title: On the critical role of Rayleigh scattering in single-molecule surface-enhanced Raman scattering via a plasmonic nanogap.
abstract: Electromagnetic and chemical enhancement mechanisms are commonly used to account for single-molecule surface-enhanced Raman scattering (SM-SERS). Due to many practical limitations, however, the overall enhancement factor summed up from these two mechanisms is typically 5-6 orders of magnitude below the level of 10(14)-10(15) required for SM-SERS. Here, we demonstrate that the multiple elastic Rayleigh scattering of a molecule could play a critical role in further enhancing the Raman signal, when the molecule is trapped in a 2 nm gap between two Ag nanoparticles, pushing the overall enhancement factor close to the level needed for SM-SERS. As a universal physical process for all molecules interacting with light, we believe that Rayleigh scattering plays a pivotal and as yet unrecognized role in SERS, in particular, for enabling single-molecule sensitivity.
authors.affiliation: College of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, China and Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190, China. lizy@aphy.iphy.ac.cn.
authors.forename: Bao-Qin
authors.initials: BQ
authors.lastname: Chen
authors.affiliation: Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190, China. lizy@aphy.iphy.ac.cn.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190, China. lizy@aphy.iphy.ac.cn.
authors.forename: Jiafang
authors.initials: J
authors.lastname: Li
authors.affiliation: College of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, China and Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190, China. lizy@aphy.iphy.ac.cn.
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Li
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia