Self-assembled L,L-diphenylalanine (FF) nanostructures offer an attractive platform for photonics and nonlinear optics. The nonlinear optical (NLO) coefficients of FF nanotubes depend on the diameter of the tube [S. Khanra et al. Phys. Chem. Chem. Phys. 19(4), 3084-3093 (2017)]. To further enhance the NLO properties of FF, we search for structural modifications. Here, we report on the synthesis of fluorinated FF dipeptides by replacing one ortho-hydrogen atom in each of the phenyl groups of FF by a fluorine atom. Density-functional theoretical calculations yield insights into minimum energy conformers of fluorinated FF (Fl-FF). Fl-FF self-assembles akin to FF into micron-length tubes. The effects of fluorination are evaluated on the piezoelectric response and nonlinear optical properties. The piezoelectric d15 coefficient of Fl-FF is found to be more than 10 times higher than that of FF nanotubes, and the intensity of second harmonic generation (SHG) polarimetry from individual Fl-FF nanotubes is more than 20 times that of individual FF nanotubes. Furthermore, we obtain SHG images to compare the intensities of FF and Fl-FF tubes. This work demonstrates the potential of fluorine substitution in other self-assembled biomimetic peptides for enhancing nonlinear optical response and piezoelectricity.



Research Center/Lab(s)

Center for High Performance Computing Research

Keywords and Phrases

Atoms; Biomimetics; Crystallography; Density functional theory; Fluorine; Harmonic generation; Nanotubes; Optical properties; Peptides; Piezoelectricity, Biomimetic peptides; Fluorine substitution; Non-linear optical properties; Nonlinear optical response; Piezoelectric response; Self-assembled peptides; Structural modifications; Theoretical calculations, Nonlinear optics

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Article - Journal

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Final Version

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© 2019 The Authors, All rights reserved.

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This work is licensed under a Creative Commons Attribution 3.0 License.

Publication Date

01 Nov 2019

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Chemistry Commons