AuAg@CdS double-walled nanotubes: synthesis and nonlinear absorption properties.

Novel AuAg@CdS double-walled nanotubes (DWNTs) were successfully fabricated through a three-step solvothermal method, starting with silver nanowires as the template. In the DWNTs, a uniform layer of a CdS shell is coated onto the AuAg nanotubes, finally forming the one-dimensional nanocomposites. Nonlinear optical analysis indicated that the plasmon-exciton interaction in the AuAg@CdS DWNTs induced an obviously saturated absorption response under visible light excitation, in contrast to individual AuAg nanotubes and CdS shells. Furthermore, the effective nonlinear absorption coefficient of the AuAg@CdS DWNTs was 7 times larger than that of the CdS shell, which was attributed to the local field enhancement effect. Such a unique morphological configuration and optical properties make AuAg@CdS DWNTs an ideal candidate for next generation nano-photonic devices employed as a mode-locking element, optical switch, and so on.