High Sensitivity Sensors Made of Perforated Waveguides

Sensors based on surface plasmons or waveguide modes are at the focus of interest for applications in biological or environmental chemistry. Waveguide-mode spectra of 1 μm-thick pure and perforated silica films comprising isolated nanometric holes with great aspect ratio were measured before and after adhesion of streptavidin at concentrations of 500 nM. The shift of the angular position for guided modes was nine times higher in perforated films than in bulk films. Capturing of streptavidin in the nanoholes is at the origin of that largely enhanced shift in the angular position as the amplitude of the guided mode in the waveguide perfectly overlaps with the perturbation caused by the molecules. Hence, the device allows for strongly confined modes and their strong perturbation to enable ultra-sensitive sensor applications

Elongation of gold nanoparticles in silica glass by irradiation with swift heavy ions

We examined the mechanism whereby nanoparticles of gold embedded in silica become elongated and oriented parallel to each other on ion irradiation. Elongation occurred for gold particles with radii smaller than 25 nm. The process was simulated by using a thermal spike model. For small-radius nanoparticles, ion irradiation raises the temperature above the melting points of both gold and silica, whereas for larger nanoparticles neither the gold nanoparticle nor the surrounding silica matrix is melted

Trojan Horse Method experiments with radioactive ion beams

The Trojan Horse Method (THM) is an indirect method that allows to get information about a two body reaction cross-section even at very low energy, avoiding the suppression effects due to the presence of the Coulomb barrier. The method requires a very accurate measurement of a three body reaction in order to reconstruct the whole kinematics and discriminate among different reaction mechanisms that can populate the same final state. These requirements hardly match with the typical low intensity and large divergence of radioactive ion beams (RIBs), and experimental improvements are mandatory for the applicability of the method. The first reaction induced by a radio activeion beam studied by applying the THM was the 18F(p,α)15O. Two experiments were performed in two different laboratories and using different experimental set-ups. The two experiments will be discussed and some results will be presented

The 18^{18}F(nn,α\alpha ) Reaction: First Study of nn-Induced Reaction on a Radioactive Nucleus Using the Trojan Horse Method

International audienceFor the first time the Trojan Horse Method was applied to infer information about a neutron induced reaction on a radioactive nucleus at low energies relevant for astrophysics. In particular, the ^18F(n, $\alpha$)^15N reaction has been studied by using the ^18F+d reaction. A ^18F beam was produced at the CRIB facility at RIKEN, Japan, and was focused onto a CD_2 target. The beam had energy of 48 MeV, an average intensity of 10^5 pps and an average purity of 80%. A new designed experimental set-up covering a large solid angle was used to detect the ejected particles. The reaction cross section has been for the first time investigated in the energy range from 0 up to 2.5 MeV and several resonant states of ^19F have been populated