(a) Representative SEM image of horizontal as-grown peptide nanotubes deposited from the solution. (b) PFM in-plane contrast of intergrown tubes.
X-ray diffraction pattern of the crushed PNT powder after annealing at 150 °C for 1 h.
Temperature dependence of AFM and PFM signals. (a) Topography at 25 °C. (b)–(d) In-plane PFM contrast at 25 °C, 100 °C, and 150 °C, respectively. (e) Comparison of topography cross sections at different temperatures. (f) Comparison of PFM cross sections at different temperatures.
(a) Schematic of the switching experiment in the radial direction by PFM. (b) Piezoresponse hysteresis of lateral signal in as-grown state and after annealing at 150 °C.
PFM images of the annealed tubes before (a) and after (b) poling with +200 V over 10 s. (c) Time relaxation of the PFM signal after poling. The insets in (a) and (b) show topography before and after poling.
Formation of total polarization along the OZ axis in FF PNTs for a molecular model with an initial state of 2 FF rings: (a) configuration of a single F molecule containing single bond and double bond …C=C−C… moiety, providing the migration of protons (tautomerization). (b) FF molecule with amino bond, providing high mobility of torsion angles (between atoms CB7, CA3, C5, N23, CA25) and dipole DFF. (c) Formation of the molecular rings from 6 FF molecules joined by hydrogen bonds (H-bonds) between FF molecules. (d) Formation of tubular FF PNT structure joined by H-bonds between FF rings. The dashed lines denote the N−H…O H-bonding. Red, oxygen; deep blue, nitrogen; light blue, carbon; gray, hydrogen; yellow tubes, coil of amino bonding.
Schematic illustration of the molecular model for individual FF tube bundles self-assembled after annealing at 150 °C (orthorhombic phase) with a fully compensated total dipole moment (Ps = 0) before poling, then during poling ( Ps ≠ 0 ) (a), and the resulting remanent polarization hysteresis loop under varying radial electric field E el calculated in our model (b).
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