An Experimental Platform for the Analysis of Polydisperse Systems Based on Light Scattering and Image Processing

In this work an experimental platform for light scattering analysis has been developed using image sensors, as CCD or CMOS. The main aim of this activity is the investigation of the feasibility of using these types of sensors for polydisperse systems analysis. The second purpose is the implementation of an experimental platform which is enough versatile to permit the observation of different phenomena in order to develop novel sensors/approach using data fusion

Time-resolved photoelectron and photoion fragmentation spectroscopy study of 9-methyladenine and its hydrates: a contribution to the understanding of the ultrafast radiationless decay of excited DNA bases.

The excited state dynamics of the purine base 9-methyladenine (9Me-Ade) has been investigated by time- and energy-resolved photoelectron imaging spectroscopy and mass-selected ion spectroscopy, in both vacuum and water-cluster environments. The specific probe processes used, namely a careful monitoring of time-resolved photoelectron energy distributions and of photoion fragmentation, together with the excellent temporal resolution achieved, enable us to derive additional information on the nature of the excited states (pp*, np*, ps*, triplet) involved in the electronic relaxation of adenine. The two-step pathway we propose to account for the double exponential decay observed agrees well with recent theoretical calculations. The near-UV photophysics of 9Me-Ade is dominated by the direct excitation of the pp* (1Lb) state (lifetime of 100 fs), followed by internal conversion to the np* state (lifetime in the ps range) via conical intersection. No evidence for the involvement of a ps* or a triplet state was found. 9Me- Ade–(H2O)n clusters have been studied, focusing on the fragmentation of these species after the probe process. A careful analysis of the fragments allowed us to provide evidence for a double exponential decay profile for the hydrates. The very weak second component observed, however, led us to conclude that the photophysics were very different compared with the isolated base, assigned to a competition between (i) a direct one-step decay of the initially excited state (pp* La and/or Lb, stabilised by hydration) to the ground state and (ii) a modified two-step decay scheme, qualitatively comparable to that occurring in the isolated molecule

Development of a Novel Snom Probe for in Liquid Biological Samples

This work is focused on the study and implementation of a novel method for the development of probes for Scanning Near-field Optical Microscopy (SNOM). The proposed approach is based on the mechanical impedance matching between the optical fiber tip and the resonating tuning fork. This methodology allowed an increase of the quality factor of the piezoelectric resonator used as atomic force transducer in the SNOM probe, thus increasing its overall sensitivity. This kind of probes are often used on biological soft samples in liquid. The presence of water medium has a strong dumping effect on probe sensitivity. Experimental validation of the proposed methodology showed an increase of robustness of SNOM probes also for in liquid samples