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Organizing Nanorods with a Polymer Template

TEM tomography reconstruction of same film showing ordered nanorods.
Materials Sciences Division researcher Ting Xu and colleagues at the National Center for Electron Microscopy and the Advanced Light Source have discovered a route for creating complex structures of CdS nanorods by leveraging the self-assembly of large polymer molecules. This unprecedented degree of control over nanostructure assembly will enable researchers to use them more effectively in applications like solar cells and magnetic storage devices.  

Schematic of ordered rod-shaped nanoparticles embedded in block copolymer columns.
Central to the discovery are specially tailored block copolymers – large aggregate polymers comprised of repeating blocks of smaller molecules – which form a variety of morphologies, from smooth lamellar structures to columns of one polymer embedded in the other. When CdS nanorods are included in the mix, they organize themselves within the contours of the block copolymer according to a delicate balance of forces between the nanorods and the polymer.

Using this method, the researchers are able to generate a wide library of nanorod assemblies including parallel-aligned arrays, continuous nanoscopic networks, and ordered clusters. The method is compatible with solution processing and scalable nanomanafacturing techniques, presenting a critical tool for nano-scale materials design.

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K. Thorkelsson, A.J. Mastroianni, P. Ercius, and T. Xu, "Direct Nanorod Assembly Using Block Copolymer-Based Supramolecules" Nano Letters, 12 (1), 498-504, 2012. DOI: 10.1021/nl2040089