Polarization-dependent second harmonic generation in peptide crystals: effects of molecular packing

A series of chiral peptide luminophores containing the coumarin moiety was synthesized via a simple and efficient solution-based procedure. The peptides, containing either l -Phe, or l -Ala, or l -Leu (designated, respectively, as p1 , p2 , and p3 ), self-aggregate to form anti-parallel sheet-like s...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2023-02, Vol.25 (7), p.5849-5856
Main Authors: Nandi, Sujay Kumar, Roy, Samrat, Pal, Bipul, Haldar, Debasish
Format: Article
Language:English
Subjects:
Actuators
Coumarin
Crystals
Laser beams
Linear polarization
Mathematical analysis
Nonlinear control
Nonlinear optics
Organic crystals
Peptides
Second harmonic generation
Self-assembly
Switches
Symmetry
Tensors
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Summary:A series of chiral peptide luminophores containing the coumarin moiety was synthesized via a simple and efficient solution-based procedure. The peptides, containing either l -Phe, or l -Ala, or l -Leu (designated, respectively, as p1 , p2 , and p3 ), self-aggregate to form anti-parallel sheet-like structures. The self-assembly of the peptide luminophores leads to non-centrosymmetric crystals which display significant second harmonic generation (SHG). The dependence of the SHG intensity on the input laser polarization revealed a strong correlation between the SHG and the crystal packing. In the polar plots, the SHG intensity as a function of the linear polarization orientation of the input laser beam gave a four-petal pattern for p1 , a predominantly two-petal pattern for p2 , and a dumbbell-shaped pattern for p3 . This reflects the dependence of the second order optical susceptibility tensor on the crystal symmetry. The polar plots can be fitted very well with the theoretical expressions derived from the second order polarization equation after incorporating crystal symmetry in the second order optical susceptibility tensor. The strong polarization-dependent SHG from organic crystals may be interesting for polarization controlled nonlinear optical switches, sensors, and actuators. A series of coumarin-based peptides having the same molecular backbone but different substituent side chains to self-assemble to different non-centrosymmetric crystals is reported which show polarization-dependent, efficient second harmonic generation (SHG).
ISSN:1463-9076
1463-9084
DOI:10.1039/d2cp05462k