scholarly journals Chiral self-assembly of helical particles

2016 ◽  
Vol 186 ◽  
pp. 171-186 ◽  
Author(s):  
Hima Bindu Kolli ◽  
Giorgio Cinacchi ◽  
Alberta Ferrarini ◽  
Achille Giacometti
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Colloidal Suspensions ◽  
Building Blocks ◽  
Phase Behaviour ◽  
Helical Structures ◽  
Functional Theory ◽  
Azimuthal Correlations ◽  
The Many ◽  
Helix Parameters

The shape of the building blocks plays a crucial role in directing self-assembly towards desired architectures. Out of the many different shapes, the helix has a unique position. Helical structures are ubiquitous in nature and a helical shape is exhibited by the most important biopolymers like polynucleotides, polypeptides and polysaccharides as well as by cellular organelles like flagella. Helical particles can self-assemble into chiral superstructures, which may have a variety of applications,e.g.as photonic (meta)materials. However, a clear and definite understanding of these structures has not been entirely achieved yet. We have recently undertaken an extensive investigation on the phase behaviour of hard helical particles, using numerical simulations and classical density functional theory. Here we present a detailed study of the phase diagram of hard helices as a function of their morphology. This includes a variety of liquid-crystal phases, with different degrees of orientational and positional ordering. We show how, by tuning the helix parameters, it is possible to control the organization of the system. Starting from slender helices, whose phase behaviour is similar to that of rodlike particles, an increase in curliness leads to the onset of azimuthal correlations between the particles and the formation of phases specific to helices. These phases feature a new kind of screw order, of which there is experimental evidence in colloidal suspensions of helical flagella.

scholarly journals Heterocycle Effects on the Liquid Crystallinity of Terthiophene Analogues

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2314 ◽  
Author(s):  
David Ester ◽  
Declan McKearney ◽  
Khrystyna Herasymchuk ◽  
Vance Williams
Keyword(s):  
Density Functional Theory ◽  
Organic Semiconductors ◽  
Self Assembly ◽  
Density Functional ◽  
Liquid Crystalline ◽  
Variable Temperature ◽  
Phase Behaviour ◽  
Scanning Calorimetry ◽  
Functional Theory ◽  
Thiadiazole Ring

Liquid crystalline self-assembly offers the potential to create highly ordered, uniformly aligned, and defect-free thin-film organic semiconductors. Analogues of one of the more promising classes of liquid crystal semiconductors, 5,5”-dialkyl-α-terthiophenes, were prepared in order to investigate the effects of replacing the central thiophene with either an oxadiazole or a thiadiazole ring. The phase behaviour was examined by differential scanning calorimetry, polarized optical microscopy, and variable temperature x-ray diffraction. While the oxadiazole derivative was not liquid crystalline, thiadiazole derivatives formed smectic C and soft crystal lamellar phases, and maintained lamellar order down to room temperature. Variation of the terminal alkyl chains also influenced the observed phase sequence. Single crystal structures revealed the face-to-face orientation of molecules within the layers in the solid-state, a packing motif that is rationalized based on the shape and dipole of the thiadiazole ring, as corroborated by density functional theory (DFT) calculations. The solution opto-electronic properties of the systems were characterized by absorption and emission spectroscopy, cyclic voltammetry, and time-dependent density functional theory (TD-DFT).

scholarly journals On the Many-Body Expansion of an Interaction Energy of Some Supramolecular Halogen-Containing Capsules

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4431
Author(s):  
Jiří Czernek ◽  
Jiří Brus
Keyword(s):  
Density Functional ◽  
Condensed Phases ◽  
Multicomponent Mixtures ◽  
Many Body ◽  
Symmetric Form ◽  
Functional Theory ◽  
Emergent Features ◽  
The Many ◽  
Surprising Fact ◽  
Dimethyl Benzene

A tetramer model was investigated of a remarkably stable iodine-containing supramolecular capsule that was most recently characterized by other authors, who described emergent features of the capsule’s formation. In an attempt to address the surprising fact that no strong pair-wise interactions between any of the respective components were experimentally detected in condensed phases, the DFT (density-functional theory) computational model was used to decompose the total stabilization energy as a sum of two-, three- and four-body contributions. This model considers complexes formed between either iodine or bromine and the crucial D4h-symmetric form of octaaryl macrocyclic compound cyclo[8](1,3-(4,6-dimethyl)benzene that is surrounded by arenes of a suitable size, namely, either corannulene or coronene. A significant enthalpic gain associated with the formation of investigated tetramers was revealed. Furthermore, it is shown that the total stabilization of these complexes is dominated by binary interactions. Based on these findings, comments are made regarding the experimentally observed behavior of related multicomponent mixtures.

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

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.

scholarly journals Towards crystal structure prediction of complex organic compounds – a report on the fifth blind test

2011 ◽  
Vol 67 (6) ◽  
pp. 535-551 ◽  
Author(s):  
David A. Bardwell ◽  
Claire S. Adjiman ◽  
Yelena A. Arnautova ◽  
Ekaterina Bartashevich ◽  
Stephan X. M. Boerrigter ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Prediction ◽  
Density Functional ◽  
Crystal Structure Prediction ◽  
Blind Test ◽  
Functional Theory ◽  
Flexible Molecule ◽  
Successful Prediction ◽  
The Many ◽  
Complex Organic

Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories – a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome.

scholarly journals Insight into the Self-Assembly of Water-Soluble Perylene Bisimide Derivatives Through a Combined Computational and Experimental Approach

2019 ◽  
Author(s):  
Emily R. Draper ◽  
Liam Wilbraham ◽  
Dave J. Adams ◽  
Matthew Wallace ◽  
Martijn Zwijnenburg
Keyword(s):  
Density Functional Theory ◽  
Self Assembly ◽  
Density Functional ◽  
Colloidal Stability ◽  
Water Soluble ◽  
The Self ◽  
Functional Theory ◽  
Perylene Bisimide ◽  
Aggregate Growth ◽  
Perylene Bisimides

We use a combination of computational and experimental techniques to study the self-assembly and gelation of water-soluble perylene bisimides derivatised at the imide position with an amino acid. Specifically, we study the likely structure of self-assembled aggregates of the alanine-functionalised perylene bisimide (PBI-A) and the thermodynamics of their formation using density functional theory and predict the UV-vis spectra of such aggregates using time-dependent density functional theory. We compare these predictions to experiments in which we study the evolution of the UV-Vis and NMR spectra and rheology of alkaline PBI-A solutions when gradually decreasing the pH. Based on the combined computational and experimental results, we show that PBI-A self-assembles at all pH values but that aggregates grow in size upon protonation. Gelation is driven not by aggregate growth but reduction of the aggregation surface-charge and a decrease in the colloidal stability of the aggregation with respect to agglomeration.

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

2016 ◽  
Vol 18 (39) ◽  
pp. 27390-27395 ◽  
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.

scholarly journals Including dispersion in density functional theory for adsorption on flat oxide surfaces, in metal–organic frameworks and in acidic zeolites

2020 ◽  
Vol 22 (14) ◽  
pp. 7577-7585 ◽  
Author(s):  
Florian R. Rehak ◽  
GiovanniMaria Piccini ◽  
Maristella Alessio ◽  
Joachim Sauer
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Van Der Waals ◽  
Metal Organic Frameworks ◽  
Many Body ◽  
Functional Theory ◽  
Metal Organic ◽  
The Many ◽  
Acidic Zeolites ◽  
Better Than

Contrary to common believe, for eight adsorption cases, neither D3 or TS are an improvement compared to D2 nor van der Waals functionals or dDsC. Only the many body approaches are slightly better than D2(Ne) which uses Ne parameters for Mg2+ ions.

Experimental and density functional theory investigation of Pt-loaded titanium dioxide/molybdenum disulfide nanohybrid for SO2 gas sensing

2019 ◽  
Vol 43 (12) ◽  
pp. 4900-4907 ◽  
Author(s):  
Dongzhi Zhang ◽  
Maosong Pang ◽  
Junfeng Wu ◽  
Yuhua Cao
Keyword(s):  
Density Functional Theory ◽  
Titanium Dioxide ◽  
Molybdenum Disulfide ◽  
Self Assembly ◽  
High Performance ◽  
Density Functional ◽  
Gas Sensing ◽  
Layer By Layer ◽  
Functional Theory ◽  
So2 Gas

A high-performance sulfur dioxide sensor based on a platinum-loaded titanium dioxide/molybdenum disulfide ternary nanocomposite is synthesized via layer-by-layer self-assembly.

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