On the Effect of Native SiO2 on Si over the SPR-mediated Photocatalytic Activities of Au and Ag Nanoparticles

Jiale Wang; Isabel C de Freitas; Tiago V Alves; Romulo A Ando; Zebo Fang; Pedro H C Camargo

doi:10.1002/chem.201700651

On the Effect of Native SiO₂ on Si over the SPR-mediated Photocatalytic Activities of Au and Ag Nanoparticles

Chemistry. 2017 May 29;23(30):7185-7190. doi: 10.1002/chem.201700651. Epub 2017 May 19.

Authors

Jiale Wang¹, Isabel C de Freitas², Tiago V Alves³, Romulo A Ando², Zebo Fang⁴, Pedro H C Camargo²

Affiliations

¹ College of Science, Donghua University, Shanghai, 201620, P. R. China.
² Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo-SP, Brazil.
³ Departamento de Físico-Química, Instituto de Química, Universidade Federal da Bahia, Rua Barão de Jeremoabo, 147, 40170-115, Salvador-BA, Brazil.
⁴ Department of Physics, Shaoxing University, Shaoxing, 312000, P. R. China.

PMID: 28398612
DOI: 10.1002/chem.201700651

Abstract

In hybrid materials containing plasmonic nanoparticles such as Au and Ag, charge-transfer processes from and to Au or Ag can affect both activities and selectivity in plasmonic catalysis. Inspired by the widespread utilization of commercial Si wafers in surface-enhanced Raman spectroscopy (SERS) studies, we investigated herein the effect of the native SiO₂ layer on Si wafers over the surface plasmon resonance (SPR)-mediated activities of the Au and Ag nanoparticles (NPs). We prepared SERS-active plasmonic comprised of Au and Ag NPs deposited onto a Si wafer. Here, two kinds of Si wafers were employed: Si with a native oxide surface layer (Si/SiO₂ ) and Si without a native oxide surface layer (Si). This led to Si/SiO₂ /Au, Si/SiO₂ /Ag, Si/Au, and Si/Ag NPs. The SPR-mediated oxidation of p-aminothiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) was employed as a model transformation. By comparing the performances and band structures for the Si/Au and Si/Ag relative to Si/SiO₂ /Au and Si/SiO₂ /Ag NPs, it was found that the presence of a SiO₂ layer was crucial to enable higher SPR-mediated PATP to DMAB conversions. The SiO₂ layer acts to prevent the charge transfer of SPR-excited hot electrons from Au or Ag nanoparticles to the Si substrate. This enabled SPR-excited hot electrons to be transferred to adsorbed O₂ molecules, which then participate in the selective oxidation of PATP to DMAB. In the absence of a SiO₂ layer, SPR-excited hot electrons are preferentially transferred to Si instead of adsorbed O₂ molecules, leading to much lower PATP oxidation.

Keywords: gold; nanoparticles; photocatalysis; silver; surface plasmon resonance.