Limits...
Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy.

Jarvis SP - Int J Mol Sci (2015)

Bottom Line: In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed.Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure.In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds.

View Article: PubMed Central - PubMed

Affiliation: School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK. Samuel.Jarvis@nottingham.ac.uk.

ABSTRACT
A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions.

No MeSH data available.


Related in: MedlinePlus

Intermolecular artefacts in hydrogen bonded assemblies. (A) First ever observation of apparent intermolecular bonds using scanning probe microscopy (SPM) observed via the STHM technique (reprinted with permission from [58], copyright 2010 by the American Chemical Society); (B) CO-mediated NC-AFM image of 8-hydroxyquinoline (8-hq) assembly exhibiting features in the locations of hydrogen bonding (from [61], reprinted with permission from AAAS) shown with simulated data (bottom right) [59]; (C) NC-AFM image revealing apparent intermolecular features in hydrogen bonded assemblies of NTCDI [40] also shown with simulated data confirming the apparent nature of the intermolecular features [59]; (D) Schematic of the flexible tip model used to simulate images of artificial intermolecular bonding [59]; (E) Experimental and simualted NC-AFM images of a PTCDA island shown with the simulated CO probe position [59]; (F) Experimental and simulated NC-AFM images of hydrogen bonded bis(para-pyridyl)acetylene (BPPA) molecules revealing apparent intermolecular bonds even where none are present (see red arrow) (reprinted with permission from [62], copyright 2014 by the American Physical Society); (G) NC-AFM image of apparent halogen bonding between the Fluorine atoms (see pink arrows in zoom of area marked with a yellow box) of three BPEPE-F18 (fluoro-substituted phenyleneethynylene) molecules (reprinted with permission from [63], copyright 2015 by the American Chemical Society). All figures from [59] reprinted with permission, copyright 2014 by the American Physical Society
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4581333&req=5

ijms-16-19936-f003: Intermolecular artefacts in hydrogen bonded assemblies. (A) First ever observation of apparent intermolecular bonds using scanning probe microscopy (SPM) observed via the STHM technique (reprinted with permission from [58], copyright 2010 by the American Chemical Society); (B) CO-mediated NC-AFM image of 8-hydroxyquinoline (8-hq) assembly exhibiting features in the locations of hydrogen bonding (from [61], reprinted with permission from AAAS) shown with simulated data (bottom right) [59]; (C) NC-AFM image revealing apparent intermolecular features in hydrogen bonded assemblies of NTCDI [40] also shown with simulated data confirming the apparent nature of the intermolecular features [59]; (D) Schematic of the flexible tip model used to simulate images of artificial intermolecular bonding [59]; (E) Experimental and simualted NC-AFM images of a PTCDA island shown with the simulated CO probe position [59]; (F) Experimental and simulated NC-AFM images of hydrogen bonded bis(para-pyridyl)acetylene (BPPA) molecules revealing apparent intermolecular bonds even where none are present (see red arrow) (reprinted with permission from [62], copyright 2014 by the American Physical Society); (G) NC-AFM image of apparent halogen bonding between the Fluorine atoms (see pink arrows in zoom of area marked with a yellow box) of three BPEPE-F18 (fluoro-substituted phenyleneethynylene) molecules (reprinted with permission from [63], copyright 2015 by the American Chemical Society). All figures from [59] reprinted with permission, copyright 2014 by the American Physical Society

Mentions: The first SPM images of apparent intermolecular bonding were observed by Weiss et al. using the STHM technique on the herringbone phase of PTCDA on Au(111) [58] where both the internal bond structure of the molecule and sharp features extending across regions of intermolecular bonding were observed, as shown in Figure 3A. Later, it was shown that a variety of molecular terminations could achieve the same resolution [17], each resolving exceptionally-sharp features between the individual PTCDA molecules. Although for many years, the true origin of the observed contrast remained unclear, the molecular tip was assumed to mediate the interaction, somehow acting as a transducer, modulating the observed tunnel current signal via either Pauli repulsion or longer range electrostatic forces [16,17,58]. Similar to the results described below, through an elegant model incorporating flexible molecularly-terminated tips and a numerical model for the tunnelling process through the mediating molecule, it has been recently shown that the observed intermolecular features are a direct consequence of the flexible tip geometry [59,60].


Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy.

Jarvis SP - Int J Mol Sci (2015)

Intermolecular artefacts in hydrogen bonded assemblies. (A) First ever observation of apparent intermolecular bonds using scanning probe microscopy (SPM) observed via the STHM technique (reprinted with permission from [58], copyright 2010 by the American Chemical Society); (B) CO-mediated NC-AFM image of 8-hydroxyquinoline (8-hq) assembly exhibiting features in the locations of hydrogen bonding (from [61], reprinted with permission from AAAS) shown with simulated data (bottom right) [59]; (C) NC-AFM image revealing apparent intermolecular features in hydrogen bonded assemblies of NTCDI [40] also shown with simulated data confirming the apparent nature of the intermolecular features [59]; (D) Schematic of the flexible tip model used to simulate images of artificial intermolecular bonding [59]; (E) Experimental and simualted NC-AFM images of a PTCDA island shown with the simulated CO probe position [59]; (F) Experimental and simulated NC-AFM images of hydrogen bonded bis(para-pyridyl)acetylene (BPPA) molecules revealing apparent intermolecular bonds even where none are present (see red arrow) (reprinted with permission from [62], copyright 2014 by the American Physical Society); (G) NC-AFM image of apparent halogen bonding between the Fluorine atoms (see pink arrows in zoom of area marked with a yellow box) of three BPEPE-F18 (fluoro-substituted phenyleneethynylene) molecules (reprinted with permission from [63], copyright 2015 by the American Chemical Society). All figures from [59] reprinted with permission, copyright 2014 by the American Physical Society
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581333&req=5

ijms-16-19936-f003: Intermolecular artefacts in hydrogen bonded assemblies. (A) First ever observation of apparent intermolecular bonds using scanning probe microscopy (SPM) observed via the STHM technique (reprinted with permission from [58], copyright 2010 by the American Chemical Society); (B) CO-mediated NC-AFM image of 8-hydroxyquinoline (8-hq) assembly exhibiting features in the locations of hydrogen bonding (from [61], reprinted with permission from AAAS) shown with simulated data (bottom right) [59]; (C) NC-AFM image revealing apparent intermolecular features in hydrogen bonded assemblies of NTCDI [40] also shown with simulated data confirming the apparent nature of the intermolecular features [59]; (D) Schematic of the flexible tip model used to simulate images of artificial intermolecular bonding [59]; (E) Experimental and simualted NC-AFM images of a PTCDA island shown with the simulated CO probe position [59]; (F) Experimental and simulated NC-AFM images of hydrogen bonded bis(para-pyridyl)acetylene (BPPA) molecules revealing apparent intermolecular bonds even where none are present (see red arrow) (reprinted with permission from [62], copyright 2014 by the American Physical Society); (G) NC-AFM image of apparent halogen bonding between the Fluorine atoms (see pink arrows in zoom of area marked with a yellow box) of three BPEPE-F18 (fluoro-substituted phenyleneethynylene) molecules (reprinted with permission from [63], copyright 2015 by the American Chemical Society). All figures from [59] reprinted with permission, copyright 2014 by the American Physical Society
Mentions: The first SPM images of apparent intermolecular bonding were observed by Weiss et al. using the STHM technique on the herringbone phase of PTCDA on Au(111) [58] where both the internal bond structure of the molecule and sharp features extending across regions of intermolecular bonding were observed, as shown in Figure 3A. Later, it was shown that a variety of molecular terminations could achieve the same resolution [17], each resolving exceptionally-sharp features between the individual PTCDA molecules. Although for many years, the true origin of the observed contrast remained unclear, the molecular tip was assumed to mediate the interaction, somehow acting as a transducer, modulating the observed tunnel current signal via either Pauli repulsion or longer range electrostatic forces [16,17,58]. Similar to the results described below, through an elegant model incorporating flexible molecularly-terminated tips and a numerical model for the tunnelling process through the mediating molecule, it has been recently shown that the observed intermolecular features are a direct consequence of the flexible tip geometry [59,60].

Bottom Line: In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed.Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure.In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds.

View Article: PubMed Central - PubMed

Affiliation: School of Physics & Astronomy, University of Nottingham, Nottingham NG7 2RD, UK. Samuel.Jarvis@nottingham.ac.uk.

ABSTRACT
A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions.

No MeSH data available.


Related in: MedlinePlus