Search results for " Self-Assembly"
showing 10 items of 74 documents
Decisive influence of substitution positions in molecular self-assembly
2014
Molecular self-assembly provides a versatile tool for creating functional molecular structures at surfaces. A rational design of molecular structure formation requires not only an in-depth understanding of the subtle balance between intermolecular and molecule-surface interactions, but might also involve considering chemical changes of the molecules, such as deprotonation. Here, we present a systematic investigation of a comparatively simple class of molecules, namely dihydroxybenzoic acid, which, nevertheless, enables creating a rich variety of structures when deposited onto calcite (10.4) held at room temperature. Based on non-contact atomic force microscopy measurements in ultra-high vac…
How deprotonation changes molecular self-assembly – an AFM study in liquid environment
2013
We study the influence of Alizarin Red S deprotonation on molecular self-assembly at the solid-liquid interface of the natural cleavage plane of calcite immersed in aqueous solution. To elucidate the adsorption details, we perform pH dependent high-resolution atomic force microscopy measurements. When Alizarin Red S is deposited onto calcite(10.4) in a liquid environment at an acidic pH of 5, weakly bound, ordered islands with a (3 x 3) superstructure are observed. A sharp structural transition is revealed when increasing the pH above 8. Above this pH, stable needle-like structures oriented along the [01.0] direction form on the surface. Comparing these results with potentiometric titration…
Interfacial Self-Assembly to Spatially Organize Graphene Oxide Into Hierarchical and Bioactive Structures
2020
Multicomponent self-assembly holds great promise for the generation of complex and functional biomaterials with hierarchical microstructure. Here, we describe the use of supramolecular co-assembly between an elastin-like recombinamer (ELR5) and a peptide amphiphile (PA) to organize graphene oxide (GO) flakes into bioactive structures across multiple scales. The process takes advantage of a reaction—diffusion mechanism to enable the incorporation and spatial organization of GO within multiple ELR5/PA layers. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ImageJ software were used to demonstrate the hierarchical organization of GO flakes within the ELR5/PA lay…
POSS-tetraalkylammonium salts: A new class of ionic liquids
2012
A series of new polyhedral oligomeric silsesquioxane ionic liquids (POSS-ILs) based on the trimethylpropylammonium dielectric constants, which, conversely, display slight differences originating from the nature of the anions. The long alkyl-chain substituents on the POSS core infer on this series of ILs an overall hydrophobic character and solution properties comparable to those of classic cationic surfactants, resulting in an effective extractant capability of polyanions from aqueous solutions. Their solution diffusion properties, as investigated by room-temperature dynamic light scattering, solution conductivity, density, and osmometric measurements, do not provide evidence for the occurr…
Facile Fabrication of Natural Polyelectrolyte-Nanoclay Composites: Halloysite Nanotubes, Nucleotides and DNA Study
2020
Complexation of biopolymers with halloysite nanotubes (HNTs) can greatly affect their applicability as materials building blocks. Here we have performed a systematic investigation of fabrication of halloysite nanotubes complexes with nucleotides and genomic DNA. The binding of DNA and various nucleotide species (polyAU, UMP Na2, ADP Na3, dATP Na, AMP, uridine, ATP Mg) by halloysite nanotubes was tested using UV-spectroscopy. The study revealed that binding of different nucleotides to the nanoclay varied but was low both in the presence and absence of MgCl2, while MgCl2 facilitated significantly the binding of longer molecules such as DNA and polyAU. Modification of the nanotubes with DNA an…
Xyloglucan self-assembled nanostructures and gels for biomedical applications
Guest-Induced Folding of the N-Benzyl Substituents in an Ammonium Resorcinarene Chloride and the Formation of a Halogen-Bonded Dimer of Capsules
2016
In methanol, N-benzyl ammonium resorcinarene chloride (Bn-NARCl) crystallizes as a solvate with the benzyl groups oriented in an open flower-like manner parallel to the cation–anion seam. 1,4-Dioxane as guest triggers a “semi-closed” single-molecule capsule with two benzyl “arms” enclosing the guest. The introduction of halogen bond (XB) donor 1,4-diiodoperfluorobutane (1,4-DIOFB) additionally folds the remaining two benzyl arms thus resulting in a fully closed capsule. Two 1,4-DIOFB molecules bridge two such Bn-NARCl capsules, forming a 2:2:2 XB held dimeric assembly of single-molecule capsules. The peculiar behavior was not observed in the bromide analog under similar experimental conditi…
Definition of the chalcogen bond (IUPAC Recommendations 2019)
2019
Abstract This recommendation proposes a definition for the term “chalcogen bond”; it is recommended the term is used to designate the specific subset of inter- and intramolecular interactions formed by chalcogen atoms wherein the Group 16 element is the electrophilic site.
Molecular Self-Assembly of Enantiopure Heptahelicene-2-Carboxylic Acid on Calcite (1014)
2012
Chirality can have a decisive influence on the molecular structure formation upon self-assembly on surfaces. In this paper, we study the structures formed by enantiopure (M)-heptahelicene-2-carboxylic acid ((M)-[7]HCA) on the calcite (10 (1) over bar4) cleavage plane under ultrahigh vacuum conditions. Previous noncontact atomic force microscopy studies have revealed that the racemic mixture of (M)-[7]HCA and (P)-[7]FICA (1:1) self-assembles into well-defined molecular double rows that are oriented along the calcite [01 (1) over bar0] direction. Here, we investigate the enantiopure (M)[7]HCA compound, resulting in distinctly different molecular structures upon deposition onto calcite (10 (1)…
Aggregation processes of perylene bisimide diimidazolium salts
2015
The supramolecular aggregation of three diimidazolium- functionalized perylene bisimides, differing in the alkyl chain length was investigated. These salts form aggregates in solvents like chloroform, dichloromethane, and glycerol. Solvent-, concentration-, and temperature-dependent spectroscopic studies were carried out, evidencing the occurrence of an isodesmic, enthalpy-driven aggregation process, underpinned by p–p stacking and hydrogen bonding. Moreover, dynamic light scattering (DLS) measurements and SEM images revealed that these salts aggregate in chloroform into elongated structures.