title: Self-assembly of subwavelength nanostructures with symmetry breaking in solution.
abstract: Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm for Au nanospheres; 100-160 nm for Ag nanocubes) and meanwhile control the nanogaps through ultrathin silica shells of 1-5 nm thickness. The Raman tag of 4-mercaptobenzoic acid (MBA) assists the self-assembly process and endows the subwavelength asymmetric nanostructures with surface-enhanced Raman scattering (SERS) activity. Moreover, thick silica shells (above 50 nm thickness) can be coated on the self-assembled nanostructures in situ to stabilize the whole nanostructures, paving the way toward bioapplications. Single particle scattering spectroscopy with a 360° polarization resolution is performed on individual Ag nanocube and Au nanosphere dimers, correlated with high-resolution TEM characterization. The asymmetric dimers exhibit strong configuration and polarization dependence Fano resonance properties. Overall, the solution-based self-assembly method reported here is opening up new opportunities to prepare diverse multicomponent nanomaterials with optimal performance.
authors.affiliation: Xiamen Institute of Rare-earth Materials, Chinese Academy of Sciences, Xiamen 361005, China. tianxd@fjirsm.ac.cn zhangy@fjirsm.ac.cn.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Tian
authors.affiliation: Department of Physics, Xiamen University, Xiamen 361005, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China. li@xmu.edu.cn.
authors.forename: Yue-Jiao
authors.initials: YJ
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China. li@xmu.edu.cn.
authors.forename: Jin-Chao
authors.initials: JC
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China. li@xmu.edu.cn.
authors.forename: Rajapandiyan
authors.initials: R
authors.lastname: Panneerselvam
authors.affiliation: Xiamen Institute of Rare-earth Materials, Chinese Academy of Sciences, Xiamen 361005, China. tianxd@fjirsm.ac.cn zhangy@fjirsm.ac.cn.
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Physics, Xiamen University, Xiamen 361005, China.
authors.forename: Zhi-Lin
authors.initials: ZL
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China. li@xmu.edu.cn.
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Li
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China. li@xmu.edu.cn.
authors.forename: Zhong-Qun
authors.initials: ZQ
authors.lastname: Tian