Self-Assembling Nanofibers from Thiophene–Peptide Diblock Oligomers: A Combined Experimental and Computer Simulations Study (original) (raw)
Related papers
Advanced Materials, 2009
Investigation of self-organization behavior of organic (semi)conductors became very important recently, since their physical properties and performance in organic electronic devices strongly depend on ordering effects, on both molecular and nanoscale levels. [1] In this respect, bioinspired functionalization of conjugated systems might greatly enhance the diversity of electronically interesting assemblies, and potentially allow for the rational design of hierarchically ordered nanostructures. Thus, from possible hybrids of conjugated backbones, the combination of oligo-or polythiophenes with biomolecules, such as nucleotides, [3] carbohydrates, or peptides, are interesting. Particularly, the latter appears to be attractive, because interplay between different intermolecular forces in the peptide and oligothiophene segments results in competing self-assembly motifs. Hence, very specific organization properties can be expected. Whereas thiophene-based materials typically form well-organized 2D lamellar superstructures due to van der Waals interactions of alkyl side chains, and stack into the third dimension via p-p interactions, [6] secondary structures of peptides, preferentially bsheets or a-helices, are governed by stronger and directed hydrogen-bond formation. The high tendency of peptides to adopt well-defined secondary-structure motifs has been exploited recently to guide self-organization of a broad range of synthetic polymers. [8] Attention has mainly been devoted to the b-sheet motif, leading to anisotropic fibrillar or fiber-like structures. [9] However, other highly interesting assembly motifs, for example the coiled-coil motif, were exploited, resulting in distinct nanoobjects by the lateral assembly of amphiphilic a-helices. We recently presented the first conjugate between a regioregularly alkylated quaterthiophene and a pentapeptide consisting of a silk-inspired sequence of alanine-glycine repeats, which is known to adopt b-sheet structures. [5a] Unexpected and novel 3D nanostructures were found, suggesting that short peptide sequences may indeed influence the nanoscale structure, and ultimately, properties of organic semiconducting materials.
Self-organizing bioinspired oligothiophene–oligopeptide hybrids
Beilstein Journal of Nanotechnology, 2011
In this minireview, we survey recent advances in the synthesis, characterization, and modeling of new oligothiophene-oligopeptide hybrids capable of forming nanostructured fibrillar aggregates in solution and on solid substrates. Compounds of this class are promising for applications because their self-assembly and stimuli-responsive properties, provided by the peptide moieties combined with the semiconducting properties of the thiophene blocks, can result in novel opportunities for the design of advanced smart materials. These bio-inspired molecular hybrids are experimentally shown to form stable fibrils as visualized by AFM and TEM. While the experimental evidence alone is not sufficient to reveal the exact molecular organization of the fibrils, theoretical approaches based on quantum chemistry calculations and large-scale atomistic molecular dynamics simulations are attempted in an effort to reveal the structure of the fibrils at the nanoscale. Based on the combined theoretical and experimental analysis, the most likely models of fibril formation and aggregation are suggested.
Self-Assembly of a Structurally Defined Chiro-Optical Peptide–Oligothiophene Hybrid Material
ACS Omega, 2018
Conducting polymers are routinely used in optoelectronic biomaterials, but large polymer polydispersity and poor aqueous compatibility complicate integration with biomolecular templates and development of discrete and defined supramolecular complexes. Herein, we report on a chiro-optical hybrid material generated by the self-assembly of an anionic peptide and a chemically defined cationic pentameric thiophene in aqueous environment. The peptide acts as a stereochemical template for the thiophene and adopts an α-helical conformation upon association, inducing optical activity in the thiophene π−π* transition region. Theoretical calculations confirm the experimentally observed induced structural changes and indicate the importance of electrostatic interactions in the complex. The association process is also probed at the substrate−solvent interface using peptide-functionalized gold nanoparticles, indicating that the peptide can also act as a scaffold when immobilized, resulting in structurally well-defined supramolecular complexes. The hybrid complex could rapidly be assembled, and the kinetics of the formation could be monitored by utilizing the local surface plasmon resonance originating from the gold nanoparticles. We foresee that these findings will aid in designing novel hybrid materials and provide a possible route for the development of functional optoelectronic interfaces for both biomaterials and energy harvesting applications.
Nanoscale, 2017
Targeted control of the aggregation, morphology and optical properties of conjugated polymers is critical for the development of high performance optoelectronic devices. Here, self-assembly approaches are used to strategically manipulate the order, conformation and spatial distribution of conjugated polymers in solution and subsequently prepared thin films. The supramolecular complex organisation of phosphonium-functionalised homo- (P3HTPMe3) and diblock (P3HT-b-P3HTPMe3) ionic conjugated polythiophenes upon solvent-mediation and co-assembly with oppositely charged surfactants is investigated. UV/Vis absorption and photoluminescence spectroscopies, small-angle neutron scattering (SANS), cryo-transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM) are used to probe the organisation and photophysical response of the aggregates formed. Subtle differences in the surfactant mole fraction and structure, as well as the solvent polarity, yield differences in the nature...
Oligothiophene-based nanostructures: from solution to solid-state aggregates
Synthetic Metals, 2004
The possibility to develop optoelectronic devices with improved properties by controlling the degree of organization at the molecular level of organic materials has been driving the design of new-conjugated systems. In particular, the organization by self-assembling processes (interactions, hydrogen bonding) of well-defined oligomeric systems such as disubstituted oligothiophene derivatives has been demonstrated as a promising approach to conjugated materials with a high degree of structural order of the constituent building blocks. Here, tapping-mode atomic force microscopy is used to investigate the morphologies of (i) thin deposits made from assembly of thiophene-based oligomers starting from molecularly dissolved solutions or (ii) aggregates already formed in solution. In order to understand the results in terms of supramolecular organization, comparisons with molecular modeling simulations are performed. During the self-assembly processes, the interplay between the conjugated molecules, the solvent, and the substrate surface is of primary importance. Depending on the interactions between the molecules and the substrate, one-dimensional (nanowires) or two-dimensional (platelets) objects can be generated. The self-organization of conjugated building blocks in solution or in solid-state on surfaces represents a starting point for the construction of molecular electronics or even circuits, through surface patterning with nanometer-sized objects.
JOURNAL OF PHYSICAL CHEMISTRY C, 2008
The formation of self-assembled monolayers of bithiophene-fluorenone conjugated oligomers, 2,7-bis-(4octyl-thien-2-yl)-fluoren-9-one (B4OTF) and 2,7-bis-(5-octyl-thien-2-yl)-fluoren-9-one (B5OTF), has been studied on highly oriented pyrolitic graphite (HOPG) by scanning tunneling microscopy (STM), with the aim of determining the influence of the molecular structure and conformation on the supramolecular organization. The experimental data are discussed in light of a modeling study of the molecular conformation and the adsorption on graphite using molecular mechanics and molecular dynamics simulations. It is shown that molecules with alkyl groups grafted in the C4 position (B4OTF) self-assemble into an anti-anti chiral lattice which is favored both by dipole-dipole and Van der Waals interactions. The short-range organization appears more complex for molecules with alkyl groups grafted in the C5 position (B5OTF). Due to a competition between dipole-dipole and Van der Waals interactions, the modeled assemblies based on syn-syn, synanti, and anti-anti B5OTF conformers are all stable and very close in energy, but do not explain the feature of a long-range periodicity evidenced from large-scale STM images. On the basis of the comparative analysis between the experimental data and the modeling, it is then suggested that the supramolecular self-assembly of B5OTF on HOPG implies the presence of several conformers in the monolayer.
Macromolecules, 2017
The development of chiral optoelectronic materials are of great interest due to their potential of being utilized in electronic devices, biosensors and artificial enzymes. Herein, we report the chiral-optical properties and architectural arrangement of optoelectronic materials generated from non-covalent self-assembly of a cationic synthetic peptide and five chemically defined anionic pentameric oligothiophenes. The peptide-oligothiophene hybrid materials exhibit a three dimensional ordered helical structure and optical activity in the π-π* transition region that are observed due to a single chain induced chirality of the conjugated thiophene backbone upon interaction with the peptide. The latter property is highly dependent on electrostatic interactions between the peptide and the oligothiophene, verifying that a distinct spacing of the carboxyl groups along the thiophene backbone is a major chemical determinant for having a hybrid material with distinct optoelectronic properties. The necessity of the electrostatic interaction between specific carboxyl functionalities along the thiophene backbone and the lysine residues of the peptide, as well as the induced circular dichroism of the thiophene backbone, was also confirmed by theoretical calculations. We foresee that our findings will aid in designing optoelectronic materials with dynamic architectonical precisions, as well as offer the possibility to create the next generation of materials for organic electronics and organic bioelectronics.
Solid-State Supramolecular Organization of Polythiophene Chains Containing Thienothiophene Units
Advanced Materials, 2009
Conjugated polymers are widely investigated for organic electronics as they can be processed at low cost over large areas and yield mechanically flexible devices. When used as active semiconducting layers in organic field-effect transistors (FETs), thiophene-based polymers have demonstrated carrier mobilities ranging from 0.1 to 1 cm 2 V À1 s À1 (i.e., values high enough for many applications [1-4]) that are intimately linked to their supramolecular organization in the solid state. Solution-processible semiconducting polymers such as regioregular poly(3-hexylthiophene) (P3HT) are made of a conjugated backbone along which alkyl groups are grafted to improve solubility. During film formation, these two components self-segregate, often giving rise to a lamellar structure with stacks of conjugated backbones separated by layers of alkyl groups. The lamellae can orient differently-parallel or normal-to the substrate, dramatically changing the mobility in the plane of the film (by more than a factor of 100 for P3HT). [1] Such a high anisotropy reflects an interchain transport of the charge carriers that is much more efficient along the p-stacking direction and along the backbones than through the layers of packed alkyl groups. The mobility is thus maximized when the p-stacking direction or the long chain axes is aligned along the flow of current, i.e., when the lamellae are parallel to the substrate. Recently, poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) has been reported to have improved stability to air and light, and higher mobilities (up to 0.6 cm 2 V À1 s À1 in long channel and 1 cm 2 V À1 s À1 in short channel FETs) relative to P3HT. [2,4] This high charge carrier mobility is achieved by thermally annealing cast films into a liquid-crystalline mesophase and then by cooling back to room temperature. The annealing improves the structural ordering in the films, as evidenced by X-ray scattering and atomic force microscopy measurements: large lateral terraces extending over several hundreds of nanometers are observed. [2,5] Additionally, since the specific volume difference between crystalline and liquid-crystalline phases is small, the polymer segments located between the crystalline domains are probably less disordered upon crystal growth, thus potentially