Enhanced Nanoparticle Response From Coupled Dipole Excitation for Plasmon Sensors

• Published in: IEEE sensors journal 2011-12, Vol.11 (12), p.3332-3340
• Main Authors: Blake, P., Obermann, J., Harbin, B., Roper, D. K.
• Format: Article
• Language: English
• Subjects: Arrays; Chemical sensors; Dipoles; Electromagnetic coupling; Excitation; Finite difference methods; gold nanoparticle arrays; localized surface plasmon resonance; Mathematical analysis; Nanocomposites; Nanomaterials; Nanoparticles; Nanoscale devices; Nanostructure; optical chemical sensor; Plasmons; Sensor arrays; Studies; Time domain analysis
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2011.2158417

Regular lattices of metallic nanoparticles exhibit extraordinary spectral features that arise from electromagnetic coupling between the dipole component of localized surface plasmons and constructive interference from diffracted far-field radiation. The present work introduces this coupled dipole excitation as an additional method to perform refractive index-based sensing using gold nanoparticle arrays. These arrays exhibit an aggregate sensitivity of 31 nm·RIU -1 using the coupled dipole peak in transmission UV-vis spectroscopy. This aggregate sensitivity is in good agreement with values predicted by three models for coupled dipole excitation: an analytical coupled dipole approximation, a discrete dipole approximation, and finite difference time domain. A particle-based sensitivity, S NP , of 389 nm·RIU -1 was determined for a fabricated array. Plasmon sensing based on the coupled dipole excitation in a gold nanoparticle array was possible even when the local surface plasmon signal from individual nanoparticles was indistinguishable from noise. Further increases in sensitivity and signal-to-noise are predicted as coupled dipole excitation parameters are optimized in high-precision fabrication of nanoparticle arrays.