Figure 5. UV/vis-spectrum of viologen, measured eight times at 20-second intervals, with an applied potential of -0.9 V

From

Electrochromism of Methylviologen (Paraquat)

N. Aristov, A. Habekost

World Journal of Chemical Education. 2015, 3(4), 82-86 doi:10.12691/wjce-3-4-1