Enhanced second-harmonic generation of asymmetric Au@CdSe heterorods

The plasmon-enhanced second-harmonic generation (SHG) of Au nanorods (NRs), Au-Ag NRs, and asymmetric Au@CdSe heterorods are comparatively investigated. The Au@CdSe tip- and side-heterorods are synthesized by precisely controlling the concentration of Cd2+ precursor, and the plasmon resonances can be well tuned simultaneously. The SHG of asymmetric Au@CdSe heterorods has been greatly enhanced with up to 617.7-fold enhancement compared with the Au NRs because of the asymmetric morphology and local field enhancement. Moreover, the harmonic energy transfer induced by the local interband transition of Au has also been demonstrated by the excitation-wavelengthdependent SHG in the Au NRs and Au@CdSe side-heterorods, while it is negligible in the Au-Ag NRs and Au@CdSe tipheterorods because of the presence of Ag. The plasmon-enhanced SHG of asymmetric Au@CdSe heterorods enables potential applications ranging from sensing to biological spectroscopy.