ChemNanoMat最新文献

This study introduces snake gourd (trichosanthes cucumerina) pericarp as a novel source of activated carbon, achieved through KOH activation and carbonization. The resulting sample has a surface area of 1841 m²/g and demonstrates excellent supercapacitor performance, with a specific capacitance of 206 F/g and 95 % capacitance retention over 5000 cycles, highlighting its potential for high-performance energy storage. More information can be found in the Research Article by Tiju Thomas and co-workers.

The cover image shows the first well-characterized single source precursor for the solution-phase synthesis of two-dimensional MoSe₂ materials. This work illustrates the importance of thoughtful selection of appropriate metal reagents and ligand sets, careful control of the reaction conditions as well as deeper knowledge of their reactivity and decomposition mechanism for the scale-up production of high-quality nanomaterials under moderate processing conditions for advanced applications. More information can be found in the Research Article by Shashank Mishra and co-workers. Image created with BioRender.com.

Supported Pd catalysts have been widely studied due to their enormous potential as candidates for heterogeneous Suzuki–Miyaura coupling reactions. However, the sintering and low activity of active sites still remain challenges. A vesicle-shaped LaFeO₃-supported Pd catalyst (I−Pd/LaFeO₃) was successfully fabricated using the impregnation method and tested for the Suzuki–Miyaura coupling reaction. Compared to P−Pd/LaFeO₃ prepared with photo-deposition and Pd/Al₂O₃ prepared with impregnation, the I−Pd/LaFeO₃ catalyst exhibits significantly higher catalytic activity, stability, and reusability. The chemical composition and electron states of different Pd-based catalysts were well studied based on various characterizations and the results indicated that the excellent performance of I−Pd/LaFeO₃ can be attributed to its unique nanostructure and the strong interactions between LaFeO₃ and palladium nanoparticles. The impregnation method and the choice of the LaFeO₃ support show a great influence on the electronic properties of Pd species, their reducibility, and, consequently, their reaction behavior. This unique LaFeO₃ supported Pd catalyst provided an environmentally friendly heterogeneous method for the Suzuki–Miyaura coupling reaction.

Utilizing carbon coated ferroelectric materials to introduce polarization-induced electric field (PIEF) stimulates research of electric field-assisted catalysts for various reactions. However, effect of PIEF on carbon coating mechanism has not been studied. Herein, tourmaline nanoparticles (TNPs) with spontaneous dipole moments were applied as the PIEF supplier and sucrose was utilized as the carbon precursor to synthesize carbon coated TNPs (TNP@SC) to uncover the influence of PIEF on the carbon coating and catalytic activity of Pd toward formic acid decomposition (FAD). PIEF enhanced the adsorption capacity of TNPs for the caramelized intermediate species and increased H⁺ concentration by facilitating water ionization. Polymerization of adsorbed caramelized intermediate species on TNPs was accelerated. Uniformly coated carbon layer with more defects, larger specific surface area, and higher porosity was coated on TNP. Such surface properties of the carbon layer were beneficial for strongly anchoring ultrafine Pd nanoparticles. Owing to the specific properties of carbon layer and existence of PIEF, Pd/TNP@SC exhibited higher FAD activity than the catalysts absent of PIEF. Stronger PIEF leaded to higher initial turnover frequency. This study provides guidance to supply electric field for catalysis.

Photocatalytic nitrogen fixation is a green method for converting N₂ to NH₃, but it remains a challenging task due to the lack of effective photocatalysts. Herein, a series of porous metal covalent organic polymers (MCOPs) with the integration of dinuclear rhodium(II) catalytic centers were rationally constructed for photocatalytic N₂ fixation. Interestingly, the porous MCOPs had double-layers two-dimensional (2D) structures with the coordinated Rh(II) as the point of registry. The photocatalytic experiment showed that Rh-TAPA with significant donor-acceptor (D−A) features exhibited a high activity toward NH₃ production with a rate of 319.8 μmol g⁻¹ h⁻¹. The electron transfer process, N₂ adsorption and activation mechanism of RhCOPs were further investigated through comprehensive characterization, including DFT calculations and in situ characterization. This work provided a valuable insight into the photocatalytic N₂ fixation process with porous materials.

Barium titanate is a ferroelectric material used as a dielectric in thin film capacitors owing to its high dielectric constant. Barrier layers are utilized in these capacitors to improve the capacitors’ performance by controlling the microstructure and creating thin resistive films. In this paper, the effect of barrier layers in Pt/BT/Pt capacitors is studied using zinc oxide and aluminium oxide. The performance parameters such as capacitance density, leakage current, equivalent series resistance, dielectric loss and dielectric strength of Pt/BT/Pt thin film capacitors with barrier layers of different sizes are simulated using COMSOL Multiphysics modeling software. 2 nm thick aluminum oxide as Pt - BT barrier layer gives optimal performance. The leakage current, dielectric loss, capacitance density, equivalent series resistance and dielectric strength of Pt/BT/Pt capacitor are found to be 0.519 mA, 9.62×10⁻¹², 172.8 fF/μm², 9.62 kΩ, 10⁸ V/m respectively whereas that of Pt/ALO/BT/ALO/Pt capacitor are found to be 1.56×10⁻¹⁸ A, 7.81×10⁻¹⁸, 11.6 fF/μm², 9.01×10¹⁵ Ω, 5.05×10⁹ V/m respectively. The low capacitance in Pt/ALO/BT/ALO/Pt capacitor is due to the low dielectric constant of aluminium dioxide barrier layer. The reduced leakage current and increased equivalent series resistance is due to the low conductivity of the aluminium oxide barrier layer. The use of aluminium oxide barrier layer between the conductive surfaces can reduce the electric field and increase the breakdown voltage, leading to improved dielectric strength and reduced dielectric loss.

Direct formic acid fuel cells have attracted significant attention due to their low fuel crossover, high safety, and high theoretical power density among all proton-exchange membrane fuel cells. Numerous efforts have been dedicated to studying formic acid oxidation, particularly in the fabrication of high-performance electrocatalysts with economical utilization of Pt metal. In this work, we report a synthetic strategy to create PtAg dots supported on plate-like Au nanoparticles and explore their applications in electrocatalytic formic acid oxidation. The highly dispersed nature of the catalytic Pt centers and the successful construction of PtAg−Au trimetallic interfaces makes the current nanostructure an ideal system to allow for a synergetic effect between Pt, Au, and Ag, leading to improved electrocatalysis. Compared with commercial Pt/C, our PtAg-on-Au heterogenous nanoplates exhibit superior mass activity, along with enhanced reaction kinetics and long-term durability for FAOR in an acidic medium. Density functional theory (DFT) simulation results indicate that AgPtAu(111) exhibits a relatively high activity for HCOOH oxidation into CO₂ among the various Au-based catalysts. This work provides a viable strategy for constructing Pt-based electrocatalysts with controlled Pt ensembles, offering insights into the development of fuel cell catalysts that make highly efficient use of costly noble metals.

Potential applications of known compounds from the V₂O-Y₂O₃ system, i. e. YVO₄, Y₈V₂O₁₇ and Y₁₀V₂O₂₀, were the inspiration to undertake research, the main goal of which was to determine whether unknown phases of the solid solution type are formed in this system. Solid solutions are still sought-after phases because their properties depend on their chemical composition. In this work it was experimentally demonstrated that a new substitute solid solution with the formula Y_2-xV_xO_3+x (0.00<×<0.60) is formed from mixtures of V₂O₅ with Y₂O₃ as a result of mechanochemical synthesis. Its properties were examined by using, i.a. XRD (X-ray diffraction) and UV-Vis-DRS (ultraviolet-visible light spectroscopy with diffusion reflectance) methods. It was found among other things, that it crystallizes in a regular system, exhibits a Y₂O₃ structure and is thermally stable up to at least 800 °C (for x=0.40). Moreover, the estimated value of the band gap width indicated that the solid solution Y_2-xV_xO_3+x belongs to the class of semiconductors. The study of dielectric properties of new phase was performed by means of broadband dielectric spectroscopy. The obtained measurement data showed the presence of relaxation type dielectric mechanisms. The thermally activation energies of the relaxation processes related to the electric conductivity were calculated.

Folic acid (FA) protected copper nanoclusters (FA-CuNCs, λ_ex=350 nm, λ_em=445 nm) were synthesized and used as a fluorescent “on-off-on” probe for the cascade detection of Ag⁺ and ascorbic acid (AA). The fluorescence emission of FA-CuNCs at 445 nm was quenched significantly by Ag⁺ due to the analyte-induced aggregation followed by the formation of larger nanoparticles. However, when AA was added to the in-situ generated Ag@FA-CuNCs, the fluorescence emission of FA-CuNCs was recovered at 445 nm because of the AA-directed reduction of Ag⁺ to Ag⁰. The experimental conditions, such as pH, incubation time, and quencher Ag⁺ concentrations, were optimized to achieve improved sensitivity. The detection limit for Ag⁺ and AA was estimated as 37.1 nM and 0.27 μM with a linearity range of 2.49–22 μM and 4.71–81.53 μM, respectively. In real sample analysis, the recoveries of Ag⁺ ions in river water and AA in orange juice samples were found between 99–93 % and 97–94 % using the probes FA-CuNCs and Ag@FA-CuNCs, respectively. Overall, this work offers a viable method for the sequential detection of Ag⁺ and AA using FA-CuNCs via a fluorescence “on-off-on” switch mechanism.

Zirconium-based metal-organic frameworks (Zr-MOFs) represent an important class of MOFs with high stability and outstanding properties, the green preparation and shaping of which are still challengeable works to hinder their real-world applications. In this presentation, UiO-66-NH₂ MOFs were in-situ grown accompanied by alginate (Alg) hydrogelation under aqueous conditions, achieving UiO-66-NH₂/Alg composite hydrogels. Relevant characterizations demonstrate the in-situ generated UiO-66-NH₂ MOFs were evenly distributed in hydrogel networks by attaching on Alg fiber surfaces. The network structure became denser, but both specific surface area and pore volume were augmented due to the presence of MOFs, which in turn increased active sites to interact with adsorbates. Thus, the adsorption capacity to methylene blue (MB) of composite hydrogels became higher with more dosage of MOF ligand, and the pH sensitivity of Alg adsorption to MB in the pH range of 4 to 10 was eliminated. Furthermore, the study of adsorption kinetics and isotherm reveals MB adsorption on the obtained hydrogels belong to rate controlling chemisorption mechanism. In summary, this manuscript presents a facile approach to realizing the green synthesis and shaping of Zr-MOFs by one-step compositing of UiO-66-NH₂ with Alg-based hydrogels in aqueous system, achieving MOFs-based composite hydrogels with enhanced MB adsorption.