We report a facile approach to prepare an artificial enzyme system for tandem catalysis. NiPd hollow nanoparticles and glucose oxidase (GOx) were simultaneously immobilized on the zeolitic ...imidazolate framework 8 (ZIF‐8) via a co‐precipitation method. The as‐prepared GOx@ZIF‐8(NiPd) nanoflower not only exhibited the peroxidase‐like activity of NiPd hollow nanoparticles but also maintained the enzymatic activity of GOx. A colorimetric sensor for rapid detection of glucose was realized through the GOx@ZIF‐8(NiPd) based multi‐enzyme system. Moreover, the GOx@ZIF‐8(NiPd) modified electrode showed good bioactivity of GOx and high electrocatalytic activity for the oxygen reduction reaction (ORR), which could also be used for electrochemical detection of glucose.
Flower power: NiPd hollow nanoparticles and glucose oxidase (GOx) were simultaneously immobilized on a ZIF‐8 metal–organic framework via a co‐precipitation method. The resulting artificial enzyme system maintains the GOx activity and also has oxygen reduction reaction (ORR) reactivity, building a bridge between nanozymes and natural enzymes.
Despite the fact that both electrochemical experiments and density functional theory calculations have testified to the superior electrocatalytic activity and CO-poisoning tolerance of ...platinum–ruthenium (PtRu) alloy nanoparticles toward the methanol oxidation reaction (MOR), the facet-dependent electrocatalytic properties of PtRu nanoparticles are scarcely revealed because it is extremely difficult to synthesize well-defined facets-enclosed PtRu nanocrystals. Herein, we for the first time report a general synthesis of ultrathin PtRu nanocrystals with tunable morphologies (nanowires, nanorods, and nanocubes) through a one-step solvothermal approach and a systematic investigation of the structure-directing effects of different surfactants and the formation mechanism by control experiments and time-dependent studies. In addition, we utilize these {100} and {111} facets-enclosed PtRu nanocrystals as model catalysts to evaluate the electrocatalytic characteristics of the MOR on different facets. Remarkably, {111}-terminated PtRu nanowires exhibit much higher stability and electrocatalytic mass activity toward MOR, which are 2.28 and 4.32 times higher than those of {100}-terminated PtRu nanocubes and commercial Pt/C, respectively, indicating that PtRu {111} facets possess superior methanol oxidation activity and CO-poisoning resistance relative to {100} facets. Our present work provides a series of well-defined PtRu nanocrystals with tunable facets which would be ideal model electrocatalysts for fundamental research in fuel cell electrocatalysis.
Hepatic gluconeogenesis,
glucose synthesis from available precursors, plays a crucial role in maintaining glucose homeostasis to meet energy demands during prolonged starvation in animals. The ...abnormally increased rate of hepatic gluconeogenesis contributes to hyperglycemia in diabetes. Gluconeogenesis is regulated on multiple levels, such as hormonal secretion, gene transcription, and posttranslational modification. We review here the molecular mechanisms underlying the transcriptional regulation of gluconeogenesis in response to nutritional and hormonal changes. The nutrient state determines the hormone release, which instigates the signaling cascades in the liver to modulate the activities of various transcriptional factors through various post-translational modifications like phosphorylation, methylation, and acetylation. AMP-activated protein kinase (AMPK) can mediate the activities of some transcription factors, however its role in the regulation of gluconeogenesis remains uncertain. Metformin, a primary hypoglycemic agent of type 2 diabetes, ameliorates hyperglycemia predominantly through suppression of hepatic gluconeogenesis. Several molecular mechanisms have been proposed to be metformin's mode of action.
Tunneling conductance among nanoparticle arrays is extremely sensitive to the spacing of nanoparticles and might be applied to fabricate ultra-sensitive sensors. Such sensors are of paramount ...significance for various application, such as automotive systems and consumer electronics. Here, we represent a sensitive pressure sensor which is composed of a piezoresistive strain transducer fabricated from closely spaced nanoparticle films deposited on a flexible membrane. Benefited from this unique quantum transport mechanism, the thermal noise of the sensor decreases significantly, providing the opportunity for our devices to serve as high-performance pressure sensors with an ultrahigh resolution as fine as about 0.5 Pa and a high sensitivity of 0.13 kPa
. Moreover, our sensor with such an unprecedented response capability can be operated as a barometric altimeter with an altitude resolution of about 1 m. The outstanding behaviors of our devices make nanoparticle arrays for use as actuation materials for pressure measurement.
The studies on synthesis of organosilicons via radical strategies since 2016 are reviewed, in which there are five main categories for the initiation of these radical silylations.
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...Organosilicon compounds play an important role in the fields of materials science, pharmacy, and organic synthesis. The development of effective approaches for the preparation of these compounds have also become a research focus in organic synthesis. In recent years, free radical synthesis of organosilicons has been vigorously developed, which generally has the advantages of milder synthesis conditions, higher yields and selectivity, and free of precious metal catalysts compared with traditional strategies. This article reviews research progresses in the synthesis of organosilicon compounds by free radical pathways since 2016. In most cases, the radical silylation is achieved based on the reaction of silyl radicals, which are triggered by four routes including peroxide, transition-metal-induced peroxide decomposition, alkali, photocatalysis. The alkyl radicals can also initiate the radical silylation for the generation of C(sp3)Si bonds.
Two-dimensional (2D) metal–organic framework (MOF) nanosheets, which possess the advantages of both 2D layered nanomaterials and MOFs, are considered as promising nanomaterials. However, it is still ...difficult to directly synthesize MOF nanosheets. Here we for the first time report a new bottom-up strategy for
in situ
synthesis of high-quality ZIF-67 nanosheets with the salt-template assistance. The as-prepared ZIF-67 nanosheets exhibit a uniform morphology and ultrathin structure with a thickness of 4.5 nm. Furthermore, because of the highly open structure, larger surface area, more accessible active sites and smaller diffusion barrier compared with bulk-sized MOFs, the directly carbonized Co,N-doped nanoporous carbon nanosheets also greatly boost the oxygen reduction reaction (ORR). More importantly, the general synthesis process indicates that this effective salt-template confined bottom-up strategy can be expanded to synthesize other ultrathin 2D MOF nanosheets with extensive applications in gas separation, catalysis, sensors, and energy storage and conversion.
A novel one-step strategy is proposed to fabricate three-dimensional (3D) graphene hydrogel (GH) by simultaneous self-assembly and reduction of graphene oxide (GO) at 90 °C under atmospheric ...pressure, using
l
-cysteine (
l
-Cys) as both templating and reducing agent. The preparation process can be completed within 3 h without producing any contamination, which is a fast, facile, economical and green method for the fabrication of GH. The freeze-dried product – graphene aerogel (GA) – has high mechanical strength and thermal stability, with hierarchical pore structure and large specific surface area. More importantly, the as-prepared GA exhibits outstanding adsorption capacity towards organic dyes, which could be a potential candidate for efficient adsorbents in water purification. In addition, the established method is successfully extended to the preparation of platinum nanoparticle (PtNP)-loaded 3D graphene materials
via
one-step simultaneous reduction and assembly of metal ions and GO. The as-obtained PtNPs/GA with free-standing structure can act as a heterogeneous catalyst for the chemical reduction of
p
-nitroaniline, which shows excellent catalytic activity. The developed method is promising for preparing other graphene-based multifunctional composite materials.
Free-standing nitrogen-doped carbon nanofiber (NCNF) films based on polyacrylonitrile (PAN) were prepared simply by the combination of electrospinning and thermal treatment. We reused the ...nitrogen-rich gas generated as the byproduct of PAN at elevated temperature, mainly NH3, for surface etching and nitrogen doping. The as-obtained NCNFs exhibited a rougher surface and smaller diameter than pristine carbon nanofibers. Despite the decreased total N content, a significant increase in the content of pyrrolic-N was observed for the NCNFs. In application to electrochemistry, the free-standing NCNF films showed comparable catalytic activity with a close four-electron pathway to a commercial Pt/C catalyst in alkaline medium toward oxygen reduction reaction (ORR), which can be attributed to the nitrogen doping and high hydrophilicity. More importantly, the ORR current density on the NCNFs only dropped 6.6% after 10,000 s of continuous operation, suggesting an enhanced long-time durability. In addition, the NCNFs also showed better electrocatalytic selectivity than Pt/C. Our work reveals a facile but efficient approach for the synthesis of free-standing NCNF films as a promising alternative to Pt-based electrocatalysts in fuel cells.
Aprotic Li–O2 batteries have attracted worldwide interest owing to their ultrahigh theoretical energy density. However, the practical Li–O2 batteries still suffer from high charge overpotential and ...low energy efficiency resulting from the sluggish kinetics in electrochemically oxidizing the insulating lithium peroxide (Li2O2). Recently, dissolved redox mediators in the electrolyte have enabled the effective catalytic oxidation of Li2O2 at the liquid–solid interface. Here, we report that the incorporation of N-methylphenothiazine (MPT), as a redox shuttle in Li–O2 batteries, provides a dramatic reduction in charge overpotential to 0.67 V and an improved round-trip efficiency close to 76%. Moreover, the efficacy of MPT in Li–O2 cells was further investigated by various characterizations. On charging, MPT+ cations are first generated electrochemically at the cathode surface and subsequently oxidize the solid discharge products Li2O2 through a chemical reaction. Furthermore, the presence of MPT has been demonstrated to improve the cycling stability of the cells and suppress side reactions arising from carbon and electrolytes at high potentials.
Plastic waste caused by the extensive usage of face masks during COVID‐19 pandemic has become a severe threat to natural environment and ecosystem. Herein, an eco‐friendly approach to repurpose face ...mask waste for clean water production via solar thermal evaporation is proposed. By taking advantage of its interwind structure, face mask holds the promise to be an ideal candidate material for constructing photothermal evaporator. In‐situ surface modifications are performed successively with polyvinyl alcohol and polypyrrole to improve its wettability and solar absorption (97%). The obtained face mask‐based evaporator achieves significantly enhanced solar efficiency (91.5%) and long‐term salt‐rejection stability. The harvested clean water befits plant growing to enable farming on sea surface. A floating photothermal evaporation prototype is then developed to demonstrate autonomous solar ocean farming, with plants successfully cultivated over time. As such, the proposed strategy provides a promising solution towards ecological sustainability by tapping multiple benefits.
This work presents an eco‐friendly way to recycle large amount of wasted face masks into solar absorbers for clean water production. A prototype of floating farm is further demonstrated, using recycled face mask to convert abundant seawater into portable water for plants irrigation. Plants can be well thrived, giving a promising solution to land soil crisis and polymer white pollution.
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