title: On the Effect of Native SiO2on Si over the SPR-mediated Photocatalytic Activities of Au and Ag Nanoparticles.
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 SiO2layer 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 SiO2layer was crucial to enable higher SPR-mediated PATP to DMAB conversions. The SiO2layer 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 O2molecules, which then participate in the selective oxidation of PATP to DMAB. In the absence of a SiO2layer, SPR-excited hot electrons are preferentially transferred to Si instead of adsorbed O2molecules, leading to much lower PATP oxidation.
authors.affiliation: College of Science, Donghua University, Shanghai, 201620, P. R. China.
authors.forename: Jiale
authors.initials: J
authors.lastname: Wang
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo-SP, Brazil.
authors.forename: Isabel C
authors.initials: IC
authors.lastname: de Freitas
authors.affiliation: Departamento de Físico-Química, Instituto de Química, Universidade Federal da Bahia, Rua Barão de Jeremoabo, 147, 40170-115, Salvador-BA, Brazil.
authors.forename: Tiago V
authors.initials: TV
authors.lastname: Alves
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo-SP, Brazil.
authors.forename: Romulo A
authors.initials: RA
authors.lastname: Ando
authors.affiliation: Department of Physics, Shaoxing University, Shaoxing, 312000, P. R. China.
authors.forename: Zebo
authors.initials: Z
authors.lastname: Fang
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo-SP, Brazil.
authors.forename: Pedro H C
authors.identifier: http://orcid.org/0000-0002-7815-7919
authors.initials: PHC
authors.lastname: Camargo
keywords: gold; nanoparticles; photocatalysis; silver; surface plasmon resonance