title: Optical micro-spectroscopy of single metallic nanoparticles: quantitative extinction and transient resonant four-wave mixing.
abstract: We report a wide-field imaging method to rapidly and quantitatively measure the optical extinction cross-section σ(ext) (also polarisation resolved) of a large number of individual gold nanoparticles, for statistically-relevant single particle analysis. We demonstrate a sensitivity of 5 nm(2) in σ(ext), enabling detection of single 5 nm gold nanoparticles with total acquisition times in the 1 min range. Moreover, we have developed an analytical model of the polarisation resolved σ(ext), which enabled us to extract geometrical particle aspect ratios from the measured σ(ext). Using this method, we have characterized a large number of nominally-spherical gold nanoparticles in the 10-100 nm size range. Furthermore, the method provided measurements of in-house fabricated nanoparticle conjugates, allowing distinction of individual dimers from single particles and larger aggregates. The same particle conjugates were investigated correlatively by phase-resolved transient resonant four-wave mixing micro-spectroscopy. A direct comparison of the phase-resolved response between single gold nanoparticles and dimers highlighted the promise of the four-wave mixing technique for sensing applications with dimers as plasmon rulers.
authors.affiliation: Cardiff University School of Biosciences, Museum Avenue, Cardiff CF10 3AX, United Kingdom. borrip@cf.ac.uk.
authors.forename: Lukas
authors.initials: L
authors.lastname: Payne
authors.forename: George
authors.initials: G
authors.lastname: Zoriniants
authors.forename: Francesco
authors.initials: F
authors.lastname: Masia
authors.forename: Kenton P
authors.initials: KP
authors.lastname: Arkill
authors.forename: Paul
authors.initials: P
authors.lastname: Verkade
authors.forename: Darren
authors.initials: D
authors.lastname: Rowles
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Langbein
authors.forename: Paola
authors.initials: P
authors.lastname: Borri
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D006046:Gold