Hexatomic Ring Research Articles

Anchoring ability and catalytic activity of B2C2 monolayer as the lithium-sulfur batteries cathode materials: A first principle calculation

Through first-principles calculation, the performance of B2C2 monolayer as the Li-S batteries cathode anchoring material is systematically investigated. The B2C2 monolayer exhibits excellent thermodynamic, kinetic and mechanical stability, which are helpful to resist the volume change caused by the reaction during charging and discharging process. Importantly, the adsorption energy of S8 clusters and LiPSs in the B2C2 monolayer is remarkably higher than that in the cathode electrolyte, which greatly inhibits the generation of shuttle effect. The calculations of the catalytic performance of B2C2 monolayer further suggest that the system possesses a lower the Gibbs free energy (ΔG) barrier of 0.71 eV and a fast kinetic conversion process with low diffusion barrier of 0.257 eV along hexatomic ring B2C4, implying a fast charge and discharge rate and excellent cycle performance. The B2C2 monolayer with high energy conversion efficiency and catalytic activity can be expected as an emerging sustainable clean energy source.

Synthesis, degradation Behavior, and recyclability property of novel bio-based Polyimine thermosets

Given the challenges in recycling, degradation, flammability and environmental protection of most petroleum-based thermosets, it is of great significance to develop degradable, recyclable, and flame-retardant thermosets from renewable feedstocks for material safety and promote sustainable development. Herein, novel Polyimine thermosets (PIts) were prepared from renewable vanillin and their degradation behavior and recyclability properties were systematically investigated. The prepared PIts exhibited excellent thermal properties (Tg: 91–158 °C and T5% above 250 °C), degradability and high monomer recovery rates (above 80 %). Meanwhile, the PIts demonstrated outstanding flame retardancy with a UL-94 V-0 rating achieved by forming noncombustible gas, phosphorus-containing species and nitrogen-containing hexatomic rings. Additionally, these PIts displayed high malleability with Ea ranging from 77.0-118.8 kJ.mol−1 and could be recycled via hot pressing without altering their chemical structure and original mechanical properties. This work presents a new strategy for fabricating bio-based advanced thermosets from renewable resources.

Virtual screening for an ultra-small NIR emitter with only two isolated hexatomic rings

Virtual screening for an ultra-small NIR emitter with only two isolated hexatomic rings

Zinc indium sulfide coupling with graphitic carbon nitride containing non-intrinsic oxygen vacancies to form Z-scheme heterojunction for boosting photodegradation of tetracycline

A novel graphitic carbon nitride containing non-intrinsic oxygen vacancies (Vo-CN) is interfacial coupling with zinc indium sulfide (ZIS) to form Z-scheme heterojunction (VCZ) for efficient tetracycline (TC) degradation. The TC removal rate by VCZ-1 (mass ratio of Vo-CN: ZIS is 1:20, 0.2 g/L) achieves 99.86 %. VCZ-1 reveals outstanding reusability and stability with an unchanged TC degradation rate after undergoing five cycles. VCZ-1 achieves high-efficiency TC degradation in various water matrices. The experimental and DFT calculations indicate that the built-in electric field drives charges on Vo-CN transfer to ZIS, forming a Z-scheme VCZ-1 heterojunction. The strong electronic coupling effect between Vo-CN and ZIS facilitates charge exchange at the heterojunction interface. Non-intrinsic oxygen vacancies in VCZ, as binding sites for electrons and holes, effectively lower the energy barrier for singlet excitons converting to triplet excitons. The triplet excitons are induced to transfer energies to dissolved oxygen and expedite 1O2 production. 1O2 synergizes with •O2– and •OH to attack O-containing groups and hexatomic rings in TC, inducing demethylation, hydroxylation, dihydroxylation, and ring-opening reactions. Three possible degradation pathways are inferred by UPLC/MS/MS and Fukui index of TC. The ecotoxicity evaluation of intermediate products highlights the benefits of VCZ-1 photocatalytic oxidation in ensuring environmental safety. This work proposes a novel idea for constructing efficient Z-scheme photocatalysts for environmental remediation.

Efficient extraction of lithium from alkaline solution using the synergistic extractants ethylhexyl salicylate and trialkylphosphine oxide in kerosene and stripping with acid

Efficient separation of lithium from alkaline solution with high Na/Li ratio is of great importance for the development of batteries for new energy industry. This work proposes the use of a novel extraction system composed of ethylhexyl salicylate (ES) and trialkylphosphine oxide (TRPO). The equilibrium experiment revealed that the order of metal ions extracted by ES/TRPO extraction system is Mg2+ > Ca2+ > Li+ > Na+ > K+. A recovery process including extraction, scrubbing, and stripping was designed to recover lithium from a solution of 3.25 g/L Li, 52 g/L Na and 0.8 mol/L OH−. More than 99% of lithium could be extracted to the organic phase. After stripping, a lithium-rich solution containing 25 g/L Li was obtained, and the system showed good stability in the cycling experiments. The FT-IR analysis and DFT calculation were conducted to investigate the extraction mechanism. The results demonstrated that ES mainly coordinates with metal ions through Ph-O and CO bonds to form a hexatomic ring complex, thereby allowing metal ions to enter the organic phase. The calculated binding energies of the complex are highly consistent with the equilibrium experiment. The present work may provide a novel extraction system to efficiently recover lithium from alkaline solution with high Na/Li ratio.

Room-temperature stable Perillaldehyde—Natural cyclodextrin inclusion complexes: Preparation, characterization, thermal stability, water solubility, antioxidant activity and slow–release performance

The compound Perillaldehyde (PA) is a bioactive constituent found in natural Perilla oil, exhibiting remarkable antibacterial and antioxidant activity. However, the instability of this compound caused by the easy oxidation of its aldehyde and olefin groups imposes limitations on its extensive applications. Therefore, it is crucial to develop effective strategies for enhancing the stability of PA. This study focuses on utilizing a series of natural cyclodextrins (CDs) to synthesize inclusion complexes (ICs) with PA, aiming to improve water solubility and achieve exceptional stability at room temperature, which is essential for their potential applications in biomedicine or food industries. The hydrophobic cavity of CDs can accommodate the hexatomic ring and hydrophobic chains of PA based on the well-known size-matching effect and hydrophobic interaction, thereby forming stable ICs. Additionally, the hydrophilic outer wall of CDs imparts excellent water solubility to ICs. Phase solubility investigations demonstrate successful construction of α-CD-PA IC and β-CD-PA IC with an inclusion ratio of 1:1. Their respective stability constant (KC) are determined as 342 L/mol and 180 L/mol, indicating superior stability for α-CD-PA IC compared to β-CD-PA IC. Conversely, γ-CD with a larger cavity fails to form a stable inclusion complex with PA due to inadequate size matching. Nuclear Magnetic Resonance Hydrogen Spectroscopy (1H and 2D NMR) studies reveal that PA enters the CDs cavity (α-CD or β-CD) from its wide rim with almost the entire molecule being obliquely embedded within it. Thermogravimetry Analysis (TGA) confirm that after inclusion with CDs, PA exhibits expected stability at 25 ℃. Furthermore, CDs-PA ICs demonstrate significantly improved water solubility compared to pure PA along with enhanced antioxidant activity and slow-release performance, rendering them highly favorable for various applications.

Palladium(II)-Catalyzed Tandem γ-C(sp2)-H Arylation and Cyclization for the Construction of Natural Product-Like Polycyclic Fused ortho-Quinone Scaffolds.

Here, we report a novel strategy for the direct construction of polycyclic fused ortho-quinone scaffolds through palladium(II)-catalyzed tandem γ-C(sp2)-H arylation and cyclization of arylglyoxals with aryl iodides. This transformation features unique tandem transient directing of γ-C(sp2)-H arylation and cyclization reaction mode, broad substrate scope, especially for the aromatic substrates containing oxygen and sulfur atoms, and avoiding the common issue of aromatization due to the construction of the hexatomic ring.

Pentatomic carbon ring conjugated nitrogen-doped nanographene

A N-doped nanographene 1 was synthesized. Compared to the hexatomic carbon ring conjugated TB(phen), this study focuses on the effects corresponding to the pentatomic carbon ring conjugation and substituent group of 1 on the physical properties.

Cobalt atom-cluster interactions synergistically enhance the activity of oxygen reduction reaction in seawater

Seawater electrocatalysis is highly desired for a variety of energy storage and conversion systems, such as water splitting and metal fuel cells that directly using seawater as electrolyte. However, the adsorption of chloride ions (Cl−) on active sites of cathodes would worsen the oxygen reduction reaction (ORR) activity and stability, thus lowering the battery performance. In this work, we firstly designed an electrocatalyst model, in which the Co atomic clusters were closely surrounded by satellite Co single atoms on N-doped carbon substrates, designated as Co-ACSAs. The theoretical calculation results suggested that the Co clusters possess stronger Cl− binding energy and acted as pre-adsorption group for Cl−, thus fully exposed Co single atoms as ORR active sites with stronger O2 adsorption energy to promote the oxygen reduction reaction process. Then, we developed an ultrafast high temperature shock strategy to synthesize the Co-ACSAs by controlling the N concentration in carbon substrates. Benefiting from the moderate interacting distance between Co clusters and satellite Co single atoms in Co-ACSAs, the electronic structure of Co clusters and Co single atoms was optimized through the modulation of the interconnected hexatomic ring. As a result, Co-ACSAs exhibit superior ORR activity and durability with on-set and half-wave potentials of 0.885 V and 0.782 V, respectively, and continuously catalyzing for 485 h in seawater electrolyte. The Co-ACSAs-based seawater battery exhibits a discharge voltage of 1.41 V at 5 mA cm−2 and realized stable energy supply for more than 390 h.

The synthesis of MNC5 active site for electrochemical catalysis

Metal-nitrogen-carbon (M-N-C) catalysts with M-Nx (x = 2 or 4) sites on graphene substrate are researched intensively nowadays. However, the simple and repetitive hexatomic ring structure of graphene limits the exploration of novel efficient active sites for catalysis. Herein, a new carbon material, hydrogen-substituted graphdiyne (HsGDY), is designed as the substrate to develop new active sites. Benefiting from the unique sp and sp2 hybridized carbon atoms of HsGDY, aromatic rings in HsGDY can fix Fe single atoms, creating novel FeC6 and FeNC5 active sites. The as-synthesized Fe-N-HsGDY catalyst displays much higher activity than commercial Pt/C and is found to be one of the highest activities among the reported non-noble metal catalysts for oxygen reduction reaction (ORR). FeNC5 site with graphitic-N has been verified experimentally and theoretically as an efficient active site for ORR. Those results indicate that the rational choice of specific substrate materials with novel structures will broaden the path of creating new active sites with efficient activity.

A DFT study on the promising hydrogen storage performance of a light metal atom-decorated ZnO monolayer

The potential H2 adsorption/storage performance of the ZnO monolayer decorated with alkaline or alkaline earth metal atoms was studied using first-principle density functional theory (DFT) calculations. The light metal atom (Li, Na, K, Be, Mg, or Ca) could be atomically dispersed and decorated on the Zn–O hexatomic ring in the ZnO monolayer with high binding energy. Compared to Na-, K-, Be-, Mg-, or Ca-decorated ZnO, Li-decorated ZnO exhibited significantly stronger interactions with H2, resulting in higher adsorption energy, more transferred charges, and stronger orbital hybridizations. On the ZnO decorated with a single Li atom, four H2 molecules could be stored with an average adsorption energy of −0.242 eV. By increasing the two-sided Li coverage to one, three H2 molecules could still be stored on each decorated Li due to space limitations, with an acceptable average adsorption energy of −0.216 eV. As a result, the hydrogen storage capacity of the Li-decorated ZnO monolayer could be successfully and reasonably improved to 6.92 wt%. This study suggests that fully lithiated ZnO may have promising potential as an adsorbent for outstanding hydrogen storage performance.

Elucidation of alpha‐amylase inhibition by natural shikimic acid derivates regarding the infrequent uncompetitive inhibition mode and structure–activity relationship

AbstractThe α‐amylase inhibition and binding behaviors of shikimic acid and its structural analogues were studied. Uncompetitive inhibition characteristic of shikimic acid was identified through several linear transformation equations of enzymatic data considering the good linearity. Interestingly, the change in concentrations of starch would not decrease the inhibitory effects of shikimic acid with various concentrations used in present study. The inhibitory effect reduced greatly after the ethyl esterification of shikimic acid. Gallic acid was distinguished from shikimic acid by a benzene ring and exhibited lower inhibition than shikimic acid. Shikimic acid affected the α‐amylase structure by binding to the non‐active site but did not quench the α‐amylase fluorescent intensity. However, gallic acid anchored with a subsite containing some fluorescent residues at the entrance of active pocket, quenching the fluorescence intensity of α‐amylase strongly. The difference in shikimic acid and gallic acid made the changes in their binding sites as well as the binding behavior. Conclusively, the carboxyl and hexatomic ring with one double‐bond played an important role in binding of shikimic acid with the non‐active sites of α‐amylase. Shikimic acid has potentials as a functional‐factor in α‐amylase inhibition for controlling the postprandial blood sugar level.

Electron doping induced stable ferromagnetism in two-dimensional GdI3 monolayer

As a two-dimensional material with a hollow hexatomic ring structure, Néel-type anti-ferromagnetic (AFM) GdI3 can be used as a theoretical model to study the effect of electron doping. Based on first-principles calculations, we find that the Fermi surface nesting occurs when more than 1/3 electron per Gd is doped, resulting in the failure to obtain a stable ferromagnetic (FM) state. More interestingly, GdI3 with appropriate Mg/Ca doping (1/6 Mg/Ca per Gd) turns to be half-metallic FM state. This AFM–FM transition results from the transfer of doped electrons to the spatially expanded Gd-5d orbital, which leads to the FM coupling of local half-full Gd-4f electrons through 5d–4f hybridization. Moreover, the shortened Gd–Gd length is the key to the formation of the stable ferromagnetic coupling. Our method provides new insights into obtaining stable FM materials from AFM materials.

Two-Dimensional Tri-Hex Carbon: A Promising, Efficient, and Acid-Resistant Photocatalyst for Water Splitting

Photocatalytic hydrogen production via water splitting has been a promising method to produce clean energy and effectively reduce environmental pollution. Herein, a specific bandgap-oriented structure search was performed. A two-dimensional (2D) carbon structure comprising triatomic and hexatomic carbon rings, named 2D tri-hex carbon, was proposed to possess suitable bandgap and band edge positions for photocatalytic water splitting. Our results show that 2D tri-hex carbon has a high absorption coefficient under sunlight and high photocatalytic water-splitting efficiency under acidic conditions. The study provides insight into exploring a promising candidate in 2D carbon materials for acid-corrosion-resistant photocatalytic water-splitting applications.

Managing Interfacial Hot‐Carrier Cooling and Extraction Kinetics for Inverted Ma‐Free Perovskite Solar Cells Over 23% Efficiency via Dion–Jacobson 2D Capping Layer

AbstractWhile quasi‐2D perovskite is often used in inverted perovskite solar cells (PSCs) to improve the interfacial carrier transfer, the development of pure 2D perovskite with superior stability is rarely seen and the corresponding carrier‐extraction kinetics remains unclear. Here, a variety of hexatomic ring cations including piperidine, pyridine, and cyclohexane are introduced to modify the perovskite/electron transport layer interface. The Dion–Jacobson phase 2D cladding (n = 1) based on 3‐(aminomethyl) piperidinium is proved to form a coordinated energy landscape and homogeneous surface potential distribution, and effectively prolong the electron diffusion length (≈1.58 µm) and accelerate the hot‐carrier extraction rate (2.5 times that of Control at 400 K). Furthermore, the quasi‐2D treatment (n ≈ 3,4) demonstrated a slight escalation in short‐circuit current, but failed to inhibit the interdiffusion of Ag, Pb, and I under illumination. Finally, one of the state‐of‐art power conversion efficiency (PCE) for MA‐free inverted PSCs is achieved at 23.62% with increased open‐circuit voltage (≈1.15 V) and fill factor (≈82.8%). Most importantly, 89% and 93.6% of initial PCE are retained after 720 h under 85 °C heating and 1000 h under maximum power point tracking, illustrating satisfactory thermal and operational stability with pure 2D perovskite capping layer.

Organic carboxylate-assisted engineering for fabricating Fe, N co-doped porous carbon interlinked carbon nanotubes towards boosting the oxygen reduction reaction for Zn-air batteries

Fe-Nx sites have been identified as core descriptors for Fe-N/C based oxygen reduction reaction catalysts. However, the low density and less utilization of Fe-Nx sites render these catalysts with inefficient catalytic performance. Herein, we develop an organic carboxylate-assisted engineering to construct Fe, N co-doped porous carbon interlinked carbon nanotubes (Fe/N-CCNTs) with high-density and sufficiently exposed Fe-Nx sites based on self-catalyzed effect. The existing forms of Fe include Fe-imidazole configuration and coordination with unsaturated Zn sites via organic carboxylate as linkers, leading to high-density Fe-Nx sites after pyrolysis. Besides, hexatomic carbon rings of organic carboxylate lower cyclization energy barrier for CNT formation, resulting in CNTs interlinked with separated active sites through “active point-conductive line-active point” connections. The optimal sample (Fe-BOAc-PNC) exhibits the onset potential of 0.93 V (vs. RHE) and half-wave potential of 0.84 V in alkaline solution. The liquid-state Zn-air battery (ZAB) employing Fe-BOAc-PNC generates large power density (160 mW/cm2) and stability over 160 h. Moreover, the assembled flexible ZAB displays superb power density of 93 mW/cm2 with robust flexibility. This work provides an insightful perspective for designing Fe-N/C catalysts with high-density and sufficiently exposed active sites for energy storage application.

Unraveling the Key Atomic Interactions in Determining the Varying Li/Na/K Storage Mechanism of Hard Carbon Anodes

AbstractHard carbons have been identified as competitive anodes for Li/Na/K‐ion batteries but their Li/Na/K‐ion storage mechanisms significantly vary in different batteries. It is fundamental to understand the basic science behind the difference. Herein, it is theoretically revealed that defects on the carbon layers generally have an influential impact on the atomic interactions including the metal–metal (M–M) and metal–carbon (M–C) interactions, thereby determining whether the stored alkali‐metal atoms are in ionic or quasi‐metallic states. Upon increasing the number of metal atoms on a carbon layer composed of only hexatomic rings, K tends to be stored in an ionic state similar to Li due to the dominant M–C interaction, while on a carbon layer with defects, K tends to be stored in a quasi‐metallic state similar to Na due to the dominant M–M interaction. For experimental verification, a glassy carbon, the extreme form of hard carbon with dominant sp2 hybridization and only Stone–Wales defects, is selected as a model anode, and its Li/Na/K‐ion storage mechanisms are exactly consistent with the theoretical prediction. More profoundly, for the first time, the quasi‐metallic K cluster information is captured by ex situ electron paramagnetic resonance.

A G-quadruplex/hemin structure-undamaged method to inhibit peroxidase-mimic DNAzyme activity for biosensing development

Damaging the structure of the G-quadruplex (G4) to prevent the formation of the G4/hemin complex is presently the only available method to inhibit the activity of the peroxidase-mimic DNAzyme. In this study, a unique intramolecular inhibitory effect of the adjacent base-pair (InE(N:N)), by installing a rationally adjacent base-pair of the G4 core sequence, is proposed for the inhibition of the DNAzyme activity, which eliminates the need to damage the entire G4 structure. Various base pairs show different abilities to inhibit DNAzyme activity. The adjacent adenine: thymine pair possesses the best inhibitory efficiency (17 times). Through detailed investigations of the InE(N:N), it was revealed that the adjacent adenine: thymine pair downregulated the formation of compound I in the catalytic process, thus inhibiting the G4 DNAzyme activity. The mechanism of inhibition indicated that the carbonyl group on the hexatomic ring of the complementary base played an important role. To further reflect the advantages of the proposed strategy, two InE(N:N)-based biosensors were developed for DNA analysis and Uracil-DNA glycosylase (UDG) detection. Compared with existing DNAzyme-based methods, the application of InE(N: N) facilitates the real-time assay and simplifies the design difficulty. Therefore, InE(N:N) provides new insights into the regulation of the DNAzyme activity and offers an efficient approach for the future application of DNAzyme.

Photoluminescence mechanisms of red-emissive carbon dots derived from non-conjugated molecules

Red-emissive carbon dots (R-CDs) have been widely studied because of their potential application in tissue imaging and optoelectronic devices. At present, most R-CDs are synthesized by using aromatic precursors, but the synthesis of R-CDs from non-aromatic precursors is challenging, and the emission mechanism remains unclear. Herein, different R-CDs were rationally synthesized using citric acid (CA), a prototype non-aromatic precursor, with the assistance of ammonia. Their structural evolution and optical mechanism were investigated. The addition of NH3·H2O played a key role in the synthesis of CA-based R-CDs, which shifted the emission wavelength of CA-based CDs from 423 to 667 nm. Mass spectrometry (MS) analysis indicated that the amino groups served as N dopants and promoted the formation of localized conjugated domains through an intermolecular amide ring, thereby inducing a significant emission redshift. The red-emissive mechanism of CDs was further confirmed by control experiments using other CA-like molecules (e.g., aconitic acid, tartaric acid, aspartic acid, malic acid, and maleic acid) as precursors. MS, nuclear magnetic resonance characterization, and computational modeling revealed that the main carbon chain length of CA-like precursors tailored the cyclization mode, leading to hexatomic, pentatomic, unstable three/four-membered ring systems or cyclization failure. Among these systems, the hexatomic ring led to the largest emission redshift (244 nm, known for CA-based CDs). This work determined the origin of red emission in CA-based CDs, which would guide research on the controlled synthesis of R-CDs from other non-aromatic precursors.

Conformation-related excited-state charge transfer/separation of donor-π-acceptor chromophores.

Understanding the excited-state charge transfer/separation (CT/CS) of donor-π-acceptor chromophores can provide guidance for designing and synthesizing advanced dyes to improve the performance of dye-sensitized solar cells (DSSCs) in practical applications. Herein, two newly synthesized electronic push-pull molecules, CS-14 and CS-15, that consist of carbazole donor and benzothiadiazole acceptor segments are chosen to explore the ultrafast dynamics of intramolecular CT/CS processes. The theoretical calculation results depict an excited-state intramolecular CT character for both dyes, while the dihedral angle between donor and acceptor of CS-14 is larger than that of CS-15, suggesting a more significant CT character of CS-14. Furthermore, compared to CS-14, the bond rotation of CS-15 between donor and π-bridge is restricted by employing the hexatomic ring, indicating the stronger molecular planarization of CS-15. Ultrafast spectroscopy clearly shows a solvent polarity-dependent excited-state species evolution from CT to CS-the CT character is observed in low-polar toluene solvent, while the feature of the CS state in polar tetrahydrofuran and acetone solvents is captured, which successfully proved a solvent polarity modulated excited-state CT/CS characters. We also found that though the generation of the CS state within CS-14 is slightly faster than that of CS-15, the charge recombination process of CS-15 with excellent planar conformation is much slower, providing enough time for a higher charge migration efficiency in DSSCs.