Surfactant-directed synthesis of silver nanorods and characteristic spectral changes occurred by their morphology evolution

• CTAB volume is a key factor to determine the polydispersity of silver nanorods.
• The aging time plays a critical role in the morphology evolution of silver nanorods.
• Characteristic spectral changes occurred due to the morphology evolution of silver nanorods.
• The ablation of silver nanorods in the top end was accompanied by the growth of other nanoparticles.

Silver nanorods with different polydispersity were synthesized in the cetyltrimethylammonium bromide (CTAB) rod-shaped micelles by inducing the orientation growth of silver seeds and adjusting the volumes of CTAB. The reaction for the formation of silver nanorods had basically finished in 10 min. A suitable volume of CTAB (i.e., 15.0 mL of 0.1 M CTAB) is beneficial to obtain high-quality silver nanorods in the given reaction system. That is, the volume of added CTAB is a key factor to determine the polydispersity of the formed nanorods. The aging time plays a critical role in the morphology evolution of silver nanorods due to the oxidation of silver nanorods with Br−, O2 and the Ostwald ripening of the nanoparticles. As a result, the characteristic spectral changes occurred due to the morphology evolution of silver nanorods. The ablation in the top ends of the longer nanorods is often accompanied by the growth of some shorter nanorods and nanospheres. The size distribution of silver nanorods might be more uniform in the early aging stage. All the nanorods in the colloidal solution should turn into the near-spherical nanoparticles with larger sizes and thus the characteristic absorption should change to single peak centered at about 400 nm. Based on the research results, mathematical models are proposed for explaining the formation and morphology changes of silver nanorods. The morphology evolution of silver nanorods may be important and can be used as a reference for preparing silver nanorods, nanowires and other anisotropic nanomaterials.

We have developed the surfactant-directed synthetic method to synthesize silver nanorods with different polydispersity in the cetyltrimethylammonium bromide (CTAB) rod-shaped micelles by adjusting the volumes of CTAB. We have suggested that CTAB volume of addition is a key factor to determine the polydispersity of the formed nanorods and the aging time plays a critical role in the morphology evolution of silver nanorods.Figure optionsDownload as PowerPoint slide