Probe Of Dynamics Of Polymer Film By Single Molecule Optics

The spectroscopy of single molecule removes the average of ensemble, which can reflect the characteristic of single molecules. Moreover, because of the sensitivity of the response of single molecule to the local environment, single molecule can be used as a probe to measure the dynamics of surrounding nanometer environment. The study of the spectroscopy of single molecule has been carried out by many groups in the world and significant achievements have been accomplished. Furthermore, single molecule plays a very important action in the quantum security communication. The experiments of single molecules can be carried out at both low temperature and room temperature. In this paper, we report the measurements of photophysics parameters of single molecules and the application of single molecule as a sensitive probe to the dynamics of polymer film. Our main work is as follows:1. We have established the setup for polymer dynamics measurement based on single molecule probes. The optimal condition for high signal-to-noise ratio is presented. We also give the method for sample preparations and the detection and process for the experimental data.2. The measurement of photophysics parameters, including the lifetime of single molecule, the effect of electric field on the fluorescence intensity and fluorescence lifetime and the photobleaching mechanism. It is found that the lifetime of single molecule fluctuates with varying electric field and the fluorescence intensity of single molecule can be modulated by electric field. Moreover, it is found that the two-photon photobleaching is the main photobleaching mechanism.3. The detection of dynamics of single molecule. In our investigation, picosecond pulse diode laser is used to excite single molecule and the fluorescence from single molecule is detected by the single photon detector. The characteristic of fluorescence of single molecule reflects the dynamics and structure of single molecule and the interaction between single molecule and its surrounding local environment. It is found that fluorescence of single molecule can be modulated by electric field and the lifetime of single molecule depend on the electric field. The autocorrelation and crosscorrelation function between the two orthogonal polarization lights of single molecules fluorescence shown that the dynamics of the surface of the polymer film is much more active than the inside.