Nano-silicon for light-controlled energy transfer to molecular oxygen

Abstract

This thesis presents the results of several physical and magneto-optical experiments using nanostructured silicon fabricated by an electrochemical etching method. Quantum confinement causes the efficient visible light emission of nanocrystalline silicon. Long lived excitons confined in silicon nanocrystals are applied as an energy storage medium for energy transfer to oxygen. Nanocrystalline silicon-silica aerogel composites are synthesised and examined the sensitivity with adsorbed oxygen molecules.

Efficient energy transfer from photo-excited excitons to molecular oxygen to create singlet oxygen is presented in the experimental results. Spin exchange interactions are a key aspect controlling the energy transfer between silicon nanoparticles and molecular oxygens. Hence, modifications of the spins alter the dynamics of the energy transfer process. Spin distributions of the participating states are changed by applying magnetic fields or by changing excitation powers. Therefore, the dependences of the transfer process on magnetic field, excitation power and oxygen concentration were studied.

The energy transfer model is constructed based on a rate equation approach. The model produces simulations that are in good agreement with the overall data. The dynamic parameters are provided and indicate the characteristics of the silicon nanostructures. Possibilities for future work in this research area are included.

Date of Award	3 Jul 2014
Original language	English
Awarding Institution	University of Bath
Sponsors	Government of Thailand
Supervisor	Daniel Wolverson (Supervisor)