Stable Transient Spectroscopy Study Of Energy Transfer Between Quantum Dots And Organic Molecules

In physics,the energy transfer process refers to the transfer of energy from the ground state to the excited state during the relaxation of the excited state molecule to the ground state.In the energy transfer mechanism,the most important two mechanisms are the resonance mechanism and the electronic exchange mechanism.The resonance mechanism is also called as the F?STER mechanism.The F?STER resonance excitation energy transfer theory is an important theory and involved in many research fields,especially biology.This thesis focuses on the energy transfer process in the quantum dot-organic dye hybrid system.As an emerging material,quantum dots are highly favored by scientists for their unique characteristics.From the aspect of energy state,the structure of quantum dots is similar to the structure of separated energy levels of atoms.From the aspect of performance,quantum dots has become a hot topic in the current research because of its adjustable wavelength,high fluorescence and strong stability.Porphyrin and rhodamine B are two traditional organic dyes,they can be used as fluorescent dyes that can selectively combine with macromolecules and partially enter into specific locations of cells.They have been used in physical and biochemical analysis for more than 120 years.This thesis makes studies of the energy transfer characteristics between the steady-state and femtosecond time-resolved absorption spectroscopy detection system using femtosecond pulse as the excitation light source and the composite material system consists of the water-insoluble tetraphenyl porphyrin as the energy acceptor and the CdSe/ZnS core-shell quantum dot as the energy donor.The result shows that the fluorescence intensity of the donor gradually decreases when the receptor concentration increases.The type of energy transfer between the two is non-radiative energy transfer.In this thesis,CdTe/CdS/ZnS core-shell quantum dots are used as energy donors,and Rhodamine B is an energy acceptor.This thesis makes studies of the fluorescence resonance energy transfer between the two aqueous mixed systems.Using a femtosecond pulsed laser as the excitation light source,time-resolved absorption spectroscopy was obtained.The result showed that there was a clear positive correlation between the rise of the transient absorption signal and the Rhodamine B receptor concentration,the efficiency of the fluorescence resonance energy transfer is increased with the increase of the receptor concentration.Theoretical analysis shows that the energy transfer mechanism between these two is the F?STER mechanism.