One-Way Optoelectronic Switching of Photochromic Molecules on Gold

Abstract

We investigate photochromic molecular switches that are self-assembled on gold. We use two experimental techniques; namely, the mechanically controllable break-junction technique to measure electronic transport, and UV/Vis spectroscopy to measure absorption. We observe switching of the molecules from the conducting to the insulating state when illuminated with visible light ($\lambda =546\mathrm{n}\mathrm{m}$), in spite of the gold surface plasmon absorption present around this wavelength. However, we fail to observe the reverse process which should occur upon illumination with UV light ($\lambda =313\mathrm{n}\mathrm{m}$). We attribute this to quenching of the excited state of the molecule in the open form by the presence of gold.