Light Scattering and Turbidimetry Techniques for the Characterization of Nanoparticles and Nanostructured Networks.

Light scattering and turbidimetry techniques are classical tools for characterizing the dynamics and structure of single nanoparticles or nanostructured networks. They work by analyzing, as a function of time (Dynamic Light Scattering, DLS) or angles (Static Light Scattering, SLS), the light scattered by a sample, or measuring, as a function of the wavelength, the intensity scattered over the entire solid angle when the sample is illuminated with white light (Multi Wavelength Turbidimetry, MWT). Light scattering methods probe different length scales, in the ranges of ~5−500 nm (DLS), or ~0.1−5 µm (Wide Angle SLS), or ~1−100 µm (Low Angle SLS), and some of them can be operated in a time-resolved mode, with the possibility of characterizing not only stationary, but also aggregating, polymerizing, or self-assembling samples. Thus, the combined use of these techniques represents a powerful approach for studying systems characterized by very different length scales. In this work, we will review some typical applications of these methods, ranging from the field of colloidal fractal aggregation to the polymerization of biologic networks made of randomly entangled nanosized fibers. We will also discuss the opportunity of combining together different scattering techniques, emphasizing the advantages of a global analysis with respect to single-methods data processing.

Laser-Induced Breakdown Spectroscopy Analysis of Lead Aerosol in Nitrogen and Air Atmosphere.

In this work, laser-induced breakdown spectroscopy (LIBS) is applied for quantitative measurements of Pb in aerosols. In order to investigate the carrier gas role and, in particular, the effect of O2 addition to the gas itself, measurements are carried out in nitrogen and air atmosphere. Aerosol particles are produced by nebulizing Pb(CH3COO)2 * 3H2O aqueous solutions of known concentration and the atomic line of 405.8 nm is detected as Pb signature. The plasma generated with the laser pulse is characterized in terms of plasma temperature and electron density, showing no substantial differences with the two carrier gases used. The behavior of the LIBS signal as a function of the delay time with respect to the laser pulse is investigated changing the environmental conditions and, in particular, the Pb concentration values. The different trends registered in the case of relatively short (up to 20 µs) and long delay time, resulting to be the same whatever the Pb concentration value, could have a significant effect on the calibration curve performed in different experimental conditions.

Mapping the transverse coherence of the self amplified spontaneous emission of a free-electron laser with the heterodyne speckle method.

The two-dimensional single shot transverse coherence of the Self-Amplified Spontaneous Emission of the SPARC_LAB Free-Electron Laser was measured through the statistical analysis of a speckle field produced by heterodyning the radiation beam with a huge number of reference waves, scattered by a suspension of particles. In this paper we report the measurements and the evaluation of the transverse coherence along the SPARC_LAB undulator modules. The measure method was demonstrated to be precise and robust, it does not require any a priori assumptions and can be implemented over a wide range of wavelengths, from the optical radiation to the x-rays.