Spinning nanorods--active optical manipulation of semiconductor nanorods using polarised light

In this letter we show how a single beam optical trap offers the means for three-dimensional manipulation of semiconductor nanorods in solution. Furthermore rotation of the direction of the electric field provides control over the orientation of the nanorods, which is shown by polarisation analysis of two photon induced fluorescence. Statistics over tens of trapped agglomerates reveal a correlation between the measured degree of polarisation (DLP) and the size of the agglomerate which was determined by the escape frequency and the intensity of the emitted fluorescence. We estimate that we have trapped agglomerates with a volume of close to 10 times the volume of a single nanorod, which exhibited DLPs as high as 52%.