Alejandro Heredia

Temperature-driven phase transformation in self-assembled diphenylalanine peptide nanotubes

Diphenylalanine (FF) peptide nanotubes (PNTs) represent a unique class of self-assembled functional biomaterials owing to a wide range of useful properties including nanostructural variability, mechanical rigidity and chemical stability. In addition, strong piezoelectric activity has recently been observed paving the way to their use as nanoscale sensors and actuators. In this work, we fabricated both horizontal and vertical FF PNTs and examined their optical second harmonic generation and local piezoresponse as a function of temperature. The measurements show a gradual decrease in polarization with increasing temperature accompanied by an irreversible phase transition into another crystalline phase at about 140‐150 ◦ C. The results are corroborated by the molecular dynamic simulations predicting an order‐disorder phase transition into a centrosymmetric (possibly, orthorhombic) phase with antiparallel polarization orientation in neighbouring FF rings. Partial piezoresponse hysteresis indicates incomplete polarization switching due to the high coercive field in FF PNTs. S Online supplementary data available from stacks.iop.org/JPhysD/43/462001/mmedia (Some figures in this article are in colour only in the electronic version)

Piezoelectric resonators based on self-assembled diphenylalanine microtubes

Piezoelectric actuation has been widely used in microelectromechanical devices including resonance-based biosensors, mass detectors, resonators, etc. These were mainly produced by micromachining of Si and deposited inorganic piezoelectrics based on metal oxides or perovskite-type materials which have to be further functionalized in order to be used in biological applications. In this work, we demonstrate piezoelectrically driven micromechanical resonators based on individual self-assembled diphenylalanine microtubes with strong intrinsic piezoelectric effect. Tubes of different diameters and lengths were grown from the solution and assembled on a rigid support. The conducting tip of the commercial atomic force microscope was then used to both excite vibrations and study resonance behavior. Efficient piezoelectric actuation at the fundamental resonance frequency ≈2.7 MHz was achieved with a quality factor of 114 for a microtube of 277u2009μm long. A possibility of using piezoelectric dipeptides for biosensor a...

Piezoelectricity and Ferroelectricity in Biomaterials: From Proteins to Self-assembled Peptide Nanotubes

Piezoelectricity is one of the common ferroelectric material properties, along with pyroelectricity, optical birefringence phenomena, etc. There has been widespread observation of piezoelectric and ferroelectric phenomena in many biological systems and molecules, and these are referred to as biopiezoelectricity and bioferroelectricity. Investigations have been made of these properties in biological and organic macromolecular systems on the nanoscale, by techniques such as atomic force microscopy (AFM) and piezoresponse force microscopy (PFM). This chapter presents a short overview of the main issues of piezoelectricity and ferroelectricity, and their manifestation in organic and biological objects, materials and molecular systems. As a showcase of novel biopiezomaterials, the investigation of diphenylalanine (FF) peptide nanotubes (PNTs) is described in more detail. FF PNTs present a unique class of self-assembled functional biomaterials, owing to a wide range of useful properties, including nanostructural variability, mechanical rigidity and chemical stability. The discovery of strong piezoactivity and polarization in aromatic dipeptides [ACS Nano 4, 610, 2010] opened up a new perspective for their use as nanoactuators, nanomotors and molecular machines as well for possible biomedical applications.

BioFerroelectricity: Diphenylalanine Peptide Nanotubes Computational Modeling and Ferroelectric Properties at the Nanoscale

Ferroelectricity and piezoelectricity are two of the common ferroelectric material properties, which have widespread observations in many biological systems, and these are referred to as biopiezoelectricity and bioferroelectricity. This paper presents a short overview of the main issues of piezoelectricity and ferroelectricity, their manifestation in organic, biological, and molecular systems. As a showcase of novel biopiezomaterials, the investigation of diphenylalanine (FF) peptide nanotubes (PNTs) is described by computational molecular modeling, as well by experimental AFM/PFM measurements. FF PNTs present a unique class of self-assembled functional biomaterials, owing to their wide range of useful properties, including nanostructural piezoelectric and ferroelectric properties.

Preferred deposition of phospholipids onto ferroelectric P(VDF-TrFE) films via polarization patterning

Ferroelectric polarization can be used to assemble various organic and inorganic species and to create nanostructures with controlled properties. In this work , we used P(VDF TrFE) ultrathin films deposited by La ngmuir -Blodgett technique as templates for the assembly of various phospholipids that are the essential components of cell membranes. It was observed that 1,2 -Di -O-hexadecyl -sn -glycero -3-phosphoco line phospholipids (DHPC) form self -assembled structures (mo lecular domains) on bare P(VDF -TrFE) surface s. These were revealed by the formation of homogenous and stable round ed blobs with diameters in the range 0.5 -3 µm . Further, ferroelectric polymer films were polarized by the application of various voltages via conducting tip using Piezoresponse Force Microscopy (PFM) setup and PFM images were obtained showing controlled polarization distribution. After this, phospholipid molecules were deposited from the solution. Conventional Atomic Force Microscopy (AFM) exper iments were then performed to assess the selectivity of the deposition process. It was observed that the deposition process is very sensitive to the concentration of the solution. The selective deposition was observed mainly at the polarization boundaries where the selectivity reached a maximum value of about 20 -40%. In this way, the controlled assembly of organic molecules on the polymer surfaces could be achieved. In addition, the PFM tip s could be functionalized by the phospholipids and switchable lines of the DHPC molecules on the P(VDF -TrFE) surface were then visualized by PFM.