Unusual Topology Research Articles

Therapeutic Voyage of Graphene-based Biosensor

: The study of carbon-based materials and nanoparticles is currently an exciting field of study in the domain of material science. One of the most prominent of these materials is graphene, along with its related components graphene oxide and reduced graphene oxide. A single-layer, twodimensional nanomaterial called graphene (GN) is employed in many different industries, such as electronics and biology. Graphene is a remarkable two-dimensional substance that has earned the title of "wonder material." Its remarkable electrical, optical, thermal, and mechanical qualities have attracted significant attention. Graphene's intriguing characteristics have led to its integration into numerous biosensing applications. Graphene possesses remarkable chemical, electrical, and physical qualities. The distinctive properties of graphene, particularly its electrical conductivity, large surface area, and significant electron mobility, are focusing more attention on applications in biomedicine that facilitate easier health monitoring. Biosensors with high sensitivity and precision can enhance patient care, and offer an opportunity for an early illness diagnosis and clinical pathogen identification. Additionally, a wide range of biological molecules, including glucose, hydrogen peroxide, cholesterol, dopamine, etc., can be detected using graphene-based biosensors. This study evaluates contemporary developments regarding graphene-based biosensors and their prospects and difficulties in this rapidly developing profession in the coming era. Graphene-based nanomaterials are appropriate to be employed in various biological and sensory contexts, including medicine and gene transfer, because of their unusual topologies and extraordinary properties. Graphene's outstanding characteristics enable biosensing applications to obtain the appropriate sensitivity, selectivity, and repeatability for a range of targets.

A Sodium Germanosilicide with Unusual Network Topology.

The germanosilicide Na4-xGeySi16-y (0.4 ≤ x ≤ 1.1, 4.7 ≤ y ≤ 9.3) was synthesized under high-pressure, high-temperature conditions. The novel guest-host compound comprises a unique tetrel framework with dual channels housing sodium and smaller, empty (Si,Ge)9 units. The arrangement represents a new structure type with an overall structural topology that is closely related to a hypothetical carbon allotrope. Topological analysis of the structure revealed that the guest environment space cannot be tiled with singular polyhedra as in cage compounds (e.g., clathrates). The analysis of natural tilings provides a convenient method to unambiguously compare related tetrel-rich structures and can help elucidate new possible structural arrangements of intermetallic compounds.

Elastic wave spin and unidirectional routing in thin rod systems

The unusual topology of elastic waves in continuum systems has been recently uncovered. Prominently, the spin of Rayleigh-Lamb waves has been experimentally observed and used to achieve the unidirectional wave propagation. In this work, the elastic wave spin in thin rod systems is theoretically predicted and experimentally observed, for all the three basic wave modes, i.e., the zero-order flexural, longitudinal and torsional modes. By elaborately building up the subwavelength chiral sources, the spin-momentum locking has been achieved for these three modes within broad frequency range. Interestingly and surprisingly, the spin-momentum locking occurs for flexural and longitudinal modes in both circular and non-circular thin rods; the spin-momentum locking for torsional modes only exits in non-circular thin rods, due to the warping effect in non-circular cross-section rods. Our results open up the door for elastic wave spin in thin rod systems, and provide general tips for the research on basic modes in diverse thin rods, based on either the continuum media or the artificial metamaterials in future.

A comparative study of nickel and cadmium coordination polymers: Framework topology and proton conductivity

Two new coordination polymers (CPs), [Ni2(dip)2(obb)2]⋅2H2O, and [Cd2(dip)2(obb)2(H2O)]⋅5.5H2O, were successfully synthesized via hydrothermal processes utilizing the organic linkers 4,4′-oxybisbenzoate (obb) and 2,6-di(1H-imidazole-1-yl)pyridine (dip). The unique structures of both CPs were confirmed by single-crystal X-ray diffraction studies. Ni-CP presents an intricate three-fold interpenetrated 3D framework, featuring a rare cag topology centered around dinuclear nodes. In contrast, Cd-CP exhibits a distinctive non-interpenetrated 2D framework with an unusual kIa topology. Despite Cd-CP's water coordination and the inclusion of substantial guest water molecules, it unexpectedly exhibited lower proton conductivity than Ni-CP, which is non-porous and contains much less water content.

RNA recognition by Npl3p reveals U2 snRNA-binding compatible with a chaperone role during splicing

The conserved SR-like protein Npl3 promotes splicing of diverse pre-mRNAs. However, the RNA sequence(s) recognized by the RNA Recognition Motifs (RRM1 & RRM2) of Npl3 during the splicing reaction remain elusive. Here, we developed a split-iCRAC approach in yeast to uncover the consensus sequence bound to each RRM. High-resolution NMR structures show that RRM2 recognizes a 5´-GNGG-3´ motif leading to an unusual mille-feuille topology. These structures also reveal how RRM1 preferentially interacts with a CC-dinucleotide upstream of this motif, and how the inter-RRM linker and the region C-terminal to RRM2 contribute to cooperative RNA-binding. Structure-guided functional studies show that Npl3 genetically interacts with U2 snRNP specific factors and we provide evidence that Npl3 melts U2 snRNA stem-loop I, a prerequisite for U2/U6 duplex formation within the catalytic center of the Bact spliceosomal complex. Thus, our findings suggest an unanticipated RNA chaperoning role for Npl3 during spliceosome active site formation.

Optimal mass variables for semivisible jets

Strongly coupled hidden sector theories predict collider production of invisible, composite dark matter candidates mixed with standard model hadrons in the form of semivisible jets. Classical mass reconstruction techniques may not be optimal for these unusual topologies, in which the missing transverse momentum comes from massive particles and has a nontrivial relationship to the visible jet momentum. We apply the artificial event variable network, a semisupervised, interpretable machine learning technique that uses an information bottleneck, to derive superior mass reconstruction functions for several cases of resonant semivisible jet production. We demonstrate that the technique can extrapolate to unknown signal model parameter values. We further demonstrate the viability of conducting an actual search for new physics using this method, by applying the learned functions to standard model background events from quantum chromodynamics.

Four Cd(II)-CPs as dual-responsive luminescent probes for the sensing of Co2+/Hg2+ and chlortetracycline

Four new ternary Cd(II) coordination polymers (CPs) based on rarely-used 2-(pyridin-2-yl)-1-(pyridin-3-ylmethyl)-1H-benzo[d]imidazole (L) were synthesized via hydrothermal method, namely {[Cd(L)(H2DOBDC)]·H2O}n (1), {[Cd(L)(TP)]·2H2O}n (2), [Cd2(L)(DCTP)2(H2O)]n (3) and {[Cd2(L)(NDA)2]·H2O}n (4) (H4DOBDC = 2,5-dihydroxy terephthalic acids, H2TP = terephthalic acid, H2DCTP = 2,5-dichloroterephthalic acid and H2NDA = 1, 4-naphthalenedicarboxylic acid). 1 and 2 are 4-connected 2D sql layers, in which 2 is further expanded into a 3D supramolecular network by π − π stacking interaction, while 3 and 4 exhibit three-dimensional frameworks with unusual topology. 1 and 3/2 and 4 can act as dual-functional fluorescent sensors for the sensing of Hg2+/Co2+and chlortetracycline (CTC) with response times of 30 s for Hg2+/Co2+ and 20 s for CTC, respectively, in which 2 and 3 as promising fluorescence probes for analytes with detection limits of 1.44 and 0.91 μmoL/L, 3.34 and 0.66 μmoL/L, respectively. The fluorescence sensing mechanism was discussed in detail.

Beyond the Limits of Atropochirality: Design of Highly Conformationally Restrained Biaryls with Bridgehead Phosphine Oxide.

In the last three decades, reacting sterically congested ortho-substituted arenes to form atropochiral biaryls is an appealing venture and a challenging subject that has garnered significant attention. Therefore, there is interest in developing methods to prepare these compounds. In this study, an efficient approach to produce a new class 2,2' disubstituted biaryls bridgehead phosphine oxides with an unusual topology and exceptional conformational stability is presented. Our methodology demonstrates that depending on the substitution pattern on the aryl moieties, the methanophosphocine backbone could be rigid enough to observe a double atropochirality, resulting in an under covered class of molecules. Notably, our studies revealed that replacing only one hydrogen at the ortho position by a fluorine atom led to sufficiently restricted rotation at temperatures below 80 °C, extending "far away" the limits of atropostability. Finally, our investigations, which employed variable-temperature NMR spectroscopy and DFT calculations, yielded unique insights into the isomerisation mechanism, indicating that the two biaryl motifs are fully independent in spite of their proximity.

Water-Soluble Pd6L3 Molecular Bowl for Separation of Phenanthrene from a Mixture of Isomeric Aromatic Hydrocarbons.

Phenanthrene is a high-value raw material in chemical industries. Separation of phenanthrene from isomeric anthracene continues to be a big challenge in the industry due to their very similar physical properties. Herein, we report the self-assembly of a water-soluble molecular bowl (TB) from a phenothiazine-based unsymmetrical terapyridyl ligand (L) and a cis-blocked 90° Pd(II) acceptor. TB featured an unusual bowl-like topology, with a wide rim diameter and a hydrophobic inner cavity fenced by the aromatic rings of the ligand. The above-mentioned features of TB allow it to bind polyaromatic hydrocarbons in its confined cavity. TB shows a higher affinity for phenanthrene over its isomer anthracene in water, which enables it to separate phenanthrene with ∼93% purity from an equimolar mixture of phenanthrene and anthracene. TB is also able to extract pyrene with around ∼90% purity from an equimolar mixture of coronene, perylene, and pyrene. Moreover, TB can be reused for several cycles without significant degradation in its performance as an extracting agent. This clean strategy of separation of phenanthrene and pyrene from a mixture of hydrophobic hydrocarbons by aqueous extraction is noteworthy.

Three robust Zn(Ⅱ)-coordination polymers as dual-responsive chemosensors for efficient sensing of enrofloxacin and acetylacetone

Designing efficient and stable non-precious coordination polymers remains a challenge for the luminescent sensing of enrofloxacin and acetylacetone. Three Zn(Ⅱ)-coordination polymers with the formula {[Zn2(L)(BTC)(OH)]·H2O}n (1), [Zn1.5(L)(MIP)(OH)]n (2) and [Zn(L)(DBT)]n (3); L = 2-(2-Pyridin-3-yl-vinyl)-1H-benzimidazole, H3BTC = 1,3,5-benzene tricarboxylic acid, H2MIP = 5-methylisophthalic acid, and H2DBT = 2,5-dibromoterephthalic acid were hydrothermally synthesized and characterized. 1 reveals an unusual 3D topology, 2 displays a 3D mog framework, while 3 exhibits (4,5)-connected 3D xah framework. 1∼3 are firstly dual-functional luminescence sensors for detecting enrofloxacin and acetylacetone, expressing high selectivity and sensitivity. Quick and visual detection of enrofloxacin and acetylacetone without any pretreatment is realized by using CP 1∼3 paper-based sensors. Furthermore, the fluorescence sensing mechanism was discussed in detail.

High Proton Conductivity of a Bismuth Phosphonate Metal–Organic Framework with Unusual Topology

Despite the interest in proton exchange membrane (PEM) technologies (fuel cells and electrolyzers) for energy applications, the low stability of the electrolyte materials under working conditions (i.e., humidity and temperature) is one of their major limitations. Metal–organic frameworks (MOFs) have recently emerged as promising electrolytes due to their higher stability compared with the currently applied organic polymers, proton conductivity, and outstanding porosity. Here, a novel robust Bi phosphonate MOF (branded as IEF-7) was successfully synthesized and fully characterized, exhibiting an unusual topology due to the irregular coordination geometry of the bismuth cations. Furthermore, IEF-7 exhibited potential porosity, very high chemical and thermal stability, and free −PO3H groups involved in its ultrahigh proton conductivity, reaching 1.39 × 10–2 S cm–1 at 90 °C and 90% relative humidity for, at least, 3 cycles. In order to improve the consolidation and shaping of the powder for testing its ion conductivity properties, a highly MOF-loaded composite (90 wt %) was prepared by adding a proton conductive sulfonated polysulfone binder. The proton conductivity of the resulting composite was in the same order of magnitude as the compacted MOF powder, making this polymeric composite electrolyte very promising for PEM technologies.

Why and how could an aliphatic bridge allow for a long-range photoinduced charge separation in Tröger’s bases derivatives

Tröger’s bases (TBs) have shown great potential to be used in different fields of science, such as biology, organic synthesis, photoelectronic applications, among others. As we have recently shown, a series of asymmetrically substituted Tröger’s base derivatives showed unexpected pull–push behavior. The aliphatic diazocine heterocycle which connect an electron donor and an electron acceptor moiety efficiently couples both electronic subsystems as if it were a typical π-conjugated linker. A thorough computational study was intended to shed light on the origin of the observed photophysical properties. A modified version of the CAM-B3LYP functional yielded an accurate prediction of the absorption and emission spectra of these species. In contrast, range-corrected and classical hybrid approaches showed too high and remarkably too low excited states energies, respectively.Unlike the typical π-linked donor/acceptor systems, a threshold was found in the redox gap of the centers in order to obtain a full charge separation. The role of the aliphatic bridge was found to be related to the unusual topology of the frontier orbitals involved, to the tension and particular molecular shape of the Tröger bicycle and to a contribution due to homoconjugation as well. Calculations on the actual Tröger derivatives and specific models were able to quantify the magnitude of the different contributions that make possible the charge separation.

Emissive Substoichiometric Covalent Organic Frameworks for Water Sensing and Harvesting.

Emissive covalent organic frameworks (COFs) have recently emerged as next-generation porous materials with attractive properties such as tunable topology, porosity, and inherent photoluminescence. Among the different types of COFs,substoichiometric frameworks (so-called Type III COFs) are especially attractive due to the possibility of not only generating unusual topology and complex pore architectures but also facilitating the introduction of well-defined functional groups at precise locations for desired functions. Herein, the first example of a highly emissive (PLQY 6.8%) substoichiometric 2D-COF (COF-SMU-1) featuring free uncondensed aldehyde groups is reported. In particular, COF-SMU-1 features a dual-pore architecture with an overall bex net topology, tunable emission in various organic solvents, and distinct colorimetric changes in the presence of water. To gain further insights into its photoluminescence properties, the charge transfer, excimer emission, and excited state exciton dynamics of COF-SMU-1 are investigated using femtosecond transient absorption spectroscopy in different organic solvents. Additionally, highly enhanced atmospheric water-harvesting properties of COF-SMU-1 are revealed using FT-IR and water sorption studies.The findings will not only lead to in-depth understanding of structure-property relationships in emissive COFs but also open new opportunities for designing COFs for potential applications in solid-state lighting and water harvesting.

Uncovering Topological Edge States in Twisted Bilayer Graphene.

Twisted bilayer graphene (t-BLG) has recently been introduced as a rich physical platform displaying flat electronic bands, strongly correlated states, and unconventional superconductivity. Studies have hinted at an unusual Z2 topology of the moiré Dirac bands of t-BLG. However, direct experimental evidence of this moiré band topology and associated edge states is still lacking. Herein, using superconducting quantum interferometry, we reconstructed the spatial supercurrent distribution in t-BLG Josephson junctions and revealed the presence of edge states located in the superlattice band gaps. The absence of edge conduction in high resistance regions just outside the superlattice band gap confirms that the edge transport originates from the filling of electronic states located inside the band gap and further allows us to exclude several other edge conduction mechanisms. These results confirm the unusual moiré band topology of twisted bilayer graphene and will stimulate further research to explore its consequences.

Vps68 cooperates with ESCRT-III in intraluminal vesicle formation.

The endosomal sorting complex required for transport (ESCRT)-III mediates budding and abscission of intraluminal vesicles (ILVs) into multivesicular endosomes. To further define the role of the yeast ESCRT-III-associated protein Mos10 (also known as Vps60) in ILV formation, we screened for new interaction partners by using stable isotope labeling of amino acids in cell culture (SILAC) and mass spectrometry. Here, we focused on the newly identified interaction partner Vps68. Our data suggest that Vps68 cooperates with ESCRT-III in ILV formation. The deletion of VPS68 caused a sorting defect similar to that of the SNF7 deletion strain when the cargo load was high. The composition of ESCRT-III was altered, the level of core components was higher and the level of associated proteins was lower in the VPS68 deletion strain. Our data further indicate that at some point in the functional cycle of ESCRT-III, Snf7 could be replaced by Mos10. Vps68 has an unusual membrane topology. Two of its potential membrane helices are amphipathic helices that localize to the luminal side of the endosomal membrane. Based on this membrane topology, we propose that Vps68 and ESCRT-III cooperate in the abscission step by weakening the luminal and cytosolic leaflets of the bilayer at the abscission site.

Tailoring higher-order topological phases via orbital hybridization

Higher-order topological insulators (HOTIs) have attracted much attention in photonics due to the tightly localized disorder-robust corner and hinge states. Here, we reveal an unconventional HOTI phase with vanishing dipole and quadrupole polarizations. This phase arises in the array of evanescently coupled waveguides hosting degenerate $s$- and $d$-type orbital modes arranged in a square lattice with four waveguides in the unit cell. As we prove, the degeneracy of the modes with the different symmetry gives rise to the nontrivial topological properties rendering the system topologically equivalent to the two copies of the anisotropic two-dimensional Su-Schrieffer-Heeger model rotated by ${90}^{\ensuremath{\circ}}$ with respect to each other and based on $s\ifmmode\pm\else\textpm\fi{}d$ hybridized orbitals. We probe the unusual topology of the model by constructing a quantized Fu-Kane-type pseudospin pump. Our results introduce a route to tailor higher-order band topology leveraging both crystalline symmetries and accidental degeneracies of the different orbital modes.

Synthesis, structure and luminescent properties of Zn(II) metal–organic frameworks constructed by flexible and rigid ligands

The synthesis of new coordination polymers based on flexible ligands is a challenging task. The use of two types of ligands is a possible approach to obtain crystalline compounds. The combination of flexibility and rigidity can lead to unusual topologies and properties. We are managed to obtain two new metal–organic frameworks (MOFs) based on flexible 1,3-bis(2-methylimidazolyl)propane and rigid isophtalic (1,3-benzenedicarboxylic) acid: [Zn2(iph)2(bmip)2] (1) and [Zn4(iph)4(bmip)3]·2DMF·3.5H2O (2). Structure of both compounds were determined by single-crystal X-ray analysis. Compound 1 is 3-fold interpenetrating 3D framework with dmp topology. Compound 2 is 2-fold interconnecting 3D framework with rare topology, described as (4,6)-c net. Compound 2 contains guest DMF and water molecules. Interestingly, compound 2 easily loses guest molecules in air and undergoes to another crystalline compound 2a. The photoluminescence at room temperature of the compounds 1 and 2a were investigated in the solid state. Quantum yields (QY) of luminescence for 1 and 2a are 30.5% and 39.8%, respectively. The short decay times are allowed to attribute the emission to fluorescence characteristic for intraligand transitions.

An Adaptable Water-Soluble Molecular Boat for Selective Separation of Phenanthrene from Isomeric Anthracene.

Anthracene crude oil is a common source of phenanthrene for its industrial use. The isolation of phenanthrene from this source is a challenging task due to very similar physical properties to its isomer anthracene. We report here a water-soluble Pd(II) molecular boat (MB1) with unusual structural topology that was obtained by assembling a flexible tetrapyridyl donor (L) with a cis-Pd(II) acceptor. The flexible backbone of the boat enabled it to breathe in the presence of a guest optimizing the fit within the cavity. The boat binds phenanthrene more strongly than anthracene, which enabled separation of phenanthrene with an >98% purity from an equimolar mixture of the two isomers using MB1 as an extracting agent. MB1 represents a unique example of a coordination receptor suitable for selective aqueous extraction of phenanthrene from anthracene with reusability of several cycles.

On‐Surface Synthesis of [3]Radialenes via [1+1+1] Cycloaddition

[3]Radialenes are the smallest carbocyclic structures with unusual topologies and cross-conjugated π-electronic structures. Here, we report a novel [1+1+1] cycloaddition reaction for the synthesis of aza[3]radialenes on the Ag(111) surface, where the steric hindrance of the chlorine substituents guides the selective and orientational assembling of the isocyanide precursors. By combining scanning tunneling microscopy, non-contact atomic force microscopy, and time-of-flight secondary ion mass spectrometry, we determined the atomic structure of the produced aza[3]radialenes. Furthermore, two reaction pathways including synergistic and stepwise are proposed based on density functional theory calculations, which reveal the role of the chlorine substituents in the activation of the isocyano groups via electrostatic interaction.

On-Surface Synthesis of [3]Radialenes via [1+1+1] Cycloaddition.

[3]Radialenes are the smallest carbocyclic structures with unusual topologies and cross-conjugated π-electronic structures. Here, we report a novel [1+1+1] cycloaddition reaction for the synthesis of aza[3]radialenes on the Ag(111) surface, where the steric hindrance of the chlorine substituents guides the selective and orientational assembling of the isocyanide precursors. By combining scanning tunneling microscopy, non-contact atomic force microscopy, and time-of-flight secondary ion mass spectrometry, we determined the atomic structure of the produced aza[3]radialenes. Furthermore, two reaction pathways including synergistic and stepwise are proposed based on density functional theory calculations, which reveal the role of the chlorine substituents in the activation of the isocyano groups via electrostatic interaction.