Quantitative extinction and transient resonant four-wave mixing

<p>The data refer to two optical imaging methods. 1. Wide-field imaging optical extinction method to rapidly and quantitatively measure the optical extinction cross-section (also polarisation resolved) of a large number of individual gold nanoparticles, for statistically-relevant single particle analysis. Using this method, we have characterized nominally-spherical gold nanoparticles in the 10-100nm size range. The data are the measured extinction cross-sections (as images and .dat ascii files) for these particles. Data of the optical extinction cross-section for in-house fabricated nanoparticle conjugates are also available, demonstrating distinction of individual dimers from single particles and larger aggregates. 2. Transient resonant four-wave mixing micro-spectroscopy. This is a nonlinear optical microscopy method which detects single gold nanoparticles through light-matter interaction at the localised surface plasmon resonance. Owing to an interferometric and time-resolved detection, this technique is very specific to metallic nanoparticles and background-free. Rather than providing the absolute value of the optical extinction cross-section, the technique is sensitive to the change in the nanoparticle extinction induced by a short pump pulse. In turn, owing to the phase-sensitivity of the interferometric detection, we can measure the pump-induced ultrafast change in the particle polarisability as a complex quantity, i.e. separating its real and imaginary parts. The data shown are the measurements of these quantities, and theoretical models to them, for single gold nanoparticles and dimers.<br><br>Results derived from these data are published at http://dx.doi.org/10.1039/C5FD00079C<br></p>