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

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.

scholarly journals Insight Into the Superlubricity and Self-Assembly of Liquid Crystals

2021 ◽  
Vol 9 ◽  
Author(s):  
Shanchao Tan ◽  
Jiayu Tao ◽  
Wendi Luo ◽  
Hongyu Shi ◽  
Bin Tu ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Self Assembly ◽  
Density Functional ◽  
Pyrolytic Graphite ◽  
Interaction Strength ◽  
Dft Method ◽  
The Self ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Friction Coefficients

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.

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

Crystals ◽  
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.

scholarly journals Structural and Nanotribological Properties of a BODIPY Self-Assembly

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.

scholarly journals Scanning Tunneling Microscope Investigation of Self-Assembled Rosette Nanotubes on Highly Ordered Pyrolytic Graphite

2010 ◽  
Vol 16 (S2) ◽  
pp. 470-471 ◽  
Author(s):  
J-Y Cho ◽  
G Borzsonyi ◽  
H Fenniri
Keyword(s):  
Scanning Tunneling Microscope ◽  
Pyrolytic Graphite ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Microscope Investigation ◽  
Rosette Nanotubes ◽  
Highly Ordered Pyrolytic Graphite ◽  
Self Assembled

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

scholarly journals Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4387 ◽  
Author(s):  
Vladyslav Savchenko ◽  
Markus Koch ◽  
Aleksander S. Pavlov ◽  
Marina Saphiannikova ◽  
Olga Guskova
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Computer Modelling ◽  
Light Stimulus ◽  
Dipole Moments ◽  
Intermolecular Forces ◽  
Binding Energies ◽  
The Self ◽  
Assembly Mechanism ◽  
Lateral Displacements

In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analyzed theoretically by applying a combination of computer simulation techniques. Without a light stimulus, the azobenzene arms adopt the trans-state and build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies—fibers, spheres, gels, and others. Here, we determine the most favorable mutual orientations of the trans-stars in the stack in terms of (i) the π – π distance between the cores lengthwise the aggregate, (ii) the lateral displacements due to slippage and (iii) the rotation promoting the helical twist and chirality of the aggregate. To this end, we calculate the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of the stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moments and the binding energies as functions of the columnar length. For this, molecular dynamics trajectories are analyzed. Finally, we conclude about the cooperative nature of the self-assembly of star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core in aqueous solution.

scholarly journals Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism

2014 ◽  
Vol 10 ◽  
pp. 2774-2782 ◽  
Author(s):  
Joscha Vollmeyer ◽  
Friederike Eberhagen ◽  
Sigurd Höger ◽  
Stefan-S Jester
Keyword(s):  
Interior Design ◽  
Pyrolytic Graphite ◽  
Self Assembled Monolayers ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Conformational Polymorphism ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
Solid Liquid Interface ◽  
Solid Liquid

Three shape-persistent naphthylene–phenylene–acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar) nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D) crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

scholarly journals Плотность свободных электронных состояний полупроводниковых пленок молекул нафталина и дифенилфталида, модифицированных электроактивными функциональными группами

2020 ◽  
Vol 62 (7) ◽  
pp. 1116
Author(s):  
А.С. Комолов ◽  
Э.Ф. Лазнева ◽  
Н.Б. Герасимова ◽  
А.В. Барамыгин ◽  
В.С. Соболев ◽  
...  
Keyword(s):  
Fermi Level ◽  
Dicarboxylic Acid ◽  
Density Functional ◽  
Pyrolytic Graphite ◽  
Electronic States ◽  
Dft Method ◽  
Layer By Layer ◽  
Total Current ◽  
Peak Structure ◽  
The Difference

The results on comparing the peak structure of the density of unoccupied electronic states (DOUS) of ultrathin films of naphthalene anhydride-1,4,5,8-teracabonic acid (NTCDA) and naphthalene-1,8-dicarboxylic acid anhydride (NDCA) and of two types of phthalide-based films: 3,3-bis (phenyl) phthalide (DPP) and 3,3-bis (phenyl) phthalide-4 ′, 4′-dicarboxylic acid (DPP-DCA) are presented. The measurements of the structure of the unoccupied electronic states in the energy range from 5 eV to 20 eV above the Fermi level of the films studied having thickness of 8–10 nm were conducted using the total current spectroscopy (TCS) technique. Analysis of the experimental results was conducted using the model total current spectra and DOUS dependences generated using the calculated orbital energies of the studied molecules by means of the density functional theory (DFT) method at the B3LYP/6-31G(d) level. The difference in the DOUS spectra of NTCDA and NDCA films is characterized by the shift of the main DOUS maxima of the NTCDA film to lower energies by about 1 eV at energies less than 12.5 eV, and at higher energies the DOUS maxima are shifted by 1.5-2 eV. The energy positions of the maxima of the total current spectra of the DPP-DCA and DPP films practically do not change when using various substrates: highly ordered pyrolytic graphite (HOPG) and layer-by-layer deposited CdS. The relative intensities of the maxima differ when using different substrates. The characteristic shift of the maxima of the total current spectra of DPP-DCA films is about 1 eV at energies less than 12.5 eV above the Fermi level and 1.5-2 eV and at higher energies, compared with the position of the corresponding maxima of the DPP films.

scholarly journals Self-assembly and wetting properties of gold nanorod–CTAB molecules on HOPG

2019 ◽  
Vol 10 ◽  
pp. 696-705 ◽  
Author(s):  
Imtiaz Ahmad ◽  
Floor Derkink ◽  
Tim Boulogne ◽  
Pantelis Bampoulis ◽  
Harold J W Zandvliet ◽  
...  
Keyword(s):  
Self Assembly ◽  
Cetyltrimethylammonium Bromide ◽  
Pyrolytic Graphite ◽  
The Self ◽  
Gold Nanorod ◽  
Force Microscopy ◽  
Wetting Properties ◽  
Atomic Force ◽  
Highly Ordered Pyrolytic Graphite ◽  
Self Assembled

The formation of self-assembled superstructures of cetyltrimethylammonium bromide (CTAB) after drying on a nonwetting highly ordered pyrolytic graphite (HOPG) surface have been investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Although SEM did not reveal coverage of CTAB layers, AFM showed not only CTAB assembly, but also the dynamics of the process on the surface. The self-assembled layers of CTAB molecules on the HOPG terraces prior to nanorod deposition were shown to change the wettability of the surface, and as a result, gold nanorod deposition takes place on nonwetting HOPG terraces.

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