SHG and MDC spectroscopy of chiral organic monolayer at the air-water interface

Dielectric properties of the S-citronelloxy-cyanobiphenyl (S-CCB) and 4'-hexyloxy-4-cyanobiphenyl (6OCB) monolayer were investigated with the optical second harmonic generation (SHG) and Maxwell displacement current (MDC) measurement. With the MDC measurement coupled with the SHG, molecular motion of S-CCB monolayer on the water surface was observed during compression process. SHG circular dichroism (SHG-CD) measurement and the polarized angle dependence measurement were performed to reveal the chirality of the monolayer on the silica substrate and the water surface, respectively. Opposite dichroic ratio observed for S-CCB and R-CCB LB monolayer indicates that the capability of detecting the chirality of LB monolayer. According to the polarized angle dependence measurement, relationship between two tensor components, s(14) and s(15), can be obtained as s(14)/s(15) approximate to 1/30 for the S-CCB monolayer on the water surface where the tensor component s(14) exhibits the molecular chirality. (c) 2004 Elsevier B.V. All rights reserved.