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Significant Chiral Signal Amplification of Langmuir Monolayers Probed by Second Harmonic Generation
journal contribution
posted on 2015-12-17, 08:08 authored by Kai Lv, Lu Lin, Xiaoyu Wang, Li Zhang, Yuan Guo, Zhou Lu, Minghua LiuWith the development of the nonlinear
optical technique such as
SHG (second harmonic generation), the in situ measurements of the
chirality in the monolayers at the air/water interface have become
possible. However, when performing the SHG measurement of the chirality
in a monolayer, it is still a great challenge to obtain the chiral
signals with a good S/N (signal-to-noise) ratio. In this Letter, interfacial
assemblies with induced supramolecular chirality were used to amplify
the weak chiral SHG signals from the monolayers at the air/water interface.
Tetrakis(4-sulfonatophenyl) porphyrin (TPPS) J aggregates were used
as the subphase, and when chiral amphiphilic molecules were spread
on it, chiral domains of the amphiphile/TPPS J aggregates were formed
and then significantly amplified chiral signals that otherwise could
not be detected. Moreover, the sign of the DCE (degree of chiral excess)
changed with the chirality of the amphiphilic molecules, thus providing
a possible way to obtain the absolute chiral information in situ in
the monolayers.