Çevrelenmiş geometrilerde tek moleküllerin izlenmesi

Single molecule experiments were performed utilizing total internal reflection fluorescence microscopy technique at room temperature for understanding diffusion dynamics of single molecules in confined geometries of diblock copolymer thin films. The characteristic behavior of single molecules such as blinking and photobleaching were first shown indicating the observation of real dyes rather than some scattering. Then, ~1.5 nm resolution of our experimental setup in positioning fluorescent dyes was shown which allowed us to study the dynamics of single molecules inside the obtained confined geometries (channel diameters ~12-30 nm) and to analyze the surface morphology of different block copolymer thin films. For this purpose, terrylene and rhodamine B dye molecules were used and embedded in PS, PMMA and three different molecular weight PB-PEO diblock copolymers. Rhodamine B and terrylene dye molecules were incorporated with PMMA and PS polymers for understanding and observation of characteristic behavior of single molecules, respectively. They were also utilized for the determination of resolution of our experimental setup in positioning single dye molecules. The usage of terrylene molecules in PB-PEO diblock copolymer samples was for studying the confined diffusion of single molecules.After spun-casting the thin films which were prepared by using PB-PEO diblock copolymer solutions including terrylene molecules, they were annealed to obtain better intended morphology. By this way, cylindrical channels of PB inside PEO crystalline matrix and 2-dimensional layer of PB at air film interface on top of PEO layer were obtained for providing 1- and 2-dimensional diffusion of terrylene dyes. After that, the trajectories of diffusion single molecules were obtained and analyzed. In this manner, the motion of terrylene probe molecules in confined PB channels having different channel diameter of two asymmetric PB-PEO diblock copolymers and the normal diffusion of terrylene dyes in 2-dimensional PB layer of symmetric PB-PEO diblock copolymer were investigated.The distribution of 1-dimensional diffusion coefficients were found to have narrower distribution compared to 2-dimensional diffusion coefficients in PB. In addition to normal diffusion of terrylene dyes, directed motion of them was also observed through the trajectories of some single molecules and their analysis where mean square displacement had parabolic time dependence. The origin of this behavior was explained by the presence of some defects in channel formations, i.e. change in local density inside the channel due to local variations in the PB channel width. Furthermore, effects of non-uniformities and heterogeneities in channels on motion of single molecule were studied demonstrating the sensitivity of single molecule tracking in characterizing self-assembled block copolymer morphologies where the trajectories of single molecules were well correlated with AFM and SEM results.