Espectroscopia de Femtosegundos de Banda Ancha, Fundamentos y Aplicaciones

Se repasará el formalismo de la teoría de señal para Espectroscopia no lineal de tercer y quinto orden y se analizarán las contribuciones resultantes con la ayuda de diagramas de energía, análogos a los diagramas de Feynman de doble lado. A continuación, se describirán las técnicas de Espectroscopia de absorción transitoria de banda ancha y resolución de femtosegundos y la técnica ultrarrápida de resonancia Raman estimulada. Se concluirá con dos aplicaciones de ambas técnicas en el ámbito de la fotobiología: activación de criptocromos y desactivación ultrarrápida de beta-caroteno.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Charge Transfer from Photoexcited Semiconducting Single-Walled Carbon Nanotubes to Wide-Bandgap Wrapping Polymer

As narrow optical bandgap materials, semiconducting single-walled carbon nanotubes (SWCNTs) are rarely regarded as charge donors in photoinduced charge-transfer (PCT) reactions. However, the unique band structure and unusual exciton dynamics of SWCNTs add more possibilities to the classical PCT mechanism. In this work, we demonstrate PCT from photoexcited semiconducting (6,5) SWCNTs to a wide-bandgap wrapping poly-[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(6,6′)-(2,2′-bipyridine)] (PFO–BPy) via femtosecond transient absorption spectroscopy. By monitoring the spectral dynamics of the SWCNT polaron, we show that charge transfer from photoexcited SWCNTs to PFO–BPy can be driven not only by the energetically favorable E$_{33}$ transition but also by the energetically unfavorable E$_{22}$ excitation under high pump fluence. This unusual PCT from narrow-bandgap SWCNTs toward a wide-bandgap polymer originates from the up-converted high-energy excitonic state (E$_{33}$ or higher) that is promoted by the Auger recombination of excitons and charge carriers in SWCNTs. These insights provide new pathways for charge separation in SWCNT-based photodetectors and photovoltaic cells