The short peptides that specifically bind to SnO 2 nanoparticles (NPs) were selected by using a phage display method. After the fourth round selection, ten kinds of amino acid sequences were identified, and it was revealed that affinities of the obtained phages for SnO 2 NPs were relatively higher than that of the unselected library phages. The identified peptide sequences showed that amino acids having a hydroxy group and hydrophobic amino acids were enriched in the selection process. Binding constants (K a) of the chemically synthesized heptapeptides having the identified sequences were quantitatively estimated. The pTO-7 peptide (Ser-Ser-Ile-Leu-Arg- Phe-Pro) showed the greatest K a value (5.80 × 10 5 M -1 at 25°C) among the investigated peptides, and also showed binding specificity to SnO 2. The SnO 2-recognizing peptides functioned as nanostructure stabilizer during pH-dependent preparation of water-insoluble tin-based compound (Sn 6O 4(OH) 4) at room temperature. These effects as stabilizers to disperse nanostructures in water phase were greater than that of a general purpose stabilizer poly(vinylpyrrolidone). Dynamic light scattering and transmission electron microscope analyses revealed that the formed structures in the presence of the pTO-7 peptide were squarish NPs with an approximately 60 nm diameter, and wide-angle powder X-ray diffraction analyses suggested that its crystallinity was increased by existence of the peptide.
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