Chlorophyll switch
Four-step single molecule switch. Left: STM images of single chlorophyll-a after switching from 1 to 2 (a, b), 2 to 3 (c), and 4 (d). Right: Calculated structures of molecular conformations corresponding to 1, 2, 3 and 4. Below: Cartoons demonstrating the STM-tip induced switching process and a two-step current signal recorded during 1-2 switching (Courtesy: Saw-Wai Hla).