Chuanxin He

Nitrogen and Sulfur Dual-Doped Non-Noble Catalyst Using Fluidic Acrylonitrile Telomer as Precursor for Efficient Oxygen Reduction

In order to make polyacrylonitrile (PAN) fluidic, acrylonitrile telomer (ANT) is synthesized by radical telomerization and used as a nitrogen and carbon precursor to prepare a non-noble oxygen reduction reaction (ORR) catalyst. This fluidic precursor greatly increases the contact between Fe salt aggregates and the polymer so that more active sites are formed during stabilization and carbonization. Such prepared catalysts and the commercial Pt/C catalyst have comparable ORR performance and stability.

Activity and thermal stability improvements of glucose oxidase upon adsorption on core-shell PMMA-BSA nanoparticles.

The interaction and adsorption of enzyme, glucose oxidase (GOx), on poly(methyl methacrylate)-bovine serum albumin (PMMA-BSA) particles were studied by using a quartz crystal microbalance with dissipation (QCM-D) and laser light scattering (LLS). The enzyme was irreversibly immobilized on the PMMA-BSA particle surface. The amount of enzyme immobilized on PMMA-BSA particles and the enzymatic activity were determined by UV/vis measurements. The influences of pH and ionic strength on the adsorption indicate that the electrostatic interaction plays a major role on the immobilization. The adsorbed GOx can retain at least 80% of the free enzyme activity. Thermal stability studies reveal that the adsorbed GOx only losses 28% of its activity in comparison with a 64% activity loss of free GOx when it is incubated at 50 degrees C for 35 h.

In situ coating of nitrogen-doped graphene-like nanosheets on silicon as a stable anode for high-performance lithium-ion batteries

Carbon coating is an effective approach to improve the cycling stability of silicon (Si) anodes for lithium-ion batteries. In this research, we report a facile one-step carbon-thermal method to coat Si nanoparticles with nitrogen-doped (N-doped) graphene-like nanosheets derived from a liquid-polyacrylonitrile (LPAN) precursor. The coated Si anode displays an initial coulombic efficiency of 82%, which is about three times greater than its pristine counterpart, as well as superior cycling stability. The performance improvement is a result of the N-doped graphene-like nanosheet conformal coating, which not only creates an electrically conductive network for the electrode, but also provides a buffering matrix to accommodate the volume change of Si during charging and discharging processes.

Liquid metal sponges for mechanically durable, all-soft, electrical conductors

Liquid metal sponges were developed by loading liquid metals (GaInSn) into elastomer sponges. The elasticity of 3D-interconnected networks and the fluidic nature of liquid metals led to the formation of all-soft structures for electrical conductors with high electrical conductivity and mechanical flexibility.

Novel hybrid anti-biofouling coatings with a self-peeling and self-generated micro-structured soft and dynamic surface

We prepared hybrid antifouling coatings with a self-generated topographical microgel surface by mixing small surface-functionalized microgels with a self-peeling resin and a poly-functional cross-linking agent (axiridine). The microgels were prepared by copolymerizing acrylamide (AAm) and methacrylic acid (MAA). The resin is a random terpolymer made of methyl methacrylate (MMA), acrylic acid (AA) and triisopropylsilyl methacrylate (TIPSM). During the coating process, the microgels and terpolymer chains are cross-linked together to form a hard thin film. After it is immersed into sea water, the microgels dispersed and embedded on the film surface are swollen, generating small and soft bumps, and at the same time, the hydrolysis of TIPSM makes the surface layer hydrophilic, forming a thin layer of soft hydrogel. A combination of these two effects leads to a soft and dynamic topographical surface layer with many well-structured microgel bumps. Such a soft and dynamic surface is self-generating; namely, the hydrolysis of TIPSM eventually makes the terpolymer chains on the surface soluble so that a thin layer of them is gradually dissolved and washed away and the inner layer is further exposed to sea water. Here, both the self-peeling and topographically structured surface by small microgel bumps lead to antifouling properties. To test such a novel idea, we prepared a set of coatings with different microgel and TIPSM contents and evaluated their antifouling properties in a real marine environment. We found some optimal composition at which the coatings showed excellent antifouling properties in the field tests. Moreover, adding the microgels reduces the amount of expensive TIPSM required so that the coatings become more cost-effective, which is vitally important for industrial applications.

Hydrophilic Sponges for Leaf-Inspired Continuous Pumping of Liquids

A bio‐inspired, leaf‐like pumping strategy by mimicking the transpiration process through leaves is developed for autonomous and continuous liquid transport enabled by durable hydrophilic sponges. Without any external power sources, flows are continuously generated ascribed to the combination of capillary wicking and evaporation of water. To validate this method, durable hydrophilic polydimethylsiloxane sponges modified with polyvinyl alcohol via a “dip‐coat‐dry” method have been fabricated, which maintains hydrophilicity more than 2 months. The as‐made sponges are further applied to achieve stable laminar flow patterns, chemical gradients, and “stop‐flow” manipulation of the flow in microfluidic devices. More importantly, the ease‐of‐operation and excellent pumping capacity have also been verified with over 24 hs pumping and quasi‐stable high flow rates up to 15 µL min−1. The present strategy can be easily integrated to other miniaturized systems requiring pressure‐driven flow and should have potential applications, such as cell culture, micromixing, and continuous flow reaction.

Self-assembly of lyotropic liquid crystal phases in ternary systems of 1,2-dimethyl-3-hexadecylimidazolium bromide/1-decanol/water

Ternary mixtures of 1,2-dimethyl-3-hexadecylimidazolium bromide/1-decanol/water form two types of well-ordered lyotropic ionic liquid crystals, a hexagonal phase linked to the ionic liquid-water axis, and a lamellar phase located at the center of their phase diagram. The lamellar and hexagonal phases span a wide temperature range from 3 to 40 degrees C, depending on the composition. The spontaneous self-assembly of the mixtures arises from strong association between the hydroxyl groups of 1-decanol or water and the polar head-groups of the ionic liquid (head-group solvent), aromatic stacking interaction between the imidazolium rings and the hydrophobic effect.

Microfluidic Patterning of Metal Structures for Flexible Conductors by In Situ Polymer‐Assisted Electroless Deposition

A low‐cost, solution‐processed, versatile, microfluidic approach is developed for patterning structures of highly conductive metals (e.g., copper, silver, and nickel) on chemically modified flexible polyethylene terephthalate thin films by in situ polymer‐assisted electroless metal deposition. This method has significantly lowered the consumption of catalyst as well as the metal plating solution.

Preparation of well-defined core-shell particles by Cu2+-mediated graft copolymerization of methyl methacrylate from bovine serum albumin.

Small well-defined core-shell poly(methyl methacrylate)-bovine serum albumin (PMMA-BSA) particles have been prepared in a direct one-step graft copolymerization of MMA from BSA at 75 degrees C in water with a trace amount of Cu2+ (5 microM). Initially, BSA generates free radicals and acts as a multifunctional macroinitiator, which leads to the formation of an amphiphilic PMMA-BSA grafting copolymer. Such formed copolymer chains act as a polymeric stabilizer to promote further emulsion polymerization of MMA inside, resulting in surfactant-free stable core-shell particles, confirmed by a transmission electron microscopic (TEM) analysis. The PMMA-BSA copolymers as well as PMMA homopolymer inside the particles were isolated by Soxhlet extraction and characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry (TG). The highest grafting efficiency was approximately 80%. Effects of the reaction temperature, the MMA/BSA ratio, and the concentrations of Cu2+ and BSA on such core-shell particle formation have been systematically studied. Due to their inert PMMA core and biocompatible BSA shell, these small polymer particles are potentially useful in biomedical applications.

Organic sponge photocatalysis

The successfully developed polydimethylsiloxane (PDMS, a green and highly transparent polymer material) sponge photocatalyst can catalyze cross-dehydrogenative coupling (CDC) of tertiary amines and various nucleophiles with high efficiency and reusability under visible light irradiation. Through an easy-to-build continuous flow reactor, the sponge photocatalytic reaction can be facilely scaled up.