Nitrogen-Tungsten Oxide Nanostructures on Nickel Foam as High Efficient Electrocatalysts for Benzyl Alcohol Oxidation.

Electrocatalytic alcohol oxidation (EAO) is an attractive alternative to the sluggish oxygen evolution reaction in electrochemical hydrogen evolution cells. However, the development of high-performance bifunctional electrocatalysts is a major challenge. Herein, we developed a nitrogen-doped bimetallic oxide electrocatalyst (WO-N/NF) by a one-step hydrothermal method for the selective electrooxidation of benzyl alcohol to benzoic acid in alkaline electrolytes. The WO-N/NF electrode features block-shaped particles on a rough, inhomogeneous surface with cracks and lumpy nodules, increasing active sites and enhancing electrolyte diffusion. The electrode demonstrates exceptional activity, stability, and selectivity, achieving efficient benzoic acid production while reducing the electrolysis voltage. A low onset potential of 1.38 V (vs. RHE) is achieved to reach a current density of 100 mA cm-2 in 1.0 M KOH electrolyte with only 0.2 mmol of metal precursors, which is 396 mV lower than that of water oxidation. The analysis reveals a yield, conversion, and selectivity of 98.41%, 99.66%, and 99.74%, respectively, with a Faradaic efficiency of 98.77%. This work provides insight into the rational design of a highly active and selective catalyst for electrocatalytic alcohol oxidation.

An Efficient Continuous Flow Synthesis for the Preparation of N-Arylhydroxylamines: Via a DMAP-Mediated Hydrogenation Process.

The selective hydrogenation of nitroarenes to N-arylhydroxylamines is an important synthetic process in the chemical industry. It is commonly accomplished by using heterogeneous catalytic systems that contain inhibitors, such as DMSO. Herein, DMAP has been identified as a unique additive for increasing hydrogenation activity and product selectivity (up to >99%) under mild conditions in the Pt/C-catalyzed process. Continuous-flow technology has been explored as an efficient approach toward achieving the selective hydrogenation of nitroarenes to N-arylhydroxylamines. The present flow protocol was applied for a vast substrate scope and was found to be compatible with a wide range of functional groups, such as electron-donating groups, carbonyl, and various halogens. Further studies were attempted to show that the improvement in the catalytic activity and selectivity benefited from the dual functions of DMAP; namely, the heterolytic H2 cleavage and competitive adsorption.

A high activity mesoporous Pt@KIT-6 nanocomposite for selective hydrogenation of halogenated nitroarenes in a continuous-flow microreactor.

In this study, we designed a Pt@KIT-6 nanocomposite prepared by impregnating platinum nanoparticles on the nanopores of the KIT-6 mesoporous material. This Pt@KIT-6 nanocomposite was used as a catalyst in a micro fixed bed reactor (MFBR) for the continuous-flow hydrogenation of halogenated nitroarenes, which demonstrates three advantages. First, the Pt@KIT-6 nanocomposite has a stable mesoporous nanostructure, which effectively enhances the active site and hydrogen adsorption capacity. The uniformly distributed pore structure and large specific surface area were confirmed by electron microscopy and N2 physisorption, respectively. In addition, the aggregation of the loaded metal was avoided, which facilitated the maintenance of high activity and selectivity. The conversion and selectivity reached 99% within 5.0 minutes at room temperature (20 °C). Furthermore, the continuous-flow microreactor allows precise control and timely transfer of the reaction system, reducing the impact of haloid acids. The activity and selectivity of the Pt@KIT-6 nanocomposite showed virtually no degradation after 24 hours of continuous operation of the entire continuous-flow system. Overall, the Pt@KIT-6 nanocomposite showed good catalysis for the hydrogenation of halogenated nitroarenes in the continuous-flow microreactor. This work provides insights into the rational design of a highly active and selective catalyst for selective hydrogenation systems.

Nanohole-Array Induced Metallic Molybdenum Selenide Nanozyme for Photoenhanced Tumor-Specific Therapy.

Deficient catalytic sensitivity to the tumor microenvironment is a major obstacle to nanozyme-mediated tumor therapy. Electron transfer is the intrinsic essence for a nanozyme-catalyzed redox reaction. Here, we developed a nanohole-array-induced metallic molybdenum selenide (n-MoSe2) that is enriched with Se vacancies and can serve as an electronic transfer station for cycling electrons between H2O2 decomposition and glutathione (GSH) depletion. In a MoSe2 nanohole array, the metallic phase reaches up to 84.5%, which has been experimentally and theoretically demonstrated to exhibit ultrasensitive H2O2 responses and enhanced peroxidase (POD)-like activities for H2O2 thermodynamic heterolysis. More intriguingly, plenty of delocalized electrons appear due to phase- and vacancy-facilitated band structure reconstruction. Combined with the limited characteristic sizes of nanoholes, the surface plasmon resonance effect can be excited, leading to the broad absorption spectrum spanning of n-MoSe2 from the visible to near-infrared region (NIR) for photothermal conversion. Under NIR laser irradiation, metallic MoSe2 is able to induce out-of-balance redox and metabolism homeostasis in the tumor region, thus significantly improving therapeutic effects. This study that takes advantage of phase and defect engineering offers inspiring insights into the development of high-efficiency photothermal nanozymes.

Visible light-driven oxidative coupling of dibenzylamine and substituted anilines with a 2D WSe2 nanomesh material.

A novel 2D WSe2 nanomesh material was synthesized with a 3D SBA-15 mesoporous material via a nanocasting strategy. The formation of the 2D sheet-like nanomesh structure of WSe2 inside a 3D confined pore space is mainly attributed to the synergistic effect arising from the crystal self-limitation growth caused by the layered crystal structure of the WSe2 material and to the space-limitation effect coming from the unique pore structure of the SBA-15 template. The 2D WSe2 nanomesh material possesses extremely high exposure of crystal layer edges, making it an excellent photocatalyst. It shows good visible light-driven photocatalytic performance in oxidative coupling of dibenzylamine and 2-amino/hydroxy/mercaptoanilines to prepare a group of heterocyclic compounds, including benzimidazoles, benzoxazoles and benzothiazoles with oxygen as the sole oxidant. A gram-scale experiment was also carried out to exhibit the scope of this method.

2D Single Crystal WSe2 and MoSe2 Nanomeshes with Quantifiable High Exposure of Layer Edges from 3D Mesoporous Silica Template.

The design and fabrication of layered transition metal chalcogenides with high exposure of crystal layer edges is one of the key paths to achieve distinctive performances in their catalysis and electrochemistry applications. Two-dimensional WSe2 and MoSe2 nanomeshes with orderly arranged nanoholes were synthesized by using a mesoporous silica material KIT-6 with three-dimensional mesoporous structure as a hard template via a nanocasting strategy. Each piece of the nanomesh is a single crystal, and its c axis is always perpendicular to the nanomesh plane. The highly porous structure brings these nanomeshes extremely high exposure of layer edges, and the well-defined nanostructure provides an opportunity to quantitatively estimate the specific length of the crystal layer edges for the WSe2 and MoSe2 nanomeshes synthesized in this work, which are estimated to be 3.8 × 1010 and 6.0 × 1010 m g-1, respectively. The formation of a 2D sheet-like nanomesh structure inside a 3D confined pore space should be attributed to the synergistic effect from the crystal self-limitation growth that is caused by their layered crystal structures and the space-limitation effect coming from the unique pore structure of the KIT-6 template. The catalytic activities of the nanomeshes in an electrocatalytic hydrogen evolution reaction were also investigated.

Rapid microwave-assisted dispersive micro-solid phase extraction of mycotoxins in food using zirconia nanoparticles.

Mycotoxins are a group of secondary fungi metabolites present in foods that cause adverse effects in humans and animals. The objective of this study was to develop and validate a reliable and sensitive method to determine the presence of fumonisin B1, aflatoxin B1, ochratoxin B, T-2 toxin, ochratoxin A and zearalenone. A rapid, effective process, which involves microwave-assisted dispersive micro-solid phase extraction (MA-d-µ-SPE), has been proposed for the extraction and detection of 6 mycotoxins in peach seed, milk powder, corn flour and beer sample matrixes, for subsequent analysis by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS). Several experimental parameters (type of dispersant, concentration of dispersant, vortex time, type of desorption solvent and pH) affecting the extraction efficiency were systematically studied and optimized. The optimum extraction conditions involved immersing 2.5 µg/mL of nano zirconia (as dispersant) in a 5 mL sample solution. After 2 min of extraction by vigorous shaking, the target analytes were desorbed by 100 µL of chloroform at pH 4.5. The results indicated good linearity in the range of 0.0074-3.6 µg/mL (r ≥ 0.9982), low limits of detection (0.0036-0.033 µg/kg for solid samples and 0.0022-0.017 ng/mL for beer), acceptable reproducibility (relative standard deviation (RSD%) 2.08-2.76% for retention time and 3.51-4.59% for peak area, n = 3), and satisfactory spiked recoveries (84.27-104.96%) for studied mycotoxins in sample matrixes, which demonstrated that MA-d-µ-SPE coupled with UHPLC-Q-TOF/MS is a useful tool for analysis of multi-mycotoxin.

Nickel(II)-Catalyzed Site-Selective C-H Bond Trifluoromethylation of Arylamine in Water through a Coordinating Activation Strategy.

The first example of nickel(II)-catalyzed site-selective C-H bond trifluoromethylation of arylamine in water is established. In this transformation, a coordinating activation strategy is performed by the utilization of picolinamide as a directing group, and target products are obtained in moderate to good yields. In addition, the catalyst-in-water system can be reutilized eight times with a slight loss of catalytic activity and applied in the green, concise synthesis of acid red 266. Furthermore, a series of control experiments verify that a single-electron transfer mechanism is responsible for this reaction.