The extinction spectra of silver nanoparticle arrays: Influence of array structure on plasmon resonance wavelength and width

LinLin Zhao, K. Lance Kelly, George C Schatz

Research output: Contribution to journalArticle

482 Citations (Scopus)

Abstract

We use high-quality electrodynamics methods to study the extinction spectra of one-dimensional linear chains and two-dimensional planar arrays of spherical silver nanoparticles, placing emphasis on the variation of the plasmon resonance wavelength and width with array structure (spacing, symmetry), particle size, and polarization direction. Two levels of theory have been considered, coupled dipoles with fully retarded interactions and T-matrix theory that includes a converged multipole expansion on each particle. We find that the most important array effects for particles having a radius of 30 nm or smaller are captured by the couple dipole approach. Our calculations demonstrate several surprising effects that run counter to conventional wisdom in which the particle interactions are assumed to be governed by electrostatic dipolar interactions. In particular, we find that for planar arrays of particles with polarization parallel to the plane the plasmon resonance blue shifts as array spacing D decreases for D larger than about 75 nm and then it red shifts for smaller spacings. In addition, we find that the plasmon narrows for D > 180 nm but broadens for smaller spacings. The results can be rationalized using a simple analytical model, which demonstrates that the plasmon wavelength shift is determined by the real part of the retarded dipole sum while the width is determined by the imaginary part of this sum. The optimal blue shifts and narrowing are found when the particle spacing is slightly smaller than the plasmon wavelength, while red shifts and broadening can be found for spacings much smaller than the plasmon wavelength at which electrostatic interactions are dominant. We also find that the array spectrum does not change significantly with array symmetry (square or hexagonal) or irradiated spot size (i.e., constant array size or constant particle number).

Original languageEnglish
Pages (from-to)7343-7350
Number of pages8
JournalJournal of Physical Chemistry B
Volume107
Issue number30
Publication statusPublished - Jul 31 2003

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Silver
extinction
silver
Nanoparticles
Wavelength
nanoparticles
spacing
Coulomb interactions
wavelengths
Polarization
Particle interactions
Electrodynamics
dipoles
blue shift
red shift
Analytical models
Particle size
electrostatics
matrix theory
interactions

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

The extinction spectra of silver nanoparticle arrays : Influence of array structure on plasmon resonance wavelength and width. / Zhao, LinLin; Lance Kelly, K.; Schatz, George C.

In: Journal of Physical Chemistry B, Vol. 107, No. 30, 31.07.2003, p. 7343-7350.

Research output: Contribution to journalArticle

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