Highly dispersed Pt nanoparticles on ultrasmall EMT zeolite: A peroxidase-mimic nanoenzyme for detection of H2O2 or glucose.

In past decade, Pt-based nanomaterials as peroxidase mimics have attracted much attention for H2O2 and glucose detection. However, easy aggregation of Pt nanoparticles (Pt NPs) greatly decreases their peroxidase-like activity. In this work, novel Pt/EMT nanocomposites were prepared by uniformly loading Pt NPs (5-8 nm) onto the support of ultrasmall EMT zeolite (15-20 nm), a kind of low-silica microporous aluminosilicate material. The hybrid Pt/EMT nanomaterials could be well dispersed in water to form a homogeneous suspension, and were then utilized as a superior peroxidase-like catalyst for oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). The optimal catalyst of 2.6Pt/EMT nanocomposite exhibited excellent catalytic performance toward H2O2 and TMB than natural enzyme of horseradish peroxidase (HRP) by using a steady-state kinetic analysis based on the typical Michaelis-Menten kinetics theory. The peroxidase-like catalyst showed a promising activity in a wide pH and temperature range as well as the long-term stability. A facile and reliable colorimetric assay based on the peroxidase mimic of Pt/EMT nanocomposite was constructed for precise detection of H2O2 and glucose in a wide linear range, with low limits of detection of 1.1 µM and 13.2 µM, respectively. Due to high selectivity to glucose against other sugars on the catalyst, the method was demonstrated to accurately measure the concentration of glucose in real samples including human blood serum and fruit juices, indicating a potential application of the Pt/EMT nanocomposites as a robust peroxidase mimic and a reliable biosensor in the fields of clinical diagnosis, pharmaceutical, food research and so on.

Surface Anchoring Approach for Growth of CeO2 Nanocrystals on Prussian Blue Capsules Enable Superior Lithium Storage.

Prussian blue (PB) and its analogues (PBAs) have been acknowledged as promising materials for the catalysis, energy storage, and bioapplications because of different constructions and tunable composition. The approach for surface modification with metal oxides for boosting the performance, however, is rarely reported. Herein, a facile surface anchoring strategy has been proposed to realize CeO2 nanocrystals uniformly depositing on the surface of PB. Besides, the size, thickness, and depositing density of CeO2 nanocrystals can be regulated by adjusting the amount of the precursor and the proportion of ethanol and deionized water. Furthermore, after a step of confined pyrolysis treatment under an air atmosphere, CeO2 nanocrystals with an encapsulated iron oxide structure have been obtained. This shows a remarkable cycling and rate performance when evaluated as an anode of the lithium-ion battery. The surface anchoring approach of the CeO2 nanocrystals may not only promote the various applications of PB-based materials but also provide an opportunity for developing the architecture of other CeO2-based core-shell nanostructures.

Carbon-Encapsulated Copper Sulfide Leading to Enhanced Thermoelectric Properties.

Copper sulfide has been regarded as a promising thermoelectric material with relatively high thermoelectric performance and abundant resource. Large-scale synthesis and low-cost production of high-performance thermoelectric materials are keys to widespread application of thermoelectric technology. Here, Cu2- xS particles encapsulated in a thin carbon shell are fabricated by a scalable wet chemical method (19.7 g/batch). The synthesized particles go through the crystal-phase transition from orthorhombic to tetragonal during high-temperature annealing and sintering. After the phase transition, electrical conductivity of this composite (Cu2- xS@C) increases by approximately 50% compared to that of the pure Cu2- xS sample, and can be attibuted to an increase in carrier concentration. Phonon scattering interface formation and superionic phase of Cu2- xS@C results in very low lattice thermal conductivity of 0.22 W m-1 K-1, and maximum thermoelectric figure of merit ( ZT) of 1.04 at 773 K, which is excellent for thermoelectric performance in pure-phase copper sulfide produced via chemical synthesis. This discovery sets the stage for the use of facile wet chemical synthesis methods for large-scale transition-metal chalcogenide thermoelectric material production.

Mesoporous WO3 Nanofibers With Crystalline Framework for High-Performance Acetone Sensing.

Semiconducting metal oxides with abundant active sites are regarded as promising candidates for environmental monitoring and breath analysis because of their excellent gas sensing performance and stability. Herein, mesoporous WO3 nanofibers with a crystalline framework and uniform pore size is successfully synthesized in an aqueous phase using an electrospinning method, with ammonium metatungstate as the tungsten sources, and SiO2 nanoparticles and polyvinylpyrrolidone as the sacrificial templates. The obtained mesoporous WO3 nanofibers exhibit a controllable pore size of 26.3-42.2 nm, specific surface area of 24.1-34.4 m2g-1, and a pore volume of 0.15-0.24 cm3g-1. This unique hierarchical structure, with uniform mesopores and interconnected channels, could facilitate the diffusion and transportation of gas molecules in the framework. Gas sensors, based on mesoporous WO3 nanofibers, exhibit an excellent performance in acetone sensing with a low limit of detection (<1 ppm), short response-recovery time (24 s/27 s), a linear relationship in a broad range, and good selectivity.

Achieving high-performance nitrate electrocatalysis with PdCu nanoparticles confined in nitrogen-doped carbon coralline.

Complex porous carbon nanostructures with homogeneously embedded nanoparticles and intricate architectures show promise as high-performance catalysts. Herein, we demonstrate a direct surfactant co-assembly approach for the fabrication of well-dispersed PdCu nanoparticles encapsulated in N-doped porous carbon with three-dimensional coralline structures. Owing to their porous features and unique frameworks, the PdxCuy@N-pC coralline-like nanostructures offer large surface areas, accessible active sites, and excellent nitrate electrocatalytic ability. The composite catalyst Pd4Cu4@N-pC exhibits outstanding catalytic performance with a high nitrate removal rate of ∼95%, nitrogen selectivity of ∼80%, and removal capacity of 22 000 mg N per g PdCu. More importantly, the present work opens up a broad horizon for architectures of nanoparticles confined in coralline-like 3D porous carbon structures with superior performance and promising large-scale applications.

Iron nanoparticles in capsules: derived from mesoporous silica-protected Prussian blue microcubes for efficient selenium removal.

A spatially confined reduction strategy for the fabrication of small nanoparticles in a micro-box is reported, where iron nanoparticles with uniform diameter are highly distributed in a carbon matrix and surrounded by a mesoporous silica layer. Due to their unique confined nanostructure, the Fe/C@mSiO2 capsules could effectively remove and recycle Se(iv) from a low concentration solution.