Insight Into the Superlubricity and Self-Assembly of Liquid Crystals

Liquid crystals are promising molecular materials in the application of lubrication. Herein, the microscale solid superlubricity is accomplished by the construction of uniform and ordered self-assembly of several liquid crystals. The self-assembly structures on a highly oriented pyrolytic graphite (HOPG) surface are explicitly revealed by using scanning tunneling microscopy (STM). Meanwhile, the nanotribological performance of the self-assemblies are measured by using atomic force microscopy (AFM), revealing ultralow friction coefficients lower than 0.01. The interaction energies are calculated by density functional theory (DFT) method, indicating the positive correlation between friction coefficients and interaction strength. The effort on the self-assembly and superlubricity of liquid crystals could enhance the understanding of the nanotribological mechanism and benefit the further application of liquid crystals as lubricants.

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Structural and Nanotribological Properties of a BODIPY Self-Assembly

Frontiers in Chemistry ◽

10.3389/fchem.2021.704915 ◽

2021 ◽

Vol 9 ◽

Author(s):

Shanchao Tan ◽

Wendi Luo ◽

Yongjie Zhang ◽

Xiang-Kui Ren ◽

Yuhong Liu ◽

...

Keyword(s):

Self Assembly ◽

Density Functional ◽

Supramolecular Assembly ◽

Dft Method ◽

The Self ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Force Microscopy ◽

Atomic Force ◽

Assembly Mechanism

Boron-dipyrromethenes (BODIPY) are promising functional dyes, whose exceptional optical properties are closely related to their supramolecular assembly. Herein, the self-assembly of a BODIPY derivative functionalized with uracil groups is explicitly and thoroughly investigated by using scanning tunneling microscopy (STM). Based on the simulation and calculation by density functional theory (DFT) method, it can be concluded that the construction of ordered self-assembly structure is attributed to the formation of hydrogen bonds between uracil groups. Moreover, the nanotribological property of the self-assembly on HOPG surface is measured by using atomic force microscopy (AFM). The effort on self-assembly of the BODIPY derivative could enhance the understanding of surface assembly mechanism.

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Halogen Bonds Fabricate 2D Molecular Self-Assembled Nanostructures by Scanning Tunneling Microscopy

Crystals ◽

10.3390/cryst10111057 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1057

Author(s):

Yi Wang ◽

Xinrui Miao ◽

Wenli Deng

Keyword(s):

Scanning Tunneling Microscopy ◽

Self Assembly ◽

Density Functional ◽

Deep Understanding ◽

Halogen Bonding ◽

The Self ◽

Scanning Tunneling ◽

Halogen Bonds ◽

Tunneling Microscopy ◽

Self Assembled

Halogen bonds are currently new noncovalent interactions due to their moderate strength and high directionality, which are widely investigated in crystal engineering. The study about supramolecular two-dimensional architectures on solid surfaces fabricated by halogen bonding has been performed recently. Scanning tunneling microscopy (STM) has the advantages of realizing in situ, real-time, and atomic-level characterization. Our group has carried out molecular self-assembly induced by halogen bonds at the liquid–solid interface for about ten years. In this review, we mainly describe the concept and history of halogen bonding and the progress in the self-assembly of halogen-based organic molecules at the liquid/graphite interface in our laboratory. Our focus is mainly on (1) the effect of position, number, and type of halogen substituent on the formation of nanostructures; (2) the competition and cooperation of the halogen bond and the hydrogen bond; (3) solution concentration and solvent effects on the molecular assembly; and (4) a deep understanding of the self-assembled mechanism by density functional theory (DFT) calculations.

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Light-Controlled Friction by Carboxylic Azobenzene Molecular Self-Assembly Layers

Frontiers in Chemistry ◽

10.3389/fchem.2021.707232 ◽

2021 ◽

Vol 9 ◽

Author(s):

Dandan Xue ◽

Liran Ma ◽

Yu Tian ◽

Qingdao Zeng ◽

Bin Tu ◽

...

Keyword(s):

Density Functional ◽

Light Stimulus ◽

Rapid Development ◽

Pyrolytic Graphite ◽

Light Regulation ◽

Dft Method ◽

The Self ◽

Scanning Tunneling ◽

Regulatory Structure ◽

Self Assembled

Nowadays, reversible friction regulation has become the focus of scientists in terms of the flexible regulatory structure of photosensitive materials and theories since this facilitates rapid development in this field. Meanwhile, as an external stimulus, light possesses great potential and advantages in spatiotemporal control and remote triggering. In this work, we demonstrated two photo-isomerized organic molecular layers, tetra-carboxylic azobenzene (NN4A) and dicarboxylic azobenzene (NN2A), which were selected to construct template networks on the surface of the highly oriented pyrolytic graphite (HOPG) to study the friction properties, corresponding to the arrangement structure of self-assembled layers under light regulation. First of all, the morphology of the self-assembled layers were characterized by a scanning tunneling microscope (STM), then the nanotribological properties of the template networks were measured by atomic force microscope (AFM). Their friction coefficients are respectively changed by about 0.6 and 2.3 times under light control. The density functional theory (DFT) method was used to calculate the relationship between the force intensity and the friction characteristics of the self-assembled systems under light regulation. Herein, the use of external light stimulus plays a significant role in regulating the friction properties of the interface of the nanometer, hopefully serving as a fundamental basis for further light-controlling research for the future fabrication of advanced on-surface devices.

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Self-assembly of N-heterocyclic carbenes on Au(111)

Nature Communications ◽

10.1038/s41467-021-23940-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Alex Inayeh ◽

Ryan R. K. Groome ◽

Ishwar Singh ◽

Alex J. Veinot ◽

Felipe Crasto de Lima ◽

...

Keyword(s):

Self Assembly ◽

Density Functional ◽

Surface Coverage ◽

High Mobility ◽

Heterocyclic Carbenes ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Surface Geometry ◽

Functional Theory ◽

Interesting Alternative

AbstractAlthough the self-assembly of organic ligands on gold has been dominated by sulfur-based ligands for decades, a new ligand class, N-heterocyclic carbenes (NHCs), has appeared as an interesting alternative. However, fundamental questions surrounding self-assembly of this new ligand remain unanswered. Herein, we describe the effect of NHC structure, surface coverage, and substrate temperature on mobility, thermal stability, NHC surface geometry, and self-assembly. Analysis of NHC adsorption and self-assembly by scanning tunneling microscopy and density functional theory have revealed the importance of NHC-surface interactions and attractive NHC-NHC interactions on NHC monolayer structures. A remarkable way these interactions manifest is the need for a threshold NHC surface coverage to produce upright, adatom-mediated adsorption motifs with low surface diffusion. NHC wingtip structure is also critical, with primary substituents leading to the formation of flat-lying NHC2Au complexes, which have high mobility when isolated, but self-assemble into stable ordered lattices at higher surface concentrations. These and other studies of NHC surface chemistry will be crucial for the success of these next-generation monolayers.

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Self-assembly of [Et,Et]-Bacteriochlorophyll cF on Highly Oriented Pyrolytic Graphite Revealed by Scanning Tunneling Microscopy†¶

Photochemistry and Photobiology ◽

10.1562/0031-8655(2002)0750619saoeeb2.0.co2 ◽

2007 ◽

Vol 75 (6) ◽

pp. 619-626

Author(s):

H. Möltgen ◽

K. Kleinermanns ◽

A. Jesorka ◽

K. Schaffner ◽

A. R. Holzwarth

Keyword(s):

Scanning Tunneling Microscopy ◽

Self Assembly ◽

Pyrolytic Graphite ◽

Scanning Tunneling ◽

Highly Oriented Pyrolytic Graphite ◽

Tunneling Microscopy

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STM study on the self-assembly of oligothiophene-based organic semiconductors

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.2.88 ◽

2011 ◽

Vol 2 ◽

pp. 802-808 ◽

Cited By ~ 16

Author(s):

Elena Mena-Osteritz ◽

Marta Urdanpilleta ◽

Erwaa El-Hosseiny ◽

Berndt Koslowski ◽

Paul Ziemann ◽

...

Keyword(s):

Organic Semiconductors ◽

Self Assembly ◽

Theoretical Calculations ◽

The Self ◽

Scanning Tunneling ◽

Ambient Conditions ◽

Tunneling Microscopy ◽

Substitution Pattern ◽

Electronic Density ◽

The Individual

The self-assembly properties of a series of functionalized regioregular oligo(3-alkylthiophenes) were investigated by using scanning tunneling microscopy (STM) at the liquid–solid interface under ambient conditions. The characteristics of the 2-D crystals formed on the (0001) plane of highly ordered pyrolitic graphite (HOPG) strongly depend on the length of the π-conjugated oligomer backbone, on the functional groups attached to it, and on the alkyl substitution pattern on the individual thiophene units. Theoretical calculations were performed to analyze the geometry and electronic density of the molecular orbitals as well as to analyze the intermolecular interactions, in order to obtain models of the 2-D molecular ordering on the substrate.

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Understanding molecular self-assembly of a diol compound by considering competitive interactions

Physical Chemistry Chemical Physics ◽

10.1039/c6cp05818c ◽

2016 ◽

Vol 18 (39) ◽

pp. 27390-27395 ◽

Cited By ~ 4

Author(s):

Oscar Díaz Arado ◽

Maike Luft ◽

Harry Mönig ◽

Philipp Alexander Held ◽

Armido Studer ◽

...

Keyword(s):

Density Functional Theory ◽

Scanning Tunneling Microscopy ◽

Self Assembly ◽

Density Functional ◽

Competitive Interactions ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Functional Theory ◽

Chemical Groups

With a combination of scanning tunneling microscopy and density functional theory, effects on molecular self-assembly involving two distinct chemical groups were investigated.

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