Synthesis and applications of functional nanostructures using chemically or genetically controlled templates

Abstract

Functional nanostructures can be used for a wide range of potential applications in energy conversion and storage devices, catalytic systems, sensors, electronic devices, etc. While they provide a large surface area and unique properties originated form confined nanoscale sizes, poor dispersion stability and consequent structural changes often impose limitations to their practical uses. Recent studies revealed that surface-engineered templates can prevent aggregation and maintain intrinsic properties of functional nanostructures. In addition, it provides porous structures with a large surface area and guides the formation of functional nanostructures and the well-controlled assembly of small molecules. Here, we introduce chemical and biological methods for surface modification to synthesize and assemble functional nanostructures and their applications to catalysis and piezoelectric energy harvesting. As for a chemical approach, polydopamine (PDA), a mussel-inspired adhesive, is applied to functional coatings of polymer nanofibers prepared using an electrospinning process. Electrospining is a widely used facile method to fabricate porous polymer nanofibers with a large surface area. Gold nanoparticles are synthesized onto the PDA-coated poly (e-caprolactone) nanofibers through spontaneous reduction of gold ions on the polymer surface. The catechol group of PDA has a redox potential of 0.53 V (vs. NHE) at pH 7. As for a biological approach, genetically programmed M13 virus is used as a genetically modified template for the synthesis of anisotropic BaTiO3 (BTO) nanostructures. M13 virus is genetically modified to display a glutamate trimer (E3), making the surface of M13 virus negatively charged in alkaline conditions and realizing the self-assembly of cationic metal precursors. After thermal treatment, tetragonal BTO nanostructures with a high crystallinity and piezoelectricity are generated. Since the M13 virus has a filamentous structure, the synthesized BTO n...