Scientists discover new properties of organic piezoelectric materials

The research team consisted of Marat Ziganshin, Director of the Institute of Chemistry, Sufia Ziganshina, external collaborator (at the time of the research work) of the Laboratory of the Synthesis of New materials for Biomedical Purposes, Elena Kudryavtseva, master's student of the Institute of Chemistry (at the time of the research work), Anna Morozova, Nadezhda Kurbatova, and Anastas Bukharaev.

Dipeptides are molecules consisting of two amino acid residues, capable of self-assembly to form a variety of biocompatible micro- and nanostructures, the properties of which can be easily modified and fine-tuned. Nevertheless, to date, piezoelectric properties have been studied in detail for only one dipeptide—diphenylalanine.

According to Marat Ziganshin, piezoelectric materials capable of generating electrical energy in response to mechanical deformation and vice versa are currently the subject of active research.

"Typically, such materials are made from inorganic compounds such as lead zirconate titanate and barium titanate. However, most inorganic piezoelectrics are not biocompatible and can cause harm to living organisms when used as elements of bio-electronics," the Director notes. "Therefore, biocompatible piezoelectric materials are preferable for these purposes. They can be used as diagnostic tools to control temperature and blood pressure, to create implantable devices that collect biomechanical energy from body movements."

To date, organic piezoelectrics based on polymers, polysaccharides, and viruses have become the most widespread. However, their piezoelectric response is usually in the range of 1- 40 pm V-1, which is insufficient for many potential applications.

Recent research by KFU scientists with colleagues indicates that there is a challenge to reproducibly produce dipeptide-based piezoelectric materials.

"The task that researchers usually set for themselves is to obtain one high-quality micro- or nano-object: a crystal, tube, rod, and study its piezoelectric properties," Dr. Ziganshin emphasizes. "In our work, we first decided to develop a technology for scaling, i.e., obtaining a large number of objects close in size. As a result, we proposed a technique for controlling the size of structures using the example of leucyl-phenylalanine dipeptide, which allows us to obtain the necessary number of micro-objects with the required size. Using this technique, we obtained microcrystals of leucyl-phenylalanine and microstrands of phenylalanyl-leucine, thus demonstrating that the order of amino acid residues in dipeptides is the most important factor determining the final structure into which these molecules will assemble."

The effective piezoelectric coefficients for vertical and lateral displacements were determined by atomic force microscopy: 71 pm B-1 and -73 pm B-1 for phenylalanyl-leucine-based structures and 87 pm B-1 and -19 pm B-1 for leucyl-phenylalanine microcrystals, respectively. The measured piezoelectric coefficients were found to be larger than those for the previously studied diphenylalanine-based nanostructures.

Now the plan is to create a composite material—a flexible matrix in which dipeptide piezoelectrics will be embedded.

More information:
New piezoelectric materials based on Phe-Leu and Leu-Phe dipeptides
www.sciencedirect.com/science/ … 2352940724005092?via%3Dihub

Provided by Kazan Federal University