The Study Of Quantum Dots-organic Dyes Energy Transfer Under Two-photon Excitation Of Femtosecond Laser

The Energy Transfer process is said to occur from the excited state in one system to the ground state in another system, or between two excited states in two systems, thus increasing the energy content of one system while decreasing the energy content of the other system by the same amount. Energy Transfer theory, especially Fluorescence Resonance Energy Transfer theory(FRET), as an important theory, it plays a key role in many fields, especially in biology. In addition, two-photon absorption process, as a kind of three order nonlinear effect, is an interaction of light and matter under the radiation of high power laser. Comparing to one-photon absorption process, the two-photon absorption process holds its unique characteristics, for example, high spatial selectivity, high penetration etc. As a result, it can make a huge difference in many fields. Besides, quantum dots(QDs) are a new material that possesses the discrete energy level structure which is similar to atom, and QDs has many excellent optical properties like wavelength tunability, high fluorescence efficiency, stability etc. That is why QDs becomes a hot research spot. It is well known that biological tissue has its unique properties needs significantly high requirement of research method, for instance, safety, need Real time observation, special wavelength, need precise location etc. Based on the above reasons, this paper combines the FRET theory, two-photon absorption theory and QDs in order to promote the development of biology technology. The research of FRET in QDs-organic dye system under the two-photon excitation has important implications.In the previous articles, the research of FRET that involves QDs is uncommon, while this study under the two-photon excitation is rare. In order to explore the property of FRET of QDs-organic dyes system under two-photon radiation, this paper study the FRET characteristics of Cd Te quantum dots-Copper phthalocyanine(Cd Te QDs-Cu Pc) aqueous system by using time-correlated single-photon counting techniques. Result shows the efficiency of Cd Te QDs-Cu Pc system increases with the power of laser under the two-photon excitation of 800 nm laser and the efficiency can reach to 43.8%Then the Cd Te QDs-Rh B aqueous system(QDs as donor while Rh B as acceptor) is studied for the sake of further research. Result indicates the FRET efficiency of this system climbs with the increase of spectrum overlap between fluorescence spectra of acceptor and absorption spectra of donor. The lifetime of QDs has negative correlation with concentration radio of A/D, while the FRET efficiency in QDs-Rh B system holds positive correlation with concentration radio of A/D. The two-photon FRET efficiency in this system can reach to 40.1%...