Langmuir monolayer of organoalkoxysilane for vitamin B12-modified electrode

In order to develop a novel type of vitamin B12-functionalized electrode, the monolayer properties of the vitamin B12 mimics, which have a core structurally identical with the naturally occurring vitamin B12 and seven ester chains on the outside, have been investigated as a mixed monolayer with an organosilane amphiphile. Vitamin B12 derivatives having seven C8 chains were stably incorporated into the matrix organosilane monolayer, while the short C3 chain derivatives were easily squeezed out from the matrix monolayer upon compression. Analyses of the molecular areas revealed that the long chain derivatives had a face-on orientation in the matrix monolayer. The mixed monolayers of the vitamin B12 with the long chains and the organosilane amphiphile were transferred as an X-type LB film on a quartz plate that showed reasonable UV absorbance. The monolayer containing the vitamin B12 derivative was similarly immobilized on an ITO electrode. A cyclic voltammetric measurement of this electrode in aqueous solution showed a Co(II)/Co(I) redox couple at − 0.65 V s. Ag/AgCl which is in good agreement with the corresponding value of the vitamin B12 derivative dissolved in methanol. It indicates that this modified electrode can be used as a reactive electrode with a vitamin B12 function.