Selection of peptides with semiconductor binding specificity for directed nanocrystal assembly

In biological systems, organic molecules exert a remarkable level of contro l over the nucleation and mineral phase of inorganic materials such as calc ium carbonate and silica, and over the assembly of crystallites and other n anoscale building blocks into complex structures required for biological fu nction(1-4). This ability to direct the assembly of nanoscale components in to controlled and sophisticated structures has motivated intense efforts to develop assembly methods that mimic or exploit the recognition capabilitie s and interactions found in biological systems(5-10). Of particular value w ould be methods that could be applied to materials with interesting electro nic or optical properties, but natural evolution has not selected for inter actions between biomolecules and such materials. However, peptides with lim ited selectivity for binding to metal surfaces and metal oxide surfaces hav e been successfully selected(10,11). Here we extend this approach and show that combinatorial phage-display libraries can be used to evolve peptides t hat bind to a range of semiconductor surfaces with high specificity, depend ing on the crystallographic orientation and composition of the structurally similar materials we have used. As electronic devices contain structurally related materials in close proximity, such peptides may rnd use for the co ntrolled placement and assembly of a variety of practically important mater ials, thus broadening the scope for 'bottom-up' fabrication approaches.