Twisted Nanoribbons Research Articles

Helically twisted nanoribbons via stereospecific annulative π-extension reaction employing [7]helicene as a molecular wrench.

Over the past decade, significant progress has been made in synthesizing atomically precise carbon nanostructures, particularly graphene nanoribbons (NRs), employing advanced synthetic methodologies. Despite these advancements, achieving control over the stereochemistry of twisted NRs has proven to be a formidable challenge. This manuscript presents a strategic approach to achieve absolute control over the single-handed helical conformation in a cove-edged NR. This strategy leverages enantiopure helicenes as a molecular wrench, intricately influencing the overall conformation of the NR. [7]helicenes stitched to the terminal K-regions of a conjugated pyrene NR through a stereospecific annulative π-extension reaction to produce a helically twisted NR with an end-to-end twist of 171°. Furthermore, a detailed investigation of the impact of twisting on the conformational population was studied by quantum chemical calculations.

Twisted bilayer zigzag-graphene nanoribbon junctions with tunable edge states

Stacking two-dimensional layered materials such as graphene and transitional metal dichalcogenides with nonzero interlayer twist angles has recently become attractive because of the emergence of novel physical properties. Stacking of one-dimensional nanomaterials offers the lateral stacking offset as an additional parameter for modulating the resulting material properties. Here, we report that the edge states of twisted bilayer zigzag graphene nanoribbons (TBZGNRs) can be tuned with both the twist angle and the stacking offset. Strong edge state variations in the stacking region are first revealed by density functional theory (DFT) calculations. We construct and characterize twisted bilayer zigzag graphene nanoribbon (TBZGNR) systems on a Au(111) surface using scanning tunneling microscopy. A detailed analysis of three prototypical orthogonal TBZGNR junctions exhibiting different stacking offsets by means of scanning tunneling spectroscopy reveals emergent near-zero-energy states. From a comparison with DFT calculations, we conclude that the emergent edge states originate from the formation of flat bands whose energy and spin degeneracy are highly tunable with the stacking offset. Our work highlights fundamental differences between 2D and 1D twistronics and spurs further investigation of twisted one-dimensional systems.

A “core determination” phenomenon in four dichiral liquid crystals containing two lactate groups

Four dichiral liquid crystals with one perfluoroalkyl chain and two lactate groups were synthesized. They all exhibit an enantiotropic SmA phase. An enantiotropic SmCd* phase was identified in a pair of enantiomers. Their optical activity was mainly controlled by the chirality of the lactate residue near mesogenic core. These liquid crystals could self-assemble into twisted nanoribbons or helical nanofibers. The stacking handedness of mesogenic cores and the handedness of nanoribbons/nanofibers were also dominated by the chirality of lactate group near mesogenic core. This “core determination” phenomenon was proposed to originate from the π–π stacking among mesogenic cores.

Short Peptides Derived from a Block Copolymer-like Barnacle Cement Protein Self-Assembled into Diverse Supramolecular Structures

Peptides capable of self-assembling into different supramolecular structures have potential applications in a variety of areas. The biomimetic molecular design offers an important avenue to discover novel self-assembling peptides. Despite this, a lot of biomimetic self-assembling peptides have been reported so far; to continually expand the scope of peptide self-assembly, it is necessary to find out more novel self-assembling peptides. Barnacle cp19k, a key underwater adhesive protein, shows special block copolymer-like characteristics and diversified self-assembly properties, providing an ideal template for biomimetic peptide design. In this study, inspired by Balanus albicostatus cp19k (Balcp19k), we rationally designed nine biomimetic peptides (P1-P9) and systematically studied their self-assembly behaviors for the first time. Combining microscale morphology observations and secondary structure analyses, we found that multiple biomimetic peptides derived from the central region and the C-terminus of Balcp19k form distinct supramolecular structures via different self-assembly mechanisms under acidic conditions. Specifically, P9 self-assembles into typical amyloid fibers. P7, which resembles ionic self-complementary peptides by containing nonstrictly alternating hydrophobic and charged amino acids, self-assembles into uniform, discrete nanofibers. P6 with amphipathic features forms twisted nanoribbons. Most interestingly, P4 self-assembles to form helical nanofibers and novel ring-shaped microstructures, showing unique self-assembly behaviors. Apart from their self-assembly properties, these peptides showed good cytocompatibility and demonstrated promising applications in biomedical areas. Our results expanded the repertoire of self-assembling peptides and provided new insights into the structure-function relationship of barnacle cp19k.

Preliminary study on the self-assembly of a pair of azobenzene liquid crystals derived from alanine

A series of azobenzene liquid crystals containing one amino acid residue were synthesized. They exhibit smectic mesophases. The compounds derived from alanine can self-assemble into twisted nanoribbons. The molecules organized in a monolayer structure within the nanoribbon. Circular dichroism characterization indicated that the neighboring liquid crystal cores packed in a chiral structure. FT-IR spectra indicated that the nanoribbons were caused by H-bonding and association of hydrocarbon chains.

Inducing Single-Handed Helicity in a Twisted Molecular Nanoribbon.

Molecular conformation has an important role in chemistry and materials science. Molecular nanoribbons can adopt chiral twisted helical conformations. However, the synthesis of single-handed helically twisted molecular nanoribbons still represents a considerable challenge. Herein, we describe an asymmetric approach to induce single-handed helicity with an excellent degree of conformational discrimination. The chiral induction is the result of the chiral strain generated by fusing two oversized chiral rings and of the propagation of that strain along the nanoribbon’s backbone.

Handedness inversion of the self-assemblies of lipotetrapeptides regulated by the shift of the methyl group

Four lipotetrapeptides containing three glycines and one l-alanine self-assembled into twisted nanoribbons. Handedness inversion was observed with the movement of l-alanine.

Band Structure and Spatial Localization of Electrons in Twisted Bilayer Graphene Nanoribbons

We have studied the band structure, density of states and spatial localization of electron in twisted bilayer nanoribbons by means of tight binding calculation. In Chiral geometries, edge states are also related to the presence of zig-zag edge atoms, although they presented remarkable size effects. Physical properties of chiral graphene nanoribbons and general edges can have a stong dependence on chirality. We have analysed the properties of edge states in twisted bilayaer ribbons, explaining their energy dispersion and spatial localization. The different splittings were found in edge bands due to the inhomogeneous interplay coupling. For stacked zig-zag atoms the coupling was larger than corresponding edge states splitted apart, but edge states stemming from regions with stacking, where the interlayer coupling was smaller and gave rise to zero energy bands. We have also been found that in the edge regions where top and bottom zig-zag terminations were stacked, inter-ribbon tunneling between the dispersions less zero energy states created bonding and antibonding combination with energies away from the energy of the Dirac point. The obtained results were found in good agreement with previously obtained results.

Synthesis of ultrathin rhenium disulfide nanoribbons using nano test tubes

The synthesis of ultrathin rhenium disulfide (ReS2) nanoribbons within single-walled carbon nanotubes (SWNTs) has been established. Dirhenium decacarbonyl complex is encapsulated into the SWNTs to provide a source of confined rhenium atoms, which readily react with iodine to form discrete nm-sized clusters of rhenium iodide [Re6I14]2− embedded in the nanotubes. The final step of the synthesis is accomplished by admitting hydrogen sulfide gas into nano test tubes, yielding twisted nanoribbons of rhenium disulfide encapsulated in carbon nanotubes, ReS2@SWNTs. The width, structure, and composition of rhenium disulfide nanoribbons are strictly controlled by the extreme confinement of the host-SWNT. A holistic analytical approach combining complementary imaging and analysis methods is used at each synthetic step to elucidate the structure and composition of the guest material and reveal the role of the SWNT contributing towards the electronic interactions with encapsulated inorganic structures. As ReS2 nanoribbons are expected to retain the electronic properties of the bulk material, such as direct bandgap, the low dimensional form of this material can be of interest for use in nanoscale electronic devices.

STEM Tomography of Au Helical Assemblies.

Composite, helical nanostructures formed using cooperative interactions of liquid crystals and Au nanoparticles were studied using a scanning transmission electron microscopy (STEM) mode. The investigated helical assemblies exhibit long-range hierarchical order across length scales, as a result of the crystallization (freezing) directed growth mechanism of nanoparticle-coated twisted nanoribbons and their ability to form organized bundles. Here, STEM methods were used to reproduce the 3D structure of the Au nanoparticle double helix.

Twisted Molecular Nanoribbons with up to 53 Linearly-Fused Rings.

The synthesis of three molecular nanoribbons with a twisted aromatic framework is described. The largest one shows a 53 linearly fused rings backbone (12.9 nm) and 322 conjugated atoms in its aromatic core (C296N24S2). This new family of nanoribbons shows extremely high molar absorptivities, reaching 986 100 M-1 cm-1, and red-emitting properties.

Nanoribbons of discotic liquid crystal molecules

Discotic liquid crystal molecules are interesting not only due to their mesophases as a function of temperature but also due to their potential to self-assemble into nanostructures. In this article, we facilitate the self-assembly of triphenylene based discotic liquid crystal (TP) molecules in solvent medium to obtain nanoribbons. The flat nanoribbons undergo a morphological transformation to twisted helical nanoribbons due to incorporation of silver nanoparticles. The electrical characterization by measuring current–voltage (I-V) curves from flat and twisted nanoribbons indicated semiconducting behavior. The charge transfer is governed by the classical hopping mechanism. The activation energy reduces due to incorporation of silver nanoparticles in the liquid crystal matrix. The lowest activation energy was found for a doped system of 0.1 wt%.

Chiral optical scattering from helical and twisted silica nanoribbons.

Helical and twisted silica nanoribbons, deposited in an in-plane direction and with a random orientation, on a quartz substrate showed chiral optical scattering, and the helical nanoribbons had a g-factor of the order of 10-2 below 250 nm. Their signs depend on the handedness of the nanohelices. The effect of the morphology and the orientation of the helices on the chiral optical scattering were investigated with simulations via the boundary element method.

Self-assembly of virulent amyloid-derived peptides into nanoantibacterials.

Current strategies for the design of antibacterial peptides show limitations in the development of assembled antibacterial peptides due to the challenges in simultaneously balancing the antibacterial activity and assembling behavior. Herein, we report on one strategy for the design of antibacterial peptides derived from virulent amyloids and investigate their self-assembly into nanostructures with remarkable antibacterial activity. The peptides were either directly truncated from virulent amyloid peptide PSM α3 or mutated from the original sequence by replacing the lysine and phenylalanine residues with arginine or tryptophan, leading to three undecapeptides. Conformational and morphological results indicated the formation of nanotubes and twisted nanoribbons by the truncated peptide and the mutated peptide, respectively, predominately driven by anti-parallel β-sheets. Bacterial culturing experiments revealed that the two mutated peptides possessed remarkable antibacterial activity against both Gram-positive and Gram-negative bacteria by disrupting the bacterial membrane at a concentration above their critical aggregation concentrations, thus leading to two nanoantibacterials. Our findings demonstrate that biomimetic peptides originated from virulent amyloids exhibit great potential in the development of assembled antibacterial peptides, thus providing a new strategy for simultaneously addressing the antibacterial activity and pharmacokinetics of natural antibacterial peptides in the future.

Twistons in graphene nanoribbons on a substrate

Twisted nanoribbons from two-dimensional materials possess many unusual properties tunable by changing the twist angle, for example, electro- and thermal conductivity, chemical properties, and stability against buckling. New interesting phenomena can be observed when a twisted nanoribbon interacts with a substrate. Here we report the results of a classical molecular dynamics study of a graphene nanoribbon twisted about its long axis and interacting with a graphite substrate. Van der Waals interactions with the substrate lead to localization of twisting and the formation of topological solitons called twistons. The topological charge of a twiston obtained with the twist angle $\ensuremath{\beta}$ multiple of $\ensuremath{\pi}$ can be defined as $q=\ensuremath{\beta}/\ensuremath{\pi}$; it can be positive or negative. Twistons can move along the nanoribbon with very little radiation in the form of small-amplitude phonons. Scenarios of twiston collisions are described depending on their topological charge and on the nanoribbon width. In narrow nanoribbons twistons collide practically elastically, preserving their profiles and speeds after the collision, and inelasticity of collisions increases with increasing nanoribbon width. Our results contribute to an understanding of the behavior of two-dimensional material nanoribbons on a substrate.

Twisting of graphene nanoribbons partially located on flat substrates

The molecular dynamics simulation of longitudinal twisting of graphene nanoribbons hanging from the edge of a flat substrate formed by the surface of a hexagonal boron nitride crystal has been performed. It has been shown that rotation of the free end of a nanoribbon causes twisting of the suspended region accompanied by monotonous sliding of the nanoribbon over the substrate. At the beginning, a regular screw-like shape is formed in the suspended section, next a super-twisted section emerges inside it, further growth of which occurs due to pulling of the nanoribbon from the substrate. After separation from the substrate, the twisted nanoribbon folds into a roll, so that further twisting results only in free rotation of the roll.

Molecular packing handedness dominated by the chirality of the lactic acid residue near the liquid crystalline core

ABSTRACT Eight dichiral compounds containing two lactic acid residues and one perfluorocarbon chain are synthesised. Six of them are liquid crystals with an enantiotropic SmA phase. Two of them are liquid crystals with enantiotropic SmA and SmC* phases. Although (R,R)-3 and (R,R)-4 molecules pack in monolayer structures at the crystalline states, (S,R)-3 and (R,S)-4 molecules pack in bilayer structures at the crystalline states. The optical activity of these compounds is mainly controlled by the chirality of the lactic acid residue near the liquid crystalline core. The dichiral compounds can self-assemble into nanotubes or twisted nanoribbons in methanol. Circular dichroism characterisation indicated that the stacking handedness of the liquid crystalline cores in the organic self-assemblies was also dominated by the chirality of the lactic acid residue near the liquid crystalline core.

Nanoribbon self-assembly and hydrogel formation from an N[sbnd]Octanoyl octapeptide derived from the antiparallel β-Interface of a protein homotetramer

The effect of installing different lipid chains (C6, C8, C10, and C16) on the N-terminus of an octapeptide derived from the antiparallel β-interface of the diaminopimelate decarboxylase protein homotetramer has been investigated. Notably, the C8 peptide conjugate assembled into wide twisted nanoribbons and formed hydrogels, which to the best of our knowledge constitutes the first example of a peptide containing an eight carbon alkyl chain that demonstrates these properties, a space typically occupied by peptide amphiphiles with long lipid chains. Furthermore, this self-assembling lipopeptide exhibited pH and temperature stability with shear thinning properties suitable for biomedical applications. Importantly, in this work the application of the polystyrene-based sorbent Diaion™ HP20SS for the simple large-scale purification of self-assembling peptides is presented as an alternative to the use of time-consuming and labor-intensive reverse-phase high-performance liquid chromatography. Statement of SignificancePeptides that can self-assemble into defined nanostructures are highly attractive for many biomedical applications given their unique physical and chemical properties. It is recognized that self-assembling peptides derived from naturally occurring proteins offer an unlimited source of functionalities and structures, which are hard to uncover with designed sequences. In this study, we have investigated the effect of installing different lipids chains on the N-terminus of an octapeptide derived from the antiparallel β-interface of the diaminopimelate decarboxylase protein homo tetramer. We also reported the use of polymeric DiaionⓇ HP20SS beads as an alternative solid support to purify self-assembling peptides.

A Theoretical Study on Charge Transfer of Twisted T-Graphene Nanoribbon Surface

Non-equilibrium Green’s functions (NEGF) combined with tight-binding (TB) model, are utilized to study the charge transport properties of the twisted armchair tetragonal-graphene nanoribbons (ATGNRs). The present work has considered twisted deformation of ATGNR for the different angles. The results revealed that the action of twisting leads to an outstanding effect on the charge transport features of a T-graphene device. It will be stated that bandstructure is reduced by increasing the width of ATGNR. Moreover, I-V characteristics are carefully illustrated and it is proved that the electronic conduction becomes gradually stronger with the twisted angle increasing from 0° to 360° angles. Bandstructure of electrodes, Density of states (DOS), transmission spectrum, the molecular projected self-consistent Hamiltonian (MPSH) and I-V characteristics are discussed thus making the charge transport properties of ATGNR devices elucidated. The obtained results can provide a valuable guideline for designing of T-graphene nanoribbons in developing nano-scale devices.

Peptide interdigitation-induced twisted nanoribbons as chiral scaffolds for supramolecular nanozymes.

Establishing reliable strategies for rationally manipulating the organization of peptide building blocks and thereby precisely creating chiral nanostructures is challenging, while meaningful toward development of advanced functional materials. Here we report on a peptide-interdigitating mechanism for the reliable self-assembly of lipid-inspired amphiphiles (LIPIAs) into robust twisted nanoribbons by grafting domains to one alkyl tail of lipids as an extended element. Peptide interdigitation promoted the self-assembly of LIPIAs into twisted or flat nanoribbons driven by antiparallel or parallel β-sheet hydrogen bonds, respectively, strongly associated with the connecting direction of the incorporated domains. We found that the LIPIAs containing N-terminus-connected domains with either bulky or small side chain groups formed twisted nanoribbons in a broad pH range, thus implying a sequence- and pH-independent strategy for creation of robust chiral nanostructures. Integrating the resulting twisted nanoribbons with gold nanoparticles led to supramolecular nanozymes exhibiting the excellent catalytic activity and enantioselectivity of asymmetric oxidation of 3,4-dihyroxy-phenylalanine molecules. Our finding demonstrates that the peptide-interdigitating mechanism is a reliable strategy for precise creation of chiral nanostructures serving as chiral matrices for supramolecular nanozymes with improved catalytic performance, thus potentially paving the way towards advanced biomimetic systems resembling natural systems.