Latest ArticlesHerein, a facile glycol reduction route is successful employed to synthesize bimetallic PtAg alloys with homogeneous distribution of sizes and elements. Experimental studies reveal that the ultrafine PtAg alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO2 microsphere, which remarkably enhances the catalytic performances for CO oxidation. Importantly, quasi in-situ X-ray photoelectron spectroscopy (XPS) result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O2 molecules, and the oxygen vacancy sites could be replenished and excited by gas-phase O2.
It is well known that zero-valent iron (ZVI) could catalyze the oxidation of various oxidants to realize the rapid oxidation removal of pollutants. However, in this study, we found that the addition of different oxidants could regulate the redox function of ZVI system. In three different co-treatment systems, the effects of different oxidizers (peroxymonosulfate (PMS), persulfate (PDS), hydrogen peroxide (H2O2)) dosages on the ratios of oxidative degradation rate and reductive degradation rate of p-nitrophenol (PNP) were studied. The effect of the H+ released from oxidizers and the generated reactive oxygen species (ROS) in ZVI/PMS, ZVI/PDS, ZVI/H2O2 systems were detailed discussed. Especially, the contribution of generated ROS for reductive degradation of PNP was quantified in the ZVI/H2O2 system. Based on the results of TOC removal, UV–vis absorption spectra, and intermediates concentration curves, it was found that the degradation of PNP changed from reduction to oxidation with the increase of oxidant proportion. When the molar ratio of ZVI to oxidizer equal to 100, PNP was mainly degraded by reduction accompanied by slight oxidation. Combined with the results of SEM-EDS and XPS, it was confirmed that the enhanced degradation of PNP under the addition of oxidant was mainly related to the generated ROS, the additional H+, and the corrosion products of ZVI.
Green and recyclable solid acid catalysts are in urgent demand as a substitute for conventional liquid mineral acids. In this work, a series of novel sulfonic acid-functionalized core-shell Fe3O4@carbon microspheres (Fe3O4@C-SO3H) have been designed and synthesized as an efficient and recyclable heterogeneous acid catalyst. For the synthesis, core-shell Fe3O4@RF (resorcinol-formaldehyde) microspheres with tunable shell thickness were achieved by interfacial polymerization on magnetic Fe3O4 microspheres. After high-temperature carbonization, the microspheres were eventually treated by surface sulfonation, resulting in Fe3O4@C-x-SO3H (x stands for carbonization temperature) microspheres with abundant surface SO3H groups. The obtained microspheres possess uniform core-shell structure, partially-graphitized carbon skeletons, superparamagnetic property, high magnetization saturation value of 10.6 emu/g, and rich SO3H groups. The surface acid amounts can be adjusted in the range of 0.59–1.04 mmol/g via sulfonation treatment of carbon shells with different graphitization degrees. The magnetic Fe3O4@C-x-SO3H microspheres were utilized as a solid acid catalyst for the acetalization reaction between benzaldehyde and ethylene glycol, demonstrating high selectivity (97%) to benzaldehyde ethylene glycol acetal. More importantly, by applying an external magnetic field, the catalysts can be easily separated from the heterogeneous reaction solutions, which later show well preserved catalytic activity even after 9 cycles, revealing good recyclability and high stability.
Energy transfer and electron transfer are both fundamental mechanisms enabling numerous functional materials and applications. While most materials systems employ either energy transfer or electron transfer, the combined effect of energy and electron transfer processes in a single donor/acceptor system remains largely unexplored. Herein, we demonstrated the energy transfer followed by electron transfer (ETET) process in a molecular dyad TPE-NBD. Due to energy transfer, the fluorescence of TPE-NBD was greatly enhanced in non-polar solvents. In contrast, polar solvents activated subsequent electron transfer and markedly quenched the emission of TPE-NBD. Consequently, ETET endows TPE-NBD with significant polarity sensitivities. We expect that employing ETET could generate many functional materials with unprecedented properties, i.e., for single laser powered multicolor fluorescence imaging and sensing.
The reaction of a metallo-organic ligand (LA) in which two "V"-shaped bisterpyridines attaching to meta-position of "X"-shaped tetraterpyridine via < tpy-Ru2+-tpy > connectivity and Zn2+ ions gave rise to 3D supramolecular architectures: octagram (Zn8LA4). However, a position varied ligand (LB) in which two "V"-shaped bisterpyridines locating at the ortho-position of "X"-shaped tetraterpyridine afforded a different 3D hexagram (Zn6LB3). Full characterizations included NMR (1H, 13C, 2D COSY, NOESY and DOSY), ESI-MS, TWIM-MS, TEM and AFM. The resulted structures were directly determined by the position of two "V"-shaped bisterpyridines attaching to "X"-shaped tetraterpyridine.
A nitro group is a common fluorescence quencher, but its quenching efficiency can be easily affected by the surrounding environment. To date, there has been no systematic study on the effects of electron-withdrawing groups on the quenching efficiency of nitro groups. Herein, by virtue of experimental validation and theoretical calculations, we found that strong electron-withdrawing groups, such as pyridinium and dicyanovinyl groups, are detrimental to the quenching effect of nitro groups. Decreasing the electron-withdrawing ability could restore the nitro group's quenching effect.
Vaccine adjuvants have been widely used to enhance the immunogenicity of the antigens and elicit long-lasting immune response. However, only few vaccine adjuvants have been approved by the FDA for human use so far. Therefore, there is still an urgent need to develop novel adjuvants for the potential applications in clinical trials. Herein, non-nucleotide small molecule STING agonist diABZI was employed to construct glycopeptide antigen based vaccines for the first time. Immunological evaluation indicated diABZI not only enhanced the production of antibodies and T cell immune responses, but also inhibited tumor growth in tumor-bearing mice in glycopeptide-based subunit vaccines. These results indicated that di-ABZI demonstrates a high potential as adjuvant for the development of cancer vaccines.
The sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have always restricted the development of lithium oxygen batteries (LOBs). Herein, hollow carbon spheres loaded with Pd/Pd4S heterostructure (Pd/Pd4S@HCS) were successfully prepared via the in-situ deposition to improve the electrocatalytic activities for both ORR and OER in LOBs. With the well-dispersed Pd/Pd4S nanoparticles, the hierarchical composite with large specific surface area offers favorable transport channels for ions, electron and oxygen. Especially, the Pd/Pd4S nanoparticles could exhibit excellent electrochemical performance for ORR and OER due to their intrinsic catalytic property and interfacial effect from the heterostructure. Therefore, the LOBs with Pd/Pd4S@HCS as cathode catalyst show improved specific capacities, good rate ability and stable cycling performance.
Physical adsorption is a common method to solve the contamination of methylene blue in dyeing wastewater. As a kind of adsorption material, cellulose aerogels with high porosity and surface areas have great potential application in methylene blue removal. However, the week hydrogen bonding between cellulose nanofibers making the cellulose aerogels with the poor mechanical properties and can be easily destroyed during adsorption. Hence, the preparation of cellulose aerogels with high mechanical strength is still a great challenge. Here, we report a robust super-assembly strategy to fabricate cellulose aerogels by combining cellulose nanofibers with PVA and M-K10. The resulting cellulose aerogels not only has a robust chemically cross-linked network, but also has strong H-bonds, which greatly enhance the mechanical properties. The resulting cellulose aerogels possess a low density of 19.32 mg/cm3. Furthermore, the cellulose aerogel shows 93% shape recovery under 60% strain (9.5 kPa under 60% strain) after 100 cycles, showing excellent mechanical property. The adsorption capacity of cellulose aerogel to methylene blue solution of 20 mg/L is 2.28 mg/g and the adsorption kinetics and adsorption isotherms have also been studied. Pseudo-second-order kinetic model and Freundlich isotherm model are more acceptable for indicating the adsorption process of methylene blue on the cellulose aerogel. Thus, this compressible and durable cellulose aerogel is a very prospective material for dyeing wastewater cleanup.
Amino group protective strategy has consequently emerged in multistep organic synthesis. Easy and selective deprotection procedures are crucial to facilitate the chemical transformation. Recently, Zhang's group from Henan Normal University collaborating with Chen's group of Nankai University developed a novel strategy for the regiospecific cleavage of inert aryl C—N bonds in N-aryl amides by hypervalent iodine(V) reagents. These procedures allow removal of sort of aryl groups under mild conditions to give primary amides in high efficiency. It bestows these aryl groups with the characteristics of amino protecting groups that might be the supplement of amino protecting group chemistry.
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