Piezoelectric properties of diphenylalanine microtubes prepared from the solution

Biomimetic self-assembling peptides form a variety of structures that can be used for the fabrication of functional devices. We are witnessing the emergence of a new era of bionanotechnology that opens up new possibilities for novel electronic, photonic and energy functionalities based on supramolecular green and lightweight structures. In this work, we study the emergent piezoelectric properties of linear di peptide diphenylalanine (FF) that can self-assemble in the shape of microtubes. The matrix of piezoelectric coefficients is derived for the first time based on the hexagonal symmetry of FF structures and different configurations of the tubes are tested by the advanced Piezoresponse Force Microscopy (PFM). Strong piezoelectric anisotropy of piezoelectric coefficients is explained by the self-assembled structure of FF peptides. Possible applications of piezoelectric microtubes in functional devices are discussed. (C) 2016 Elsevier Ltd. All rights reserved

The Application of Chitosan for Protection of Cultural Heritage Objects of the 15–16th Centuries in the State Tretyakov Gallery

Microorganisms are one of the main factors in the deterioration of cultural heritage, in particular art paintings. The antiseptics currently used in painting have significant limitations due to insufficient effectiveness or increased toxicity and interaction with art materials. In this regard, the actual challenge is the search for novel materials that effectively work against microorganisms in the composition with painting materials and do not change their properties. Chitosan has pronounced antimicrobial properties but was not used previously as an antiseptic for paintings. In our study we developed a number of mock layers based on sturgeon glue, supplemented which chitosan (molecular weight 25 kDa or 45 kDa), standard antiseptics for paintings (positive controls) or without additives (negative control). According to Fourier transform infrared spectroscopy and atomic force microscopy, the addition of chitosan did not significantly affect the optical and surface properties of this material. The ability of chitosan to effectively protect paintings was shown after inoculation on the created mock-up layers of 10 fungi-destructors of tempera painting, previously isolated from cultural heritage of the of the 15–16th centuries in the State Tretyakov Gallery, on the created mock layers. Our study demonstrated the principled opportunity of using chitosan in the composition of painting materials to prevent biodeterioration for the first time

In Situ Observation of the Humidity Controlled Polymorphic Phase Transformation in Glycine Microcrystals

Glycine is a model crystal exhibiting three polymorphic phases and important functional properties such as piezoelectricity and ferroelectricity. We report here in situ observation of the irreversible transformation of the solution-grown glycine crystals from a β phase into a γ phase. The slow transformation process was monitored by piezoresponse force microscopy at room temperature. The process of β to γ conversion was entirely controlled by the variation of relative humidity in the sample chamber. The results show that the rate of phase transformation in glycine is humidity dependent with a threshold of about 25% RH. It is demonstrated that the phase boundary is highly rugged and the transformation front propagates inhomogeneously along the polar axis of the β phase. The mechanism of the phase transformation is discussed

Evaporation-Driven Crystallization of Diphenylalanine Microtubes for Microelectronic Applications

Self-assembly of supramolecular biomaterials such as proteins or peptides has revealed great potential for their use in various applications ranging from scaffolds for cell culture to light-emitting diodes and piezoelectric transducers. Many of these applications require controlled growth,of individual objects in the configuration allowing simple transfer to the desired device. In this work, we grew millimeter-long diphenylalanine (FF) self-assembled microtubes with high aspect ratio via evaporation-driven crystallization of nonsaturated FF solutions, making use of the Marangoni flow in the drying droplets. The growth mechanism was investigated by measuring the microtube length as a function of time. Jerky (steplike) growth behavior was observed and explained by a self-activated process in which additional activation energy is provided through condensation. The calculated growth rate due to the diffusion-controlled process is in agreement with the experimentally measured values. The grown microtubes were successfully transferred to metallized patterned substrates, and their specific conductivity and piezoelectric properties were evaluated as a function of the applied voltage and frequency. A number of piezoelectric resonances were observed and attributed to different vibrational modes excited by the piezoelectric effect inherent to the FF structure

Self-Assembly of Organic Ferroelectrics by Evaporative Dewetting: A Case of β-Glycine

Self-assembly of ferroelectric materials attracts significant interest because it offers a promising fabrication route to novel structures useful for microelectronic devices such as nonvolatile memories, integrated sensors/actuators, or energy harvesters. In this work, we demonstrate a novel approach for self-assembly of organic ferroelectrics (as exemplified by ferroelectric β-glycine) using evaporative dewetting, which allows forming quasi-regular arrays of nano- and microislands with preferred orientation of polarization axes. Surprisingly, self-assembled islands are crystallographically oriented in a radial direction from the center of organic “grains” formed during dewetting process. The kinetics of dewetting process follows the t–1/2 law, which is responsible for the observed polygon shape of the grain boundaries and island coverage as a function of radial position. The polarization in ferroelectric islands of β-glycine is parallel to the substrate and switchable under a relatively small dc voltage applied by the conducting tip of piezoresponse force microscope. Significant size effect on polarization is observed and explained within the Landau–Ginzburg–Devonshire phenomenological formalism

<i>In</i><i>Situ</i> Observation of the Humidity Controlled Polymorphic Phase Transformation in Glycine Microcrystals

Glycine is a model crystal exhibiting three polymorphic phases and important functional properties such as piezoelectricity and ferroelectricity. We report here <i>in situ</i> observation of the irreversible transformation of the solution-grown glycine crystals from a β phase into a γ phase. The slow transformation process was monitored by piezoresponse force microscopy at room temperature. The process of β to γ conversion was entirely controlled by the variation of relative humidity in the sample chamber. The results show that the rate of phase transformation in glycine is humidity dependent with a threshold of about 25% RH. It is demonstrated that the phase boundary is highly rugged and the transformation front propagates inhomogeneously along the polar axis of the β phase. The mechanism of the phase transformation is discussed

Evaporation-Driven Crystallization of Diphenylalanine Microtubes for Microelectronic Applications

Self-assembly of supramolecular biomaterials such as proteins or peptides has revealed great potential for their use in various applications ranging from scaffolds for cell culture to light-emitting diodes and piezoelectric transducers. Many of these applications require controlled growth of individual objects in the configuration allowing simple transfer to the desired device. In this work, we grew millimeter-long diphenylalanine (FF) self-assembled microtubes with high aspect ratio via evaporation-driven crystallization of nonsaturated FF solutions, making use of the Marangoni flow in the drying droplets. The growth mechanism was investigated by measuring the microtube length as a function of time. Jerky (steplike) growth behavior was observed and explained by a self-activated process in which additional activation energy is provided through condensation. The calculated growth rate due to the diffusion-controlled process is in agreement with the experimentally measured values. The grown microtubes were successfully transferred to metallized patterned substrates, and their specific conductivity and piezoelectric properties were evaluated as a function of the applied voltage and frequency. A number of piezoelectric resonances were observed and attributed to different vibrational modes excited by the piezoelectric effect inherent to the FF structure

Chirality-dependent growth of self-assembled diphenylalanine microtubes

The difference in the crystal structure and growth kinetics of microtubes formed from l- and d-enantiomers of diphenylalanine dipeptide is investigated both experimentally and theoretically by computer simulation. The microtubes of l- and d-enantiomers grown simultaneously and under identical experimental conditions possess different crystallographic space groups, have essential difference in sizes, and demonstrate different growth kinetics. Computer simulation by molecular mechanics methods revealed a fundamental difference in the interaction between structural units of microtubes of different chiralities. A model describing chirality-dependent growth of microtubes is proposed