title: Probing nonlinear optical coefficients in self-assembled peptide nanotubes.
abstract: Self-assembled l,l-diphenylalanine (FF) peptide micro/nanotubes represent a class of biomimetic materials with a non-centrosymmetric crystal structure and strong piezoelectricity. The peptide nanotubes synthesized by a liquid phase method yield tube lengths in the hundreds of micron range, inner diameters in the few hundred nanometer range, and outer diameters in the 5-15 μm range. Second harmonic generation (SHG) polarimetry from individual self-assembled FF nanotubes is used to obtain the nonlinear (NLO) optical coefficients as a function of the tube diameter and thermal treatment. The ratio of the shear to the longitudinal component (d15/d33) of the NLO coefficient increases with the diameter of the tubes. One of the transverse components of the nonlinear coefficient is found to be negative, and its magnitude with respect to the longitudinal component increases with the tube diameter. Thermal treatment of individual FF tubes has a similar effect upon increasing the diameter of the tubes in SHG polarimetry. Concurrent Raman scattering measurements from individual FF tubes show a distinct change in the low frequency (100 cm-1) region with the diameter of the tubes reflecting subtle effects of water.
authors.affiliation: Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA. guhas@missouri.edu yuping@missouri.edu.
authors.forename: Soma
authors.initials: S
authors.lastname: Khanra
authors.affiliation: Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897, USA.
authors.forename: Kartik
authors.initials: K
authors.lastname: Ghosh
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09219-580 Santo Andre, Sao Paulo, Brazil.
authors.forename: Fabio F
authors.identifier: http://orcid.org/0000-0003-1516-1221
authors.initials: FF
authors.lastname: Ferreira
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09219-580 Santo Andre, Sao Paulo, Brazil.
authors.forename: Wendel A
authors.identifier: http://orcid.org/0000-0002-8394-2751
authors.initials: WA
authors.lastname: Alves
authors.affiliation: Dipartimento di Scienze del Farmaco, Sezione Chimica, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy.
authors.forename: Francesco
authors.identifier: http://orcid.org/0000-0003-4212-8064
authors.initials: F
authors.lastname: Punzo
authors.affiliation: Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA. guhas@missouri.edu yuping@missouri.edu.
authors.forename: Ping
authors.initials: P
authors.lastname: Yu
authors.affiliation: Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA. guhas@missouri.edu yuping@missouri.edu.
authors.forename: Suchismita
authors.identifier: http://orcid.org/0000-0002-6269-2298
authors.initials: S
authors.lastname: Guha
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D006358:Hot Temperature; D045333:Nanotubes, Peptide / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014867:Water / Q000737:chemistry
chemical_list: D045333:Nanotubes, Peptide; D014867:Water