The ultimate test for nanoscience will be to deliver practically useful materials and devices. Recognizing this challenge, our group uses self-assembly to synthesize new nanostructured materials with real-world applications.


In one of our key projects, we focus on the assembly schemes that allow building macroscopic structures from nanoscopic building blocks. Since bridging more than six orders of magnitude that separate nano from macro is not an easy task, we have developed a hierarchical approach, in which metal nanoobjects are first assembled into intermediate aggregates ("supraspheres") that contain more than 90% w/w metal but but behave like sticky pieces of wax or Play-doh. These sticky supraspheres can then glue with one another upon light irradiation and can form macroscopic materials. Remarkably, these materials look like metals and conduct electricity but they behave like moldable plastics. They can contain one or more elements (e.g., Au/Ag, Au/Pt, Pt/Pd nanoalloys) and can be hardened at room temperature. No kidding. For more details, please see our recent paper in Science (Science, 316, 261, 2007).

In another materials-oriented work, we use charged metal nanoparticles to form ultrathin coatings. Since we use electrostatic forces and not material-specific chemical ligation schemes, our coatings form on all kinds of materials, from plastics through glasses to semiconductors. These coatings not only have some intriguing optical properties (cf. picture below), but they also can be made bacteriostatic (i.e., they kill all kinds of bugs). The latter property drives our effort to use these coatings in implantable materials (especially, silicones) where sterility of the surface is required but is often compromised during implantation procedures.
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