Figure 1.

Well-defined crystallographic chirality in Au chiral nanocubes (helicoids) results in pronounced chiral optical response. (a) A schematic illustration of optical activity in hyper-Rayleigh scattering from helicoid nanoparticles (NPs), illuminated with left and right circularly polarized light (LCP and RCP, respectively), with frequency ω. (b) Scanning electron microscopy (SEM) images of the chiral forms (enantiomorphs) of the l- and d-helicoids. The average edge length of the helicoids is approximately 150 nm. (c) Ellipticity (in the linear optical regime) and extinction spectra of the two helicoid enantiomorphs, suspended in 1 mM aqueous cetrimonium bromide (CTAB) solution. The extinction spectra were normalized to the maximum value. (d) Ellipticity (in the linear optical regime) and normalized extinction spectra of silica coated l- and d-helicoids suspended in a 9:1 solution of 1 mM CTAB and ethanol. The thickness of the silica shell was approximately 20 nm.