Nanoscale optical biosensor

Short range distance dependence of the localized surface plasmon resonance of noble metal nanoparticles

Amanda J. Haes, Shengli Zou, George C Schatz, Richard P. Van Duyne

Research output: Contribution to journalArticle

518 Citations (Scopus)

Abstract

Silver and gold nanotriangles were fabricated by nanosphere lithography (NSL) and their localized surface plasmon resonance (LSPR) spectra were measured by UV-vis extinction spectroscopy. It is demonstrated that the short range (viz., 0-2 nm) distance dependence of the electromagnetic fields that surround these nanoparticles when resonantly excited can be systematically tuned by changing their size, structure, and composition. This is accomplished by measuring the shift in the peak wavelength, λ max, of their LSPR spectra caused by the adsorption of hexadecanethiol as a function of nanoparticle size (in-plane width, out-of-plane height, and aspect ratio), shape (truncated tetrahedron versus hemisphere), and composition (silver versus gold). We find that the hexadecanethiol-induced LSPR shift for Ag triangles decreases when in-plane width is increased at fixed out-of-plane height or when height is increased at fixed width. These trends are the opposite to what was seen in an earlier study of the long range distance dependence in which 30 nm thick layers were examined (Haes et al. J. Phys. Chem. B 2004, 108, 109), but both the long and short range results are-confirmed by a theoretical analysis based on finite element electrodynamics. The theory results also indicate that the short range results are primarily sensitive to hot spots (regions of high induced electric field) near the tips of the triangles, so this provides an example where enhanced local fields play an important role in extinction spectra. Our measurements further show that the hexadecanethiol-induced LSPR peak shift is larger for nanotriangles than for hemispheres with equal volumes and is larger for Ag nanotriangles than for Au nanotriangles with the same in-plane widths and out-of-plane heights. The dependence of the alkanethiol-induced LSPR peak shift on chain length for Ag nanotriangles is approximately size-independent. We anticipate that the improved understanding of the short range dependence of the adsorbate-induced LSPR peak shift on nanoparticle structure and composition reported here will translate to significant improvements in the sensitivity of refractive-index-based nanoparticle nanosensors.

Original languageEnglish
Pages (from-to)6961-6968
Number of pages8
JournalJournal of Physical Chemistry B
Volume108
Issue number22
DOIs
Publication statusPublished - Jun 3 2004

Fingerprint

Metal nanoparticles
Surface plasmon resonance
Precious metals
noble metals
bioinstrumentation
surface plasmon resonance
Biosensors
nanoparticles
shift
Nanoparticles
hemispheres
Silver
triangles
Gold
extinction
Chemical analysis
silver
gold
Nanosensors
Nanospheres

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Nanoscale optical biosensor : Short range distance dependence of the localized surface plasmon resonance of noble metal nanoparticles. / Haes, Amanda J.; Zou, Shengli; Schatz, George C; Van Duyne, Richard P.

In: Journal of Physical Chemistry B, Vol. 108, No. 22, 03.06.2004, p. 6961-6968.

Research output: Contribution to journalArticle

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