Large Converse Piezoelectric Effect Measured on a Single Molecule on a Metallic Surface

Abstract

The converse piezoelectric effect is a phenomenon in which mechanical strain is generated in a material due to an applied electrical field. In this work, we demonstrate the converse piezoelectric effect in single heptahelicene-derived molecules on the Ag(111) surface using atomic force microscopy (AFM) and total energy density functional theory (DFT) calculations. The force-distance spectroscopy acquired over a wide range of bias voltages reveals a linear shift of the tip-sample distance at which the contact between the molecule and tip apex is established. We demonstrate that this effect is caused by the bias-induced deformation of the spring-like scaffold of the helical polyaromatic molecules. We attribute this effect to coupling of a soft vibrational mode of the molecular helix with a vertical electric dipole induced by molecule-substrate charge transfer. In addition, we also performed the same spectroscopic measurements on a more rigid o-carborane dithiol molecule on the Ag(111) surface. In this case, we identify a weaker linear electromechanical response, which underpins the importance of the helical scaffold on the observed piezoelectric response.

Heterochiral recognition among functionalized heptahelicenes on noble metal surfaces

“…Previously performed density functional theory (DFT) calculations for AT [7]H on Ag(111) showed that a sulphur atom gets pinned to a single Ag surface atom. 14 The proximal phenanthrene groups, however, show a similar distance (3 Å) to the surface as plain [7]H on various surfaces, 12 suggesting an additional surface binding through that group. DFT calculations for [5]H on Cu(111) 24 and db [7]H on Ag(111) 28 showed that the C6 rings of the proximal phenanthrene group tend to be placed above threefold hollow sites.…”

“…10 Beyond chiral recognition, the surface self-assembly of helical aromatic hydrocarbons, so-called helicenes, is motivated by studying novel physical effects, such as chiroptical responses, electron spin selectivity or molecular electro-mechanics. [11][12][13][14] Consequently, synthesis and functionalization of surfaces with helicenes has received increasing attention recently. [15][16][17] There have been several reports on the fate of chiral crystallization of helicenes on various surfaces.…”

“…Chemical synthesis of the helicene derivatives has been described previously. 14,26,28 Samples were prepared in ultrahigh vacuum by Ar ion sputtering of the metal surface, annealing and deposition by thermal sublimation of the [7] The outcome of self-assembly of Br [7]H was studied at 60 K. For the close-packed monolayer (ML) the molecules form ordered domains built up by zigzag rows (Figure 2) ‡. The arrangement of the enantiomers into zigzag rows is similar to the one determined for [7]H on Au(111), Ag(111) and Cu(111), 18,29 including the fact that the rows are oriented parallel to the highsymmetry directions in case of Ag(111) and Au(111).…”

Origins of Negative and Positive Electromechanical Response of Oligopeptide Piezoelectrics

“…There is an increasing interest in the electromechanical response of organic and biomaterials, 5,[32][33] and computational design of peptides with increased response will guide efforts to produce new active materials for applications including touch and force sensors, and electroactive actuators.…”

Fiber‐Based Energy Conversion Devices for Human‐Body Energy Harvesting

“…The piezoelectric effect is the linear electromechanical interaction between mechanical and electrical states in certain solid materials ( Figure a) . In this way, piezoelectric materials can be used to harvest mechanical energy and convert it into electricity through a mechanical‐to‐electrical transformation mechanism .…”