Polyhedral Structure Research Articles

Unveiling the dual tunability of dimension and pore structure in MAX-derived carbon via molten salt electrolysis

3D construction or pore-forming of carbon nanosheets brings the materials exceptional energy storage performance. However, these strategies involve complicated procedures and challenging conditions. Herein, based on the structural regulation of a MAX phase, a facile method was proposed to prepare MAX-derived carbon (MDC) with dual tunability of dimension and pore structure via molten salt electrochemical etching-gaseous sulfur delamination coupling. Polyhedral structure Ti2SC and highly oriented structure Ti2SC were transformed into 3D Mesopore carbon nanoshells (3D Meso-CNSL) and 2D Mesopore carbon nanosheets (2D Meso-CNST) in one step. By matching the decomposition voltage of TiClx with that of PS-Ti2SC, Cl2 gas generated in situ was employed to enhance the porosity of the 3D Meso-CNSL, resulting in the formation of 3D meso/macro-porous carbon nanoshells (3D Meso/Macro-CNSL) with doubled pore volume (1.45 cm3 g−1) and specific surface area (649.97 m2 g−1). The 3D Meso/Macro-CNSL exhibits excellent capacity performance and cycle stability under high current density. The capacities are 674.8 mAh g−1 and 501.5 mAh g−1 after 1000 cycles at 5 A g−1 and 10 A g−1, respectively. It is the first report on the direct delamination of MAX phases into 3D nanomaterials, presenting a new pathway for the precise regulation of the nanostructure of the MDCs.

Construction of binary metal sulfide nanoparticles to boost catalytic activity for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered viable options for the next generation of energy storage devices owing to their remarkable theoretical advantages.However, the further practical implementation the LSBs is hindered by certain challenges, including the shuttle effect and the slow reaction kinetics associated with soluble lithium polysulfides (LiPSs). Herein, Co9S8–MoS2/PC nanoparticles with a polyhedral structure are designed as effective host materials to tackle these challenges.The electrocatalysis activity of Co9S8–MoS2/PC nanoparticles can be maximized via tuning the ratio of metal ions in the precursor. The experimental results reveal that Co9S8–MoS2/PC nanoparticles could enhance the transfer of electrons and ions, reinforce the interaction with LiPSs, and accelerate the redox reaction kinetics of LiPSs. The LSBs with optimal S@Co9S8–MoS2/PC(5:1) cathode achieve an enhanced rate capability, a high specific capacity, and long cycle life with a capacity decay of 0.059 % per cycle over 500 cycles at 0.5C. This work demonstrates the great potential of binary metal sulfide nanoparticles for the effective conversion of LiPSs in LSBs.

Fixed Yellow-to-Blue Intensity Ratio of Dy3+ in KY(CO3)2 Host for Emission Color Tuning.

Dy3+, Ce3+ co-doped KY(CO3)2 phosphors with a monoclinic structure were synthesized using the hydrothermal method to create a fixed yellow-to-blue ratio emission. The [YO8] polyhedron, consisting of a Y atom and eight oxygen atoms, forms a relatively independent microstructure within the KY(CO3)2 host. Y3+ ions are partially replaced by Ce3+ or Dy3+ ions to construct the [CeO8] or [DyO8] polyhedral fluorescence emission unit. The spectral measurements indicate that Ce3+ and Dy3+ can maintain relatively independent fluorescence emission characteristics in the KY(CO3)2 host. The yellow-to-blue intensity ratio of Dy3+ remains close to 1 and does not change with the variation in the doping concentration of KY(CO3)2:Dy3+ and KY(CO3)2:Dy3+,Ce3+ phosphors. When Ce3+ and Dy3+ are co-doped with KY(CO3)2, the emission intensities of Dy3+ under 339 nm and 365 nm excitation increase by 8.43 and 2.32 times, respectively, through resonance energy transfer and cross-relaxation. All Ce3+-doped KY(CO3)2:Dy3+ phosphors can emit white light. Among them, the emitted light of KY(CO3)2:3%Dy3+,5%Ce3+ is closest to standard daylight. Therefore, a stable [YO8] polyhedral structure can be used to achieve more color tuning of light.

Pickering emulsion stabilized by grass carp myofibrillar protein via one-step: Study on microstructure, processing stability and stabilization mechanism

In this study, edible Pickering emulsions stabilized with GMP particles were prepared for the first time using low-value grass carp myofibrillar protein (GMP). To elucidate the emulsion formation mechanism, the grass carp myofibrillar protein particles were first characterized, and the results showed that the lyophilized GMP particles had an irregular polyhedral structure and were amphiphilic nanoparticles. The stability of GMP-based emulsions tended to stabilize with the increase of GMP concentration at an appropriate oil-to-water volume ratio, with a decrease in droplet particle size and an increase in water-holding capacity, storage stability, and rheological stability, whereas the phenomenon of droplet aggregation after storage appeared at 4.0% additive level. Therefore, appropriate concentrations of GMP at a certain oil-to-water volume ratio can stabilize Pickering emulsions, which have an important future as a potential food-grade active substance delivery carrier for biological applications.

In situ Surface Reconstruction in Pure Water by Ice‐Confined Freeze‐Thaw Strategy for High‐Performance Core–Shell Structural Perovskite Nanocrystals

AbstractConstructing core–shell structure is recognized as an effective approach for the conventional colloidal semiconductor nanocrystals (NCs) to improve their stability and optical performance in optoelectronic applications. It is, however, still a challenge to develop green manufacture for core–shell lead halide perovskite NCs (PeNCs). Herein, an ice‐confined freeze‐thaw strategy using pure water solvent is devised, which results in the surface reconstruction of CsPbBr3 PeNCs thereby formatting the CsPb2Br5 shell on the CsPbBr3 core to achieve core–shell CsPbBr3@CsPb2Br5. The in situ formation of the CsPb2Br5 shell is attributed to the transformation of the intermediate polyhedral structure with the help of amphiphilic 4‐dodecylbenzene sulfonic acid ligand in the precursor solution. The PeNCs show ultrahigh photoluminescence quantum yield of 95%, remarkable stability and humidity‐resistance. Moreover, both light‐emitting diodes and stretchable fluorescence hydrogels based on the PeNCs exhibit a boosted optical performance and excellent operation stability. The organic solvent‐free and recyclability of this strategy pave a novel way to the environmentally friendly and large‐scale manufacture of high‐quality PeNCs for optoelectronic application.

Tetrahexahedral binary transition metal compound sub-nanoclusters

We explore new transition metal (TM) compound sub-nanoclusters, TM8X6 (TM = Mn, Fe, Co and X = P, B, As), using density functional theory. Their optimized geometric structures show the same polyhedral structure (tetrahexahedron) independent of a kind of TM and metalloid (X), where eight TM atoms form a cubic structure capped with six metalloid (X) atoms. Incorporating an extra TM atom into the TM cubic results in an endohedral structure, TM9X6. Encapsulation of an additional TM atom merely changes the binding energy except for the Co boride cluster. The binding energy of Co8B6 increases by incorporating an additional Co atom, in which it is observed that the electron density is accumulated between B and all Co atoms (Co atoms both at the center and at the edges), but in other clusters, the electron excess is found mainly between TM atoms. The MnnP6 (n = 8 and 9) clusters have a high adiabatic electron affinity (>6 eV) due to the relatively large difference in electronegativity between Mn and P. The highest occupied molecular orbital and lowest unoccupied molecular orbital gaps of all clusters lie in the visible range. The interaction between nanoclusters and graphene with a single vacancy is studied as a function of the different cluster landing site on the graphene, where the geometric structure change of the clusters strongly depends on the adsorption site.

Precise Post-Synthetic Modification of Heterometal-Organic Capsules for Selectively Encapsulating Tetrahedral Anions.

Post-synthetic modification plays a crucial role in precisely adjusting the structure and functions of advanced materials. Herein, we report the self-assembly of a tubular heterometallic Pd3Cu6L16 capsule that incorporates Pd(II) and CuL1 metalloligands. This capsule undergoes further modification with two tridentate anionic ligands (L2) to afford a bicapped Pd3Cu6L16L22 capsule with an Edshammer polyhedral structure. By employing transition metal ions, acid, and oxidation agents, the bicapped capsule can be converted into an uncapped one. This uncapped form can then revert back to the bicapped structure on the addition of Br- ions and a base. Interestingly, introducing Ag+ ions leads to the removal of one L2 ligand from the bicapped capsule, yielding a mono-capped Pd3Cu6L16L2 structure. Furthermore, the size of the anions critically influences the precise control over the post-synthetic modifications of the capsules. It was demonstrated that these capsules selectively encapsulate tetrahedral anions, offering a novel approach for the design of intelligent molecular delivery systems.

Hollow nanocages heterostructured NiCo-LDH/MWCNTs electrocatalyst for highly sensitive and non-invasive detection of saliva glucose

Monitoring salivary glucose has gained increased attention as a non-invasive approach to prevent and diagnose diabetes. Since the glucose concentration in saliva is lower than that in blood, the development of effective electrocatalysts for highly sensitive glucose detection is thus of great significance. In this study, a hollow nanocage from NiCo-layered double hydroxides (LDH) modified with multi-walled carbon nanotubes (MWCNTs) is designed and further employed as the sensing material to construct a novel non-enzymatic glucose electrochemical sensor with high sensitivity. It is synthesized by utilizing pre-synthesized zeolitic imidazolate framework (ZIF-67)/MWCNTs as a sacrificial template and subsequently conducting a simple solvent-thermal reaction with Ni(NO3)2. Such a hollow nanocage preserves the polyhedral framework structure of the used precursor, where the hollow frame-like structure of NiCo-LDH offers accessible catalytic sites, and MWCNTs provides good conductivity. Their combination brings in a bridging effect between MWCNTs and NiCo-LDH, further leading to a large electrochemical active area and excellent catalytic activity of this hollow nanocage. The constructed sensor exhibits a detection limit as low as 0.03 μM for the glucose detection as well as wide linear ranges of 0.1–3000 μM and 3000–9231.8 μM, corresponding to the sensitivity of 2.55 and 1.15 μA mM−1 cm−2, respectively. Moreover, this sensor enables the tracking of glucose concentration change in salivary before and after food intake. This work offers new highly sensitive sensing materials and potentially valuable approaches for non-invasive glucose detection.

Hydrogen atom in γ-irradiated synthetic isopropylamine silica clathrate

Silica clathrates have polyhedral cage structures with guest molecules and are naturally found under various forms such as melanophlogite, chibaite, or bosoite. Although electron spin resonance (ESR) could be potentially used to date their formation, the evaluation of the thermal stability of the radiation-induced radicals is not simple, like in the case of chibaite. Decay mechanism of the radical should be understood to ensure reliable ESR dating results. To investigate the behavior of radiation-induced radical in silica clathrate, isopropylamine silica clathrate was synthesized from mixed solutions of orthosilicic acid and isopropylamine. Hydrogen atom and (CH3)2C·(NH2) radical are mainly formed by γ-ray irradiation at 77 K. Hydrogen atom decay around 230 K by following a first-order kinetics and its activation energy is 65 ± 4 kJ/mol. Since the amount of hydrogen atom decrease was similar to that of the (CH3)2C·(NH2) radical increase, it is hypothesized that hydrogen atom abstracts hydrogen from isopropylamine in the silica clathrate.

Highly efficient peroxymonosulfate activation by Fe[sbnd]Co bimetallic modified metal-organic frameworks-derived polyhedron with enriched oxygen vacancy for tetracycline degradation

It is important to propose a targeted solution strategy for the rate-limiting step in peroxymonosulfate activation in order to promote its wider application in advanced oxidation processes. In this study, a novel catalyst with FeCo bimetal doping, rich oxygen vacancy and porous polyhedral structure was prepared by using Fe, Co-doped Metal-Organic Framework as the precursor, which strategically enhanced the abundance and stability of active sites and promoted the adsorption of contaminates and PMS molecules. The M-450 (oxygen vacancy-rich)/PMS system demonstrated superior catalytic activity and interference resistance, in which 100 % of TC could be removed within 5 min. The corresponding reaction rate constant is 1.119 min−1, which is much higher than that of M-0 (without oxygen vacancy). Moreover, a series of studies proved that nonradical pathway (singlet oxygen) accompanied free radicals (sulfate radicals and hydroxyl radicals) collectively contributed to the tetracycline degradation. This study provides new ideas for the design and improvement of the functional catalyst for application in sulfate radicals based advanced oxidation processes.

Efficient removal and transformation of Cr(VI) from alkaline wastewater to form a ferrochromium spinel multiphase via a modified ferrite process

Chromium-containing wastewater causes serious environmental pollution due to the harmfulness of Cr(VI). The ferrite process is typically used to treat chromium-containing wastewater and recycle the valuable chromium metal. However, the current ferrite process is unable to fully transform Cr(VI) into chromium ferrite under mild reaction conditions. This paper proposes a novel ferrite process to treat chromium-containing wastewater and recover valuable chromium metal. The process combines FeSO4 reduction and hydrothermal treatment to remove Cr(VI) and form chromium ferrite composites. The Cr(VI) concentration in the wastewater was reduced from 1040 mg L−1 to 0.035 mg L−1, and the Cr(VI) leaching toxicity of the precipitate was 0.21 mg L−1 under optimal hydrothermal conditions. The precipitate consisted of micron-sized ferrochromium spinel multiphase with polyhedral structure. The mechanism of Cr(VI) removal involved three steps: 1) partial oxidation of FeSO4 to Fe(III) hydroxide and oxy-hydroxide; 2) reduction of Cr(VI) by FeSO4 to Cr(III) and Fe(III) precipitates; 3) transformation and growth of the precipitates into chromium ferrite composites. This process meets the release standards of industrial wastewater and hazardous waste and can improve the efficiency of the ferrite process for toxic heavy metal removal.

Morphologies and magnetic properties of α-Fe2O3 nanoparticles calcined at different temperatures.

Different morphologies and sizes of α-Fe2O3 were prepared by a coprecipitation method using polyvinylpyrrolidone as a dispersant. In the preparation process, homogeneous and dispersed nanoscale FeOOH particles were first obtained by the coprecipitation method, and then the FeOOH particles were calcined at high temperature to form α-Fe2O3. The growth and aggregation of the α-Fe2O3 particles at different calcination temperatures resulted in α-Fe2O3 powders with diversiform morphologies (nanoscale microsphere, pinecone ellipsoidal, polyhedral, and quasi-spherical structures). By analyzing the SEM images, it was inferred that the polyhedral structure of α-Fe2O3 particles was formed by the accumulation of rhomboid sheet structures and high-temperature growth. In terms of the magnetic properties, the samples belonged to the class of canted antiferromagnetic materials, and the morphology, particle size, and crystallite size of the α-Fe2O3 particles were important factors affecting the coercivity. Among these, when the calcination temperature was increased from 700 °C to 800 °C, the growth rate of the particle size was significantly faster than that of the crystallite size, and the coercivity increased substantially from 1411 Oe to 2688 Oe.

Bubble dynamics manipulation in polymeric foaming.

The release of pressure from a high-pressure-stable polymer/gas solution is a common method for creating gas bubbles and forming foam with a typical polyhedral cell structure. We propose a new approach to control the foaming process by pausing the bubble growth at intermediate pressure before reaching ambient pressure. This allows us to control the growth of the bubbles and investigate various physical phenomena involved in polymer foaming, such as Ostwald ripening, bubble interactions, coalescence, and different bubble growth regimes. We conducted these studies in a model system PP/N2 by subjecting the solution to non trivial pressure histories. Our method will have an impact on the study of fundamental phenomena involved in foaming and their application in creating new materials.

Enhanced Magnetic Properties and Spin-Phonon Coupling in Ni-Substituted α-Cu2V2O7: The Role of Bond Length, Bond Angles, and Distorted Polyhedral Structure

Enhanced Magnetic Properties and Spin-Phonon Coupling in Ni-Substituted α-Cu2V2O7: The Role of Bond Length, Bond Angles, and Distorted Polyhedral Structure

On the energetic and magnetic stability of potassium atomic clusters doped by yttrium.

The abstract should be a single paragraph which summarises the content of the article. This study utilizes density functional theory (DFT) calculations to explore the energetic and magnetic stability of neutral and charged potassium (K) clusters doped with yttrium (Y). We aim to elucidate the influence of Y doping on the energetics and structures of these clusters, comparing them to undoped K clusters. Ground states of 64 polyhedral structures, all of them encapsulating at least one Y atom, were obtained. Y doping generally increased the spin magnetic moment, with charged clusters exhibiting the highest values. Notably, the K12Y+ cluster, possessing an icosahedral geometry and a magnetic moment of 6μB, is classified as a magnetic superatom. Additionally, we identified 14 superatoms with high magnetic robustness. The density of states (DOS) and spin density calculations additionally highlighted the substantial role played by yttrium in the electronic density of the electrons responsible for inducing magnetism in these clusters.

Ab initio study of longitudinal and transverse dynamics, including fast sound, in molten UO2 and liquid Li–Pb alloys

The disparity between the masses of the two components in a binary liquid system can lead to the appearance of a peculiar phenomenon named “fast sound,” which was identified for the first time in Li4Pb several decades ago and later observed in other Li based alloys. However, the exact characteristics and nature of this phenomenon and the reasons behind its appearance have not totally been identified yet. In this work, we analyze the longitudinal and transverse current correlation functions of UO2, Li4Pb, and Li0.17Pb0.83, as obtained from ab initio molecular dynamics simulations. We find that fast sound appears to occur in the two former systems but not in the latter. Additionally, we discuss some of the properties of the liquid mixtures that may be related to the appearance (or absence) of the phenomenon, such as the composition, the polyhedral structure of the melt, and the type of bonding in the system.

Morphological, Structural, Thermal, Pasting, and Digestive Properties of Starches Isolated from Different Varieties of Rice: A Systematic Comparative Study.

The aim of this study was to compare the properties of isolated starches from ten commonly consumed rice varieties in China and to investigate their possible association. In addition, principal component analysis (PCA) and correlation analysis were performed to demonstrate the weight or relevance of different properties. The starch granules had an irregular polyhedral structure. The crystalline structure had an orthogonal arrangement, which is characteristic of A-type starch with nanocrystals with an orthorhombic crystal structure. In addition, higher levels of rapidly digestible starch (72.43 to 74.32%) and resistant starch (2.27 to 2.3%) were found in glutinous rice starch. The highest content of slowly digestible starch (59.48%) was found in starch isolated from black rice, which may be an ideal rice variety for controlling blood glucose and weight. Starch isolated from red Hani terrace rice showed the highest thermal stability during cooking and the highest resistance to a high shear force treatment. In addition, the PCA suggests that the amylose content of starch largely determines the functional properties of starch and positively correlates with the peak viscosity and setback viscosity of the starch pasting. The results of this study will enrich the scientific knowledge of various rice starches and promote their application in the food industry and other industries.

Utilizing a defective MgO layer for engineering multifunctional Co-MOF hybrid materials with tailored leaf-like and polyhedral structures for optimal electrochemical and photocatalytic activities

The hybridization of metal-organic framework (MOF) with inorganic layers would lead to the discovery of novel hybrid materials that can provide a compelling strategy for enhancing its photocatalytic and electrochemical response. In the present study, a highly efficient multifunctional hybrid material was developed by exploiting the defective layer formed on AZ31 Mg alloy through plasma electrolytic oxidation (PEO) as a nucleation and growth site for Co-MOF. The concentrations of the organic linker 2-Methylimidazole (2,MIm) and cobalt nitrate as a source of Co2+ ions were varied to control the growth of the obtained Co-MOF. Lower concentrations of the 2, MIm ligand favored the formation of leaf-like MOF structures through an anisotropic, two-dimensional growth, while higher concentrations led to rapid, isotropic nucleation and the creation of polyhedral Co-MOF structures. The sample characterized by polyhedral Co-MOF structures exhibited superior electrochemical stability, with the lowest corrosion current density (3.11 ​× ​10−9 A/cm2) and the highest top layer resistance (2.34 ​× ​106 ​Ω ​cm2), and demonstrated outstanding photocatalytic efficiency, achieving a remarkable 99.98 ​% degradation of methylene blue, an organic pollutant, in model wastewater. To assess the active adsorption sites of the Co-MOF, density functional theory (DFT) was utilized. This study explores the changes in morphologies of the coatings of Co-MOF with the change of solution concentration to form coatings with enhanced properties on the metallic substrate, which could establish the groundwork for the development of next-generation multifunctional frameworks with diverse applications.

Preparation of Spinel-Type Black Pigments Using Microwave-Assisted Calcination of Stainless Steel Dust: The Effect of Manganese Molar Content

Stainless steel dust is rich in valuable metal elements including Fe, Cr, Ni and Mn, which can be utilized to prepare Fe–Cr–Ni–Mn series black pigments. Meanwhile, manganese can absorb the majority of the visible light wavelength range, which improves the color rendering performance of Fe–Cr–Ni–Mn series black pigments. However, the coloring mechanism of manganese in the above black pigments is not clear. Therefore, the effect of manganese oxide content on the preparation of spinel-type black pigments from microwave-assisted calcination of stainless steel dust was studied in this work. The results show that with the increase in MnO content in the raw mixture, the crystal plane spacing of black pigments increases from 0.2525 nm to 0.2535 nm, the grain size grows from 61.4619 nm to 79.7171 nm, and the lattice constant grows from 0.8377 to 0.8406 nm. Moreover, the band gap is decreased from 1.483 eV to 1.244 eV, the absorbance increases significantly and has a consistent absorbance in the visible range, and the L*, a* and b* values reduce from 41.8, 0.6, 1.6 to 32.0, 1.0, 0.8, respectively. MnO can react with the spinel in stainless steel dust, forming Mn3O4, MnCr2O4 and Ni (Fe,Cr)O4 in the system, with a regular polyhedral structure. The prepared pigments have excellent thermal stability at 1100 °C and good compatibility with transparent glazes, which can be adhered to the surface of ceramic tiles after calcination to demonstrate better compatibility as the content of MnO increases.

Mixed‐Phase Niobium Oxide as a Durable and Ultra‐Fast Charging Anode for High‐Power Lithium‐Ion Batteries

AbstractThe development of low‐cost, high‐power lithium‐ion batteries requires durable anode materials that can store and release lithium quickly. Here a mixed phase of H‐Nb2O5 and M‐Nb2O5 (denoted as d‐H,M‐Nb2O5) that demonstrates excellent performance as an anode material for lithium storage is reported. Experimental and computational analyses reveal several salient features of d‐H,M‐Nb2O5. First, the edge‐sharing arrangement between the mixed niobium oxygen polyhedral block structures helps alleviate volume expansion during cycling, thereby enhancing stability and reversibility. Second, the mixed‐phase structure facilitates a continuous pathway for lithium ion adsorption These characteristics allow for sequential transport of lithium ions, enabling fast charging. As a result, the d‐H,M‐Nb2O5 electrode material exhibits a high capacity of 142 mAh g−1 at an ultra‐fast charging rate of 100 C, while maintaining 85% of its initial capacity after 5000 cycles. Moreover, its practical feasibility is established by demonstrating full‐cell performance at a 5 C discharge/charge rate (13 mA cm−2), maintaining 79% of its capacity over 1000 cycles.