Press Releases
Dec. 7, 2007

A new molecular-sized photo-switching using electrochemical reaction

  • Prof. Hiroshi Nishihara (Department of Chemistry)

Single-light photo-switching of a molecule placed on an electrode was achieved. This switching system could contribute to the development of molecular-sized switching materials.

Azobenzene is a photo-switchable molecule that changes its shape triggered by light. Molecules that can be switched by outer stimuli could be used as nanoscale memory devices by their on-off behaviors. Azobenzene-based photoswitches are usually manipulated with two different light sources, UV light for a trans-to-cis isomerization and blue light for a cis-to-trans reverse isomerization.

Nishihara previously reported a reversible switching of iron-containing azobenzene, 3-ferrocenlyazobenzene, which can be switched with a single source of green light by combination of photochemistry and electrochemistry. In the present study, Nishihara constructed a 3-ferrocenylazobenzene modified transparent electrode and tried to control the direction of molecular photo-switching by electric stimuli. Photo-switching behavior was monitored by the careful measurements of tiny absorbance changes caused by the molecular switching. As a result, photo-switching direction by green light with positive electrode voltage was opposite to that without electric stimuli. This behavior indicates that the system can be switched by single light source and could contribute to the molecular-sized switching device by eliminating the need of focusing dual light sources on the same small region to switch molecules.