Fabrication of a peptide–AuNP–TiO2 nanocomposite and its application as a VOC sensor

Abstract

We fabricated a volatile organic compound (VOC) sensor with a peptide–Au nanoparticle (AuNP)–TiO₂ nanocomposite in which AuNPs were linked with TiO₂-coated conductive peptide nanowires. The conductive peptide nanowires were formed between the AuNPs via self-assembly through the complexation of amphiphilic peptides, LESEHEKLKSKHKSKLKEHESEL, and Co(II). Furthermore, TiO₂ mineralization on the surface of the peptide nanowires yielded mixed crystals of rutile and anatase, which exhibited highly effective photolytic activity. In particular, the obtained TiO₂ exhibited three times greater photodecomposition activity in the unsintered state toward organic matter than did commercially available TiO₂. Next, we constructed a VOC sensor by immobilizing peptide–AuNP–TiO₂ nanocomposites on a comb electrode. The electrochemical properties of the nanocomposite changed drastically under light irradiation in the presence of VOCs, indicating transport of the VOC-decomposition-generated photoexcited electrons of TiO₂ to AuNPs through conductive peptide nanowires, which prevented electron–hole recombination. The obtained sensor exhibited a sensing range of 2–100 ppm for dichloromethane, which was used as a representative VOC. Therefore, nanocomposites made of AuNPs linked with conductive TiO₂ nanotubes may be highly effective for TiO₂-driven VOC decomposition. Moreover, we believe that this nanocomposite has high sensitivity for sensing VOCs.