Second-Harmonic Scattering-Defined Topological Classes for Nano-Objects

Nano-object topology determination is a central question in nanoscience and remains a challenge to achieve in the absence of a supporting substrate and atomic resolution techniques. In this work, we demonstrate how second-harmonic scattering (SHS) is sensitive to the balance between the nano-object shape symmetry and size, thereby allowing for a SHS-defined topological definition. Although many data on nano-objects have been reported with this method so far, in most cases dispersed in liquid suspensions, no topological retrieval has been proposed. To reach this task, we have measured the second-harmonic scattered light from a series of representative nano-objects along two collection directions for well-defined polarization states. The experimental results are then recast within a general framework involving nonlinear emitting sources and the size as critical elements. This analysis leads to the classification of the nano-objects according to the topology defined by their SHS response.