Vladimiro Mujica at Arizona State University is funded by the Chemical Theory, Models and Computational Methods program in an International Collaboration in Chemistry, with partners Arne Keller at the University of Paris in Orsay as well as Osman Atabek and Monica Calatayd all funded by France's Agence Nationale de la Recherche. This is co-funded by the NSF Office of International Science and Engineering (OISE). This project aims at a theoretical investigation of the influence of the chemical bond between a molecule and a semiconducting nanoparticle on the Raman and fluorescence responses of these hybrid systems. These processes must be jointly considered, as the excitation and decay pathways become interdependent due to the appearance of midgap states, induced by the formation of the chemical bond and interfacial charge transfer that play a fundamental role in both photoexcitation and electron injection into the nanoparticle. This involves the calculation of the cross section for both Raman scattering and fluorescence, based on the properties of the time-correlation function of the effective dipole moment of the system. The emphasis is on processes that are resonant in the hybrid but not in the separate components, due to the reduction of the energy gap for electron excitation. Laser photoexcitation simultaneously provokes the creation of an electron-hole exciton and probes the Raman and fluorescence responses.
By developing reliable procedures to predict the light that emerges when laser light shines on these molecule-nanoparticle hybrid systems, greater understanding will be obtained of the fundamental physical and chemical processes in bio-sensors and also in solar cells and photocatalysis. These three areas are crucial for energy and health-related research and for the technological implementation of new photovoltaic devices and sensors. The project involves a strong international scientific cooperation between teams of researchers in France and the U.S and it also contemplates active collaboration with experimental groups and human resources formation.