Electroconductive Langmuir-Blodgett films containing a carotenoid amphiphile for sugar recognition

Fabrication of electroconductive molecules has attracted the most interest in nanotechnology. To date, molecules bearing a long conjugated bond have been synthesized, and they exhibited electric conduction. If molecular recognition sites could be attached to the conducting molecules, the conducting molecules can be connected with each other or wired to the desired joints, and further be applied to the chemical sensors or the nanoscale electric circuits. In this study, we synthesized a carotenoid amphiphile, which bears both the conducting part, a carotenoid moiety, and the molecular recognition site, a boronic acid moiety for specific binding of sugars. The carotenoid amphiphile was mixed with a polymerizable amphiphile, spread at the air-water interface to form a monolayer, and then polymerized by light. The resulting polymerized monolayer was deposited on gold electrodes. The electric conduction and the molecular recognition ability of the monolayer on the electrode were studied by cyclic voltammetry. The electrode responded preferentially to the redox-active sugar derivative in the solution. The electric conduction was also microscopically confirmed by the AFM-current imaging technique. This manuscript has demonstrated a key step for designing molecular electronic devices based on molecular assembling, by which molecules are orientated spontaneously.