Sebastiano Trusso

The controlled pulsed laser deposition of Ag nanoparticle arrays for surface enhanced Raman scattering

An effective method for the production of surface enhanced Raman scattering (SERS) active substrates is presented. Nanostructured silver thin films are pulsed laser deposited in an argon atmosphere. The films consist of arrays of nanoparticles whose size is controlled by the Ar pressure. The surface morphology of the films can be tuned by the laser pulse number. Nanoparticle size is calculated by a phenomenological model taking into account the dynamics of the laser generated silver plasma. The SERS activity of the films is investigated by Raman scattering of adsorbed rhodamine 6G at different concentrations.

Ag nanocluster synthesis by laser ablation in Ar atmosphere: A plume dynamics analysis

Ag thin films were deposited by pulsed laser ablation in a controlled Aratmosphere. The deposition process was performed at different Ar pressure values in the range between 10 and 100 Pa to investigate the influence of ambient gas pressure on the plasma expansion dynamics and on the film structural properties. Position, velocity and volume of the laser generated plasma as functions of time were obtained by time resolved fast photography. The morphological properties of the films were investigated by transmission electron microscopy which shows that film growth proceeds via aggregation on the substrates of nanoclusters formed in the expanding plume. The formation of nanoparticles takes place as a consequence of plasma confinement induced by the interaction with ambient gas species. Data from fast photography analysis were used as input parameters to calculate the size of the nanoparticles using a model that takes into account the collisional nature of the laser generated silver plasma.

Time resolved imaging studies of the plasma produced by laser ablation of silicon in O 2 0Ar atmosphere

The dynamics of the expansion plasma produced by excimer laser ablation of a silicon target into oxygen and mixed O20Ar atmosphere were studied by means of time-resolved imaging of the expanding plume. Experiments were performed in pure oxygen, ranging between 0.13 and 13.33 Pa, and at different O20Ar ratios at a fixed total pressure of 13.33 Pa. The occurrence of a shock wave ~SW! generated by the supersonic expansion of the plasma was observed at high pressure values. The presence of the SW had a strong influence on the structure of SiOx thin films. In fact, silicon dioxidethinfilmswerealwaysobtainedinpresenceoftheSW,irrespectiveoftheoxygencontentinthegaseousmixture. On the contrary, suboxide thin films were obtained when the expansion occurred at lower pressure values ~no SW presence!. The temperature rise following the developing of the SW, is supposed to enhance the oxygen molecules dissociation by increasing the efficiency of the silicon oxidation reaction.

Raman microscopy study of pulsed laser ablation deposited silicon carbide films

Silicon carbide films have been deposited by pulsed laser ablation. The sample microstructure was studied by means of SEM imaging and spatially resolved Raman spectroscopy. Some inhomogeneities, on an otherwise structureless sample surfaces, were evident in the SEM images. A detailed Raman imaging study was carried out over a properly selected area including some inhomogeneous spots. Analysis of the spectral features relative to phonon modes revealed a variety of structural configurations. In the homogeneous region, the amorphous phases of silicon carbide, graphitic carbon and silicon were identified. On the other hand the inhomogeneous spots contained predominantly microcrystalline phases of both silicon and graphitic and/or tetrahedral carbon species. Micro-Raman spectroscopy provided an excellent tool, in giving local structural information by selectively probing a microscopic scattering volume.

Nano-Raman imaging of Cu–TCNQ clusters in TCNQ thin films by scanning near-field optical microscopy

We have combined scanning near-field optical microscopy (SNOM) techniques with Raman scattering in order to measure the topography and the local optical properties of solid samples together with the chemical properties of molecular adsorbates, on subwavelength scales. The proposed experimental setup is simple, but very sensitive. In particular, we have focussed our attention on the optimization of the collection and detection of the scattered light, in order to circumvent the limited imaging capabilities of the SNOM due to the low cross-section of the Raman effect. The sample we will report on is a tetracyanoquinodimethane (TCNQ) thin film kept in contact with Cu powder in order to give rise to local complexes of Cu–TCNQ. A comparative investigation based on independent micro- and nano-Raman maps, allows us to chemically discriminate the aggregates and to assess the enhanced lateral resolution of the SNOM in the nanometre range.

Surface-enhanced Raman scattering of SnO2 bulk material and colloidal solutions

Surface enhanced Raman scattering (SERS) effects on tin dioxide in the form of bulk material, nanostructured thin films and colloidal solutions were investigated. Raman spectra are characterized by the three Raman scattering peaks at 478, 633, and 776 \invcm, assigned to the E

Excimer laser ablation of silicon carbide ceramic targets

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Phage-AgNPs complex as SERS probe for U937 cell identification.

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Materials analysis opportunities on the new neutron imaging facility IMAT@ISIS

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Investigation of a nanocrystalline silicon phase embedded in SiOx thin films grown by pulsed laser deposition

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