Detection of invisible phonon modes in individual defect-free carbon nanotubes by gradient-field Raman scattering
Yang Feng1, 3, 4, Ji Yinglu2, ‡, Zhang Xiao1, 4, Fan Qingxia1, 4, Zhang Nan1, 4, Gu Xiaogang1, 3, 4, Xiao Zhuojian1, 3, 4, Zhang Qiang1, 4, Wang Yanchun1, 3, Wu Xiaochun2, 4, Li Junjie1, Zhou Weiya1, 3, 4, †
       

(color online) Raman spectra of the SWNT coupled with Au NP cluster shown in Fig. 2(b), excited by 514 nm laser (a) and 785 nm laser (b), respectively.