Electrical and Optical Properties of Fullerenol Langmuir−Blodgett Films Deposited on Polyaniline Substrates

The synthesis of fullerenol with various degrees of hydroxylation and the use of a low hydroxylated product to form stable Langmuir films are reported in this work, along with the optical and electrical properties of Langmuir−Blodgett (LB) films obtained on glass and polyaniline (PANI) substrates. The data suggest that an average of 9−12 hydroxyl groups are bound preferentially on one side of the C 60 cage and this allows the formation of stable two-layer films at the air/water interface. The large anisotropy of the hydroxylated molecule provides organized LB films of the type substrate − (D − C 60 − D − C 60 − ) n, with D representing the hydroxyl groups. The electrical conductivity of LB films deposited on glass is equivalent to that reported for highly conductive polymeric C 60 but several orders of magnitude higher than that for disordered fullerenol pellets. UV−vis absorptions provide evidence that fullerenol layers cause the deprotonation of PANI, rendering a polymer with low conductivity. The loss of conductivity disagrees with the behavior expected for a donor (PANI)/acceptor (fullerenol) interface, even though current−voltage ( I − V ) curves of fullerenol LB /PANI junctions indicate some degree of electrical rectification. Additionally, transients observed at large bias on the I − V curves agree with the reported proton conductivity of fullerenol.