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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

The effect of tip flexibility in high-resolution imaging. (A) CO bending observed in measurements of the CO–CO molecular pair potential (reprinted with permission from [55], copyright 2011 by the American Physical Society); (B) NC-AFM images showing bond length enhancement and sharpening due to flexibility at very small tip-sample distances (from [29], reprinted with permission from AAAS); (C) NC-AFM image showing variations in carbon ring size due to corrugation of Ir(111)-supported graphene (reprinted with permission from [56], copyright 2014 by the American Chemical Society); (D) Measurement and simulation of image distortions observed in NC-AFM images of 4-(4-(2,3,4,5,6-pentafluorophenylethynyl)-2,3,5,6-tetrafluorophe-nylethynyl) phenylethynylbenzene (FFPB) (reprinted with permission from [53], copyright 2014 by the American Chemical Society); (E) Image correction from lateral force analysis for pentacene imaged with NC-AFM on Cu(111) and NaCl (2 ML)/Cu(111) (reprinted with permission from [57], copyright 2014 by the American Physical Society).
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ijms-16-19936-f002: The effect of tip flexibility in high-resolution imaging. (A) CO bending observed in measurements of the CO–CO molecular pair potential (reprinted with permission from [55], copyright 2011 by the American Physical Society); (B) NC-AFM images showing bond length enhancement and sharpening due to flexibility at very small tip-sample distances (from [29], reprinted with permission from AAAS); (C) NC-AFM image showing variations in carbon ring size due to corrugation of Ir(111)-supported graphene (reprinted with permission from [56], copyright 2014 by the American Chemical Society); (D) Measurement and simulation of image distortions observed in NC-AFM images of 4-(4-(2,3,4,5,6-pentafluorophenylethynyl)-2,3,5,6-tetrafluorophe-nylethynyl) phenylethynylbenzene (FFPB) (reprinted with permission from [53], copyright 2014 by the American Chemical Society); (E) Image correction from lateral force analysis for pentacene imaged with NC-AFM on Cu(111) and NaCl (2 ML)/Cu(111) (reprinted with permission from [57], copyright 2014 by the American Physical Society).

Mentions: This is particularly true in submolecular resolution imaging with NC-AFM. Even as early as the seminal 2009 paper by Gross et al. [24] it was noted that a Cl-terminated tip produced images where the carbon rings of pentacene appeared smaller in diameter compared with a CO-terminated tip, and did so without an asymmetry where the rings appeared elongated in one direction (particularly noticeable when imaged on NaCl (2 ML)/Cu(111)). This was followed by quantitative measurements of the molecular pair potential between two CO molecules by Sun et al. [55] who noted that the Cu-adsorbed CO molecules are far from an idealised rigid probe, and in reality show a great deal of flexibility, as shown in Figure 2A, making the point that “... chemical repulsion between the CO molecules is relaxed at the expense of weaker bonding of the CO molecules to the Cu atoms of the tip and substrate, respectively”.


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

Jarvis SP - Int J Mol Sci (2015)

The effect of tip flexibility in high-resolution imaging. (A) CO bending observed in measurements of the CO–CO molecular pair potential (reprinted with permission from [55], copyright 2011 by the American Physical Society); (B) NC-AFM images showing bond length enhancement and sharpening due to flexibility at very small tip-sample distances (from [29], reprinted with permission from AAAS); (C) NC-AFM image showing variations in carbon ring size due to corrugation of Ir(111)-supported graphene (reprinted with permission from [56], copyright 2014 by the American Chemical Society); (D) Measurement and simulation of image distortions observed in NC-AFM images of 4-(4-(2,3,4,5,6-pentafluorophenylethynyl)-2,3,5,6-tetrafluorophe-nylethynyl) phenylethynylbenzene (FFPB) (reprinted with permission from [53], copyright 2014 by the American Chemical Society); (E) Image correction from lateral force analysis for pentacene imaged with NC-AFM on Cu(111) and NaCl (2 ML)/Cu(111) (reprinted with permission from [57], 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-f002: The effect of tip flexibility in high-resolution imaging. (A) CO bending observed in measurements of the CO–CO molecular pair potential (reprinted with permission from [55], copyright 2011 by the American Physical Society); (B) NC-AFM images showing bond length enhancement and sharpening due to flexibility at very small tip-sample distances (from [29], reprinted with permission from AAAS); (C) NC-AFM image showing variations in carbon ring size due to corrugation of Ir(111)-supported graphene (reprinted with permission from [56], copyright 2014 by the American Chemical Society); (D) Measurement and simulation of image distortions observed in NC-AFM images of 4-(4-(2,3,4,5,6-pentafluorophenylethynyl)-2,3,5,6-tetrafluorophe-nylethynyl) phenylethynylbenzene (FFPB) (reprinted with permission from [53], copyright 2014 by the American Chemical Society); (E) Image correction from lateral force analysis for pentacene imaged with NC-AFM on Cu(111) and NaCl (2 ML)/Cu(111) (reprinted with permission from [57], copyright 2014 by the American Physical Society).
Mentions: This is particularly true in submolecular resolution imaging with NC-AFM. Even as early as the seminal 2009 paper by Gross et al. [24] it was noted that a Cl-terminated tip produced images where the carbon rings of pentacene appeared smaller in diameter compared with a CO-terminated tip, and did so without an asymmetry where the rings appeared elongated in one direction (particularly noticeable when imaged on NaCl (2 ML)/Cu(111)). This was followed by quantitative measurements of the molecular pair potential between two CO molecules by Sun et al. [55] who noted that the Cu-adsorbed CO molecules are far from an idealised rigid probe, and in reality show a great deal of flexibility, as shown in Figure 2A, making the point that “... chemical repulsion between the CO molecules is relaxed at the expense of weaker bonding of the CO molecules to the Cu atoms of the tip and substrate, respectively”.

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