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Optical Patterning and Photochemical Fixation of Polymer Nanoparticles on Glass Substrates


Laser Manipulation and Fixation of Single Nanoparticles in Solution at Room Temperature



Recently, nanoparticles have received much attention and been investigated as one of representative materials in nanoscience and nanotechnology. They show interesting properties originating from intermediate size between single atoms and bulk. In many cases, studies on nanoparticles have been conducted for an ensemble of many particles, so that distributions in size, shape, defect, and so on cannot be analyzed directly. It is important and indispensable to manipulate, investigate spectroscopically, and fabricate nanoparticles one by one, and thus manipulation and fixation of individual nanoparticles is considered to be one of key technologies for various fields of nanoscience and nanotechnology. It is quite ordinary to apply scanning tunneling microscope and atomic force microscope (AFM) under vacuum at low temperature at the present stage of investigation, while manipulation, characterization, and fixation technique of individual nanoparticles in solution at room temperature is expected to be more fruitful.

Laser manipulation is a very useful method to handle fine objects in small domains, and has been developed to trap, characterize, modify, and fabricate small particles in solution under an optical microscope at room temperature [1-3]. Most studies have been concentrated on µm-sized objects such as polymer latex, crystals, biocells, and so forth, and application for nm-sized ones has been rarely explored because of the difficulty in identifying them by eye. However, we have already demonstrated that 10 ~ 20 nm sized entangled polymer chains could be trapped and assembled in solution at the focal point of a trapping beam [4]. Also, Svoboda and Block have shown to trap a single 36-nm-diameter gold particle in water [5].

In this report, we describe our recent results on laser manipulation and fixation of nanoparticles in solution at room temperature; (1) patterning of optically gathered fluorescent polymer nanoparticles, (2) fixation of a trapped single polymer nanoparticle by local photopolymerization, and (3) trapping of a single gold nanoparticle and its fixation by photothermal effect.


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