Sp2 Carbon Research Articles

Enhanced electrochemical performance of flexible carbon substrates via carbonized layer of oxidant-induced polydopamine for high-performance supercapacitors

Flexible substrates are essential for advancing energy storage materials in portable and wearable devices. Carbon cloth is a promising option due to its flexibility and lightweight properties, but its high electrical resistance and hydrophobic surface present challenges for solution-based electrolytes. To overcome these issues, a surface modification technique was developed that coats carbon cloth with dopamine and subsequently carbonizes it. This process enhances hydrophilicity while preserving the sp2 carbon structure, significantly improving electrical conductivity. The chemical bath deposition of Ni(OH)2 onto the carbonized polydopamine-coated carbon cloth produced a uniform layer that increased specific capacitance dramatically. At a current density of 1 A/g, the specific capacitance reached 1100F/g, compared to 919F/g for Ni(OH)2 on unmodified carbon cloth. Furthermore, the electrodes maintained high specific capacitance at higher current densities, showcasing superior rate capability. Overall, carbonized polydopamine layers effectively reduce electrical resistivity and hydrophobicity, enhancing the performance of carbon-based materials for energy storage applications.

The origin of ferroelectricity in HfO2 from orbital hybridization and covalency

Fluorite-structured HfO2 ferroelectrics exhibit remarkable ferroelectricity owing to the robust thickness scalability, rendering them promising for next-generation ferroelectric memories. Unlike the well-understood perovskite structured ferroelectrics, such as Pb(Zr,Ti)O3, the origin of ferroelectricity in HfO2 remains elusive, which impedes the experimental fabrication of pure and stable ferroelectric orthorhombic phase in films. This study seeks to elucidate its origin by analyzing the covalent nature of local chemical bonding and changes in orbital hybridization and by catching the typical feather of the half-unit-cell spacer/polar layer in the orthorhombic phase. Notably, we find that the differences in the hybridization intensity of the 2s orbitals of two types of O atoms (OI and OII) and 5d orbitals of Hf atoms play a crucial role in inducing ferroelectric distortion. Furthermore, we demonstrate that the intrinsic mechanisms of stress in enhancing the ferroelectricity of HfO2 originate from the modulation of orbital hybridization intensity of the Hf–O bonds. These insights provide a vital theoretical foundation for further exploration of ferroelectric phase transitions and property modulation in HfO2 and similar fluorite-structured ferroelectrics.

Potassium tert-Butoxide Promoted α-Keto Ester Synthesis through C(O)–N Bond Cleavage of Isatins

AbstractWe present a novel and cost-effective method for synthesizing biologically important α-keto esters in a single-step reaction. This approach involves a sequential cascade process within a single reaction vessel facilitated by t-BuOK, which promoted the cleavage of the sp2 C(O)–N bond of an isatin and the formation of a new N–C(sp2)(O) bond with benzoyl chloride. To the best of our knowledge, this is the first instance of the construction of an α-keto ester scaffold adjacent to an amide group through a one-pot process. In comparison to existing methods, our protocol offers several advantages: readily available starting materials, mild reaction conditions, a concise synthetic pathway, high sustainability, and excellent tolerance towards various functional groups. Given these strengths, we anticipate widespread use of this method in the synthesis of related α-keto ester scaffolds.

Effect of edge dual-hydrogenation on electronic and magnetic properties of armchair silicon carbide nanoribbons

Using the first-principles calculations, we investigate the electronic and magnetic properties of armchair silicon carbide nanoribbon (aSiCNR) with different combinations of edge dual-hydrogenation. The dual-hydrogenation on the boundary Si or C atom changes it from sp2 hybridization to sp3 hybridization, which will have an important role on the stability of aSiCNR. Only the full dual-hydrogenation on the one edge or two edges don't change the band structure and magnetic moment of aSiCNR. However, the other different combinations of edge dual-hydrogenation can result in aSiCNR exhibiting metallic, semiconductor, and half-metallic properties under non-magnetism state, ferromagnetic and anti-ferromagnetic states. These results may present a new avenue for band engineering of aSiCNR, as well as valuable suggestions for the practical application of SiC based nanomaterials in spintronics and multifunctional nanodevices.

Proximity-induced ferromagnetism of platinum thin film on magnetic insulating CrI3 nanoflakes

The induced magnetization of Pt holds significant promise for the development of spintronic devices. In this study, we constructed a two-dimensional heterostructure consisting of a ferromagnetic insulating CrI3 nanoflake and metallic Pt thin films. The observation of anomalous Hall effect suggests the emergence of a ferromagnetic long-range order in the Pt thin film induced by the magnetic proximity effect. Density functional theory calculations were performed to investigate the underlying mechanisms. We propose that the spontaneous magnetization of Pt in Pt/CrI3 stems from an intensified exchange interaction between Pt 5d and Cr 3d electrons, which is facilitated by the interface coupling and the formation of interfacial hybrid orbitals. These results contribute to a deeper understanding of spin-based phenomena and have potential implications for advancements in the field of spintronics.

Decision threshold models in medical decision making: a scoping literature review

BackgroundDecision thresholds play important role in medical decision-making. Individual decision-making differences may be attributable to differences in subjective judgments or cognitive processes that are captured through the decision thresholds. This systematic scoping review sought to characterize the literature on non-expected utility decision thresholds in medical decision-making by identifying commonly used theoretical paradigms and contextual and subjective factors that inform decision thresholds.MethodsA structured search designed around three concepts—individual decision-maker, decision threshold, and medical decision—was conducted in MEDLINE (Ovid) and Scopus databases from inception to July 2023. ProQuest (Dissertations and Theses) database was searched to August 2023. The protocol, developed a priori, was registered on Open Science Framework and PRISMA-ScR guidelines were followed for reporting on this study. Titles and abstracts of 1,618 articles and the full texts for the 228 included articles were reviewed by two independent reviewers. 95 articles were included in the analysis. A single reviewer used a pilot-tested data collection tool to extract study and author characteristics, article type, objectives, theoretical paradigm, contextual or subjective factors, decision-maker, and type of medical decision.ResultsOf the 95 included articles, 68 identified a theoretical paradigm in their approach to decision thresholds. The most common paradigms included regret theory, hybrid theory, and dual processing theory. Contextual and subjective factors that influence decision thresholds were identified in 44 articles.ConclusionsOur scoping review is the first to systematically characterizes the available literature on decision thresholds within medical decision-making. This study offers an important characterization of the literature through the identification of the theoretical paradigms for non-expected utility decision thresholds. Moreover, this study provides insight into the various contextual and subjective factors that have been documented within the literature to influence decision thresholds, as well as these factors juxtapose theoretical paradigms.

Modular alkene synthesis from carboxylic acids, alcohols and alkanes via integrated photocatalysis.

Alkenes serve as versatile building blocks in diverse organic transformations. Despite notable advancements in olefination methods, a general strategy for the direct conversion of carboxylic acids, alcohols and alkanes into alkenes remains a formidable challenge owing to their inherent reactivity disparities. Here we demonstrate an integrated photochemical strategy that facilitates a one-pot conversion of these fundamental building blocks into alkenes through a sequential C(sp3)-C(sp3) bond formation-fragmentation process, utilizing an easily accessible and recyclable phenyl vinyl ketone as the 'olefination reagent'. This practical method not only offers an unparalleled paradigm for accessing value-added alkenes from abundant and inexpensive starting materials but also showcases its versatility through various complex scenarios, including late-stage on-demand olefination of multifunctional molecules, chain homologation of acids and concise syntheses of bioactive molecules. Moreover, initiating from carboxylic acids, alcohols and alkanes, this protocol presents a complementary approach to traditional olefination methods, making it a highly valuable addition to the research toolkit for alkene synthesis.

Nickel-Catalyzed Stereoconvergent C(sp2)-F Alkenylation of Monofluoroalkenes.

The stereoconvergent synthesis of a single stereoisomer from E/Z-olefin mixtures remains one of the foremost challenges in organic synthesis. Herein, we describe a nickel-catalyzed stereoconvergent cross-coupling between E- and Z-mixed monofluoroalkenes and alkenyl electrophiles, which allows the construction of C(sp2)-C(sp2) bonds. This defluorinative transformation offers facile access to various 1,3-dienes with E-selectivity and good functional group tolerance. Preliminary mechanistic studies indicate that the reaction most likely proceeds through a migratory insertion/β-F elimination/isomerization process.

Asymmetric Alkyl-Alkyl Cross-Coupling Enabled by Ni-Catalyzed Cross-Hydrodimerization of Enamides with Unactivated Alkenes

AbstractSaturated stereogenic centers containing C(sp3)–C(sp3) bonds comprise a major portion of organic molecules. Over the past decades, transition-metal-catalyzed asymmetric C(sp3)–C(sp3) cross-coupling has evolved into an efficient strategy for constructing such stereogenic centers. However, reaction modes to build asymmetric C(sp3)–C(sp3) bonds remain limited. Herein, a nickel-catalyzed enantioselective cross-hydrodimerization between distinct alkenes to enable the enantioselective construction of alkyl–alkyl bonds has been developed. In this reaction mode, N-acyl enamines (enamides) and unactivated alkenes undergo oxidative enantioselective cross-hydrodimerization with excellent levels of chemo- and head-to-tail regioselectivity to give enantioenriched N-acyl α-branched amines by forging the C(sp3)–C(sp3) bond with control of the enantioselectivity. The presence of both reducing and oxidizing reagents in the reaction allows the use of alkenes as sole precursors to forge enantioselective C(sp3)–C(sp3) bonds, representing a new reaction mode for asymmetric alkyl–alkyl cross-coupling. The asymmetric cross-hydrodimerization between distinct alkenes provides a new strategy for constructing saturated stereogenic centers containing C(sp3)–C(sp3) bonds.

Uncovering an Interfacial Band Resulting from Orbital Hybridization in Nickelate Heterostructures.

The interaction of atomic orbitals at the interface of perovskite oxide heterostructures has been investigated for its profound impact on the band structures and electronic properties, giving rise to unique electronic states and a variety of tunable functionalities. In this study, we conducted an extensive investigation of the optical and electronic properties of epitaxial NdNiO3 synthesized on a series of single-crystal substrates. Unlike nanofilms synthesized on other substrates, NdNiO3 on SrTiO3 (NNO/STO) gives rise to a unique band structure featuring an additional unoccupied band situated above the Fermi level. Our comprehensive investigation, which incorporated a wide array of experimental techniques and density functional theory calculations, revealed that the emergence of the interfacial band structure is primarily driven by orbital hybridization between the Ti 3d orbitals of the STO substrate and the O 2p orbitals of the NNO thin film. Furthermore, exciton peaks have been detected in the optical spectra of the NNO/STO film, attributable to the pronounced electron-electron (e-e) and electron-hole (e-h) interactions propagating from the STO substrate into the NNO film. These findings underscore the substantial influence of interfacial orbital hybridization on the electronic structure of oxide thin films, thereby offering key insights into tuning their interfacial properties.

Spin-dependent electronic phenomena in heavily-doped monolayer graphene

The controlled manipulation of doping levels in graphene is crucial for advancing next-generation low-power electronics. Owing to its peculiar band structure, graphene's electronic functionalities can be easily tuned by electron doping, resulting in the bandgap openings, orbital hybridization, and induced spin-polarization. Here, we unveil the substantial doping of the graphene layer and the emergence of a significant bandgap by sandwiching a monolayer graphene, supported on ferromagnetic cobalt, between two europium layers. Our angle- and spin-resolved photoemission spectroscopy experiments, accompanied by dedicated density functional theory calculations, demonstrate that single-spin electron pockets form as a result of the hybridization of the topmost europium majority bands with graphene, while hybridization gaps are induced in the graphene π∗ bands by the Eu minority bands. Spin-resolved measurements further emphasize a single-spin dispersionless contribution proximal to the Fermi level, possibly arising from the coupling of single-spin polarized graphene bands to optical phonons. This work provides crucial insights into the phase diagram of heavily doped graphene, with significant potential for the design and development of novel 2D systems.

Metal clusters modified hexagonal boron nitride for adsorption and sensing of lithium batteries thermal runaway gases

Developing efficient gas sensing materials for monitoring lithium batteries thermal runaway gases is essential for human safety. In this study, a detailed examination of the CH4, CO2, CO, and H2 adsorption property for the h-BN with metal clusters modification was conducted utilizing density functional theory. The incorporation of metal clusters (Pd4, Rh4, and Ru4) significantly improved the adsorption energy and charge transfer of h-BN towards gases compared to the unmodified h-BN. The Ru4/h-BN system demonstrated the highest adsorption capacity across all four gases, while the Pd4/h-BN system displayed remarkable recovery ability at room temperature (298 K). Furthermore, studying the adsorption mechanism via DOS revealed enhanced gas adsorption due to orbital hybridization. The work offers reliable theoretical foundation for the detection and prevention of thermal runaway gases in lithium batteries through the use of h-BN modified with metal clusters.

First-principles calculations of phase stability, electronic structure, mechanical properties and thermal conductivities of TMH2 (TM=V, Nb, Ta) metal hydrides

TMH2 (TM = V, Nb, Ta) metal hydrides can be used as potential hydrogen storage materials. However, there have been no available data on the mechanical and thermodynamic properties of these hydrides, especially TaH2. Herein, based on first-principles calculations, the phase stability, electronic structure, mechanical properties and thermal conductivities of TMH2 (TM = V, Nb, Ta) hydrides are investigated. The results show that VH2, NbH2, and TaH2 are thermodynamically and dynamically stable. The calculated electronic structures show that these three hydrides possess electron orbital hybridization among atoms and strong chemical bonding. The chemical bonds in TMH2 are mainly ionic and partially covalent. According to the calculated Poisson's ratios, Pugh’s ratio and Cauchy pressures, VH2, NbH2, and TaH2 are ductile. Moreover, these three hydrides have elastic anisotropy and good damage tolerance. Finally, the predicted thermodynamic properties indicate that TMH2 can be used as potential thermal insulating materials.

Allenyl Thianthrenium Salt: A Bench-Stable C3 Synthon for Annulation and Cross-Coupling Reactions.

Herein, we report the first bench-stable and nonhygroscopic monosubstituted allenyl sulfonium salt (ATT) synthesized from thianthrene and propargyl alcohol. We demonstrate its use in annulation chemistry to synthesize heterocycles, such as 2-hydroxy morpholine, 2-methyl quinoxalines, and benzodioxepinone derivatives, with an exocyclic double bond. The reagent is the first allenyl sulfonium salt that can undergo palladium-catalyzed cross-coupling reactions to form a C(sp2)-C(sp2) bond via Suzuki coupling and a C(sp3)-C(sp2) bond formation via reductive coupling.

Modulating Hydrogen Adsorption by Unconventional p–d Orbital Hybridization over Porous High‐Entropy Alloy Metallene for Efficient Electrosynthesis of Nylon‐6 Precursor

AbstractRenewable electricity driven electrosynthesis of cyclohexanone oxime (C6H11NO) from cyclohexanone (C6H10O) and nitrogen oxide (NOx) is a promising alternative to traditional environment‐unfriendly industrial technologies for green synthesis of C6H11NO. Precisely controlling the reaction pathway of the C6H10O/NOx‐involved electrochemical reductive coupling reaction is crucial for selectively producing C6H11NO, which is yet still challenging. Herein, we report a porous high‐entropy alloy PdCuAgBiIn metallene (HEA‐PdCuAgBiInene) to boost the electrosynthesis of C6H11NO from C6H10O and nitrite, achieving a high Faradaic efficiency (47.6 %) and almost 100 % yield under ambient conditions. In situ Fourier transform infrared spectroscopy and theoretical calculations demonstrate that unconventional orbital hybridization between d‐block metals and p‐block metals could regulate the local electronic structure of active sites and induce electron localization of electron‐rich Pd sites, which tunes the active hydrogen supply, facilitates the generation and enrichment of key intermediates NH2OH* and C6H10O*, and efficiently promotes their C−N coupling to selectively produce C6H11NO.

Modulating Hydrogen Adsorption by Unconventional p-d Orbital Hybridization over Porous High-Entropy Alloy Metallene for Efficient Electrosynthesis of Nylon-6 Precursor.

Renewable electricity driven electrosynthesis of cyclohexanone oxime (C6H11NO) from cyclohexanone (C6H10O) and nitrogen oxide (NOx) is a promising alternative to traditional environment-unfriendly industrial technologies for green synthesis of C6H11NO. Precisely controlling the reaction pathway of the C6H10O/NOx-involved electrochemical reductive coupling reaction is crucial for selectively producing C6H11NO, which is yet still challenging. Herein, we report a porous high-entropy alloy PdCuAgBiIn metallene (HEA-PdCuAgBiInene) to boost the electrosynthesis of C6H11NO from C6H10O and nitrite, achieving a high Faradaic efficiency (47.6 %) and almost 100 % yield under ambient conditions. In situ Fourier transform infrared spectroscopy and theoretical calculations demonstrate that unconventional orbital hybridization between d-block metals and p-block metals could regulate the local electronic structure of active sites and induce electron localization of electron-rich Pd sites, which tunes the active hydrogen supply, facilitates the generation and enrichment of key intermediates NH2OH* and C6H10O*, and efficiently promotes their C-N coupling to selectively produce C6H11NO.

Insights into irradiation-affected structural evolution and mechanical behavior of amorphous carbon

The distinctive hybridization structure of amorphous carbon (a-C) imparts remarkable mechanical and tribological characteristics, making it highly relevant for lubrication applications, particularly in critical sectors such as nuclear energy. In this work, we employed molecular dynamics simulations to examine the effects of irradiation on the structural evolution and mechanical behavior of a-C. The findings indicate that with increasing irradiation doses, the short-range order within the a-C is disrupted, leading to a substantial increase in sp2 hybridization. Then, nanoindentation simulations revealed a reduction in both hardness and elastic modulus as a consequence of irradiation damage, associated with the transition in hybridization from sp3 to sp2 and the associated creation of free volume. Furthermore, nanoscratch mechanical testing showed a slight increase in the friction, primarily attributed to the weakened load-bearing ability of a-C after irradiation. Interestingly, a metastable transition from sp2 to sp3 hybridization was observed on the scratched surface, which was concurrently validated by experiments as Raman spectroscopy and TEM-EELS. This study provides a detailed atomic-level mechanism for the irradiation-induced damage on the structural bonding and mechanical properties of a-C, offering guidance for its performance in nuclear reactors and the aerospace industry.

Advanced design of metal single-atom (Pt, Mn, Fe or Cu) loaded S-Ni(OH)2 nanosheets array catalysts to achieve high-performance overall water splitting

Designing catalysts at atomic level fine-tune the electronic structure of surface-active site for efficient water splitting, is a highly desirable approach but also poses significant challenges. This study focuses on the synthesis of a series of electronically tunable metal single-atom (M−SAs) catalysts: M9@S-Ni(OH)2 (M=Pt, Mn, Fe or Cu). Experimental results reveal that introduction of trace S-heteroatoms and metal atoms into Ni(OH)2 lattice can effectively modulate the electronic structure of M9@S-Ni(OH)2 through modulation of p-d and d-d orbital hybridization, resulting in exceptional performance in water electrolysis. Among M9@S-Ni(OH)2, Pt9@S-Ni(OH)2 and Fe9@S-Ni(OH)2 exhibit excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance, respectively, the overpotential requiring only 7 mV and 269 mV, respectively, at current density of 10 mA cm−2. (−) Pt9@S-Ni(OH)2||Fe9@S-Ni(OH)2 (+) presents a high current density of 531.07 mA cm−2 at cell-voltage of 1.80 V in overall-water splitting (OWS), which is 14.07 times higher than that of the commercial (−) Pt/C||IrO2 (+) (37.86 mA cm−2) system. This work achieves the development of cost-effective and stable electrocatalysts, offering a solution for large-scale and sustainable water-hydrogen conversion.

A decarbonylative approach to alkylnickel intermediates and C(sp3)-C(sp3) bond formation.

The myriad nickel-catalyzed cross-coupling reactions rely on the formation of an organonickel intermediate, but limitations in forming monoalkylnickel species have limited options for C(sp3) cross-coupling. The formation of monoalkylnickel(II) species from abundant carboxylic acid esters would be valuable, but carboxylic acid derivatives are primarily decarboxylated to form alkyl radicals that lack the correct reactivity. In this work, we disclose a facile oxidative addition and decarbonylation sequence that forms monoalkylnickel(II) intermediates through a nonradical process. The key ligand, bis(4-methylpyrazole)pyridine, accelerates decarbonylation, stabilizes the alkylnickel(II) intermediate, and destabilizes off-cycle nickel(0) carbonyl species. The utility of this new reactivity in C(sp3)-C(sp3) bond formation is demonstrated in a reaction that is challenging by purely radical methods-the selective cross-coupling of primary carboxylic acid esters with primary alkyl iodides.

Thickness and sp3 bond modulation of (Ti/tetrahedral amorphous carbon)n multilayer coatings

Thickness and sp3 bond modulation of (Ti/tetrahedral amorphous carbon)n multilayer coatings