Unique determination of the -CN group tilt angle in Langmuir monolayers using sum-frequency polarization null angle and phase

作者：Velarde Luis; Wang Hong fei^*

来源：Chemical Physics Letters, 2013, 585: 42-48.

DOI：10.1016/j.cplett.2013.07.052

The relative phase and amplitude ratio between the ssp and ppp polarization combinations of the vibrational sum-frequency generation (SFG) response can be uniquely and accurately determined by the polarization null angle (PNA) method for orientational analysis. With PNA measurement we show that the -CN group in the 4-n-pentyl-4'-cyanoterphenyl (5CT) Langmuir monolayer is tilted around 25 degrees +/- 2 degrees from the interface normal, while that in the 4-n-octyl-4'-cyanobiphenyl (8CB) is tilted around 57 degrees +/- 2 degrees, consistent with the significant differences in the phase diagrams and hydrogen bonding SFG spectra of the two Langmuir monolayers reported in the literature.

• 出版日期2013-10-14