Time-resolved spectroscopy applied to the study of the electronic energy transfer in organic molecules and energy transfer in gold nanoparticles

Author(s)

Guilherme Ferreira Ferbonink

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2014-02-20

Examining board members

René Alfonso Nome Silva; Leandro Martínez; Lino Misoguti

• Advisor: René Alfonso Nome Silva

Abstract

Structure-property relationships for electronic energy transfer have been investigated in recent years. One of the goals of the present research is to perform an experimental study vibronic structure effects in electronic energy transfer between small organic molecules according to Forster¿s model. We have chosen organic molecules with well-defined spectral overlap between vibronic bands, which enabled us to experimentally characterize a decrease in donor emission intensity at the acceptor absorption wavelengths thereby indicating radiative energy transfer. A decrease in the emission integrated intensity characterizes energy transfer by the Forster mechanism. Forster energy transfer rates were higher when the spectral overlap involved 0-1 and 0-2 vibronic bands rather than 0-0 band. In the second part of this work, we have employed ultrafast transient absorption spectroscopy to investigated gold nano prisms deposited over two different substrates: Au over glass (Au/glass) and Au over ITO deposited on glass (Au/ITO/glass). In the present work, we describe the preparation and characterization of these two samples employing the nanosphere lithography technique. The linear absorption spectra of Au/glass and Au/ITO/glass respectively show surface plasmon resonances at 800 nm and 870 nm, with a 70nm redshift attributed to the ITO refractive index. We have performed femtosecond one-color pump-probe measurements with 100 fs time resolution below the surface plasmon resonance, at resonance, and above the surface plasmon resonance for each of these two systems. For both systems, the ultrafast dynamics can be well described with a model that takes into account electron-electron scattering, electron-phonon coupling, phonon-phonon coupling and acoustic damping. The wavelength-dependence observed can be explained in terms of the sample frequency-dependent complex refractive index which modulates the measured pump-probe signals (AU)

• FAPESP's process: 12/01425-2 - How does vibronic structure affect electronic energy transfer in organic molecules?
• Grantee: Guilherme Ferreira Ferbonink
• Support Opportunities: Scholarships in Brazil - Master