Open Access Nano Express

Facile purification of colloidal NIR-responsive gold nanorods using ions assisted self-assembly

Lianke Liu1, Zhirui Guo2, Lina Xu3, Ruizhi Xu4 and Xiang Lu2*

Author Affiliations

1 Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China

2 The Second Affiliated Hospital of Nanjing Medical University, Nanjing 210011, China

3 State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China

4 Department of Radiotherapy, the First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China

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Nanoscale Research Letters 2011, 6:143  doi:10.1186/1556-276X-6-143

Published: 14 February 2011

Abstract

Anisotropic metal nanoparticles have been paid much attention because the broken symmetry of these nanoparticles often leads to novel properties. Anisotropic gold nanoparticles obtained by wet chemical methods inevitably accompany spherical ones due to the intrinsically high symmetry of face-centred cubic metal. Therefore, it is essential for the purification of anisotropic gold nanoparticles. This work presents a facile, low cost while effective solution to the challenging issue of high-purity separation of seed-mediated grown NIR-responsive gold nanorods from co-produced spherical and cubic nanoparticles in solution. The key point of our strategy lies in different shape-dependent solution stability between anisotropic nanoparticles and symmetric ones and selective self-assembly and subsequent precipitation can be induced by introducing ions to the as-made nanorod solution. As a result, gold nanorods of excellent purity (97% in number density) have been obtained within a short time, which has been confirmed by SEM observation and UV-vis-NIR spectroscopy respectively. Based on the experimental facts, a possible shape separation mechanism was also proposed.