Fig. 2: Titration of AzPy and proton scavenger proton sponge (PS) with methanolic HCl and 365 nm light.
From: A cautionary tale of basic azo photoswitching in dichloromethane finally explained

a Titration of 60 μM AzPy by 0.01 mM methanolic HCl added in DCM. Inset shows the \(n\to {{{{\rm{\pi }}}}}^{* }\) band. b Irradiation of 60 μM PS in DCM by 365 nm light in 30 s intervals. All UV-vis measurements were performed at 21 °C.