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, s14 and s15 , can be obtained as s14/s15≈1/30 for the S-CCB monolayer on the water surface where the tensor component s14 exhibits the molecular chirality.