Asymmetric Overgrowth of Au/AuPt/PtSe₂ and Au/AgPtSe₂ Heterorods for Optimizing Nonlinear Enhancements

Abstract Favorable growth of asymmetric hetero‐nanostructures consisting of plasmonic metals and semiconductors or topological nanomaterials is highly desired because the performance of nonlinear optical antennas is closely related to their composition and morphology symmetry. In this work, two methods are proposed to overgrow PtSe₂, a semiconductor or topological semimetal material, onto Au nanorods (AuNRs) to form Au/AuPt/PtSe₂ and Au/AgPtSe₂ heterorods via wet chemical technique. Both Au/AuPt/PtSe₂ and Au/AgPtSe₂ heterorods show asymmetric morphologies: the Au/AuPt/PtSe₂ heterorods show a partially hollow morphology with an etched AuNR coated by AuPt and PtSe₂ shells; the Au/AgPtSe₂ heterorods prepared by Ag‐mediated overgrowth method have a toothbrush shape with AgPtSe₂ attached on the side surface near one end of AuNRs. The two asymmetric heterorods show significantly enhanced nonlinear radiations of second harmonic generation with the excitation laser wavelength tuning from 1220 to 1315 nm, and a maximal nonlinear enhancement factor of 16 is achieved, which is attributed to the interaction of gold core with platinum selenide shell and the broken symmetry of heterostructures. The findings provide a strategy to prepare metal‐topological heterostructures as optical antennas with optimized performance in the application of nonlinear photonic nanodevices.