The era of carbon allotropes

Fullerene and fullerene whisker are not carcinogenic to the lungs and pleura in rat long-term study after 2-week intra-tracheal intrapulmonary administration

Fullerene whiskers (FLW)s are thin rod-like structures composed of C60 and C70 fullerene (FL). The shape of FLWs suggests potential toxic effects including carcinogenicity to the lung and pleura, similar to effects elicited by asbestos and multi-walled carbon nanotubes (MWCNT)s. However, no long-term carcinogenic studies of FL or FLW have been conducted. In the present study we investigated the pulmonary and pleural carcinogenicity of FL and FLW. Twelve-week-old male F344 rats were administered 0.25 or 0.5 mg FL, FLW, MWCNT-7, and MWCNT-N by intra-tracheal intra-pulmonary spraying (TIPS). Acute lung lesions and carcinogenicity were analyzed at 1 and 104 weeks after 8 doses/15 days TIPS administration. At week 1, FLW, MWCNT-7, and MWCNT-N significantly increased alveolar macrophage infiltration. Expression of Ccl2 and Ccl3, reactive oxygen species production, and cell proliferation were significantly increased by administration of MWCNT-7 and MWCNT-N but not FL or FLW. At week 104, the incidence of bronchiolo-alveolar adenoma plus adenocarcinoma was significantly increased in the MWCNT-7 and MWCNT-N groups, and the incidence of mesothelioma was significantly increased in the MWCNT-7 group. No significant induction of pulmonary or pleural tumorigenesis was observed in the FL or FLW groups. The number of 8-OHdG-positive cells in the alveolar epithelium was significantly increased in the MWCNT-7 and MWCNT-N groups but not in the FL or FLW groups. FL and FLW did not exert pulmonary or pleural carcinogenicity in our study. In addition, oxidative DNA damage was implicated in MWCNT-induced lung carcinogenesis, suggesting that it may be a useful initial marker of carcinogenicity.

Low-voltage single-atom electron microscopy with carbon-based nanomaterials

The properties of materials are strongly correlated with their atomic scale structures. Achieving a comprehensive understanding of the atomic-scale structure-property relationship requires advancements of imaging and spectroscopy techniques. Aberration-corrected scanning transmission electron microscopy (STEM) has seen rapid development over the past decades and is now routinely employed for atomic-scale characterization. However, quantitative STEM imaging and spectroscopy analysis at the single-atom level is challenging due to the extremely weak signals generated from individual atom, thus imposing stringent requirements for analysis sensitivity. This review discusses the development and application of low-voltage STEM techniques with single-atom sensitivity, primarily based on recent research presented on an invited talk at the 5th 2D23 SALVE Symposium, including annular dark-field (ADF) imaging, functional imaging and electron energy-loss spectroscopy (EELS) analysis. Carbon-based nanomaterials were chosen as model systems for demonstrating the capabilities of single-atom STEM imaging and EELS analysis, due to their structural stability under low accelerating voltages and their rich physical and chemical properties. Moreover, this review summarizes recent advancements and applications of low-voltage single-atom STEM imaging and spectroscopy in the study of functional materials and discusses prospects for future developments.

A Negatively Curved Nanographene with Four Embedded Heptagons

Negatively curved nanographenes are considered as cutouts of three-dimensional fully sp2-hybridized carbon allotropes such as Schwarzites. Here we present the synthesis of a C76 cut-out of the Schwarzite 8-4-1-p proposed by Lenosky et al. and investigate its optical as well as electrochemical properties. Furthermore, supramolecular interactions with fullerenes C60 and C70 were studied.

Aromaticity of biphenylene networks

Magnetically induced ring-currents and magnetic susceptibilities have been calculated for the series of biphenylene sheets and biphenylene nanoribbons with armchair and zigzag edges with hydrogen atoms, as well as with bromine and fluorine atoms. Calculations have been performed at the density functional level of theory. It has been shown that biphenylene sheets and nanoribbons are characterized by dominant paratropic ring current, resulting in antiaromatic character. The global electron delocalization in biphenylene networks favors the edges of molecular structures, passing through cyclobutadiene units avoiding the outer contour of benzene. Replacing the hydrogen atoms with bromine and fluorine atoms slightly reduces the global ring-current strength and increases the diamagnetic property. The B3LYP functional overestimates the paramagnetic contribution of magnetic susceptibility in large molecular structures, compared with the BHandHLYP functional, which is recommended for magnetic property calculations.

Synthesis, Surface Chemistry, and Applications of Non-Zero-Dimensional Diamond Nanostructures

Diamond nanomaterials are renowned for their exceptional properties, which include the inherent attributes of bulk diamond. Additionally, they exhibit unique characteristics at the nanoscale, including high specific surface areas, tunable surface structure, and excellent biocompatibility. These multifaceted attributes have piqued the interest of researchers globally, leading to an extensive exploration of various diamond nanostructures in a myriad of applications. This review focuses on non-zero-dimensional (non-0D) diamond nanostructures including diamond films and extended diamond nanostructures, such as diamond nanowires, nanoplatelets, and diamond foams. It delves into the fabrication, modification, and diverse applications of non-0D diamond nanostructures. This review begins with a concise review of the preparation methods for different types of diamond films and extended nanostructures, followed by an exploration of the intricacies of surface termination and the process of immobilizing target moieties of interest. It then transitions into an exploration of the applications of diamond films and extended nanostructures in the fields of biomedicine and electrochemistry. In the concluding section, this article provides a forward-looking perspective on the current state and future directions of diamond films and extended nanostructures research, offering insights into the opportunities and challenges that lie ahead in this exciting field.

Curvature-Induced Electron Spin Catalysis with Carbon Spheres

Here, we report curvature-induced electron spin catalysis by using solid carbon spheres as catalysts, which were synthesized using positive curvature molecular hexabromocyclopentadiene as a precursor molecule, following a radical coupling mechanism. The curvature spin of carbon is regarded as an overlapping state of σ- and π-radical, which is identified by the inverse Laplace transform of pulse-electron paramagnetic resonance. The growth mechanism of carbon spheres abiding by Kroto's model, is supported by the density functional theory study of thermodynamics and kinetics calculations. The solid carbon spheres present excellent catalytic behaviour of oxidation coupling of amines to form corresponding imines with the conversion of >99 %, selectivity of 98.7 %, and yield of 97.7 %, which is attributed to the predominantly curvature-induced electron spin catalysis of carbon, supported by the calculation of oxygen adsorption energy. This work proposes a view of curvature-induced spin catalysis of carbon, which opens up a research direction for curvature-induced electron spin catalysis.

Accuracy, transferability, and computational efficiency of interatomic potentials for simulations of carbon under extreme conditions

Large-scale atomistic molecular dynamics (MD) simulations provide an exceptional opportunity to advance the fundamental understanding of carbon under extreme conditions of high pressures and temperatures. However, the fidelity of these simulations depends heavily on the accuracy of classical interatomic potentials governing the dynamics of many-atom systems. This study critically assesses several popular empirical potentials for carbon, as well as machine learning interatomic potentials (MLIPs), in their ability to simulate a range of physical properties at high pressures and temperatures, including the diamond equation of state, its melting line, shock Hugoniot, uniaxial compressions, and the structure of liquid carbon. Empirical potentials fail to accurately predict the behavior of carbon under high pressure-temperature conditions. In contrast, MLIPs demonstrate quantum accuracy, with Spectral Neighbor Analysis Potential (SNAP) and atomic cluster expansion (ACE) being the most accurate in reproducing the density functional theory results. ACE displays remarkable transferability despite not being specifically trained for extreme conditions. Furthermore, ACE and SNAP exhibit superior computational performance on graphics processing unit-based systems in billion atom MD simulations, with SNAP emerging as the fastest. In addition to offering practical guidance in selecting an interatomic potential with a fine balance of accuracy, transferability, and computational efficiency, this work also highlights transformative opportunities for groundbreaking scientific discoveries facilitated by quantum-accurate MD simulations with MLIPs on emerging exascale supercomputers.

Fibres-threads of intelligence-enable a new generation of wearable systems

Fabrics represent a unique platform for seamlessly integrating electronics into everyday experiences. The advancements in functionalizing fabrics at both the single fibre level and within constructed fabrics have fundamentally altered their utility. The revolution in materials, structures, and functionality at the fibre level enables intimate and imperceptible integration, rapidly transforming fibres and fabrics into next-generation wearable devices and systems. In this review, we explore recent scientific and technological breakthroughs in smart fibre-enabled fabrics. We examine common challenges and bottlenecks in fibre materials, physics, chemistry, fabrication strategies, and applications that shape the future of wearable electronics. We propose a closed-loop smart fibre-enabled fabric ecosystem encompassing proactive sensing, interactive communication, data storage and processing, real-time feedback, and energy storage and harvesting, intended to tackle significant challenges in wearable technology. Finally, we envision computing fabrics as sophisticated wearable platforms with system-level attributes for data management, machine learning, artificial intelligence, and closed-loop intelligent networks.

Souza AB, Levita DP, Mello CC, da Silva AFM, dos Santos TC, Ronconi CM. Innovating Leishmaniasis Treatment: A Critical Chemist's Review of Inorganic Nanomaterials

Leishmaniasis, a critical Neglected Tropical Disease caused by Leishmania protozoa, represents a significant global health risk, particularly in resource-limited regions. Conventional treatments are effective but suffer from serious limitations, such as toxicity, prolonged treatment courses, and rising drug resistance. Herein, we highlight the potential of inorganic nanomaterials as an innovative approach to enhance Leishmaniasis therapy, aligning with the One Health concept by considering these treatments' environmental, veterinary, and public health impacts. By leveraging the adjustable properties of these nanomaterials─including size, shape, and surface charge, tailored treatments for various diseases can be developed that are less harmful to the environment and nontarget species. We review recent advances in metal-, oxide-, and carbon-based nanomaterials for combating Leishmaniasis, examining their mechanisms of action and their dual use as standalone treatments or drug delivery systems. Our analysis highlights a promising yet underexplored frontier in employing these materials for more holistic and effective disease management.

Unconventional Band Structure via Combined Molecular Orbital and Lattice Symmetries in a Surface-Confined Metallated Graphdiyne Sheet

Graphyne (GY) and graphdiyne (GDY)-based monolayers represent the next generation 2D carbon-rich materials with tunable structures and properties surpassing those of graphene. However, the detection of band formation in atomically thin GY/GDY analogues has been challenging, as both long-range order and atomic precision have to be fulfilled in the system. The present work reports direct evidence of band formation in on-surface synthesized metallated Ag-GDY sheets with mesoscopic (≈1 µm) regularity. Employing scanning tunneling and angle-resolved photoemission spectroscopies, energy-dependent transitions of real-space electronic states above the Fermi level and formation of the valence band are respectively observed. Furthermore, density functional theory (DFT) calculations corroborate the observations and reveal that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to the Fermi level. DFT modeling also indicates an intrinsic band gap for the pristine sheet material, which is retained for a bilayer with h-BN, whereas adsorption-induced in-gap electronic states evolve at the synthesis platform with Ag-GDY decorating the (111) facet of silver. These results illustrate the tremendous potential for engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon materials.

Isothermal and non-isothermal transport properties of diluted fullerene binary and ternary aromatic solvent mixtures

We present mass transport properties of C60 fullerene in five aromatic solvents, methylnaphthalene, toluene and three xylene isomers. Optical beam deflection and thermogravitational column techniques were used to determine molecular diffusion, thermodiffusion and Soret coefficients. All thermo-optical properties necessary to determine the abovementioned coefficients are also given at a mean working temperature of 298.15 K and an atmospheric pressure of 0.101 MPa. The magnitude of all transport properties is governed by the molecular weight ratio. In the particular case of the isomers, experiments revealed that movement under isothermal conditions (described by molecular diffusion) is dominated by density, while under non-isothermal conditions viscous forces affect the displacement (thermodiffusion depends on the dynamic viscosity). In the case of the Soret coefficients, as a combination of both, density is the dominant parameter and also the moment of inertia.

Carbon-Based Nanocomposite Membranes for Membrane Distillation: Progress, Problems and Future Prospects

The development of an ideal membrane for membrane distillation (MD) is of the utmost importance. Enhancing the efficiency of MD by adding nanoparticles to or onto a membrane's surface has drawn considerable attention from the scientific community. It is crucial to thoroughly examine state-of-the-art nanomaterials-enabled MD membranes with desirable properties, as they greatly enhance the efficiency and reliability of the MD process. This, in turn, opens up opportunities for achieving a sustainable water-energy-environment nexus. By introducing carbon-based nanomaterials into the membrane's structure, the membrane gains excellent separation abilities, resistance to various feed waters, and a longer lifespan. Additionally, the use of carbon-based nanomaterials in MD has led to improved membrane performance characteristics such as increased permeability and a reduced fouling propensity. These nanomaterials have also enabled novel membrane capabilities like in situ foulant degradation and localized heat generation. Therefore, this review offers an overview of how the utilization of different carbon-based nanomaterials in membrane synthesis impacts the membrane characteristics, particularly the liquid entry pressure (LEP), hydrophobicity, porosity, and membrane permeability, as well as reduced fouling, thereby advancing the MD technology for water treatment processes. Furthermore, this review also discusses the development, challenges, and research opportunities that arise from these findings.

Electron Localization and Mobility in Monolayer Fullerene Networks

The novel 2D quasi-hexagonal phase of covalently bonded fullerene molecules (qHP C60), the so-called graphullerene, has displayed far superior electron mobilities, if compared to the parent van der Waals three-dimensional crystal (vdW C60). Herein, we present a comparative study of the electronic properties of vdW and qHP C60 using state-of-the-art electronic-structure calculations and a full quantum-mechanical treatment of electron transfer. We show that both materials entail polaronic localization of electrons with similar binding energies (≈0.1 eV) and, therefore, they share the same charge transport via polaron hopping. In fact, we quantitatively reproduce the sizable increment of the electron mobility measured for qHP C60 and identify its origin in the increased electronic coupling between C60 units.

Structural identification of single boron-doped graphdiynes by computational XPS and NEXAFS spectroscopy

Boron-doped graphdiyne (B-GDY) material exhibits an excellent performance in electrocatalysis, ion transport, and energy storage. However, accurately identifying the structures of B-GDY in experiments remains a challenge, hindering further selection of suitable structures with the most ideal performance for various practical applications. In the present work, we employed density functional theory (DFT) to simulate the X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectra of pristine graphdiyne (GDY) and six representative single boron-doped graphdiynes at the B and C K-edges to establish the structure-spectroscopy relationship. A notable disparity in the C 1s ionization potentials (IPs) between substituted and adsorbed structures is observed upon doping with a boron atom. By analyzing the C and B 1s NEXAFS spectra on energy positions, spectral widths, spectral intensities, and different spectral profiles, we found that the six single boron-doped graphdiyne configurations can be sensitively identified. Moreover, this study provides a reliable theoretical reference for distinguishing different single boron-doped graphdiyne structures, enabling accurate selection of B-GDY structures for diverse practical applications.

A π-extended molecular belt with selective binding capability for fullerene C70

A molecular belt incorporating naphthalene moieties, featuring an ellipsoidal cavity, was precisely engineered through bottom-up synthesis. Its pre-arranged geometry exhibits excellent complementarity to fullerene C70, resulting in remarkable selective binding ability (K = 1.3 × 106 M-1) for C70 compared to C60 (K = 176 M-1), forming a 1 : 1 complex. This superiority was unequivocally demonstrated by the single crystal structure of the complex, which revealed outstanding concave-convex shape complementarity between the two components. This highlights the potential application of molecular belts in the purification and separation of fullerenes.

Uniform Synthesis of Bilayer Hydrogen Substituted Graphdiyne for Flexible Piezoresistive Applications

Graphdiyne (GDY) has garnered significant attention as a cutting-edge 2D material owing to its distinctive electronic, optoelectronic, and mechanical properties, including high mobility, direct bandgap, and remarkable flexibility. One of the key challenges hindering the implementation of this material in flexible applications is its large area and uniform synthesis. The facile growth of centimeter-scale bilayer hydrogen substituted graphdiyne (Bi-HsGDY) on germanium (Ge) substrate is achieved using a low-temperature chemical vapor deposition (CVD) method. This material's field effect transistors (FET) showcase a high carrier mobility of 52.6 cm2 V-1 s-1 and an exceptionally low contact resistance of 10 Ω µm. By transferring the as-grown Bi-HsGDY onto a flexible substrate, a long-distance piezoresistive strain sensor is demonstrated, which exhibits a remarkable gauge factor of 43.34 with a fast response time of ≈275 ms. As a proof of concept, communication by means of Morse code is implemented using a Bi-HsGDY strain sensor. It is believed that these results are anticipated to open new horizons in realizing Bi-HsGDY for innovative flexible device applications.

Synthesis mechanism from graphene quantum dots to carbon nanotubes by ion-sputtering assisted chemical vapor deposition

We present the first work of the synthesis mechanism from graphene quantum dots (GQDs) to carbon nanotubes (CNTs) by an ion-sputtering assisted chemical vapor deposition. During the annealing process, a Pt thin film deposited by the ion-sputtering was dewetted and agglomerated to form many nanometer-sized particles, leading to Pt nanoparticles (PtNPs) that can act as catalysts for creating carbon allotropes. The shape of the allotropes can be effectively tailored from GQDs to CNTs by controlling three key parameters such as the dose of catalytic ions (D), amounts of carbon source (S), and thermal energy (T). In our work, it was clearly proved that the growth control from GQDs to CNTs has a comparably proportional relationship with D and S, but has a reverse proportional relationship with T. Furthermore, high-purity GQDs without any other by-products and the CNTs with the cap of PtNPs were generated. Their shapes were appropriately controlled, respectively, based on the established synthesis mechanism.

Evaluating the effect of unidirectional loading on the piezoresistive characteristics of carbon nanoparticles

The piezoresistive effect of materials can be adopted for a plethora of sensing applications, including force sensors, structural health monitoring, motion detection in fabrics and wearable, etc. Although metals are the most widely adopted material for sensors due to their reliability and affordability, they are significantly affected by temperature. This work examines the piezoresistive performance of carbon nanoparticle (CNP) bulk powders and discusses their potential applications based on strain-induced changes in their resistance and displacement. The experimental results are correlated with the characteristics of the nanoparticles, namely, dimensionality and structure. This report comprehensively characterizes the piezoresistive behavior of carbon black (CB), onion-like carbon (OLC), carbon nanohorns (CNH), carbon nanotubes (CNT), dispersed carbon nanotubes (CNT-D), graphite flakes (GF), and graphene nanoplatelets (GNP). The characterization includes assessment of the ohmic range, load-dependent electrical resistance and displacement tracking, a modified gauge factor for bulk powders, and morphological evaluation of the CNP. Two-dimensional nanostructures exhibit promising results for low loads due to their constant compression-to-displacement relationship. Additionally, GF could also be used for high load applications. OLC's compression-to-displacement relationship fluctuates, however, for high load it tends to stabilize. CNH could be applicable for both low and high loading conditions since its compression-to-displacement relationship fluctuates in the mid-load range. CB and CNT show the most promising results, as demonstrated by their linear load-resistance curves (logarithmic scale) and constant compression-to-displacement relationship. The dispersion process for CNT is unnecessary, as smaller agglomerates cause fluctuations in their compression-to-displacement relationship with negligible influence on its electrical performance.

Impact of Halogen Termination and Chain Length on π-Electron Conjugation and Vibrational Properties of Halogen-Terminated Polyynes

We explored the optoelectronic and vibrational properties of a new class of halogen-terminated carbon atomic wires in the form of polyynes using UV-vis, infrared absorption, Raman spectroscopy, X-ray single-crystal diffraction, and DFT calculations. These polyynes terminate on one side with a cyanophenyl group and on the other side, with a halogen atom X (X = Cl, Br, I). We focus on the effect of different halogen terminations and increasing lengths (i.e., 4, 6, and 8 sp-carbon atoms) on the π-electron conjugation and the electronic structure of these systems. The variation in the sp-carbon chain length is more effective in tuning these features than changing the halogen end group, which instead leads to a variety of solid-state architectures. Shifts between the vibrational frequencies of samples in crystalline powders and in solution reflect intermolecular interactions. In particular, the presence of head-to-tail dimers in the crystals is responsible for the modulation of the charge density associated with the π-electron system, and this phenomenon is particularly important when strong I··· N halogen bonds occur.

Synergistic Effects of Carbon Vacancies in Conjunction with Phosphorus Dopant across Bilayer Graphene for the Enhanced Hydrogen Evolution Reaction

Bilayer graphene (BLG) exhibits distinct physical properties under external influences, such as torsion and structural defects, setting it apart from monolayer graphene. In this study, we explore the synergistic effects of carbon vacancies, in conjunction with phosphorus dopants, across BLG, focusing on their impact on structural, magnetic, electrical, and hydrogen adsorption properties. Our findings reveal that the substitutional doping of a phosphorus atom into a single carbon vacancy in a graphene layer induces substantial structural distortion in BLG. In contrast, doping phosphorus into a double vacancy maintains the flat structure of graphene layers. These distinct layer structures affect the electron distribution and spin arrangement, leading to varied electronic configurations and intriguing magnetic behaviors. Furthermore, the presence of abundant unsaturated electrons around the vacancy promotes the capture and bonding of hydrogen atoms. Hydrogen adsorption on BLG results in substantial orbital hybridization, accompanied by significant charge transfer. The calculated Gibbs free energies for hydrogen adsorption on BLG range from -0.08 to 0.09 eV, indicating exceptional catalytic activity for the hydrogen evolution reaction. These findings carry implications for optimizing the properties of graphene layers, making them highly desirable for applications such as catalysis.

Halide-free synthesis of metastable graphitic BC3

Layered BC3, a metastable phase within the binary boron-carbon system that is composed of graphite-like sheets with hexagonally symmetric C6B6 units, has never been successfully crystallized. Instead, poorly-crystalline BC3-like materials with significant stacking disorder have been isolated, based on the co-pyrolysis of a boron trihalide precursor with benzene at around 800 °C. The halide leaving group (-X) is a significant driving force of these reactions, but the subsequent evolution of gaseous HX species at such high temperatures hampers their scaling up and also prohibits their further use in the presence of hard-casting templates such as ordered silicates. Herein, we report a novel halide-free synthesis route to turbostratic BC3 with long-range in-plane ordering, as evidenced by multi-wavelength Raman spectroscopy. Judicious pairing of the two molecular precursors is crucial to achieving B-C bond formation and preventing phase-segregation into the thermodynamically favored products. A simple computational method used herein to evaluate the compatibility of bottom-up molecular precursors can be generalized to guide the future synthesis of other metastable materials beyond the boron-carbon system.

Recent Advances in Graphene-Enabled Materials for Photovoltaic Applications: A Comprehensive Review

Graphene's two-dimensional structural arrangement has sparked a revolutionary transformation in the domain of conductive transparent devices, presenting a unique opportunity in the renewable energy sector. This comprehensive Review critically evaluates the most recent advances in graphene production and its employment in solar cells, focusing on dye-sensitized, organic, and perovskite devices for bulk heterojunction (BHJ) designs. This comprehensive investigation discovered the following captivating results: graphene integration resulted in a notable 20.3% improvement in energy conversion rates in graphene-perovskite photovoltaic cells. In comparison, BHJ cells saw a laudable 10% boost. Notably, graphene's 2D internal architecture emerges as a protector for photovoltaic devices, guaranteeing long-term stability against various environmental challenges. It acts as a transportation facilitator and charge extractor to the electrodes in photovoltaic cells. Additionally, this Review investigates current research highlighting the role of graphene derivatives and their products in solar PV systems, illuminating the way forward. The study elaborates on the complexities, challenges, and promising prospects underlying the use of graphene, revealing its reflective implications for the future of solar photovoltaic applications.

On-surface synthesis and characterization of polyynic carbon chains

Carbyne, an elusive sp-hybridized linear carbon allotrope, has fascinated chemists and physicists for decades. Due to its high chemical reactivity and extreme instability, carbyne was much less explored in contrast to the sp2-hybridized carbon allotropes such as graphene. Herein, we report the on-surface synthesis of polyynic carbon chains by demetallization of organometallic polyynes on the Au(111) surface; the longest one observed consists of ∼60 alkyne units (120 carbon atoms). The polyynic structure of carbon chains with alternating triple and single bonds was unambiguously revealed by bond-resolved atomic force microscopy. Moreover, an atomically precise polyyne, C14, was successfully produced via tip-induced dehalogenation and ring-opening of the decachloroanthracene molecule (C14Cl10) on a bilayer NaCl/Au(111) surface at 4.7 K, and a band gap of 5.8 eV was measured by scanning tunnelling spectroscopy, in a good agreement with the theoretical HOMO-LUMO gap (5.48 eV).

Beyond Planar Structure: Curved π-Conjugated Molecules for High-Performing and Stable Perovskite Solar Cells

Perovskite solar cell (PSC) shows a great potential to become the next-generation photovoltaic technology, which has stimulated researchers to engineer materials and to innovate device architectures for promoting device performance and stability. As the power conversion efficiency (PCE) keeps advancing, the importance of exploring multifunctional materials for the PSCs has been increasingly recognized. Considerable attention has been directed to the design and synthesis of novel organic π-conjugated molecules, particularly the emerging curved ones, which can perform various unmatched functions for PSCs. In this review, the characteristics of three representative such curved π-conjugated molecules (fullerene, corannulene and helicene) and the recent progress concerning the application of these molecules in state-of-the-art PSCs are summarized and discussed holistically. With this discussion, we hope to provide a fresh perspective on the structure-property relation of these unique materials toward high-performance and high-stability PSCs.

Extreme Metastability of Diamond and its Transformation to the BC8 Post-Diamond Phase of Carbon

Diamond possesses exceptional physical properties due to its remarkably strong carbon-carbon bonding, leading to significant resilience to structural transformations at very high pressures and temperatures. Despite several experimental attempts, synthesis and recovery of the theoretically predicted post-diamond BC8 phase remains elusive. Through quantum-accurate multimillion atom molecular dynamics (MD) simulations, we have uncovered the extreme metastability of diamond at very high pressures, significantly exceeding its range of thermodynamic stability. We predict the post-diamond BC8 phase to be experimentally accessible only within a narrow high pressure-temperature region of the carbon phase diagram. The diamond to BC8 transformation proceeds through premelting followed by BC8 nucleation and growth in the metastable carbon liquid. We propose a double-shock compression pathway for BC8 synthesis, which is currently being explored in experiments at the National Ignition Facility.

Space-Confined Synthesis of Monolayer Graphdiyne in MXene Interlayer

Graphdiyne (GDY) is an artificial carbon allotrope that is conceptually similar to graphene but composed of sp- and sp2 -hybridized carbon atoms. Monolayer GDY (ML-GDY) is predicted to be an ideal 2D semiconductor material with a wide range of applications. However, its synthesis has posed a significant challenge, leading to difficulties in experimentally validating theoretical properties. Here, it is reported that in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of MXene can effectively prevent out-of-plane growth or vertical stacking of the material, resulting in ML-GDY with in-plane periodicity. The subsequent exfoliation process successfully yields free-standing GDY monolayers with micrometer-scale lateral dimensions. The fabrication of field-effect transistor on free-standing ML-GDY makes the first measurement of its electronic properties possible. The measured electrical conductivity (5.1 × 103 S m-1 ) and carrier mobility (231.4 cm2 V-1 s-1 ) at room temperature are remarkably higher than those of the previously reported multilayer GDY materials. The space-confined synthesis using layered crystals as templates provides a new strategy for preparing 2D materials with precisely controlled layer numbers and long-range structural order.

Masked alkynes for synthesis of threaded carbon chains

Polyynes are chains of sp1 carbon atoms with alternating single and triple bonds. As they become longer, they evolve towards carbyne, the 1D allotrope of carbon, and they become increasingly unstable. It has been anticipated that long polyynes could be stabilized by supramolecular encapsulation, by threading them through macrocycles to form polyrotaxanes-but, until now, polyyne polyrotaxanes with many threaded macrocycles have been synthetically inaccessible. Here we show that masked alkynes, in which the C≡C triple bond is temporarily coordinated to cobalt, can be used to synthesize polyrotaxanes, up to the C68 [5]rotaxane with 34 contiguous triple bonds and four threaded macrocycles. This is the length regime at which the electronic properties of polyynes converge to those of carbyne. Cyclocarbons constitute a related family of molecular carbon allotropes, and cobalt-masked alkynes also provide a route to [3]catenanes and [5]catenanes built around cobalt complexes of cyclo[40]carbon and cyclo[80]carbon, respectively.

Soluble Nanographene C222: Synthesis and Applications for Synergistic Photodynamic/Photothermal Therapy

Nanographene C222, which consists of a planar graphenic plane containing 222 carbon atoms, holds the record as the largest planar nanographene synthesized to date. However, its complete insolubility makes the processing of C222 difficult. Here we addressed this issue by introducing peripheral substituents perpendicular to the graphene plane, effectively disrupting the interlayer stacking and endowing C222 with good solubility. We also found that the electron-withdrawing substituents played a crucial role in the cyclodehydrogenation process, converting the dendritic polyphenylene precursor to C222. After disrupting the interlayer stacking, the introduction of only a few peripheral carboxylic groups allowed C222 to dissolve in phosphate buffer saline, reaching a concentration of up to 0.5 mg/mL. Taking advantage of the good photosensitizing and photothermal properties of the inner C222 core, the resulting water-soluble C222 emerged as a single-component agent for both photothermal and photodynamic tumor therapy, exhibiting an impressive tumor inhibition rate of 96%.

Naturally Occurring Allotropes of Carbon

Carbon is one of the most important chemical elements, forming a wide range of important allotropes, ranging from diamond over graphite to nanostructural materials such as graphene, fullerenes, and carbon nanotubes (CNTs). Especially these nanomaterials play an important role in technology and are commonly formed in laborious synthetic processes that often are of high energy demand. Recently, fullerenes and their building blocks (buckybowls) have been found in natural fossil materials formed under geological conditions. The question arises of how diverse nature can be in forming different types of natural allotropes of carbon. This is investigated here, using modern analytical methods such as ultrahigh-resolution mass spectrometry and transmission electron microscopy, which facilitate a detailed understanding of the diversity of natural carbon allotropes. Large fullerenes, fullertubes, graphene sheets, and double- and multiwalled CNTs together with single-walled CNTs were detected in natural heavy fossil materials while theoretical calculations on the B3LYP/6-31G(d) level of theory using the ORCA software package support the findings.

Electronic Properties of Graphene Nano-Parallelograms: A Thermally Assisted Occupation DFT Computational Study

In this computational study, we investigate the electronic properties of zigzag graphene nano-parallelograms (GNPs), which are parallelogram-shaped graphene nanoribbons of various widths and lengths, using thermally assisted occupation density functional theory (TAO-DFT). Our calculations revealed a monotonic decrease in the singlet-triplet energy gap as the GNP length increased. The GNPs possessed singlet ground states for all the cases examined. With the increase of GNP length, the vertical ionization potential and fundamental gap decreased monotonically, while the vertical electron affinity increased monotonically. Some of the GNPs studied were found to possess fundamental gaps in the range of 1-3 eV, lying in the ideal region relevant to solar energy applications. Besides, as the GNP length increased, the symmetrized von Neumann entropy increased monotonically, denoting an increase in the degree of the multi-reference character associated with the ground state GNPs. The occupation numbers and real-space representation of active orbitals indicated that there was a transition from the nonradical nature of the shorter GNPs to the increasing polyradical nature of the longer GNPs. In addition, the edge/corner localization of the active orbitals was found for the wider and longer GNPs.

A novel 2D intrinsic metal-free ferromagnetic semiconductor Si3C8 monolayer

Metal-free magnets, a special kind of ferromagnetic (FM) material, have evolved into an important branch of magnetic materials for spintronic applications. We herein propose a silicon carbide (Si3C8) monolayer and investigate its geometric, electronic, and magnetic properties by using first-principles calculations. The thermal and dynamical stability of the Si3C8 monolayer was confirmed by ab initio molecular dynamics and phonon dispersion simulations. Our results show that the Si3C8 monolayer is a FM semiconductor with a band gap of 1.76 eV in the spin-down channel and a Curie temperature of 22 K. We demonstrate that the intrinsic magnetism of the Si3C8 monolayer is derived from pz orbitals of C atoms via superexchange interactions. Furthermore, the half-metallic state in the FM Si3C8 monolayer can be induced by electron doping. Our work not only illustrates that carrier doping could manipulate the magnetic states of the FM Si3C8 monolayer but also provides an idea to design two-dimensional metal-free magnetic materials for spintronic applications.

Recent advances in supramolecular fullerene chemistry

Fullerene chemistry has come a long way since 1990, when the first bulk production of C60 was reported. In the past decade, progress in supramolecular chemistry has opened some remarkable and previously unexpected opportunities regarding the selective (multiple) functionalization of fullerenes and their (self)assembly into larger structures and frameworks. The purpose of this review article is to provide a comprehensive overview of these recent developments. We describe how macrocycles and cages that bind strongly to C60 can be used to block undesired addition patterns and thus allow the selective preparation of single-isomer addition products. We also discuss how the emergence of highly shape-persistent macrocycles has opened opportunities for the study of photoactive fullerene dyads and triads as well as the preparation of mechanically interlocked compounds. The preparation of two- or three-dimensional fullerene materials is another research area that has seen remarkable progress over the past few years. Due to the rapidly decreasing price of C60 and C70, we believe that these achievements will translate into all fields where fullerenes have traditionally (third-generation solar cells) and more recently been applied (catalysis, spintronics).

Carbon Kagome nanotubes-quasi-one-dimensional nanostructures with flat bands

In recent years, a number of bulk materials and heterostructures have been explored due their connections with exotic materials phenomena emanating from flat band physics and strong electronic correlation. The possibility of realizing such fascinating material properties in simple realistic nanostructures is particularly exciting, especially as the investigation of exotic states of electronic matter in wire-like geometries is relatively unexplored in the literature. Motivated by these considerations, we introduce in this work carbon Kagome nanotubes (CKNTs)-a new allotrope of carbon formed by rolling up Kagome graphene, and investigate this material using specialized first principles calculations. We identify two principal varieties of CKNTs-armchair and zigzag, and find both varieties to be stable at room temperature, based on ab initio molecular dynamics simulations. CKNTs are metallic and feature dispersionless states (i.e., flat bands) near the Fermi level throughout their Brillouin zone, along with an associated singular peak in the electronic density of states. We calculate the mechanical and electronic response of CKNTs to torsional and axial strains, and show that CKNTs appear to be more mechanically compliant than conventional carbon nanotubes (CNTs). Additionally, we find that the electronic properties of CKNTs undergo significant electronic transitions-with emergent partial flat bands and tilted Dirac points-when twisted. We develop a relatively simple tight-binding model that can explain many of these electronic features. We also discuss possible routes for the synthesis of CKNTs. Overall, CKNTs appear to be unique and striking examples of realistic elemental quasi-one-dimensional materials that may display fascinating material properties due to strong electronic correlation. Distorted CKNTs may provide an interesting nanomaterial platform where flat band physics and chirality induced anomalous transport effects may be studied together.

Zinc oxide-aluminum oxide nanocomposite solid phase microextraction for diazepam and oxazepam trace determination

A new efficient ZnO-Al2O3 nanocomposite (ZANC) was synthesized to form solid-phase microextraction (SPME) fiber. The prepared fiber was used for trace determination of benzodiazepines by gas chromatography-flame ionization detector in urine samples. The effective parameters on the extraction process including extraction time, salt percentage, desorption time and sample pH were optimized by a factorial design method. The method was evaluated at the optimum conditions and limits of detection (LODs) were calculated 20 µg/L for diazepam and oxazepam. The method repeatability for oxazepam and diazepam (50 µg/L, n = 4) was calculated at 8.8 % and 6.4 %. Also, the method reproducibility was obtained, 7.45 % and 6.61 % for oxazepam and diazepam (50 µg/L, n = 4). Also, fiber-to-fiber relative standard deviation (RSDs%) for the target analytes were less than 15.5 %. The method linearity is within the range of 62-500 µg/L for diazepam and oxazepam. The ZANC-SPME fiber showed a good lifetime (60 times) with high chemical stability. The high thermal stability of ZANC-SPME fiber was attained at 280 °C. The extraction results of poly dimethylsiloxan/divinyl benzene (PDMS/DVB) fiber were compared by ZANC-SPME fiber. Therefore, the method is proposed as a suitable technique for benzodiazepines detection in the urine sample.

In Situ TEM Characterization and Modulation for Phase Engineering of Nanomaterials

Solid-state phase transformation is an intriguing phenomenon in crystalline or noncrystalline solids due to the distinct physical and chemical properties that can be obtained and modified by phase engineering. Compared to bulk solids, nanomaterials exhibit enhanced capability for phase engineering due to their small sizes and high surface-to-volume ratios, facilitating various emerging applications. To establish a comprehensive atomistic understanding of phase engineering, in situ transmission electron microscopy (TEM) techniques have emerged as powerful tools, providing unprecedented atomic-resolution imaging, multiple characterization and stimulation mechanisms, and real-time integrations with various external fields. In this Review, we present a comprehensive overview of recent advances in in situ TEM studies to characterize and modulate nanomaterials for phase transformations under different stimuli, including mechanical, thermal, electrical, environmental, optical, and magnetic factors. We briefly introduce crystalline structures and polymorphism and then summarize phase stability and phase transformation models. The advanced experimental setups of in situ techniques are outlined and the advantages of in situ TEM phase engineering are highlighted, as demonstrated via several representative examples. Besides, the distinctive properties that can be obtained from in situ phase engineering are presented. Finally, current challenges and future research opportunities, along with their potential applications, are suggested.

Electronic Structure of Pentagonal Carbon Nanocones: An ab Initio Study

In this work, we investigate the electronic structure of a particular class of carbon nanocones having a pentagonal tip and C5v symmetry. The ground-state nature of the wave function for these structures can be predicted by the recently proposed generalized Hückel rule that extends the original Hückel rule for annulenes to this class of carbon nanocones. In particular, the structures here considered can be classified as closed-shell or anionic/cationic closed-shells, depending on the geometric characteristics of the cone. The goal of this work is to assess the relationship between the electronic configuration of these carbon nanocones and their ability to gain or lose an electron as well as their adsorption capability. For this, the geometry of these structures in the neutral or ionic forms, as well as systems containing either one lithium or fluorine atom, was optimized at the DFT/B3LYP level. It was found that the electron affinity, ionization potential, and the Li or F adsorption energy present an intimate connection to the ground-state wave function character predicted by the generalized Hückel rule. In fact, a peculiar oscillatory energy behavior was discovered, in which the electron affinity, ionization energy, and adsorption energies oscillate with an increase in the nanocone size. The reasoning behind this is that if the anion is closed-shell, then the neutral nanocone will turn out to be a good electron acceptor, increasing the electron affinity and lithium adsorption energy. On the other hand, in the case of a closed-shell cation, this means that the neutral nanocone will easily lose an electron, leading to a smaller ionization potential and higher fluorine adsorption energy.

Cyclo[n]carbons and catenanes from different perspectives: disentangling the molecular thread

All-carbon atomic rings, cyclo[n]carbons, have recently attracted vivid attention of experimentalists and theoreticians. Among them, cyclo[18]carbon is the most studied system. In this paper, we summarize and review various properties of cyclo[n]carbons, emphasising the aspects of their aromaticity/antiaromaticity. In the first part, the trends in bonding patterns and selected aromaticity indices with the increasing size of the rings are discussed. In the second part we explore the properties of catenane models based on interlocked cyclo[18]carbon rings from different perspectives and investigate their behaviour under the action of external force using computational experiments.

Studying the Adsorption of Gas Molecules and Defects on Modulating the Electronic Transport Characteristics of Monolayer Penta-BN2-Based Devices

Two-dimensional atomic layer materials, as an important part of the post-Moore era, have recently become an ideal choice for the preparation of high-efficiency, low-power, and miniaturized gas sensors. In this work, our study utilized density functional theory and the nonequilibrium Green's function method to investigate the electronic properties of the pentagonal BN2 (P-BN2) monolayer, as well as its gas-sensing properties for organic and inorganic gases. We also investigated how defects affect the quantum transport properties of the P-BN2-based device. Our findings demonstrate that the CO, H2S, NH3, SO2, C2H5OH, C3H6OH, CH3OH, and CH4 undergo physisorption on the P-BN2 monolayer, while NO, NO2, C2H2, C2H4, and HCHO undergo chemisorption. Then, we analyzed the impact of gas molecules chemisorbed on the P-BN2 monolayer on the electronic transport properties of the P-BN2-based gas sensor. When these five gas molecules are adsorbed, the current of the P-BN2-based gas sensor is greatly reduced. In addition, the effect of defects on the quantum transport properties of the P-BN2-based device is investigated. The results indicate that defects of N, B, and BN atoms lead to a decrease in the current of P-BN2-based nanodevices. Moreover, both the adsorption of gas molecules and the formation of vacancy defects leading to a decrease in device current can be revealed by the local device density of states near the zero-bias Fermi level, elucidating their microscopic mechanisms. Finally, gas molecules can also cause a decrease in the current of defect systems. These theoretical studies are of great significance for exploring two-dimensional atomic layer materials as high-efficiency gas sensors.

Discovery of Ferroelectricity in the Fullerene Adduct C60S8

Fullerenes offer versatile functionalities and are promising materials for a widespread range of applications from biomedicine and energy to electronics. Great efforts have been made to manipulate the symmetries of fullerene and its derivatives for studying material properties and novel effects, such as ferroelectricity with polar symmetry; however, no documentary report has been obtained to realize their ferroelectricity. Here, for the first time, we demonstrated clear ferroelectricity in a fullerene adduct formed by C60 and S8. More is different: the combination of the most symmetric molecule C60 with the highest Ih symmetry and molecule S8 with high D4d symmetry resulted in the polar C60S8 adduct with a low crystallographic symmetry of the C2v (mm2) point group at room temperature. The presented C60S8 undergoes polar-to-polar ferroelectric phase transition with the mm2Fm notation, whose ferroelectricity was confirmed by a ferroelectric hysteresis loop and ferroelectric domain switching. This finding opens up a new functionality for fullerenes and sheds light on the exploration of more ferroelectric fullerenes.

Amorphous Carbon Films for Electronic Applications

While various crystalline carbon allotropes, including graphene, have been actively investigated, amorphous carbon (a-C) thin films have received relatively little attention. The a-C is a disordered form of carbon bonding with a broad range of the CC bond length and bond angle. Although accurate structural analysis and theoretical approaches are still insufficient, reproducible structure-property relationships have been accumulated. As the a-C thin film is now adapted as a hardmask in the semiconductor industry and new properties are reported continuously, expectations are growing that it can be practically used as active materials beyond as a simple sacrificial layer. In this perspective review article, after a brief introduction to the synthesis and properties of the a-C thin films, their potential practical applications are proposed, including hardmasks, extreme ultraviolet (EUV) pellicles, diffusion barriers, deformable electrodes and interconnects, sensors, active layers, electrodes for energy, micro-supercapacitors, batteries, nanogenerators, electromagnetic interference (EMI) shielding, and nanomembranes. The article ends with a discussion on the technological challenges in a-C thin films.

Computational Studies on Diverse Characterizations of Molecular Descriptors for Graphyne Nanoribbon Structures

Materials made of graphyne, graphyne oxide, and graphyne quantum dots have drawn a lot of interest due to their potential uses in medicinal nanotechnology. Their remarkable physical, chemical, and mechanical qualities, which make them very desirable for a variety of prospective purposes in this area, are mostly to blame for this. In the subject of mathematical chemistry, molecular topology deals with the algebraic characterization of molecules. Molecular descriptors can examine a compound's properties and describe its molecular topology. By evaluating these indices, researchers can predict a molecule's behavior including its reactivity, solubility, and toxicity. Amidst the captivating realm of carbon allotropes, γ-graphyne has emerged as a mesmerizing tool, with exquisite attention due to its extraordinary electronic, optical, and mechanical attributes. Research into its possible applications across numerous scientific and technological fields has increased due to this motivated attention. The exploration of molecular descriptors for characterizing γ-graphyne is very attractive. As a result, it is crucial to investigate and predict γ-graphyne's molecular topology in order to comprehend its physicochemical characteristics fully. In this regard, various characterizations of γ-graphyne and zigzag γ-graphyne nanoribbons, by computing and comparing distance-degree-based topological indices, leap Zagreb indices, hyper leap Zagreb indices, leap gourava indices, and hyper leap gourava indices, are investigated.

Graph-EAM: An Interpretable and Efficient Graph Neural Network Potential Framework

The development of deep learning interatomic potentials has enabled efficient and accurate computations in quantum chemistry and materials science, circumventing computationally expensive ab initio calculations. However, the huge number of learnable parameters in deep learning models and their complex architectures hinder physical interpretability and affect the robustness of the derived potential. In this work, we propose graph-EAM, a lightweight graph neural network (GNN) inspired by the empirical embedded atom method to model the interatomic potential of single-element structures. Four material systems: platinum, niobium, silicon, and amorphous-carbon, for which quantum simulation data sets are publicly available, are examined to demonstrate that graph-EAM can achieve high energy and force prediction accuracy─comparable or better than existing state-of-the-art machine learning models─with much fewer parameters. It is also shown that the explicit inclusion of the angular information via three-body atomic density increases the prediction accuracy. The accuracy and efficiency of potentials obtained from graph-EAM can help accelerate the molecular dynamics simulation.

Renaissance of elemental phosphorus materials: properties, synthesis, and applications in sustainable energy and environment

The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.

Physical mechanism on the linear spectrum and nonlinear spectrum in a twist bilayer graphdiyne nanodisk

The one-photon absorption properties (OPA), two-photon absorption properties (TPA), electronic circular dichroism (ECD) spectra and partial DOS (PDOS) of a twist bilayer graphdiyne nanodisk (TwBLGDY-ND) were investigated by using a variety of quantum chemistry and wave function analyses. The physical mechanism of the twist bilayer graphdiyne nanodisk (TwBLGDY) with optical properties regulated by twisting angles was revealed. The results show that the twist angle makes the TwBLGDY form a moiré superlattice structure, and electron excitation mainly occurs in the first ring of the moiré superlattice structure. The contribution of atomic orbitals in these fragments to transition dipole moments is greater and electronic transitions are more likely to occur. When the twist angle increases from 0° to 15°, the absorption spectrum of the system is red shifted, which is mainly due to the enhancement of electron excitation characteristics. When the twist angle increases from 15° to 27.5°, the absorption spectrum of the system is blue shifted, due to the enhanced charge transfer within the layer. On the other hand, the twist angle can regulate the TPA absorption cross section of the system to enhance the intensity of the absorption spectrum. The twist angle can also regulate chirality by adjusting the spatial distribution of electric dipole transition and magnetic dipole transition. This study can provide theoretical guidance for constructing chiral optical devices based on the TwBLGDY structure.

Prospects of 2D graphdiynes and their applications in desalination and wastewater remediation

Water is an indispensable part of human life that affects health and food intake. Water pollution caused by rapid industrialization, agriculture, and other human activities affects humanity. Therefore, researchers are prudent and cautious regarding the use of novel materials and technologies for wastewater remediation. Graphdiyne (GDY), an emerging 2D nanomaterial, shows promise in this direction. Graphdiyne has a highly symmetrical π-conjugated structure consisting of uniformly distributed pores; hence, it is favorable for applications such as oil-water separation and organic-pollutant removal. The acetylenic linkage in GDY can strongly interact with metal ions, rendering GDY applicable to heavy-metal adsorption. In addition, GDY membranes that exhibit 100% salt rejection at certain pressures are potential candidates for wastewater treatment and water reuse via desalination. This review provides deep insights into the structure, properties, and synthesis methods of GDY, owing to which it is a unique, promising material. In the latter half of the article, various applications of GDY in desalination and wastewater treatment have been detailed. Finally, the prospects of these materials have been discussed succinctly.

A topological approach to reconstructive solid-state transformations and its application for generation of new carbon allotropes

A novel approach is proposed for the description of possible reconstructive solid-state transformations, which is based on the analysis of topological properties of atomic periodic nets and relations between their subnets and supernets. The concept of a region of solid-state reaction that is the free space confined by a tile of the net tiling is introduced. These regions (tiles) form the reaction zone around a given atom A thus unambiguously determining the neighboring atoms that can interact with A during the transformation. The reaction zone is independent of the geometry of the crystal structure and is determined only by topological properties of the tiles. The proposed approach enables one to drastically decrease the number of trial structures when modeling phase transitions in solid state or generating new crystal substances. All crystal structures which are topologically similar to a given structure can be found by the analysis of its topological vicinity in the configuration space. Our approach predicts amorphization of the phase after the transition as well as possible single-crystal-to-single-crystal transformations. This approach is applied to generate 72 new carbon allotropes from the initial experimentally determined crystalline carbon structures and to reveal four allotropes, whose hardness is close to diamond. Using the tiling model it is shown that three of them are structurally similar to other superhard carbon allotropes, M-carbon and W-carbon.

One-pot synthesis of gamma-graphyne supported Pd nanoparticles with high catalytic activity

As a unique member of the graphyne family, gamma-graphyne (γ-graphyne) is a novel kind of 2D carbon allotrope with potential high carrier mobility and large surface area. It remains a great challenge to synthesize graphynes with targeted topologies and good performance. Herein, a novel one-pot method was applied to the synthesis of γ-graphyne using hexabromobenzene and acetylenedicarboxylic acid via a Pd-catalyzed decarboxylative coupling reaction, which is easy to perform with mild reaction conditions, facilitating the possibility of mass production. As a result, the synthesized γ-graphyne reveals a two-dimensional γ-graphyne structure consisting of 1 : 1 sp/sp² hybridized carbon atoms. Furthermore, γ-graphyne as a carrier for Pd (Pd/γ-graphyne) displayed a superior catalytic activity for the reduction of 4-nitrophenol with a short reaction time and high yields, even in aqueous media under aerobic conditions. Compared with Pd/GO, Pd/HGO, Pd/CNT, and commercial Pd/C, Pd/γ-graphyne showed more excellent catalytic performance with lower palladium loadings. Thus we expect that the novel approach for the synthesis of γ-graphyne will boost research on the design and application of graphyne-type functional materials for catalysis.

Electrostatic Potential for Exploring Electron Delocalization in Infinitenes, Circulenes, and Nanobelts

The π-conjugation, aromaticity, and stability of the newly synthesized 12-infinitene and of other infinitenes comprising 8-, 10-, 14-, and 16-arene rings are investigated using density functional theory. The π-electron delocalization and aromatic character rooted in infinitenes are quantified in terms of molecular electrostatic potential (MESP) topology. Structurally, the infinitene bears a close resemblance of its helically twisted structure to the infinity symbol. The MESP topology shows that infinitene possesses an infinity-shaped delocalization of the electron density that streams over the fused benzenoid rings. The parameter ∑i=13Δλi, derived from the eigenvalues (λ_i) corresponding to the MESP minima, is used for quantifying the aromatic character of arene rings of infinitene. The structure, stability, and MESP topology features of 8-, 10-, 12-, 14-, and 16-infinitenes are also compared with the corresponding isomeric circulenes and carbon nanobelts. Further, the strain in all such systems is evaluated by considering the respective isomeric planar benzenoid hydrocarbons as reference systems. The 12-infinitene turns out to be the most aromatic and the least strained among all the systems examined.

Facile Synthesis of Hydrogen-Substituted Graphdiyne Powder via Dehalogenative Homocoupling Reaction

Graphdiyne and its analogs are a series of artificial two-dimensional nanomaterials with sp hybridized carbon atoms, which can be viewed as the insertion of two acetylenic units between adjacent aromatic rings, evenly expanded on a flat surface. Although developed in recent years, new synthetic strategies for graphdiyne analogs are still required. This work proposed a new method to prepare hydrogen-substituted graphdiyne powder via a dehalogenative homocoupling reaction. The polymerization was unanticipated while the initial goal was to synthesize a γ-graphyne analog via Sonogashira cross-coupling reaction. Compared with previous synthetic strategies, the reaction time was conspicuously shortened and the Pd catalyst was inessential. The powder obtained exhibited a porous structure and high electrocatalytic activity in the hydrogen/oxygen evolution reaction, which has the potential for application in electrochemical catalysis. The reported methodology provides an efficient synthetic strategy for large-scale preparation.

Synthesis of a Wheel-Shaped Nanographdiyne

Graphdiyne, a sp- and sp²-hybridized 2D π-conjugated carbon material with well-dispersed pores and unique electronic properties, was well investigated and applied in catalysis, electronics, optics, and energy storage and conversion. Graphdiyne fragments with conjugation in 2D can provide in-depth insights for understanding the intrinsic structure-property relationships of graphdiyne. Herein, an atomic precise wheel-shaped nanographdiyne composed of six dehydrobenzo [18] annulenes ([18]DBAs, the smallest macrocyclic unit of graphdiyne), was realized through the sixfold intramolecular Eglinton coupling in the hexabutadiyne precursors obtained by the sixfold Cadiot-Chodkiewicz cross-coupling of hexaethynylbenzene. Its planar structure was revealed by X-ray crystallographic analysis. The full cross-conjugation of the six 18π electron circuits yields the π-electron conjugation along the giant π core. This work provides a realizable method for the synthesis of future graphdiyne fragments with different functional groups and/or heteroatom doping, as well as the study of the unique electronic/photophysical properties and aggregation behavior of graphdiyne.