In Situ Shape Change of Au Nanoparticles on TiO2 by CdS Photodeposition: Its Near-Field Enhancement Effect on Photoinduced Electron Injection from CdS to TiO2

Musashi Fujishima; Takuya Ikeda; Ryo Akashi; Hiroaki Tada

doi:10.1021/acsomega.8b00818

In Situ Shape Change of Au Nanoparticles on TiO₂ by CdS Photodeposition: Its Near-Field Enhancement Effect on Photoinduced Electron Injection from CdS to TiO₂

ACS Omega. 2018 Jun 6;3(6):6104-6112. doi: 10.1021/acsomega.8b00818. eCollection 2018 Jun 30.

Authors

Musashi Fujishima¹, Takuya Ikeda¹, Ryo Akashi¹, Hiroaki Tada¹

Affiliation

¹ Faculty of Science and Engineering and Graduate School of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan.

Abstract

Hemisphere-like gold nanoparticles (NPs) were loaded on TiO₂ (Au/TiO₂) by the deposition-precipitation method. Subsequent photodeposition of CdS on the Au surface of Au/TiO₂ at 50 °C yields Au(core)-CdS(shell) hybrid quantum dots with a heteroepitaxial (HEPI) junction on TiO₂ (Au@#CdS/TiO₂), whereas nonHEPI Au@CdS/TiO₂ was formed by CdS photodeposition at 25 °C. In the HEPI system, the shape of the Au core changes to an angular shape, whereas it remains in a hemisphere-like shape in the nonHEPI system. The hot photodeposition technique was applied to the Au NP-loaded mesoporous TiO₂ nanocrystalline film (Au/mp-TiO₂). Using Au@CdS/mp-TiO₂ and Au@#CdS/mp-TiO₂ as the photoanodes, two-electrode quantum dot-sensitized photoelectrochemical cells were fabricated for hydrogen (H₂) generation from water, and the performances of the cells were evaluated under illumination of simulated sunlight. In the photocurrent and the rate of H₂ evolution, the Au@#CdS/mp-TiO₂ photoanode cell surpasses the CdS/mp-TiO₂ and Au@CdS/mp-TiO₂ ones. Three-dimensional finite-difference time-domain calculations for the model systems indicated that the angular shape Au core generates an intense electric field at the corners and edges, extending the electric field distribution over the Au core-CdS shell interface. The striking shape effect on the cell performances can originate from the promotion of the CdS excitation and charge separation due to the near-field enhancement by the deformed Au core.