New technique for nanostructure assembly

Self-Assembled Colloidal Superparticles from Nanorods

Science 19 October 2012: 
Vol. 338 no. 6105 pp. 358-363 
DOI: 10.1126/science.1224221

1. Tie Wang¹, 
2. Jiaqi Zhuang¹, 
3. Jared Lynch¹, 
4. Ou Chen¹, 
5. Zhongliang Wang¹, 
6. Xirui Wang¹, 
7. Derek LaMontagne¹,
8. Huimeng Wu¹, 
9. Zhongwu Wang², 
10. Y. Charles Cao¹,*

Colloidal superparticles are nanoparticle assemblies in the form of colloidal particles. The assembly of nanoscopic objects into mesoscopic or macroscopic complex architectures allows bottom-up fabrication of functional materials. We report that the self-assembly of cadmium selenide–cadmium sulfide (CdSe-CdS) core-shell semiconductor nanorods, mediated by shape and structural anisotropy, produces mesoscopic colloidal superparticles having multiple well-defined supercrystalline domains. Moreover, functionality-based anisotropic interactions between these CdSe-CdS nanorods can be kinetically introduced during the self-assembly and, in turn, yield single-domain, needle-like superparticles with parallel alignment of constituent nanorods. Unidirectional patterning of these mesoscopic needle-like superparticles gives rise to the lateral alignment of CdSe-CdS nanorods into macroscopic, uniform, freestanding polymer films that exhibit strong photoluminescence with a striking anisotropy, enabling their use as downconversion phosphors to create polarized light-emitting diodes.