Twisted Structure Research Articles

An Ir (III) complex with multiphoton absorption in the near-infrared region as a probe for mtDNA-specific recognition and mitochondrial imaging

The multiphoton absorbing (MPA) materials have been extensively investigated due to their crucial merits of long wavelength excitation and short wavelength emission, of which the organometallic complexes are the most promising but still challenging candidates for developing efficient MPA materials. Herein, a novel cyclometallated iridium complex (abbreviated as SQ) is reported as a multiphoton absorption phosphorescent probe, which is constructed by coordinating the central metal Ir with diethoxyphenyl terpyridine, phenyl pyridine and SCN ligands. The single crystal of SQ exhibits a twisted octahedral structure that can avoid phosphorescence quenching caused by π-π stacking, and the push-pull electron effect of the ligand endows SQ with excellent nonlinear optical (NLO) properties under near-infrared excitation. As a result, two-photon imaging with deep tissue penetration depths is realized at the excitation wavelength of 750 nm. Meanwhile, the planar conjugated structure of diethoxyphenyl terpyridine facilitates the insertion of SQ into base pairs of mitochondrial DNA (mtDNA), thus limiting the intramolecular rotation. Consequently, the emission intensity of the SQ solution enhanced approximately 10-fold after mtDNA was introduced, which led to mtDNA-specific recognition. Our work proves a new way of designing a phosphorescence probe that can specifically identify mtDNA, thus realizing dynamic monitoring of mitochondria.

Mesoscale modeling of woven composite twisted structures combining digital element embedded model and affine transform

The mesoscale model with realistic yarn geometries could improve the accuracy of property prediction of woven composite structures. This paper aims to propose a novel mesoscale modeling method for the woven composite twisted structures. Firstly, the torsional deformation of the yarns in the unit cell model is simulated with high-fidelity using digital element fibers embedded into the matrix solid meshes. Then, the solid geometry model of the twisted composite structures is reconstructed from the digital element deformation model by combining the affine transforms. Finally, the elastic responses of the twisted composite structure under cantilever loading are predicted by assigning the element information of the established mesoscale model to the macroscale model. It is shown that the geometric morphology and predicted mechanical responses of the high-fidelity model are consistent with the experimental results. Furthermore, the effect of twist angles on the stiffness properties of the twisted composite structures is analyzed using the presented numerical method. The proposed digital modeling method could provide a guide for the early design of woven composite structures.

Ultraviolet Organic Laser from Rhombus Microcrystal: Benefits of Single-Molecule Emission from Twisted Structure.

Light-emitting molecular crystals with efficient emission behavior are crucial for fabricating low-threshold ultraviolet organic lasers. Herein, we demonstrated a rhombus microcrystal from a fluorene-based conjugated molecule (CL-1) with robust emission behavior for an ultraviolet organic laser. Due to the synergistic effect of twisted intramolecular conformation and weak π-interaction, the CL-1 single crystal showed an extremely high photoluminescence quantum yield (PLQY) of ∼82%, due to their single-molecule excitonic behavior. Considering the diverse noncovalent interactions, CL-1 molecules easily self-assembled into the rhombus microcrystals. Finally, a low-threshold ultraviolet organic laser was fabricated with a sharp emission at 379 nm, attributed to the 0-1 vibration band of a single CL-1 molecule, also further confirming the single twisted-molecule emission in crystal states. Precisely controlling the intramolecular twisted structure and intermolecular interaction of organic conjugated molecules is a precondition to obtain robust ultraviolet emission for optoelectronic applications.

Topological Bistability of the π-System in a Helicene Carbon Nanohoop

AbstractMolecules with a π-system that can be mapped onto a Möbius strip may display Möbius aromaticity. Such molecules are difficult to synthesize because they have a twisted structure. Recently, we combined chiral [6]helicene and fluorescent [7]cycloparaphenylene, and synthesized the first helicene para-phenylene ([6,7]HPP) carbon nanohoop. We have demonstrated that this design strategy ultimately provides a Möbius topology of the molecular π-electron system and, therefore, offers the potential to study Möbius aromaticity experimentally. In addition, the synthesized nanohoop exists as a mixture of conformers in solution. Some of the conformers possess a different orientability of their π-systems, i.e., they differ in their topology. As a result, the recorded circularly polarized luminescence of isolated enantiomers displays both left- and right-handedness of the emitted light, each emanating from a conformer with a different π-system topology. Therefore, [6,7]HPP provided the first experimental evidence of such topological bistability in carbon nanohoops.

Proton exchange membrane deriving from sulfonated N-heterocyclic poly(aryl ether ketone)s containing ether-free proton conducting units and performing enhanced physicochemical stability and conduction properties

Sulfonated aromatic polymer proton exchange membranes suffer from the trade-off relationship between physicochemical stability and proton conductivity hampering the membrane application in fuel cells. To bridge the effect, the high-performance membranes exhibiting excellent proton conduction behavior and good stability are constructed from sulfonated N-heterocyclic poly(aryl ether)s designed elaborately, in which the hydrophilic units are constructed by combining the high-density pendant benzenesulfonic groups and biphthalazindione structures without the introduction of weak linkage units like ether bonds. The twisted heterocyclic structures and the multiple interactions between heterocyclic structures and sulfonic groups enhance the physical stability and proton-conduction behavior with the highest conductivity of 256 mS cm−1 for the membranes. The membranes perform rupture time between 3.9 and 7.1 h in high temperature Fenton's oxidation test, exhibiting good chemical stability. The cells loading the membranes perform the maximum power density between 1.08 and 2.30 W cm−2. The above results verify the benefits of constructing ether-free heterocyclic hydrophilic units with high-density proton-conducting groups for the improvement of comprehensive membrane performance.

Wansing's bi-intuitionistic logic: semantics, extension and unilateralisation

ABSTRACT The well-known algebraic semantics and topological semantics for intuitionistic logic ( Int ) is here extended to Wansing's bi-intuitionistic logic ( 2 Int ). The logic 2 Int is also characterised by a quasi-twist structure semantics, which leads to an alternative topological characterisation of 2 Int . Later, notions of Fregean negation and of unilateralisation are proposed. The logic 2 Int is extended with a ‘Fregean negation’ connective ∼ , obtaining 2 In t ∼ , and it is showed that the logic N 4 ⋆ (an extension of Nelson's paraconsistent logic) results to be the unilateralisation of 2 In t ∼ via ∼ . The logic 2 In t ∼ is also characterised by a Kripke-style semantics, a twist structure semantics and a topological semantics.

Donor–acceptor hetero[6]radialene-based three-dimensional covalent organic frameworks for organic pollutant adsorption, photocatalytic degradation, and hydrogen production activity

By investigating the effects of electron donor topology and the hetero[6]radialene structure on the 3D COF photocatalytic activity, a twisted BF structure was found to improve organic pollutant degradation and water hydrogen production.

Structures and energies of twist grain boundaries in Mg[formula omitted]SiO4 forsterite

In this work, we investigate twist grain boundary (GB) energies and structures in Mg2SiO4 forsterite using atomistic simulations. We first present a new bond orientational order parameter allowing to highlight disordered regions in this low-symmetry crystal for which classical visualization tools are ineffective. Then we examine three GB planes, (010), (120) and (001), corresponding to the most favorable free surfaces of this crystal. We show that twist GB follow the same energy ordering as corresponding free surfaces. In addition, except for some misorientation angles and for the (120) GB plane, GB energies and structures are quite insensitive to microscopic translational degrees of freedom. The dislocation composition of low-angle twist GB can be related to γ-surfaces in the corresponding planes, and are in good agreement with first-principle calculations. It is also shown that the dislocation core structures in low angle twist GB can strongly differ from the ones of intracrystalline dislocations.

Fluorescence quenching of deprotonated phenylurea through twisting motion induced by an electron-donating substituent group.

The excited-state proton transfer (ESPT) reaction between anthracen-2-yl-3-phenylurea (PUA) derivatives and tetrabutylammonium acetate (TBAAc) in dimethyl sulfoxide (DMSO) solvent was theoretically investigated using time-dependent density functional theory. The electron-donating methoxy group (OMe) and electron-withdrawing trifluoromethyl group (CF3) were bonded to 2PUA to form OMe-2PUA and CF3-2PUA, respectively. Two hydrogen bonds formed in the 1 : 1 hydrogen-bonded complexes between the 2PUA derivative and acetate ion (AcO-), namely N1-H1⋯O1 and N2-H2⋯O2. Strong charge transfer (CT) due to the electron-donating OMe group led to H1 transfer in the S1 state for the OMe-2PUA:AcO- hydrogen-bonded complex. On the contrary, weak CT due to the electron-withdrawing CF3 group led to H2 transfer in the S1 state for CF3-2PUA. After the ESPT reaction, the binding energies of the hydrogen-bonded complexes strongly decreased in both cases, and this promoted the separation of contact-ion pairs (CIPs*) and formed different types of anionic species. CF3-2PUA- could keep its nearly planar structure in the S1 state and emit "abnormal" fluorescence. On the other hand, the anionic OMe-2PUA- underwent a twisting motion to form a twisted structure in the S1 state with very low energy, and this led to a rapid internal conversion (IC) to quench long-wave fluorescence in the emission spectra.

Carbones - A Classification on the Magnetic Criterion.

Carbones (carbodiphosphoranes, bent allenes and chalcogen-stabilized carbones) bear the same resonance contributor X+ -C2- -Y+ (X+ , Y+ =PR3 + , CR2 + , SR2 + , SeR2 + , S+ R2 =NR) and exhibit unique bonding and donating properties at the central carbon atom. A classification is given on basis of both the geometry and the magnetic properties (13 C chemical shift of the central carbon atom and the spatial magnetic properties, through-space NMR shieldings (TS NMRSs), actually the anisotropy effect or the ring current effect of aromatic species). TS NMRS values have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The synergy of geometry (linear or bent, orthogonal or twisted structures) and NMR characteristics (extend of the high field shift of the central carbon atom, anisotropy effect of the allene-like C=C double bonds or the ball-like anisotropy effect of carbone-like central carbon atom) provides a comprehensive picture of the dominating resonance contributor.

Synergistic actuation performance of artificial fern muscle with a double nanocarbon structure

Electrochemically powered carbon nanotube (CNT) yarn muscles are of increasing interest because of their advantageous features as artificial muscles. They are light, and have high electrical properties, mechanical strength, and chemical stability. Twist-based CNT yarn muscles show superior actuation performance: 30 times the work capacity and 85 times the power density of natural muscles. Despite achieving these high performances, there is still potential for performance improvement because their twisted structure is not fully utilized. In particular, designing a cross-sectional structure that allows ions to freely enter and exit the twisted structure of the yarn muscle is necessary. Here, we propose highly enhanced artificial muscles with high chemical stability that consist of only nanocarbon materials of carbon nanoscroll (CNS) and twisted CNT yarns. The CNS/CNT yarn muscles (CCYM) can improve the ion accessibility and utilization of the twist structure. The maximum contractile stroke, work capacity, power density, and energy conversion efficiency of the CCYM were 20.11%, 2.26 J g−1, 0.53 W g−1, and 3.39%, which are 1.4-, 1.4-, 4.8, and 4.3 times that of the pristine CNT yarn muscles, respectively. The effects of CNS on CCYM were confirmed by experimental and theoretical analyses. Additionally, in a solid electrolyte, which opens up new application possibilities, the CCYM demonstrates high actuation performance (16.38%) with very low input energy.

Waste silk selvedge/glass fiber reinforced strip-shaped composite: A critical assessment of twisting and dyeing of silk on mechanical properties

With about 11 million tons of waste silk produced each year, waste silk reinforced composites are an important way of high-value utilization. However, the mechanical stability of waste silk reinforced composites remains to be further studied. In this study, we evaluate the flexural and impact properties of waste silk selvedge/glass fiber reinforced strip-shaped composites with different twisting and dyeing structures. The findings reveal that both twisting and dyeing of silk negatively affect the mechanical properties. The twisting structure introduces yarn discontinuity, leading to a 33 % reduction in impact strength. The dyeing process disrupts silk's β-sheet structure, causing a more disordered β-strand structure and a decrease in flexural strength from 448.4 MPa to 412.4 MPa. Further, we determined that untwisting and undyeing waste silk selvedges are suitable for impact-critical application such as automotive bumper. While the twisting and dyeing waste silk selvedges are suitable for non-structural applications requiring aesthetic appeal, such as automotive interiors.This study identifies critical factors influencing mechanical properties of waste silk reinforced composites, benefiting their engineering applications.

Triple B←N Lewis Pair-Functionalized Triazatruxenes with Large Stokes Shifts.

A novel class of multiple B←N Lewis pair-functionalized polycyclic aromatic hydrocarbons with different BR2 groups (R = Cl or Et) directly attached at positions 1, 6, and 11 of triazatruxene was synthesized. The triazatruxene backbone of 4 displays a bowl shape, and its molecular skeleton shows a highly twisted propeller-like structure with C3 symmetry. The introduction of B←N Lewis pairs not only results in a large decrease in the HOMO-LUMO gap but also lowers the LUMO to -3.00 eV. Both compounds show excellent stability with large Stokes shifts of ≤8234 cm-1 and solvatochromic emission in solvents of different polarities.

A Conformationally Stable π-Expanded X-Type Double Helicene Comprising Dihydropyracylene Units with Multistage Redox Behavior.

A π-expanded X-type double [5]helicene comprising dihydropyracylene moieties was synthesized from commercially available acenaphthene. X-ray crystallographic analysis revealed the unique highly twisted structure of the compound resulting in the occurrence of two enantiomers which were separated by chiral HPLC, owing to their high conformational stability. The compound shows strongly bathochromically shifted UV/vis absorption and emission bands with small Stokes shift and considerable photoluminescence quantum yield and circular polarized luminescence response. The electrochemical studies revealed five facilitated reversible redox events, including three reductions and two oxidations, thus qualifying the compound as chiral multistage redox amphoter. The experimental findings are in line with the computational studies based on density functional theory pointing towards increased spatial extension of the frontier molecular orbitals over the polycyclic framework and a considerably narrowed HOMO-LUMO gap.

Energy Conversion by a Twisted Magnetic Structure at Magnetopause Boundary Layer: MMS Observations

AbstractThe Earth's magnetopause is an ion‐scale boundary that separates the magnetosphere from the shocked solar wind. At such boundary, energy‐conversion processes frequently occur. Previous studies suggested that such energy conversions are related to the magnetic reconnection process. Here, we report a new mechanism that the coaction between the twisted magnetic structure and lower‐hybrid waves can also drive energy conversion (J⋅ E, J is current density and E is electric field) at the magnetopause boundary layer, by using high‐resolution measurements of the four Magnetospheric Multiscale spacecraft. We find that such energy conversion is efficient (with magnitude up to 20 nW/m3) and is attributed to an intense current filament (j ≈ 3,800 nA/m2) and a fluctuating electric field driven by lower‐hybrid waves. With the help of the First‐Order Taylor Expansion method, we find that the intense current filament is driven by a twisted magnetic structure at electron scale. Our study improves the understanding of energy‐conversion processes at the Earth's magnetopause.

Molecular design and synthesis of highly soluble hole transporting materials based on phenylnaphthalene cores for solution-processible OLEDs

Highly soluble small molecules are crucial to realizing large-area solution-processible organic light-emitting diodes with consistent performance. In this study, a series of solution-processable hole transporting materials (HTMs) based on 1,4- and 2,6-phenylnaphthalene (NP) cores were synthesized. The cores had an asymmetric and twisted structure, which enhanced the solubility and thermal stability of the materials. Density functional theory calculations and MD simulations revealed that the 2,6-NP core exhibited a coplanar core structure, leading to a reduced hole reorganization energy and enhanced hole mobility compared to those of the 1,4-NP core. Furthermore, the 2,6-NP-core materials exhibited a higher solubility than the 1,4-NP-core materials. 2,6-NPNP also exhibited the highest solubility, approximately 50 times higher than that of the commercialized HTM N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB). Remarkably, when 2,6-NPNP was used as the HTM, the turn-on (Von = 2.54 V) and operating voltages (Vop = 5.67 V @ 1000 nit) of the solution-processed OLED were lower than that of the vacuum-deposited device using NPB as the HTM. Furthermore, the external quantum efficiency, current efficiency, and power efficiency of the former were 1.63 %, 4.49 cd A−1, and 3.78 lm W−1, respectively, which were higher than those of NPB.

Promoting intersystem crossing by charge transfer state of dimers for persistent room temperature phosphorescence

Efficient intersystem crossing (ISC) is essential for phosphorescence emission. The charge transfer (CT) state is traditionally constructed by highly twisted donor-acceptor type structures to facilitate the ISC process. However, the highly twisted structural properties limit the diversity of room-temperature phosphorescence (RTP) molecules. By establishing the CT state in the intermolecular dimers structure, the dependence on the distorted donor-acceptor in the single-molecule design can be well eliminated. Based on this strategy, three novel pure organic luminescent molecules with long afterglow and mechanochromic luminescence (MCL) property were designed and synthesized. All of those exhibited triple emission, including prompt fluorescence (PF), delayed fluorescence (DF) and persistent RTP (pRTP) emission. In particular, CzC4-PhCN showed great potential for application in the field of anti-counterfeiting with its ultralong phosphorescent lifetime of 862 ms. Single crystal analysis and theoretical calculation revealed that the formation of CT states of intermolecular dimers effectively reduced ΔEST and promoted ISC process. This study would be highly instructive for realizing efficient ISC process and high-efficiency pRTP emission in pure organic systems.

INFLUENCES OF ALKALI PRETREATMENT ON LYOCELL WOVEN FABRIC PROPERTIES AFTER ABRASION

In this study, alkali pretreatment in various concentrations were applied to Lyocell woven fabrics to decrease the fibrillation tendency of fibers and the influences of alkali pretreatment on tensile and tearing properties of Lyocell fabrics after abrasion were investigated. Alkali pretreatment reduced fibrillation of Lyocell fibers. However, fabric shrinkage occurred because of the increased volume and damaged twisted structure of yarns due to the lateral fiber swelling. The warp/weft densities and crimp ratios increased as the alkali concentrations increased. The breaking and tearing loads of untreated Lyocell fabrics were higher than those of alkali pretreated fabrics since the strength loss caused by alkali pretreatment. The abrasive load caused fiber breakages and fiber entanglements on fabrics and decreased the both breaking and tearing loads. The weave types with long floating interlacements on the fabric surface were more severely damaged by exposing to abrasive load and resulted as higher strength reduction.

Bioinspired hybrid helical structure in lobster Homarus Americanus: Enhancing penetration resistance and protective performance

The high impact and penetration resistance of the cuticle in the lobster Homarus americanus can be attributed to its unique twisted plywood structure. Hybridization of two helical structures was observed in the exoskeleton, with different pitch angles and ply thickness of the exocuticle and endocuticle within the exoskeleton. Given the survival challenges posed by the natural environment, it is worthwhile to study why it evolved into a hybrid helical rather than a uniform helical structure. In light of this, we have proposed an innovative bionic hybrid helical structure design strategy that goes beyond simply reducing the pitch angle. In this paper, we replicated complex biological microstructures by introducing two types of pitch angles and ply thicknesses for regional configurations. Quasi Static Indentation (QSI) full-penetration experiments were conducted. Experimental results revealed that the exocuticle with a large pitch angle and small ply thickness possesses a higher knee load under the penetration test, which provides a higher initial damage threshold. On the other hand, the endocuticle with a small pitch angle and large ply thickness induces higher damage dissipation, which provides superior protective performance. These research findings demonstrate that ply hybridization can be a promising method for microstructure design to improve the penetration resistance of thin laminates and serve as a reference for developing more refined gradient helical structure designs.

Case Report on Rare Case of Isolated Fallopian Tube Torsion

A 28 year old married female presented with complaints of severe right sided pelvic pain associated with nausea and vomiting referred for abdominal sonography. An abdominal ultrasound was done, which demonstrated right adnexal large cystic mass lesion having mobile internal echoes and adjacent twisted structure with positive whirlpool sign. Right ovary is separately visualized showing normal vascularity on Color Doppler. Uterus and left ovary also appeared normal. Computed tomography was done, which revealed well defined thick walled cystic structure in right adnexa and showing progressive narrowing towards right cornu of uterus. On the basis of the patient symptoms & radiological findings a diagnosis of fallopian torsion with hydrosalpinx was made.