Direct observation of photo switching in tethered spiropyrans using the interfacial force microscope

The interfacial force microscope has been used to establish the changes in the surface chemistry that accompany photoactivated opening and closing of rings in tethered spiropyran monolayers. Contact potential measurements show that ring opening via ultraviolet light creates a more polar surface, while exposure to visible light closes the rings and resets the surface. Normal force measurements show that open ring structures are protonated in electrolyte solutions, amplifying the switching of electrical double-layer forces.