Effect of Size, Shape, Composition, and Support Film on Localized Surface Plasmon Resonance Frequency: A Single Particle
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1208-O10-02
Effect of Size, Shape, Composition, and Support Film on Localized Surface Plasmon Resonance Frequency: A Single Particle Approach Applied to Silver Bipyramids and Gold and Silver Nanocubes Emilie Ringe1, Jian Zhang1, Mark R. Langille1, Kwonnam Sohn2, Claire Cobley3, Leslie Au3, Younan Xia3, Chad A. Mirkin1, Jiaxing Huang2, Laurence D. Marks2 and Richard P. Van Duyne1 1 Chemistry, Northwestern University, Evanston, Illinois; 2Materials Science and Engineering, Northwestern University, Evanston, Illinois; 3Biomedical Engineering, Washington University, St. Louis, Missouri.
ABSTRACT Localized surface plasmon resonances (LSPR), collective electron oscillations in nanoparticles, are being heavily scrutinized for applications in chemical and biological sensing, as well as in prototype nanophotonic devices. This phenomenon exhibits an acute dependence on the particle’s size, shape, composition, and environment. The detailed characterization of the structure-function relationship of nanoparticles is obscured by ensemble averaging. Consequently, single-particle data must be obtained to extract useful information from polydisperse reaction mixtures. Recently, a correlated high resolution transmission electron microscopy (HRTEM) LSPR technique has been developed and applied to silver nanocubes. We report here a second generation of experiments using this correlation technique, in which statistical analysis is performed on a large number of single particles. The LSPR dependence on size, shape, material, and environment was probed using silver right bipyramids, silver cubes, and gold cubes. It was found that the slope of the dependence of LSPR peak on size for silver bipyramids increases as the edges become sharper. Also, a plasmon shift of 96 nm was observed between similar silver and gold cubes, while a shift of 26 nm was observed, for gold cubes, between substrates of refractive index (RI) of 1.5 and 2.05. INTRODUCTION The plasmonic properties of nanoparticles have attracted much attention in the past decade. Their potential use in sensing devices[1, 2], waveguides[3, 4], and photonic circuits[5-7] makes them a very active area of research. The localized surface plasmon resonance (LSPR) of such nanoparticles lies at the heart of such applications. Localized surface plasmons occur when the electrons in the particle interact with electromagnetic radiation, leading to selective photon absorption and radiation, as well as enhanced electromagnetic fields around the particle. The latter property is heavily used in surface-enhanced Raman spectroscopy (SERS)[8], while the former gives rise to bright colors, leading to their use in stained glass. Understanding plasmonic properties is essential to produce optimized devices, yet the current knowledge on this subject is mostly derived from experiments performed at the ensemble-averaged level on nanoparticle solutions. While such data can be useful, for example in giving trends related to dependence on LSPR on material, shape, size, and environment, conclusions drawn using h
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