A Nonlinear Optical Approach to Patchy Particles

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TECHNICAL SUMMARY:This program, supported by the Solid State and Materials Chemistry program, aims to demonstrate a new class of "patchy particles", particles where the surface is patterned with discrete interaction sites that attract or repel complementary sites on other particles - for the purposes of guiding the self-assembly of complex structures with high precision and yield. The technique is optical in nature and relies on the propensity of the plasmonic resonances in metal nanoparticles to concentrate incident light into very small volumes where the electromagnetic field is greatly enhanced. These volumes, known as ?hotspots?, are located at sharp corner or narrow gaps on or between particles. The project will use photoreactive linkers to guide additional particles to bind exclusively at the hotspots so that colloidal molecules can be fabricated in a manner analogous to conventional chemistry, but with nanoparticles instead of atoms. Two simple examples of such structures are a dumbbell shape where two spherical particles are attached to each end of a central rod-shaped particle and a triangular prism where a sphere is attached at each corner. Since the method can be used iteratively, significantly more complex structures, such as branched chains or dendrites, are also possible. Because of the large and rapidly growing variety of silver and gold nanoparticles that can be fabricated, and the numerous types of available photoreactive compounds , this project would represent a significant increase in the number and variety of structures that are feasible within the patchy particle self-assembly paradigm.NON-TECHNICAL SUMMARY:It is now possible to create particles and structures at the nanometer scale with a great deal of variety and precision. The next great challenge is to assemble these building blocks into more complex ordered structures combining different geometries and materials. This project develops an enabling new method using nanoparticles made of silver and gold as the central building blocks. Its success will have implications both for fundamental science and for applied fields such as biomedicine and nanoelectronics, and will therefore help maintain American leadership is these technologically and economically important fields. The project will also help educate the next generation of Ph.D. level workers ready to take leadership positions in interdisciplinary projects at the forefront of science and engineering.