Optical Characteristic And Numerical Study Of Gold Nanoparticles On Al 2O3 Coated Gold Film For Tunable Plasmonic Sensing Platforms

Substrate-based tuning of plasmon resonances on gold nanoparticles (NP) is a versatile method of achieving plasmon resonances at a desired wavelength, and offers reliable nanogap sizes and large field enhancement factors. The reproducibility and relative simplicity of these structures makes them promising candidates for frequency-optimized sensing substrates. The underlying principle in resonance tuning of such a structure is the coupling between a metal nanoparticle and the substrate, which leads to a resonance shift and a polarization dependent scattering response. In this work, we experimentally investigate the optical scattering spectra of isolated 60 nm diameter gold nanoparticles on aluminum oxide (Al2O3) coated gold films with various oxide thicknesses. Dark-field scattering images and scattering spectra of gold particles reveal two distinct resonance modes. The experimental results are compared with numerical simulations, revealing the magnitude and phase relationships between the effective dipoles of the gold particle and the gold substrate. The numerical approach is described in detail, and enables the prediction of the resonance responses of a particle-on-film structure using methods that are available in many available electromagnetics simulation packages. The simulated scattering spectra match the experimentally observed data remarkably well, demonstrating the usefulness of the presented approach to researchers in the field. © 2013 SPIE

Effect Of Surface Roughness On Substrate-Tuned Gold Nanoparticle Gap Plasmon Resonances

The effect of nanoscale surface roughness on the gap plasmon resonance of gold nanoparticles on thermally evaporated gold films is investigated experimentally and numerically. Single-particle scattering spectra obtained from 80 nm diameter gold particles on a gold film show significant particle-to-particle variation of the peak scattering wavelength of ±28 nm. The experimental results are compared with numerical simulations of gold nanoparticles positioned on representative rough gold surfaces, modeled based on atomic force microscopy measurements. The predicted spectral variation and average resonance wavelength show good agreement with the measured data. The study shows that nanometer scale surface roughness can significantly affect the performance of gap plasmon-based devices. This journal i

Gap-Plasmon Enhanced Gold Nanoparticle Photoluminescence

Gap-plasmon-enhanced gold nanoparticle photoluminescence is studied experimentally at the single-particle level. The photoluminescence spectra of gold nanoparticles on an Al2O3-coated gold film under both 532 and 633 nm excitation show a clear peak near the measured gap-plasmon resonance wavelength. Comparing the collected emission spectrum with that from a gold reference film under 633 nm excitation, a peak photoluminescence enhancement factor of 28 000 is observed. The spectral shape and absolute magnitude of the enhancement factors for both excitation wavelengths are reproduced using numerical calculations without the use of any free parameters. The photoluminescence enhancement is explained in terms of a gap-mode-enhanced e-h pair generation rate and a wavelength-dependent enhancement of the emission efficiency. (Graph presented)

Wide-Band Spectral Control Of Au Nanoparticle Plasmon Resonances On A Thermally And Chemically Robust Sensing Platform

Gold nanoparticles on Al2O3-coated gold films are presented as a chemically and thermally robust platform for molecular sensing. Single particle spectroscopy as a function of Al2O3 coating thickness shows reproducible gold nanoparticle scattering spectra in the range from 690 to 610 nm as the Al2O3 thickness increases from 0 to 3.4 nm. Numerical simulation of these structures indicates that surface-enhanced Raman spectroscopy enhancement factors in excess of 10 6 can be achieved. The stability of the Al2O 3-coated structures under high-power laser irradiation was tested, revealing stable scattering spectra upon irradiation with 100 W/mm2 at the particle resonance wavelength. The presented structure solves challenges with thermal stability, wavelength tuning range, and Raman background signal associated with previously attempted approaches. © 2013 American Chemical Society

Controlled Surface Plasmon Resonance On Stable Substrates As An Optimized Sensing Platform

Precise control of localized plasmon resonance scattering spectra of gold nanoparticles on Al2O3 coated gold substrates were demonstrated. The scattering spectra remain stable after high power laser irradiation near the resonance wavelength. © 2013 Optical Society of America

Gap-Plasmon Enhanced Gold Nanoparticle Photoluminescence

Gap-plasmon-enhanced gold nanoparticle photoluminescence is studied experimentally at the single-particle level. The photoluminescence spectra of gold nanoparticles on an Al₂O₃-coated gold film under both 532 and 633 nm excitation show a clear peak near the measured gap-plasmon resonance wavelength. Comparing the collected emission spectrum with that from a gold reference film under 633 nm excitation, a peak photoluminescence enhancement factor of 28 000 is observed. The spectral shape and absolute magnitude of the enhancement factors for both excitation wavelengths are reproduced using numerical calculations without the use of any free parameters. The photoluminescence enhancement is explained in terms of a gap-mode-enhanced e<i>–</i>h pair generation rate and a wavelength-dependent enhancement of the emission efficiency

Wide-Band Spectral Control of Au Nanoparticle Plasmon Resonances on a Thermally and Chemically Robust Sensing Platform

Gold nanoparticles on Al₂O₃-coated gold films are presented as a chemically and thermally robust platform for molecular sensing. Single particle spectroscopy as a function of Al₂O₃ coating thickness shows reproducible gold nanoparticle scattering spectra in the range from 690 to 610 nm as the Al₂O₃ thickness increases from 0 to 3.4 nm. Numerical simulation of these structures indicates that surface-enhanced Raman spectroscopy enhancement factors in excess of 10⁶ can be achieved. The stability of the Al₂O₃-coated structures under high-power laser irradiation was tested, revealing stable scattering spectra upon irradiation with 100 W/mm² at the particle resonance wavelength. The presented structure solves challenges with thermal stability, wavelength tuning range, and Raman background signal associated with previously attempted approaches