Latest ArticlesGreen 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.
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.
The recent electrocatalytic three-component annulation-halosulfonylation of 1, 6-enynes toward 1-indanones is highlighted.
Due to their high specificity and affinity towards various targets, along with other unique advantages such as stability and low cost, aptamers are widely applied in analytical techniques. A typical aptamer-based electrochemical biosensor is composed of a aptamer as the biological recognition element and transducer converting the biologic interaction into electrical signals for the quantitative measurement of targets. Improvement of the sensitivity of a biosensor is significantly important in order to achieve the detection of biomolecules with low abundance, and different amplification strategies have been explored. The strategies either employ nanomaterials such as gold nanoparticles to construct electrodes which can transfer the biological reactions more efficiently, or attempt to obtain enhanced signal through multi-labeled carriers or utilize enzyme mimics to catalyze redox cycling. This review discusses recent advances in signal amplification methods and their applications. Critical assessment of each method is also considered.
In the past few years, photo-crosslinkable hydrogels have drawn a great attention in tissue engineering applications due to their high biocompatibility and extracellular matrix (ECM)-like structure. They can be easily biofabricated through exposure of a photosensitive system composed of photo-crosslinkable hydrogels, photo-initiators and other compounds such as cells and therapeutic molecules, to ultraviolet or visible light. With the development of biofabrication methods, many researchers studied the biological applications of photo-crosslinkable hydrogels in tissue engineering, such as vascular, wound dressing and bone engineering. This review highlights the biomaterials for photo-crosslinkable hydrogels, biofabrication techniques and their biological applications in tissue engineering. Meanwhile, the challenges and prospects of photo-crosslinkable hydrogels are discussed as well.
The stimulator of interferon genes (STING) shows promising clinical activity in infectious diseases and tumors. However, the lack of targeting capability and intracellular stability of STING agonists severely limits the therapeutic efficacy. Recently, drug delivery systems (DDSs) overcome these delivery barriers of STING agonists via passive or active cell targeting, prolonged blood circulation and drug release, and lysosome escape, etc. In this review, we will describe in detail how existing DDSs are designed to overcome delivery barriers and activate the STING pathway, and the current biomedical applications of STING-activating DDSs in the treatments of infectious diseases and tumors. Finally, the prospects and challenges of DDSs in STING activation are discussed.
The carbon nanotubes (CNTs) as the emerging materials for organic pollutant removal have gradually become a burgeoning research field. Herein, a mini-review of CNTs-based materials currently studies for organic pollutant elimination is presented. This review summarizes the preparation methods of CNTs-based materials. CNTs-based materials can be used as adsorbents to remove organic pollutants in wastewater. The adsorption mechanisms mainly include surface diffusion, pore diffusion and adsorption reaction. Most importantly, an in-depth overview of CNTs-based materials currently available in advanced oxidation processes (AOPs) applications for wastewater treatment is proposed. CNTs-based materials can catalyze different oxidants (e.g., hydrogen peroxide (H2O2), persulfates (PMS/PDS), ozone (O3) and ferrate/permanganate (Fe(VI)/Mn(VII)) to generate more reactive oxygen species (ROS) for organic pollutant elimination. Moreover, the possible reaction mechanisms of removing organic pollutants by CNTs-based materials are summarized systematically and discussed in detail. Finally, application potential and future research directions of CNTs-based materials in the environmental remediation field are proposed.
Clean production, as an important part of green chemistry, has received great attention and considerable development in recent years. In this perspective article, we summarized some examples of (nearly) quantitative synthesis, clean separation and purification to emphasize clean production. These reactions were carried out by using eco-friendly solvents and the pure products could be easily obtained through clean procedures.