomic oxygen.