Mineralization of semiconductor nanocrystals on peptide-coated bionanotubes and their pH-dependent morphology changes

While various mineralizing peptides have been applied to grow metal nanoparticles on bionanotube templates, the semiconductor nanoparticle growth on nanotubes has not extensively been explored yet. In this paper, various semiconductor nanocrystals were grown on the bionanotubes surfaces with controlled sizes. When three synthetic peptides, which recognize and selectively bind Ge, Ti, and Cu ions, respectively, were incorporated on template bionanotube surfaces, highly crystalline and monodisperse Ge, TiO2, and Cu2S nanocrystals were grown on the tube surfaces. The sizes of these nanocrystals could be tuned as a function of pH, and larger semiconductor nanocrystals were grown as the pH of growth solutions was increased. All of these nanocrystals from smaller sizes to larger sizes had the same crystallinity. This peptide-controlled nanocrystal growth technique will be very useful to prepare semiconductor nanowires as building blocks for future microelectronics, whose band gaps can be tuned by the sizes of coated semiconductor nanoparticles via their quantum confinement effect. The novelty of this approach in the electronic device fabrication is that the semiconductor nanocrystal size control can be achieved by controlling peptide configurations via pH change, and this control may tune electronic structures and band gaps of the resulting semiconductor nanowires.