Demonstration of a single molecule piezoelectric effect offers new design possibilities

1 min read

A single molecule piezoelectric effect is said to have been demonstrated for the first time.

The researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University Olomouc say that their work represents a breakthrough in understanding the electromechanical behaviour of individual molecules.

According to the team, this will provide a new concept of the design of molecular motors, sensors and electricity generators at nanoscale.

"In a close collaboration with physicists, it was proved for the first time that a strong converse piezoelectric effect can be observed at individual molecules of the heptahelicene derivative, which is a screw-like carbon molecule resembling a spring," said Ivo Starý, the leader of the group of chemists at IOCB Prague preparing the compound.

The effect was experimentally demonstrated by researchers from IP CAS at individual molecules on a silver surface using scanning probe microscopy.

"The magnitude of the piezoelectric constant calculated from the experimental data is significantly higher than that one of known piezoelectric polymers and is comparable to the magnitudes measured at some inorganic materials such as zinc oxide,” group leader, Pavel Jelínek said. “We explained the origin of the single molecule piezoelectric effect by employing quantum mechanics calculations."

How the converse piezoelectric effect works at nanoscale

The screw-like molecule endowed with an inner dipole stretches or squeezes itself depending on the strength and polarity of the outer electric field. It arises by applying a voltage bias between the silver pad and atomically sharp tip of the scanning microscope that resides over the studied molecule.

As the change in a molecule height can be monitored with an ultimate accuracy, the team explain it is possible to see a molecule deformation induced by the electric field. Such a coupling of the mechanical movement of a molecule and the change in electric field, which is reciprocal by theory, is said to represent an entry into the world of molecules doing mechanical work on one hand and molecular nanogenerators of electric energy on the other hand.