Characterization of a Photoswitchable Spiropyran Surface in Potassium Chloride Solution by Interfacial Force Microscopy and Atomic Force Microsocpy
The interaction forces between an oxidized silica tip and spiropyran tethered to an oxidized silicon surface in ionic solutions were measured using Interfacial Force Microscopy and characterized using Atomic Force Microscopy to observe the photoswitching capability of spiropyran. The molecules were exposed to ultraviolet light in differing concentrations of KCl solution resulting in an exponentially decaying function. Exposure to visible light did not exhibit any appreciable exponential decay. Concentrations of the KCl solution increased from 0.1 mM to 3 mM, causing the decay length to decrease from 30 nm to 3 nm. Electrical double force behavior was observed between the two charged polar surfaces indicating that exposure of spiropyran to UV light and visible light causes the molecule to alternate between polar and non-polar states.