Although challenging, assembling and orienting non-spherical nanomaterials into two- and three-dimensional (2D and 3D) ordered arrays can facilitate versatile collective properties by virtue of their shape-dependent properties that cannot be realized with their spherical counterparts. Here, we report on the self-assembly of gold nanorods (AuNRs) into 2D films at the vapor/liquid interface facilitated by grafting them with poly(ethylene glycol) (PEG). Using surface sensitive synchrotron grazing incidence small angle X-ray scattering (GISAXS) and specular X-ray reflectivity (XRR), we show that PEG-AuNRs in aqueous suspensions migrate to the vapor/liquid interface in the presence of salt, forming a uniform monolayer with planar-to-surface orientation. Furthermore, the 2D assembled PEG functionalized AuNRs exhibit short range order into rectangular symmetry with side-by-side and tail-to-tail nearest-neighbor packing. The effect of PEG chain length and salt concentration on the 2D assembly are also reported.
Available at: http://works.bepress.com/mallapragada_surya_k/77/
This article is published as Kim, Hyeong Jin, Wenjie Wang, Wei Bu, Md Mir Hossen, Alejandra Londono-Calderon, Andrew C. Hillier, Tanya Prozorov, Surya Mallapragada, and David Vaknin. "Salt Mediated Self-Assembly of poly (ethylene glycol)-functionalized Gold nanorods." Scientific Reports 9, no. 1 (2019): 1-9. DOI: 10.1038/s41598-019-56730-2. Posted with permission.