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Dr. Antonio Aloi

Chemistry Dept., Università di Bari

Tuesday, June 18th, 2013 at 10:30:00 AM  

Conference room Querzoli - LENS - via Nello Carrara 1 - Sesto Fiorentino (Florence)

Published on-line at 03:16:31 PM on Thursday, June 13th, 2013

Femtosecond transient absorption of synthetic Eumelanin solutions

Analysis of the dynamics of synthetic Melanin pigments in different solutions using femtosecond transient absorption spectroscopy.

Melanins are a very important class of biological pigments that are ubiquitous in nature, being found in most organisms. Because of their unique optical properties, such as broadband absorption spectrum, Melanins are deeply investigated. The purpose of our study is to analyze the dynamics of synthetic Eumelanin (a specific Melanin pigment) in two different solutions (DMSO-methanol, HPLC grade water) using femtosecond transient absorption spectroscopy.

Thanks to the experimental setup used we are able to tune the excitation wavelength continuously in the UV-Vis range, and probe the temporal evolution of photo-induced absorption changes with sub-picoseconds time resolution in a broad spectral range (450-800 nm). We demonstrate how Eumelanin dynamics is influenced by a non-linear optical effect (Inverse Raman Scattering - IRS, see figure) related to the solvent used. An absorption process at the anti-Stokes frequencies and an emission process at Stokes frequencies characterize this effect. Taking into account IRS effect we investigate the intrinsic Eumelanin dynamics and fit the experimental data with a convolution function between the instrumental response function and a bi-exponential decay.

For further informations, please contact Prof. Paolo Foggi.