title: Mapping the force field of a hydrogen-bonded assembly.
abstract: Hydrogen bonding underpins the properties of a vast array of systems spanning a wide variety of scientific fields. From the elegance of base pair interactions in DNA to the symmetry of extended supramolecular assemblies, hydrogen bonds play an essential role in directing intermolecular forces. Yet fundamental aspects of the hydrogen bond continue to be vigorously debated. Here we use dynamic force microscopy (DFM) to quantitatively map the tip-sample force field for naphthalene tetracarboxylic diimide molecules hydrogen-bonded in two-dimensional assemblies. A comparison of experimental images and force spectra with their simulated counterparts shows that intermolecular contrast arises from repulsive tip-sample interactions whose interpretation can be aided via an examination of charge density depletion across the molecular system. Interpreting DFM images of hydrogen-bonded systems therefore necessitates detailed consideration of the coupled tip-molecule system: analyses based on intermolecular charge density in the absence of the tip fail to capture the essential physical chemistry underpinning the imaging mechanism.
authors.affiliation: 1] School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK [2].
authors.forename: A M
authors.initials: AM
authors.lastname: Sweetman
authors.affiliation: 1] School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK [2].
authors.forename: S P
authors.initials: SP
authors.lastname: Jarvis
authors.affiliation: 1] School of Physics and Technology, Centre for Electron Microscopy and MOE Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072, China [2] Department of Physics, King's College London, The Strand, London WC2R 2LS, UK [3].
authors.forename: Hongqian
authors.initials: H
authors.lastname: Sang
authors.affiliation: School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: I
authors.initials: I
authors.lastname: Lekkas
authors.affiliation: Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112-0830, USA.
authors.forename: P
authors.initials: P
authors.lastname: Rahe
authors.affiliation: School of Physics and Technology, Centre for Electron Microscopy and MOE Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Physics and Technology, Centre for Electron Microscopy and MOE Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072, China.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: N R
authors.initials: NR
authors.lastname: Champness
authors.affiliation: Department of Physics, King's College London, The Strand, London WC2R 2LS, UK.
authors.forename: L
authors.initials: L
authors.lastname: Kantorovich
authors.affiliation: School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: P
authors.initials: P
authors.lastname: Moriarty