@article{Kang2022, 
author = {Hao-Sen Kang and Wen-Qin Zhao and Tao Zhou and Liang Ma and Da-Jie Yang and Xiang-Bai Chen and Si-Jing Ding and Qu-Quan Wang},
title = {Toroidal dipole-modulated dipole-dipole double-resonance in colloidal gold rod-cup nanocrystals for improved SERS and second-harmonic generation},
year = {2022},
journal = {Nano Research},
volume = {15},
number = {10},
pages = {9461-9469},
keywords = {surface-enhanced Raman spectroscopy (SERS), plasmon, second-harmonic generation, near-field enhancement, toroidal dipole},
url = {https://www.sciopen.com/article/10.1007/s12274-022-4562-5},
doi = {10.1007/s12274-022-4562-5},
abstract = {Colloidal metal nanocrystals (NCs) show great potential in plasmon-enhanced spectroscopy owing to their attractive and structure-depended plasmonic properties. Herein, unique Au rod-cup NCs, where Au nanocups are embedded on the one or two ends of Au nanorods (NRs), are successfully prepared for the first time via a controllable wet-chemistry strategy. The Au rod-cup NCs possess multiple plasmon modes including transverse and longitudinal electric dipole (TED and LED), magnetic dipole (MD), and toroidal dipole (TD) modulated LED resonances, producing large extinction cross-section and huge near-field enhancements for plasmon-enhanced spectroscopy. Particularly, Au rod-cup NCs with two embedded cups show excellent surface-enhanced Raman spectroscopy (SERS) performance than Au NRs (75.6-fold enhancement excited at 633 nm) on detecting crystal violet owing to the strong electromagnetic hotspots synergistically induced by MD, LED, and TED-based plasmon coupling between Au cup and rod. Moreover, the strong TD-modulated dipole-dipole double-resonance and MD modes in Au rod-cup NCs bring a 37.3-fold enhancement of second-harmonic generation intensity compared with bare Au NRs, because they can efficiently harvest photoenergy at fundamental frequency and generate large near-field enhancements at second-harmonic wavelength. These findings provide a strategy for designing optical nanoantennas for plasmon-enhanced applications based on multiple plasmon modes.}
}