title: Gold Nanobipyramid-Directed Growth of Length-Variable Silver Nanorods with Multipolar Plasmon Resonances.
abstract: We report on a method for the preparation of uniform and length-variable Ag nanorods through anisotropic Ag overgrowth on high-purity Au nanobipyramids. The rod diameters can be roughly tailored from ∼20 nm to ∼50 nm by judicious selection of differently sized Au nanobipyramids. The rod lengths can be tuned from ∼150 nm to ∼550 nm by varying the Ag precursor amount during the overgrowth process and/or by anisotropic shortening through mild oxidation. The controllable aspect ratios, high purity, and high dimensional uniformity of these Ag nanorods enable the observation of Fabry-Pérot-like multipolar plasmon resonance modes in the colloidal suspensions at the ensemble level, which has so far been demonstrated only on Au nanorods prepared electrochemically with anodic aluminum oxide templates. Depending on the mode order and geometry of the Ag nanorods, the multipolar plasmon wavelengths can be readily tailored over a wide spectral range from the visible to near-infrared region. We have further elucidated the relationships between the multipolar plasmon wavelengths and the geometric dimensions of the Ag nanorods at both the ensemble and single-particle levels. Our results indicate that the Au nanobipyramid-directed, dimensionally controllable Ag nanorods will be an attractive and promising candidate for developing multipolar plasmon-based devices and applications.
authors.affiliation: †Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Zhuo
authors.affiliation: †Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.|‡Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Xingzhong
authors.initials: X
authors.lastname: Zhu
authors.affiliation: †Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: ‡Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Yang
authors.affiliation: †Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
authors.forename: Jianfang
authors.initials: J
authors.lastname: Wang
keywords: gold nanobipyramids; multipolar plasmon resonance; plasmon resonance; scattering; seed-mediated growth; silver nanorods