Figure 18.

(a) Plasmon coupling between individual pairs of Au and Ag nanoparticles causes a spectral shift visible by dark-field microscopy. (b) Plasmon coupling can be used as a ruler for distance changes above 10 nm; here, it is used to measure the bending and cleavage of single DNA molecules by the enzyme EcoRV. (c) Intensity trace vs time shows the initial straight configuration, the high-intensity bent state, and the low-intensity cleaved state. (d) Bending kinetics are measured by pooling data from many events. Adapted from refs (229) and (230).