CONICET | Buscador de Institutos y Recursos Humanos

The optical properties of noble metal nanoparticles (NPs) are determined by the collective excitation of conduction electrons, known as localized surface plasmons, which are highly dependent of the size and shape of the NP. Its manipulation allows for a variety of applications in ultrasensitive spectroscopies, photonics, imaging, and cancer therapy. In order to achieve a rigorous quantitative understanding of the optical response accurate 3D morphological characterization, single NP spectroscopy, and electrodynamics modeling is required. The aim of this work was to measure the polarization resolved Rayleigh scattering (RS) of a single Au NP of complex shape to reconstruct accurately its 3D morphology from TEM images, and to correlate the experimental optical measurement with electrodynamics simulations based on the reconstructed morphology. The NP was perfectly identified on a TEM grid and its RS spectra was collected at different incident polarization angles using a dark-field optical microscope. The reconstruction of the 3D NP characterization was performed using STEM-HAADF on a FEI Titan 80-300 operated at 300 kV, with a convergence angle of 19 mrad and a detector inner diameter corresponding to 205 mrad. Images were recorded at tilt increments of 2° between +/-70°. For reconstruction of the 3D shape of the Au NP, we used a discrete algebraic reconstruction technique (DART). The input model and segmentation for DART was obtained by the standard iterative reconstruction technique, modified by a masking step setting all known vacuum voxels to zero. With this approach, the assignment of correct segmentation values to distinguish between gold and vacuum during DART is significantly facilitated.