Self-assembly of small molecules at hydrophobic interfaces using group effect

Although common in nature, the self-assembly of small molecules at sold–liquid interfaces is difficult to control in artificial systems. The high mobility of dissolved small molecules limits their residence at the interface, typically restricting the self-assembly to systems under confinement or with mobile tethers between the molecules and the surface. Small hydrogen-bonding molecules can overcome these issues by exploiting group-effect stabilization to achieve non-tethered self-assembly at hydrophobic interfaces. Significantly, the weak molecular interactions with the solid makes it possible to influence the interfacial hydrogen bond network, potentially creating a wide variety of supramolecular structures.*

In the paper “Self-assembly of small molecules at hydrophobic interfaces using group effect” William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky investigate the nanoscale details of water and alcohols mixtures self-assembling at the interface with graphite through group-effect. They explore the interplay between inter-molecular and surface interactions by adding small amounts of foreign molecules able to interfere with the hydrogen bond network and systematically varying the length of the alcohol hydrocarbon chain. The resulting supramolecular structures forming at room temperature are then examined using atomic force microscopy with insights from computer simulations.*

The authors show that the group-based self-assembly approach investigated in the paper is general and can be reproduced on other substrates such as molybdenum disulphide and graphene oxide, potentially making it relevant for a wide variety of systems.*

NanoWorld Arrow UHF-AuD ultra high frequency cantilevers for High Speed AFM were used for the amplitude modulation atomic force microscopy described in this paper.


Figure 4 from “Self-assembly of small molecules at hydrophobic interfaces using group effect“ by William Foster et al.:
Impact of the backbone length of primary alcohols on interfacial self-assembly on HOPG. The basic monolayer motif is visible as expected in a 50 : 50 methanol : water mixture (a), here imaged by amplitude-modulation AFM (topography image). In a 50 : 50 ethanol : water mixture (b), two organised layers are visible both in topography and in the phase where it is more pronounced, outlined by a white dashed line (blue and red arrows). In phase, the self-assembled layers appear darker than the directly exposed graphite, where no structures are present (black arrow). The lower layer shows few resolvable features and is bordered by wide rows that have a separation of 5.89 ± 0.28 nm. In 50 : 50 1-propanol : water mixture (c), novel structures with long, straight edges emerge (red arrow) and grow on top of the exposed graphite (black arrow). The structures have a row periodicity of 5.86 ± 0.25 nm. The inset shows details of the longitudinal row structures near an edge. Further variance is seen in a 50 : 50 2-propanol : water mixture (d) where two types of domains form (red and blue arrows), both demonstrating a clear phase contrast with the graphite surface (black arrow). The domains have longitudinal rows with periodicities of 6.10 ± 0.35 nm (blue arrow) and 4.91 ± 0.45 nm (red arrow). Unlike for (c), higher resolution of the row (inset) evidence curved edges. The scale bars are 50 nm in (a) and (b), 100 nm in (c) and (d) main image and 20 nm in the insets. The purple colour scale bar represents a height variation of 1 nm in (a), (b) and (d), 3 nm in (c) and 0.5 nm in the insets. The blue scale bar represents a phase variation of 1.5° in (b), 2° in (c) and its inset and 15° in (d) and its inset.

*William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky
Self-assembly of small molecules at hydrophobic interfaces using group effect
Nanoscale, 2020,12, 5452
DOI: 10.1039/c9nr09505e

Please follow this external link to read the full article: https://pubs.rsc.org/en/content/articlepdf/2020/nr/c9nr09505e

Open Access: The paper « Self-assembly of small molecules at hydrophobic interfaces using group effect»  by William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky is licensed under a Creative Commons Attribution 3.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/3.0/.

Ultra-high resolution imaging of thin films and single strands of polythiophene using atomic force microscopy

Real-space images of polymers with sub-molecular resolution could provide valuable insights into the relationship between morphology and functionality of polymer optoelectronic devices, but their acquisition is problematic due to perceived limitations in atomic force microscopy (AFM).*

In the article “Ultra-high resolution imaging of thin films and single strands of polythiophene using atomic force microscopy” Vladimir V. Korolkov, Alex Summerfield, Alanna Murphy, David B. Amabilino, Kenji Watanabe, Takashi Taniguchi and Peter H. Beton show that individual thiophene units and the lattice of semicrystalline spin-coated films of polythiophenes (PTs) may be resolved using AFM under ambient conditions through the low-amplitude (≤ 1 nm) excitation of higher eigenmodes of a cantilever.*

They authors demonstrate that the use of higher eigenmodes in tapping-mode ambient AFM can be successfully employed to characterize both individual polymer strands down to a single-atom level and also the ordering of a semi-crystalline polymer with technological relevance. The combination of AFM and solution deposition provides a simple and high-resolution approach to characterizing the structure of polymers.*

The use of NanoWorld Arrow-UHF high frequency AFM probes at their first eigenmode of ~1.4 MHz is mentioned.*


Figure 1a from “Ultra-high resolution imaging of thin films and single strands of polythiophene using atomic force microscopy” by V. Korolkov et al.: High-resolution AFM images of P3DT adsorbed on the surface of hBN. a An overview height scan of P3DT assembled on hBN, scan rate 6.51 Hz, 1024 × 1024 px; inset shows lattice frequency shift image of hBN acquired in FM-AFM tapping mode, scan rate 39 Hz, 512 × 512 px; both images were acquired with the same Arrow UHF probe oscillating at fundamental frequency of 1.42 MHz.

*Vladimir V. Korolkov, Alex Summerfield, Alanna Murphy, David B. Amabilino, Kenji Watanabe, Takashi Taniguchi and Peter H. Beton
Ultra-high resolution imaging of thin films and single strands of polythiophene using atomic force microscopy
Nature Communications, volume 10, Article number: 1537 (2019)
doi: https://doi.org/10.1038/s41467-019-09571-6

Please follow this external link to read the full article: https://rdcu.be/bLSdL

Open Access: The article « Ultra-high resolution imaging of thin films and single strands of polythiophene using atomic force microscopy » by Vladimir V. Korolkov, Alex Summerfield, Alanna Murphy, David B. Amabilino, Kenji Watanabe, Takashi Taniguchi and Peter H. Beton is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.