Influence of optical excitation on the electric field assisted assembly of CdSe nanorods

Rod-shaped CdSe nanocrystals show narrow-band, linearly polarized emission and anisotropic charge-transport properties. The alignment of nanorods (NRs) on a macroscopic scale makes it possible to prepare a novel class of materials with intrinsically anisotropic optical and electric properties. To integrate NRs in useful devices, low-cost assembly methods have to be developed and an appropriate electrical contact must be guaranteed. In this perspective, CdSe nanorods of 8 nm in diameter and 80 nm in length (aspect ratio AR = 10) were prepared by chemical synthesis. Their alignment was achieved by the application of an external electric field during the solvent evaporation after drop-cast deposition across lithographically pre-patterned metal electrodes (Ti/Au) on silicon oxide substrates. We illustrate that the application of UV excitation (365 nm) in addition to the electric field strongly enhances the alignment of the NRs parallel to the field lines. (C) 2009 Elsevier B.V. All rights reserved.