Figure 5.

Use of scattered red light intensity from a 75 × 35 nm gold nanorod (AuNR) to measure rotation at the nanoscale. (A). Color image of AuNR-scattered light viewed by dark-field microscopy through a high pass filter to eliminate all but red light and a polarizer filter when the long axis of the AuNR is perpendicular and parallel to the plane of polarization. (B). Dark-field microscope design to record changes of scattered red light intensity vs. time from a single AuNR capable of determining the direction of rotation using a beam splitter to divert half of the photons through a second polarizer set at a rotational position that will reach a maximum light intensity before the first if the AuNR is rotating counterclockwise (CCW). This figure has been modified from that in Hornung et al. (2011).