Unique Atomic Arrangement Research Articles

Green Nanotech: A Review of Carbon-Based Nanomaterials for Tackling Environmental Pollution Challenges

In recent times, nanotechnology has experienced widespread acclaim across diverse sectors, including but not limited to tissue engineering, drug delivery systems, biosensors, and the mitigation and monitoring of environmental pollutants. The unique arrangement of carbon atoms in sp3 configurations within carbon nanomaterials endows them with exceptional physical, mechanical, and chemical characteristics, driving them to the forefront of materials research. Their appeal lies in their efficacy as superior adsorbents and their exceptional thermal resistance, making them versatile in various applications. The present review extensively explores a range of carbon-based nanomaterials, delving into their synthesis methods and examining their multifaceted applications in addressing environmental pollutants. It is crucial to emphasize that the popularity of carbon-based nanomaterials arises from their potential to serve as superior adsorbents, coupled with their outstanding thermal resistance properties. These attributes contribute to their applicability in diverse environmental contexts. Looking ahead, carbon-based nanomaterials are poised to emerge as environmentally friendly and cost-effective materials, representing promising and potential avenues for the advancement of sustainable technology.

Crystal-Phase- and B-Content-Dependent Electrochemical Behavior of Pd─B Nanocrystals toward Oxygen Reduction Reaction.

The manipulation of crystal phases in metal-nonmetal interstitial alloy nanostructures has attracted considerable attention due to the formation of unique electronic structures and surface atomic arrangements, resulting in unprecedented catalytic performances. However, achieving simultaneous control over crystal phase and nonmetal elements in metal-nonmetal interstitial alloy nanostructures has remained a formidable challenge. Here, a novel synthesis approach is presented for Pd─B interstitial alloy nanocrystals (NCs) that allows investigation of the crystal-phase- and B-content-dependent catalytic performance. Through comparison of the oxygen reduction reaction (ORR) properties of Pd─BX interstitial alloy NCs with different crystal phases and B contents, achieved by precise control of reaction temperature and time, the influences of crystal phase and B contents in the Pd─BX interstitial alloy NCs on ORR are precisely investigated. The hexagonal closed packed (hcp) PdB0.5 NCs exhibit superior catalytic activity, with mass activities reaching 2.58 A mg-1, surpassing Pd/C by 10.3 times, attributed to synergistic effects by the hcp crystal phase and relatively high B contents. This study not only provides a novel approach to fabricate interstitial alloy nanostructures with unconventional crystal phases and finely controlled nonmetal elements but also elucidates the importance of crystal phase and nonmetal element content in optimizing electrocatalytic efficiency.

Properties, Synthesis and Emerging Applications of Graphdiyne: A Journey Through Recent Advancements.

Graphdiyne (GDY) is a new variant of nano-carbon material with excellent chemical, physical and electronic properties. It has attracted wide attention from researchers and industrialists for its extensive role in the fields of optics, electronics, bio-medics and energy. The unique arrangement of sp-sp2 carbon atoms, linear acetylenic linkages, uniform pores and highly conjugated structure offer numerous potentials for further exploration of GDY materials. However, since the material is at its infancy, not much understanding is available regarding its properties, growth mechanism and future applications. Therefore, in this review, readers are guided through a brief discussion on GDY's properties, different synthesis procedures with a special focus on surface functionalization and a list of applications for GDY. The review also critically analyses the advantages and disadvantages of each synthesis route and emphasizes the future scope of the material.

Analysis of multilayered two-dimensional decagonal piezoelectric quasicrystal beams with mixed boundary conditions

Piezoelectric quasicrystals have a broad spectrum of promising applications and research value due to their unique atomic arrangement and multi-field coupling effects. This paper presents a mechanical analysis of the static bending and free vibration problems of two-dimensional multilayered decagonal piezoelectric quasicrystal laminated beams. Mechanical models of the beams are established, and the differential quadrature method in conjunction with the state-space method is utilized to obtain the solutions for the beams with mixed boundary conditions. We first investigated the static response and free vibration problem of quasicrystal laminated beams. By degrading them into crystalline materials, we verified the accuracy of the method by comparing the results with the existing ones. Then, the effects of different boundary conditions and slenderness ratios on the stresses, displacements, electric potentials, and electric displacements of quasicrystal laminated beams under normal mechanical loading and free vibration are investigated. Subsequently, the effects of different laying modes on the mechanical properties of the quasicrystal laminated beams when the material principal axis of the beam is changed are also analyzed.

Pushing thermal conductivity to its lower limit in crystals with simple structures

Materials with low thermal conductivity usually have complex crystal structures. Herein we experimentally find that a simple crystal structure material AgTlI2 (I4/mcm) owns an extremely low thermal conductivity of 0.25 W/mK at room temperature. To understand this anomaly, we perform in-depth theoretical studies based on ab initio molecular dynamics simulations and anharmonic lattice dynamics. We find that the unique atomic arrangement and weak chemical bonding provide a permissive environment for strong oscillations of Ag atoms, leading to a considerable rattling behaviour and giant lattice anharmonicity. This feature is also verified by the experimental probability density function refinement of single-crystal diffraction. The particularly strong anharmonicity breaks down the conventional phonon gas model, giving rise to non-negligible wavelike phonon behaviours in AgTlI2 at 300 K. Intriguingly, unlike many strongly anharmonic materials where a small propagative thermal conductivity is often accompanied by a large diffusive thermal conductivity, we find an unusual coexistence of ultralow propagative and diffusive thermal conductivities in AgTlI2 based on the thermal transport unified theory. This study underscores the potential of simple crystal structures in achieving low thermal conductivity and encourages further experimental research to enrich the family of materials with ultralow thermal conductivity.

Nano‐bio interactions between 2D nanomaterials and mononuclear phagocyte system cells

AbstractTwo‐dimensional (2D) nanomaterials, known for their unique atomic arrangements and exceptional physicochemical properties, have garnered significant attention in biomedical applications, particularly in the realms of immunotherapy for tissue engineering and tumor therapy. These applications necessitate a thorough assessment of the potential influence of 2D nanomaterials on immune cells. Notably, the mononuclear phagocyte system (MPS) cells, which play pivotal roles in both innate and adaptive immunity, are essential for maintaining organismal homeostasis. MPS cells with phagocytic capability contribute to the prevention of foreign body invasion and the elimination of dead or senescent cells. Furthermore, MPS cells, including macrophages and dendritic cells, serve as vital bridges between innate and adaptive immune responses. Therefore, understanding the nano‐bio interactions between 2D nanomaterials and MPS cells is imperative. These nano‐bio interactions including cellular uptake, cytocompatibility, and immunological impact are invaluable for the purposeful design of 2D nanomaterials. Herein, we provide an overview of the latest advancements in understanding the nano‐bio interactions between 2D nanomaterials and MPS cells, and discuss the current challenges and future prospects of employing 2D nanomaterials in the field of nanomedicine.

Electronic and Lattice Distortions Induce Elastic Softening in Refractory Multicomponent Borides.

Borides are extensively employed in applications demanding exceptionally high hardness, which arises from the unique and strong crystallographic arrangement of boron atoms therein. Addition of multiprincipal elements in borides is expected to enhance their structural properties due to lattice distortion and high configurational entropy. In contrast, we unravel a phenomenon of elastic softening in refractory multicomponent borides from first-principle predictions, which concur with experimentally determined metrics in their single-phase multiprincipal element counterparts. The reductions in the bulk and Young's modulus of these compounds are attributed to the lengthening and distortion of the boron-boron bonds and angles, but more critically to the perturbation in the charge densities arising from the different cations and the consequential increase in statistical weights of the d5 configuration states of the transition metals present in the boride..

Kagome-like BiP3 Monolayer: An Emerging Quasi-Direct Auxetic Semiconductor Coupled with High Anisotropic Mobility toward Visible-Light-Driven Photoelectrocatalytic pH-Robust Overall Water-Splitting.

Two-dimensional (2D) Janus materials exhibit an outstanding potential that can meet the rigorous requirements of photocatalytic water splitting resulting from their unique atomic arrangement. However, these materials are quite scarce. Through ab initio density functional theory calculations, we introduce a kagome topology into the honeycomb lattice of blue phosphorene using phosphorus and bismuth atoms to build a hybrid honeycomb-like kagome lattice, realized by a hitherto unknown kagome-like Janus-like BiP3 monolayer with robust stability. Excitingly, the out-of-plane asymmetry benefiting from kagome and honeycomb topologies gives rise to a significantly negative out-of-plane Poisson's ratio and an obvious built-in electric field pointing from the sublayer of the P atom to the sublayer of the Bi atom. In conjunction with the investigations that encompass semiconducting properties, such as a quasi-direct gap, suitable band-edge positions, effective visible-light absorption, and high carrier mobility, the BiP3 monolayer achieves overall water splitting at pH 0-14 regardless of strain. Moreover, this intrinsic electric field provides a sufficient photogenerated carrier driving force for water splitting. The bare BiP3 comprises P and Bi atoms that function as catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) active sites, respectively. Upon exposure to light, the reaction of water into H2 and O2 can be observed across a pH range of 0-14. Meanwhile, by designing a transition-metal single-atom catalyst (TM@BiP3), our investigations have shown that embedding a single TM on BiP3 is a feasible route to improving the HER/OER activity by reducing the overpotentials to -0.039 and 0.58 eV for Mo and Os atoms, respectively. In this case, the positive value of the external potential acts as a sufficient OER driving force, i.e., in the light environment, the Os@BiP3 system can promote water molecules spontaneously oxidized into O2 at pH 0-14.

Electrochemical Synthesis of Nanostructured Ordered Intermetallic Materials under Ambient Conditions.

ConspectusThe enhanced catalytic properties of alloy nanostructures have made them a focus of extensive research in the field of catalysis. Alloy nanostructures can be classified into two types: disordered alloys (also known as solid solutions) and ordered intermetallics. The latter are of particular interest as they possess long-range atomic scale ordering, which leads to well-defined active sites that can be used to accurately assess structure-property relationships and their impact on (electro)catalytic performance.While many ordered intermetallics (OICs) have been synthesized and evaluated as electrocatalysts, there is still a lack of understanding on how the local structure of atoms controls their catalytic performance. Ordered intermetallics are difficult to synthesize and often require high-temperature annealing for the atoms to equilibrate into ordered structures. High temperature processing results in aggregated structures (usually >30 nm) and/or contamination from the support, which can decrease their performance and preclude these materials from being used as model systems for elucidating insight into structure and electrochemical properties. Therefore, alternative methods are required to enable more efficient atomic ordering while maintaining some level of morphological control.This Account delves into the potential of electrochemical methods as a practical alternative for synthesizing ordered intermetallics at lower temperatures. Specifically, it explores the viability of electrochemical dealloying and electrochemical deposition to synthesize Pd-Bi and Cu-Zn intermetallics at room temperature and atmospheric pressure. These methods have proven useful in synthesizing phases that are typically inaccessible under ambient conditions. The high homologous temperatures at which these materials are synthesized provide the necessary atomic mobility required for equilibration and formation of ordered phases, thus making the direct synthesis of ordered intermetallic materials at room temperature by electrochemical means a reality.Beyond synthesis, the electrocatalytic performance of these intermetallics was assessed for the oxygen reduction reaction (ORR), which is an important process employed in fuel cells. The OICs displayed increased performance with respect to commercial Pd/C and Pt/C benchmarks because of lower coverages of spectator species. Furthermore, these materials exhibited improved methanol tolerance.This Account provides valuable insights into the electrochemical synthesis of ordered intermetallics and their potential use as highly effective catalysts for electrocatalytic reactions. By using electrochemical methods, it is possible to obtain ordered intermetallics with unique atomic arrangements and tailored properties, which can be optimized for specific catalytic applications. With further research, electrochemical synthesis methods may enable the development of new and improved ordered intermetallics with even higher catalytic activity and selectivity, making them ideal candidates for use in a wide range of industrial processes. Furthermore, the ability to access intermetallics under milder conditions may accelerate the ability to use these materials as model systems for revealing fundamental insight into electrocatalyst structure and function.

Surface Reconstruction of Covellite CuS Nanocrystals for Enhanced OER Catalytic Performance in Alkaline Solution.

Oxygen evolution reaction (OER) is one of the important half-reactions in energy conversion equipment such as water-spitting devices, rechargeable metal-air batteries, and so on. It is beneficial to develop efficient and low-cost catalysts that understand the reaction mechanism of OER and analyze the reconstruction phenomenon of transition metal sulfide. Interestingly, copper sulfide and cuprous sulfide with the same components possess different reconstruction behaviors due to their different metal ion valence states and different atomic arrangement modes. Because of a unique atomic arrangement sequence and certain cationic defects, the reconstruction phenomenon of CuS nanomaterials are that S2- is firstly oxidized to SO4 2- and then Cux + is converted into CuO via Cu(OH)2 . In addition, the specific "modified hourglass structure" of CuS with excellent conductivity is easier to produce intermediates. Compared with Cu2 S, CuS exhibits excellent OER activity with a lower overpotential of 192mV at 10mA cm-2 and remarkable electrochemical stability in 1.0m KOH for 120h. Herein, this study elucidates the reconstruction modes of CuS and Cu2 S in the OER process and reveals that CuS has a stronger CuS bond and a faster electronic transmission efficiency due to "modified hourglass structure," resulting in faster reconstruction of CuS than Cu2 S.

Principal strategies for designing graphdiyne-based catalyst toward green hydrogen production from water electrolysis

Water electrolysis has attracted significant attention for large-scale production of green hydrogen as next-generation clean fuels. Recently, the development of graphdiyne (GDY), a new member of carbon allotropes, has been promisingly offering novel alternatives for acquisition of inexpensive and efficient catalysts in the water electrolyzer. The unique atomic arrangement in GDY architecture leads to coexistence of sp– and sp2–C, correspondingly brings numerous intriguing features such as heterogeneous electron distribution, wide tailorable natural bandgap, rapid electron/mass transport and rich chemical bonds. These unique intrinsic natures of GDY provide brilliant inspirations for scientists to design new-concept electrocatalyst toward cathodic hydrogen evolution reaction, anodic oxygen evolution reaction and the overall water-splitting. Based on the immense progress, in this short perspective, current principal design strategies of GDY-based catalysts are systematically summarized, including interface engineering, individual atom fixation, induced constrained growth and bottom-up fabrication. With abundant implementation examples for achieving highly efficient water electrolysis, in particular we focus on clarifying the decisive role of GDY on these design strategies with comprehensive theoretical and experimental evidences. The future direction in developing GDY-based electrocatalysts in hydrogen energy field is also depicted with the urgent anticipation of deeper understanding of structure-performance relationship and catalytic mechanism, especially those in real industry water electrolyzers.

Mathematical Description for the Hierarchy of Grain-boundary Structures

Polycrystalline materials are ubiquitous, and their macroscopic properties strongly depend on the defects in crystalline structures. Grain boundaries (GBs) are the interfaces between crystal grains, which admit unique atomic arrangements different from those of crystals. It is essential to reveal the polyhedral arrangement in GB atomic structures to identify the origin of structure-property relationships in polycrystalline materials. We found that the GB region can only be packed by the bulk or GB-type polyhedral units with minor variations. Moreover, the GB hierarchy directly follows the distribution of rational numbers that is represented by the Farey diagram. The singular GB is defined to be a GB packed by at the most two types of polyhedral units in a period, and any GB can be packed by the polyhedral units that form the singular GBs. This approach allows us to predict the polyhedral arrangement in any tilt GBs including random GBs.

Novel preparation strategy of graphdiyne (CnH2n-2): One-pot conjugation and S-Scheme heterojunctions formed with MoP characterized with in situ XPS for efficiently photocatalytic hydrogen evolution

As a new two-dimensional (2D) carbon hybrid material, graphdiyne has attracted much attention for its good electrical conductivity, tunable electronic structure and special electron transfer enhancement properties. With its unique atomic arrangement and 2D network of sp and sp2 conjugated hybridization, graphdiyne has a natural advantage in building active catalytic sites. Meanwhile, its special charge distribution gives graphdiyne the ability to be an electron acceptor or donor. Due to its special properties, it has great potential in the field of hydrogen evolution for photocatalytic water decomposition. In this work, a novel strategy for the simple synthesis of graphdiyne (CnH2n-2) by CaC2, hexabromobenzene and mixed organic solvents was firstly prepared and effectively enhanced the photocatalytic hydrogen evolution by topological semimetals (MoP). Combined with experimental tools such as in situ XPS, EPR and DFT calculations, the possible formation of S-Scheme heterojunctions between graphdiyne and MoP is proposed as an important strategy for the application of graphdiyne in the field of photocatalytic hydrogen evolution.

Direct Visualization of Localized Vibrations at Complex Grain Boundaries.

Grain boundaries (GBs) are a prolific microstructural feature that dominates the functionality of a wide class of materials. The functionality at a GB results from the unique atomic arrangements, different from those in the grain, that have driven extensive experimental and theoretical studies correlating atomic-scale GB structures to macroscopic electronic, infrared optical, and thermal properties. In this work, a SrTiO3 GB is examined using atomic-resolution aberration-corrected scanning transmission electron microscopy and ultrahigh-energy-resolution monochromated electron energy-loss spectroscopy, in conjunction with density functional theory. This combination enables the correlation of the GB structure, nonstoichiometry, and chemical bonding with a redistribution of vibrational states within the GB dislocation cores. The new experimental access to localized GB vibrations provides a direct route to quantifying the impact of individual boundaries on macroscopic properties.

Exceptional Hydrogen Diffusion Rate over Ru Nanoparticle-Doped Polar MgO(111) Surface.

Hydrogen (H) conductivity on oxide-based materials is crucially important in fuel cells and related catalysis. Here, this work measures the diffusion rate of H generated from Ru nanoparticles loaded on polar MgO(111) facet particles under H2 at elevated temperatures without moisture and compares it to conventional nonpolar MgO(110) for the first time by in situ quasielastic neutron scattering (QENS). The QENS reveals an exceptional diffusion rate on the polar facet via a proton (H+ ) hopping mechanism, which is an order of magnitude superior to that of typical H+ -conducting oxides. This work attributes this to the unique atomic arrangement of alternate layers of Mg cations and O anions of the polar MgO(111) where the strong electrostatic field of terminal oxygen anions facilitates protonic migration with a lower degree of local covalency.

Cu4TiTe4: Synthesis, Crystal Structure, and Chemical Bonding.

A new compound Cu4TiTe4 in the Cu-Ti-Te ternary system is prepared using high-temperature solid-state synthesis and characterized by single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy. The average structure of Cu4TiTe4 crystallizes in the cubic space group P4̅3m (cP9; a = 5.9484(1) Å) and adopts the Cu4TiSe4 structure type. Like Cu4TiSe4, it shows positional disorder in one of the two Cu sites. The three-dimensional structure of Cu4TiTe4 is viewed as a cubic close-packed (ccp) array of Te, where half of the tetrahedral holes are orderly occupied by three Cu and one Ti and the disordered Cu atoms effectively occupied 1/4 of the octahedral holes. The calculated density of states (DOS) discerns that the compound is a narrow-bandgap semiconductor, and the crystal orbital Hamilton population (COHP) analysis shows that though the individual Cu-Te short contact is relatively weak compared to the Ti-Te contact, Cu-Te bonds largely contribute toward the overall stability. Due to the unique atomic arrangements, some Te atoms in the unit cell have unsaturated coordination, which presents 5s2 lone pairs on the Te atoms. This has been confirmed by the density of states (DOS) and electron localization function (ELF) calculations.

Tailoring morphology of MgO catalyst for the enhanced coupling reaction of CO2 and glycerol to glycerol carbonate

Developing efficient halogen-free catalysts is still a significant challenge for adsorption and activation of CO2 and further preparing glycerol carbonate. Herein, we successfully developed heterogeneous MgO catalyst via morphology-oriented regulation to catalyze the coupling reaction of glycerol and CO2. Specifically, cubic MgO displays more low-coordinated O2– originated from the unique atomic arrangement of (111) facet, resulting in abundant strong basic sites and surface oxygen vacancies. These strong basic sites promote the adsorption of CO2 to form thermodynamically stable monodentate carbonates near the oxygen vacancies. In addition, nearby surface oxygen vacancies could further enhance the transfer of electrons into the anti-bonding orbitals of CO2 molecules. The synergistic catalytic effect between the strong basic sites and the surface oxygen vacancies significantly facilitates the cycloaddition reaction (the most critical step in the coupling reaction). Therefore, under the optimal reaction conditions (140 °C, 2 MPa CO2, and 4 h), the MgO-C catalyst showed 83 % glycerol conversion and 44 % glycerol carbonate selectivity.

Penta-graphene and phagraphene: thermal expansion, linear compressibility, and Poisson’s ratio

Nonplanar penta-graphene and planar phagraphene, which are connected by carbon pentagons and penta–hexa–hepta carbon rings, respectively, are two allotropes of graphene. Graphene as a star material in two-dimensional materials has been widely studied. However, the studies around penta-graphene and phagraphene are still insufficient. We are interested in both materials’ response to temperature, hydrostatic pressure, and stress. In this work, the thermal expansion, linear compressibility, and Poisson’s ratio of penta-graphene and phagraphene have been investigated systematically. It is found that both materials can exhibit abnormal negative thermal expansion behavior, while their linear compressibility behavior is normal. The negative Poisson’s ratio behavior only occurs in penta-graphene, which is consistent with other work. Through an analysis of the lattice vibrations and associated mode Grüneisen parameters, it is found that there are anomalies in the phonon spectra of both penta-graphene and phagraphene. It is noted that acoustic phonons contribute most to their respective anomalies, especially the transverse acoustic mode. The librational motion of the lowest-frequency optical phonon of both materials is identified and also associated with their novel properties. In general, the unique topological arrangement of carbon atoms can play a decisive role in determining the performances of penta-graphene and phagraphene.

Growth modes of single-walled carbon nanotubes on catalysts.

Understanding the growth mechanism of single-walled carbon nanotubes (SWCNTs) and achieving selective growth requires insights into the catalyst structure-function relationship. Using an in situ aberration-corrected environmental transmission electron microscope, we reveal the effects of the state and structure of catalysts on the growth modes of SWCNTs. SWCNTs grown from molten catalysts via a vapor-liquid-solid process generally present similar diameters to those of the catalysts, indicating a size correlation between nanotubes and catalysts. However, SWCNTs grown from solid catalysts via a vapor-solid-solid process always have smaller diameters than the catalysts, namely, an independent relationship between their sizes. The diameter distribution of SWCNTs grown from crystalline Co7W6, which has a unique atomic arrangement, is discrete. In contrast, nanotubes obtained from crystalline Co are randomly dispersed. The different growth modes are linked to the distinct chiral selectivity of SWCNTs grown on intermetallic and monometallic catalysts. These findings will enable rational design of catalysts for chirality-controlled SWCNTs growth.

Recent advances in wide-spectrum photodetectors based on low-dimensional semiconductors

Compared with three-dimensional semiconductors, low-dimensional (LD) semiconductors have unique atomic arrangements and excellent optical and electrical characteristics, such as high absorptivity, mechanical flexibility, and absence of dangling bonds on the surface. With these advantages, LD semiconductors are considered as a kind of promising materials in the field of photodetection. However, the applications of LD materials are limited by their dimensional constraint, large dark current, high noise, low quantum efficiency, slow response speed, and other characteristics. In this paper, the recent advances in wide-spectrum photodetectors in the ultraviolet to infrared spectrum are reviewed. The working mechanisms and performance parameters of photodetectors are described. Specific research examples based on wide-spectrum photodetectors are reviewed based on three aspects, namely the structure of photodetectors, their response mechanisms, and important performance indicators. Furthermore, the challenges in improving the performance of wide-spectrum photodetectors are discussed, along with the prospective development trends of wide-spectrum photodetectors.