Doping Elements Research Articles

High-strength and Low-Thermal-Conductivity Porous Multi-Principal Cation Mullite Ceramic

The secret of porous mullite as a thermal insulation material lies in its excellent mechanical properties and lower thermal conductivity. The optimization of performance often depends on the structure design. Herein, via NH4HCO3 as a sacrificial material to fabricate porous multi-principal cation mullite (MPCM) ceramics that have not been reported for 4 doping elements (Mg, Ti, Zr, and Cr) by a sacrificial template method. The novelties of the present work are: (1) The multiple components cause a serious lattice distortion at the microscopic scale, which increases the mechanical properties of porous MPCM ceramics. (2) Porous MPCM (total porosity ≈ 54%) exhibits superior compressive strength (≈ 93 MPa), and the compressive strength with porosity was well modeled based on the Balshin and Rice equations. (3) As a proof-of-concept, we predict the thermal conductivity of pure mullite (PM) with the same porosity as MPCM ceramics. Here it proved the superiority of MPCM (0.67 W∙m-1∙K-1, 1,000 °C) as a thermal insulation material over conventional PM. Porous MPCM prepared by NH4HCO3 will pave a new path for the design of advanced thermal-insulation materials.

Green-Synthesis of CuO and Ce-Doped CuO Nanoparticles Using Aqueous Extract of Yam Peel and their Antimicrobial Properties

The rise of drug-resistant microbes presents a critical global health challenge in the 21st century, necessitating the development of potent antimicrobial agents with broad-spectrum activity. Therefore, in this study, we explored the antimicrobial activity of copper oxide (CuO) and cerium-doped CuO (Ce-doped CuO) obtained through a facile green synthesis approach. The nanoparticles were synthesized using aqueous extract of Dioscorea spp (yam peel) and characterized for their physicochemical properties using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), electron microscopy, and UV-Vis spectroscopy. Their antimicrobial efficacy was tested against three bacterial strains—Enterococcus faecalis, Escherichia coli, and Listeria monocytogenes—and three fungal strains—Aspergillus niger, Mucor mucedo, and Penicillium chrysogenum. The results demonstrated that cerium doping significantly altered the physicochemical properties of CuO, leading to enhanced antimicrobial activity. The antibacterial zone of inhibition ranged from 7.50 to 16.55 mm for CuO and 11.80 to 19.50 mm for Ce-doped CuO. For antifungal activity, the minimum inhibitory concentration (MIC) ranged from 0.25 to 0.30 mg/mL for CuO and 0.025 to 0.03 mg/mL for Ce-doped CuO. Notably, the Ce-doped CuO nanoparticles exhibited antimicrobial effects comparable to standard antibiotics. These findings highlight the potential of green-synthesized Ce-doped CuO nanoparticles as effective antimicrobial agents. By leveraging green synthesis and elemental doping, this study offers a promising solution to combat a wide spectrum of infectious pathogens.

Fabrication of N,C-H2TiO3 Ion Sieves for Rapid Adsorption of Lithium Using Rheological Phase Methods

Modifying β-H2TiO3 by elemental doping improves its adsorption capacity and shortens the equilibrium adsorption time, which is of positive significance for its industrial application.Herein, a novel N, C co-doped Li2TiO3 lithium ion sieve precursor N,C-Li2TiO3-3 (noted as N,C-LTO-3) was successfully prepared via the rheological phase method using urea as a vital raw material. Crystal structure of N,C-LTO-3 was characterized via XRD, XPS, FT-IR, and Raman. The morphology of N,C-LTO-3 was analysed by SEM and HR-TEM. The N,C-LTO-3 was pickled and obtained to N,C-H2TiO3-3, namely N,C-HTO-3. The equilibrium adsorption capacity (Qe) of N,C-HTO-3 was as high as 40.6mg⋅g-1 in LiOH solution of 100mg·L-1 at 293K. Ti4+ dissolution loss rate is below 0.5% in the fifth cycle. Adsorption isothermal curve, kinetics, and thermodynamic behaviour were fitted with the according equations. The exchange energy of N,C-HTO-3 for Li+ was calculated by density functional theory (DFT) to assess the feasibility of lithium absorption. Furthermore, N,C-HTO-3 exhibited high regeneration and selectivity for Li+ in lithium-containing brine, making N,C-HTO-3 an ideal candidate for Li+ extraction.

Enhancing the electrochemical performance of Ni-rich cathode through an in-situ La-doping and La4NiLiO8-coating synergistic strategy

Ni-rich layered oxides offer numerous advantages such as high discharge capacity, cost-effectiveness, and environmental friendliness, making them the mainstream cathodes for high-energy density lithium-ion batteries. However, their widespread commercialization is hindered by critical challenges in cycling performance, stemming from unstable interface and structure, particularly at elevated charge cut-off voltages. Herein, a dual-modification strategy combining La doping and La4NiLiO8 coating was proposed to synergistically enhance the surface/interface and structure stability of the LiNi0.83Co0.11Mn0.06O2 (referred to as NCM83) cathode. Unlike conventional methods, a well-designed La(OH)3 coating pretreatment was employed on the Ni0.83Co0.11Mn0.06(OH)2 precursor. This pretreatment aimed to facilitate the in-situ formation of La doping and La4NiLiO8 during the lithiation of the coated precursor, while ensuring desired uniformity of the La4NiLiO8 coating and La doping. This dual-modification strategy integrated the advantages of both La doping and La4NiLiO8 coating, demonstrating excellent capability to improve the overall performance of NCM83. The La doping, acting as a pillar, not only strengthened the layered structure of the cathode to mitigate volume changes, but also enhanced Li+ diffusion by broadening the c axis spacing. The La4NiLiO8 coating efficiently protected the cathode from H2O/CO2 attack and electrolyte erosion, while also facilitating Li+ transport owing to its favorable Li-conductive properties. Such a dual-modification strategy significantly enhanced the electrochemical performance of NCM83, as demonstrated by the excellent long-term cyclic stability, rate capability, and thermal stability at a high charge cut-off voltage of 4.5 V. This work highlighted the benefits of integrating elemental doping and surface coating, while offering a promising synthetic protocol for straightforward and effective dual-modification of various cathodes.

Atomic insights of structural, electronic properties of B, N, P, S, Si-doped fullerenes and lithium ion migration with DFT-D method.

Battery interface research can effectively guide battery design and material selection to improve battery performance. However, current electrode material interface studies still have significant limitations. In this paper, by employing DFT-D method, the influences of doping elements (boron, nitrogen, phosphorus, sulfur, and silicon) on the properties of C60 fullerene, such as structural stability, electronic properties, and the adsorption and migration of lithium ion, are comprehensively investigated. It is demonstrated that doping can bolster the fullerene molecule's structural integrity and enhance charge transfer comparing with C60, thereby augmenting the material's electrical conductivity. Among the five doping elements, B-doping exhibits the most favorable adsorption energies, indicating a strong lithium binding affinity. This observation is supported with energy barrier of lithium ion migration. B-doping leads to an elevated barrier (0.37eV) comparing with pristine C60 (0.19eV), whereas Si-doping significantly reduced barrier (0.038eV) indicates enhanced lithium-ion mobility. These findings solid the efficacy of doping as a strategy to enhance the performance of fullerene electrodes. All DFT calculations were performed using the VASP software package. The chosen computational technique was a combination of the generalized approximate gradient function PBE with the dispersion correction (DFT-D3) developed by Grimme. The results of the calculations were analyzed with the help of VASPKIT.

Research on Modified Thermal Barrier Coatings Against CMAS Corrosion Driven by Mechanism–Data Hybrid Model

With the development of high-efficiency gas turbine engines and increasing inlet temperatures, the performance of thermal barrier coatings (TBCs) for hot-section components has been more severely challenged. The doping of multi-element rare earth elements significantly improves the thermodynamic properties and chemical compatibility of thermal barrier coatings so that the application performance of coatings in high-temperature environments is enhanced considerably. In this work, the doped coatings prepared by REYSZ (RE = La, Sm, Nd) were investigated and characterized in terms of crystal structure, elastic properties, and thermal–mechanical properties based on the first-principles approach, combined with various empirical and semi-empirical formulations, and a predictive model for resistance to CMAS corrosion based on machine learning approaches. The results showed that the tetragonal phase REYSZ material was mechanically stable, had a large strain damage tolerance, and was not easy to fracture under applied loads and thermal shocks. In terms of CMAS corrosion resistance, the NdYSZ interfacial model had a lower surface energy (3.130 J/m2) and Griffith fracture energy (6.934 J/m2) compared with the conventional YSZ model, and Nd2O3 had the potential to improve the CMAS corrosion resistance of zirconia-based material for thermal barrier coatings. By evaluating the machine learning prediction models, the regression coefficients of the two algorithms were 0.9627 and 0.9740, and both these two prediction models showed high prediction accuracy and strong robustness. Ultimately, this work presented a novel mechanism–data hybrid method, which would facilitate the efficient development of TBC new materials for anti-CMAS corrosion.

Supercapacitor performance evaluation with changes of microstructure in carbon electrode from perylene diimide derivative

Structural regulation of carbon electrode materials is an effective route to reinforce the performance of supercapacitors. Due to its high carbon content and easy gelation, perylene diimide derivative (PDI-d) is a good precursor for preparation of microstructure-controlled carbons. Here, PDI-d is synthesized and its gels are prepared under the action of glucono delta lactone (GDL). The PDI-d gels are subjected to freezing in liquid nitrogen or refrigerator, freeze-drying, carbonization for harvest of derived carbons with different structures and element doping. The derived carbons through liquid nitrogen freezing present fiber-woven three-dimensional connected porous structures, while those subjected to freezing in refrigerators are lamellar structures. N and Sn can be doped in the carbons using triethylamine (TEA) and K2SnO3·3H2O as solvents for PDI-d dissolution, respectively. The carbons with connected pores show higher specific surface area (454 m2 g−1), and better electrochemical performance than the carbons with lamellar structures. The optimum specific capacitance (200.1 F g−1) can be acquired in 3D porous carbons. The incorporation of N and Sn can further optimize the electrochemical performance. Specially, the Sn-doped porous structure derived carbon achieves a large energy density (27.79 Wh kg−1) and keeps good cycle stability (94.7 % after 10,000 cycles).

Quantitative Identification of Dopant Occupation in Li-Rich Cathodes.

Elemental doping is widely used to improve the performance of cathode materials in lithium-ion batteries. However, macroscopic/statistical investigation on how doping sites are distributed in the material lattice, despite being a key prerequisite for understanding and manipulating the doping effect, has not been effectively established. Herein, to solve this predicament, a universal strategy is proposed to quantitatively identify the locations of Al and Mg dopants in lithium-rich layered oxides (LLOs). Solid evidence confirms that Al prefers to occupy the transition metal (TM) layer, while Mg evenly occupies both TM and Li layers. As a result, Mg significantly reduces the thickness of LiO2 slabs at room temperature, which will increase the energy barrier of oxygen activation and enhance the structure stability of LLOs. The suppressed oxygen activity in Mg-doped LLO can be kinetically unlocked at 55°C. The different characteristics of Al and Mg enlighten an Al/Mg co-doping strategy to optimize LLOs, which significantly improves the cycle performance while lifting the capacity. These insights from the quantitative identification of doping sites shed light on the manipulation of doping effects toward better cathodes.

Synthesis-Structure-Property of High-Entropy Layered Oxide Cathode for Li/Na/K-Ion Batteries.

Increasing demand for rechargeable batteries necessitates improvements in electrochemical performance. Traditional optimal approaches such as elemental doping and surface modification are insufficient for practical applications of the batteries. High-entropy materials (HEMs) possess stable solid-state phases and unparalleled flexibility in composition and electronic structure, which facilitate rapid advancements in battery materials. This review demonstrates the properties of HEMs both qualitatively and quantitatively, and the mechanisms of their enhancement on battery properties. It also illustrates the progress in high-entropy layered oxide cathode materials (HELOs) for lithium/sodium/potassium ion batteries (LIBs/SIBs/PIBs) in the perspectives of synthesis, characterization and application, and elucidating the synthesis-structure-property relationship. Furthermore, it outlines future directions for high-entropy strategies in battery study: precise synthesis control, understanding of reaction mechanisms through structural characterization, elucidation of structure-performance correlations, and the computational and experimental methods integration for rapid screening and analysis of HEMs. The perspective aims to inspire researchers in the development of high-performance rechargeable batteries.

Effect of Rare Earth Y and Metal X (Co, Mn, Ni, Cu) Elements on Cr Diffusion Behavior of SOFC Metallic Interconnect

ABSTRACTAt present, the metallic interconnects of the solid oxide fuel cell (SOFC) can result in Cr poisoning problem of cathode after long‐term high‐temperature oxidation. Such problem seriously affects the efficiency of battery power generation. In order to optimize the performance of the metallic interconnect, this paper firstly studies the doping effect of rare earth element Y and metal element X (Co, Mn, Ni, Cu) on the diffusion behavior of Cr at the FeCr/Cr2O3 interface by the first principles method. The Cr diffusion pathway and energy barriers under different elemental doping models are calculated by CI‐NEB method. Based upon the theoretical results, the Mn1.8CoY0.2O4 spinel coating is further deposited on the surface of Crofer 22 APU substrate by sol–gel and electrophoretic deposition method to verify the theoretical results. The performance of the coating samples after high‐temperature oxidation are tested and analyzed. The experimental results show that the Mn1.8CoY0.2O4 spinel coating significantly improves the high‐temperature antioxidation, Cr resistance performance, and electrical conductivity of the interconnect, providing a feasible solution for solving the Cr poisoning problem in cathode and accelerating the application of Crofer 22 APU alloy materials in SOFC metallic interconnects.

A Facile Method to Incorporate Di-Dopant Elements (F and Sb) into Crystalline Mesoporous Tin Dioxide Nano Powder at Ambient Temperature and Pressure.

A simple two step synthetic method for di-doped crystalline mesoporous tin dioxide powder containing antimony and fluoride at ambient pressure and temperature has been developed. This approach produced materials with high surface areas and improved electrical and optoelectrical conductance. The two dopant elements; antimony and fluoride were introduced to tin dioxide by two approaches. Both approaches produced mesoporous tin dioxide with antimony and fluoride that are integrated in the framework. The structures of these materials are analyzed by powder X-ray diffraction, N2 sorption analysis, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The conductance of the materials improved by factor of 13-34 compared to undoped mesoporous tin dioxide. The effect of the di-doped elements on structure, conductance and optoelectronic properties of these materials are discussed in this paper.

Transport and material properties of doped BiSbX topological insulator films grown by physical vapor deposition

Abstract Topological Insulator (TI) BiSb is a promising material for spin-orbit torque (SOT) devices because of its high spin Hall angle, relatively higher electrical conductivity, and can be produced at room temperature by physical vapor deposition. In this work, we systematically investigate the effects of doping BiSb with several dopants. We found that doping with elemental dopants does not change the bulk conductivity, but doping with metal-nitride or metal-oxide molecular dopants can substantially increase or decrease BiSb’s bulk film conductivity with minor impacts on its TI properties. Furthermore, doping can significantly improve other TI film material properties such as increased melting point and film hardness, producing smaller grain sizes with improved interfacial roughness, and enhanced (012) film growth texture, all of which can contribute to enhanced atomic migration resistance in and out of the BiSb layer. Thus, our results open a path for using doped BiSb in integrated SOT devices

Microstructure evolution and properties of (Nb,M)C (M=Ti,V and Zr) reinforced Ni-WC coatings by laser cladding

To enhance the surface properties of AISI 1045 steel, high-performance composite carbide-reinforced coatings were prepared using laser cladding technology. Specifically, (Nb,M)C (M = Ti, V, and Zr) reinforced Ni-WC coatings were developed. The effects of various composite carbides on the microstructure and properties of the coatings were examined through a combination of first-principles calculations and experimental methods. Initially, the microstructures of (Nb,M)C (M = Ti, V, and Zr) were constructed using first-principles calculations, and the microscopic mechanical and electronic properties of these composite carbides were determined. The impact of different doping elements on the properties of the composite carbides was investigated. Subsequently, an in-situ synthesis system was designed to fabricate the composite coatings. The feasibility of synthesizing the composite carbides (Nb,M)C (M = Ti, V, and Zr) within the laser cladding coatings was confirmed using XRD, SEM, and EDS techniques. Additionally, the formation mechanism of the composite carbides was analyzed. Under different element doping conditions, the reinforcement phase in the composite coating exhibited various grain morphologies, with (Nb0.5Ti0.5)C grains showing the best particle size and density. Microalloyed interfaces were observed at the WC interfaces in each coating, indicating strong bonding between WC and the FCC matrix. The presence of WC also improved the fineness of the surrounding phase structure. Due to differences in kinetics and thermodynamics, a core-shell structure of (Nb0.5Ti0.5)C-core and WpC-shell was observed in the (Nb0.5Ti0.5)C coating. Friction-wear tests revealed that this core-shell structure helps alleviate crack sensitivity between the reinforcing phase and the matrix. Hardness analysis showed that the average hardness of the (Nb0.5Ti0.5)C, (Nb0.5V0.5)C, and (Nb0.5Zr0.5)C coatings was 62.89 HRC, 60.91 HRC, and 58.27 HRC, respectively. Among these, (Nb0.5Ti0.5)C demonstrated the most significant hardness enhancement for AISI 1045 steel, achieving a 3.51-fold increase. In the friction and wear tests, the (Nb0.5Ti0.5)C coating exhibited the best wear resistance. The primary friction-wear mechanisms of the coatings were found to be adhesive wear, oxidative wear, and minor abrasive wear. These research findings provide a theoretical basis for the preparation of high-performance composite carbide-reinforced coatings using laser cladding.

Effect of Sr2+ doping on the structure and electrical properties of hexagonal perovskite Ba7-xSrxNb4MoO20-δ electrolyte: Experimental and DFT modeling studies

Ba7Nb4MoO20 exhibits excellent oxygen ion transport properties and is a promising electrolyte material for solid oxide fuel cell (SOFC). To further enhance its oxygen ionic conductivity, element doping is an effective strategy. However, few studies have delved into the impact mechanism of doping strategies on the electrolyte's conductivity properties from the perspective of electronic structure. Here, the enhancement mechanism of oxygen ionic conductivity in Ba7Nb4MoO20 was analyzed using the the methods of density of states (DOS) and Crystal Orbital Hamilton Populations (COHP). Since the electronic conductivities of the electrolytes are negligible, their total conductivies can essentially be regarded as the conductivies of oxygen ions. As the Sr doping amount increases, the oxygen ionic conductivities of the electrolytes also increase. The bulk conductivity shows a negative correlation with the Sr doping amount, which is due to the higher bond energy of Sr-O compared to Ba-O. On the other hand, Sr promotes grain growth and reduces the number of grain boundaries, thereby decreasing the resistance to oxygen diffusion at the grain boundaries and thus enhancing the grain boundary conductivity. In the Ba7-xSrxNb4MoO20-δ (x=0, 0.1, 0.2, 0.3, and 0.4) perovskite oxides, Ba6.6Sr0.4Nb4MoO20-δ has the highest conductivity, reaching 1.12 × 10-4S cm-1 at 500°C. This work not only develops a SOFC electrolyte material with promising application prospects, but also provides theoretical guidance for its doping modification.

Potassium and Boron Co-Doping of g-C3N4 Tuned CO2 Reduction Mechanism for Enhanced Photocatalytic Performance: A First-Principles Investigation.

Graphitic phase carbon nitride (g-C3N4, abbreviated as CN) can be used as a photocatalyst to reduce the concentration of atmospheric carbon dioxide. However, there is still potential for improvement in the small band gap and carrier migration properties of intrinsic materials. K-B co-doped CN (KBCN) was investigated as a promising photocatalyst for carbon dioxide reduction via the Density Functional Theory (DFT) method. The electronic and optical properties of CN and KBCN indicate that doping K and B can improve the catalytic performance of CN by promoting charge migration and separation. In terms of the Gibbs free energy change, the CO2 reduction reaction catalysed by KBCN results in CH3OH, and its optimal pathway is CO2 → *CO2 → *COOH → CO → *OCH → HCHO → *OCH3 → CH3OH. Compared with CN, the doping elements K and B shift the rate-determining step from CO2 → *CO2 to *CO2 → *COOH. The K and B elements co-doping tuned the charge distribution between the catalyst and the adsorbate and reduced the Gibbs free energy of the rate-determining step from 1.571 to 0.861 eV, suggesting that the CO2 reduction activity of KBCN is superior to that of CN. Our work provides useful insights for the design of metallic-nonmetallic co-doped CN for photocatalytic CO2 reduction (CO2PR) reactions.

Dual-functional high-crystalline 3D core-shell hexagonal tubular sulfur-doped carbon nitride for enhanced photocatalytic H2 production and simultaneously pollutants degradation

The use of semiconductor photocatalytic technology for water splitting to produce H2 and degrade pollutants is a mild approach for clean energy conversion and environmental water purification. However, the rational design of photocatalysts with high carrier mobility remains a challenge. Herein, high-crystalline 3D core-shell hollow porous hexagonal tubular sulfur-doped carbon nitride (S-TCN) was synthesized through a simple and environmentally friendly supramolecular self-assembly strategy combined with a “salt-sealing” technique. This unique 3D structure facilitates the utilization of incident light, increases the active reaction sites, and improves interfacial mass transfer. The “salt-sealing” technique effectively enhances its crystallinity, while sulfur doping modification reduces the band gap and promotes separation and transfer of photogenerated carriers. Depend on the synergistic effect of morphology modulation, elemental doping, and high crystallinity, S-TCN exhibits significantly enhanced photoelectric conversion efficiency. It not only shows excellent performance for photocatalytic H2 production in pure water, but also rapidly degrades pollutants while maintaining H2 production activity in wastewater. The development of this dual-functional photocatalytic material holds important guiding significance for expanding the efficient application of polymer semiconductors.

Au-Doped Black Silicon Photodetector Fabricated by a Femtosecond Laser with Excellent Near-Infrared Response.

Silicon photonic devices are key components in optical imaging and sensing for communication, and the development of silicon-based photodetectors with ideal performance in the visible and infrared spectral ranges can promote the application of silicon photonics in various photoelectronic systems. Here, a Au-doped black silicon photodetector was prepared by a femtosecond laser direct writing technique. The conical micro-/nanostructures with different sizes were produced by different laser fluence irradiation. Ultrafast pump-probe technology revealed that the strong spallation process and phase explosion between Au and silicon facilitate the interfusion of Au atoms into the silicon lattice. EDS analyses, Raman spectra, and XPS spectra show the uniform distribution of Au elements, multiconfiguration amorphous phase transition, and stable chemical valence states of Au elements in Au-doped black silicon layers, respectively. The excellent geometric light trapping performance of the surface conic structure-assisted photodetector achieved a high absorptance of 95% in the 200-1100 nm band. Simultaneously, the introduction of the intermediate band by Au hyperdoping also leads to a strong absorptance of 75% in the 1100-2500 nm band. The photoelectrical response rate of the Au-doped black silicon photodetectors increased by 10 times in the infrared wavelength band by means of the introduced intermediate energy levels through Au element doping. The switching photocurrent ratio is also found to be boosted 10 times, which comes from the reduction of the photon injection barrier. The excellent photoelectronic properties lead to the increased potential of femtosecond laser processing for integration with photonics and electronics, which shows great possibilities in the further progress of energy devices, information technology, and artificial intelligence.

Core–shell upconversion nanoparticles with suitable surface modification to overcome endothelial barrier

Upconversion nanoparticles (UCNPs), capable of converting near-infrared (NIR) light into high-energy emission, hold significant promise for bioimaging applications. However, the presence of tissue barriers poses a challenge to the effective delivery of nanoparticles (NPs) to target organs. In this study, we demonstrate the core–shell UCNPs modified with cationic biopolymer, i.e., N, N-trimethyl chitosan (TMC), can overcome endothelial barriers. The core–shell UCNP is composed of NaGdF4: Yb3+,Tm3+ (16.7 ± 2.7 nm) as core materials and silica (SiO2) shell. The average particle size of UCNPs@SiO2 is estimated at 26.1 ± 3.7 nm. X-ray diffraction (XRD), transmission electron microscopy (TEM) and element mapping shows the formation of hexagonal crystal structure of β-NaGdF4 and elements doping. The surface of UCNPs@SiO2 has been modified with poly(ethylene glycol) (PEG) to enhance water dispersibility and colloidal stability, and further modified with TMC with the zeta potential increasing from -2.1 ± 0.96 mV to 26.9 ± 12.6 mV. No significant toxic effect is imposed to HUVECs when the cells are treated with core–shell UCNPs with surface modification up to 250 µg/mL. The transport ability of the core–shell UCNPs has been evaluated by using the in vitro endothelial barrier model. Transepithelial electrical resistance (TEER) and immunofluorescence staining of tight junction proteins have been employed to verify the integrity of the in vitro endothelial barrier model. The results indicate that the transport percentage of the UCNPs@SiO2 with PEG and TMC through the model is up to 4.56%, which is twice higher than that of the UCNPs@SiO2 with PEG but without TMC and six times that of the UCNPs@SiO2.

A W/Al Co-doped Na0.44MnO2 Cathode Material for Enhanced Sodium-Ion Storage.

The Na0.44MnO2 cathode has attracted enormous interest owing to its low cost, low toxicity, and stable structure, but its practical application is still hindered by the limited sodium storage sites. Element doping is widely used to improve its capacity. However, cation and anion substitution could barely reach a satisfactory compromise between the structural stability and reversible capacity. Herein, we show that the above issue could be overcome via the synergetic effect of W and Al substitution. Combining the electrochemical and in situ X-ray powder diffraction (XRD) measurements, we reveal that the substitution of W effectively facilitates the tunnel-to-layered phase transformation, while the further substitution of Al eliminates the Na+/vacancy ordering during the extraction/insertion of Na+ ions, resulting in a layered Na0.44Mn0.94W0.01Al0.05O2 (NMO-1W5Al) with negligible Na+/vacancy ordering upon cycling. In addition, NMO-1W5Al represents a wider Na+ interlayer spacing to accelerate the diffusion of Na+, which improves the rate performance. The high specific capacity, remarkable rate performance, and high cycling stability of NMO-1W5Al are promising for large-scale energy storage systems.

Synthesis of (TiyVzCr1-y-z)3C2Tx MXene for excellent electromagnetic wave absorption properties

MXenes are remarkable 2D materials for microwave absorption applications, with respect to physical and chemical properties. However, their elevated electrical conductivity and impedance mismatch results in a diminished microwave absorption rate. To overcome these issues, we have prepared TiVCrC2Tx and Ti0.5V2Cr0.5C2Tx MXenes using an element doping strategy. Thanks to their suitable dielectric constant, lattice distortion, and a large amount of defects caused by multiple transition metal atoms, results in an increase in polarization loss, enhanced impedance matching, and increased electromagnetic (EM) wave absorption capability. The experimental results showed that few-layer TiVCrC2Tx with a thickness of 3.19 mm and operating frequency as 6.88 GHz can achieve a minimum reflection loss (RLmin) of −57.8 dB. Additionally, it has an effective absorption bandwidth (EAB) of 2.88 GHz. On the other hand, few-layer Ti0.5V2Cr0.5C2Tx with a thickness of 1.95 mm and operating at a frequency of 10.72 GHz has an RLmin of −52.75 dB and an EAB of 1.44 GHz. The advantages of the element doping strategy in enhancing the microwave absorption performance of MXene are demonstrated by its excellent EM wave absorption capability, thin matching thickness, and low filling amounts of only 30 wt percent. These results suggest that doped MXene showed highly promising application in the field of EM wave absorption.