title: Strong light-matter interactions in sub-nanometer gaps defined by monolayer graphene: toward highly sensitive SERS substrates.
abstract: The interactions between visible light and sub-nanometer gaps were investigated by sandwiching graphene between two layers of vertically stacked Au nanoparticles. The optical properties of such a hybrid film have been effectively tuned by embedding a monolayer graphene, enabling a suppressed transmission of ∼16% accompanied by a red-shift of the resonant wavelength. Finite element simulations have shown that the strong coupling between two layers of plasmonic Au nanoparticles leads to an electric field enhancement of up to 88 times in graphene defined vertical gaps, in contrast to that of 14 times in the horizontal gaps between Au nanoparticles formed in the fabrication process. In addition, the size of gaps and thus the field enhancement can be readily tuned by the number of graphene layers sandwiched between Au nanoparticles. When being used as surface-enhanced Raman scattering (SERS) substrates, the Au nanoparticle/graphene/Au nanoparticle structures have demonstrated high Raman enhancement factors of up to 1.6 × 10(8) for RhB and 2.5 × 10(8) for R6G, and a detection limit of as low as 0.1 nM for Sudan III and methylene blue molecules.
authors.affiliation: Department of Materials Science and Engineering and CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei 230026, China. zhuyanwu@ustc.edu.cn.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Xiyu
authors.initials: X
authors.lastname: Li
authors.forename: Yuanxin
authors.initials: Y
authors.lastname: Du
authors.forename: Guanxiong
authors.initials: G
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Qu
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.forename: Yanwu
authors.initials: Y
authors.lastname: Zhu