Molecular Assembling by Radiation Pressure of Laser Beam

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We have studied formation process of a single microparticle in solution under a microscope by photon pressure of a focused infrared laser beam and analyzed inner structure of the microparticle. This study is regarded as a new chemistry by photon pressure, which is quite different from conventional photophysics and photochemistry.Intramolecular charge transfer molecule was chosen as a fluorescence probe, and its photophysical and photochemical properties were studied in detail. Polyacrylamide polymer bonded with the intramolecular charge transfer molecule was synthesized, and its dynamic responses to thermal, pH, and related stimuli were studied. By focusing the infrared laser beam. the polyacrylamide are gathered at the focal point of the microscope by photon pressure, forming a single microparticle. The preparation process was observed from time to time, and its characteristic inner structure was analyzed by picosecond fluorescence microscopy. Similarly, a single microparticle composed of block copolymer micelles was studied, and local environmental condition and morphology of the single microparticle were revealed by space- and time- resolved fluorescence analysis.