A gold electrode modified with a nanoparticulate film composed of a conducting copolymer for ultrasensitive voltammetric sensing of hydrogen peroxide.

A film consisting of poly(γ-glutamic acid) modified with 3-aminothiophene (ATh-γ-PGA) was prepared by macromolecular self-assembly and electropolymerization. ATh-γ-PGA is amphiphilic and electrically conductive. The copolymers undergo self-assembly to form nanoparticles (NPs) on decreasing the pH value of an aqueous solution. A conducting film of NPs was formed on the surface of a gold electrode by casting the ATh-γ-PGA NPs and subsequently electropolymerizing the thiophene units. Next, horseradish peroxidase and Nafion were cast onto the film to obtain an enzymatic biosensor for H2O2. Due to the electropolymerization step, a cross-conjugated polymer network is created that improves electron transfer rates and thus enhances the response. This endows the biosensor with high sensitivity. Two linear ranges are present, the first ranging from 1 × 10-11 to 1 × 10-8 mol·L-1, and the second from 1 × 10-8 to 1 × 10-5 mol·L-1. The detection limit is as low as 3 × 10-12 mol·L-1. The sensor is stable, repeatable, and was successfully applied to the determination of H2O2 in a commercial disinfecting solution. Graphical abstract Preparation of a conducting nanoparticle (NP) film on the gold electrode (GE) by self-assembly of poly(γ-glutamic acid) that was modified with electroactive 3-aminothiophene (ATh-γ-PGA). It served as a platform for the fabricationof an ultrasensitive voltammetric enzyme-based biosensor for H2O2.

N/O co-doped poly(γ-glutamic acid)/Ni2+/melamine/chitosan nanoparticle-based hollow graphite carbon spheres for aqueous zinc-ion hybrid supercapacitors.

Hollow carbon spheres (HCSs) have attracted broad attention in aqueous zinc-ion hybrid supercapacitors (ZIHSCs) owing to their distinctive properties. However, traditional methods for fabricating HCSs face limitations, including complex multistep procedures, the use of corrosive chemicals, and stringent reaction conditions. In this work, biomass-based poly(γ-glutamic acid)/Ni2+/melamine/chitosan nanoparticles were used as the precursors to fabricate N/O co-doped hollow graphite carbon spheres (HGCSs). Thanks to the appropriate hydrophilic characteristic, specific surface area, pore size distribution, and electrical conductivity, the fabricated HGCSs cathode exhibited superior electrochemical properties. The assembled HGCSs-based ZIHSCs device showed a satisfactory specific capacitance of 133.2 mAh·g-1 at a current density of 1.0 A·g-1, high energy densities of 75.2 Wh·kg-1 at 10,000 W·kg-1 and 107.9 Wh·kg-1 at 1000 W·kg-1, respectively. Additionally, the assembled HGCSs-based ZIHSCs device displayed an exceptional cycling stability, enduring up to 10,000 cycles at 0.5 A·g-1 with a capacity retention rate of 98.1 %. This work provides a facile and novel strategy to prepare superior electrochemical performance biomass-based HGCSs cathode for ZIHSCs.

Hollow carbon spheres derived from self-assembled chitosan/poly(γ-glutamic acid) nanoparticles for oil-in-water emulsion separation.

With the rapid science and technology advancement, the oil-water separation in oily wastewater has become an urgent problem, especially the emulsified oil-water mixtures. Hollow carbon spheres (HCSs) have tremendous potential in separating oil-water emulsions due to their rich porous channels and high surface-to-volume ratio. In this work, as-prepared chitosan/poly(γ-glutamic acid) nanoparticles crosslinked by Ni2+ (Ni2+/CS/γ-PGA NPs) were used as carbon precursor to fabricate HCSs. This strategy separated the formation process of the biomolecular microspheres and the carbonization process. Especially, the Ni2+/CS/γ-PGA NPs were fabricated from the self-assembly of chitosan and γ-PGA in aqueous solution and the crosslinking of Ni2+ via the electrostatic interactions, facilitating the formation of biomolecular microspheres and making the usable of biomolecule-based carbon precursors diversity. After lyophilization, Ni2+/CS/γ-PGA NPs powder was obtained, which was then carbonized in a tube furnace under N2 atmosphere. During the carbonization process, the nickel species aggregated together to form the core of nickel@carbon nanoparticles, and carbon formed the shell. At last, nickel nanoparticles were removed from the carbon framework by hydrochloric acid, obtaining HCSs with super-hydrophobicity and lipophilicity. The as-prepared HCSs exhibited excellent separation performance in oil-in-water emulsions.

Body temperature responsive capsules templated from Pickering emulsion for thermally triggered release of ß-carotene.

In recent years, functional foods with lipophilic nutraceutical ingredients are gaining more and more attention because of its potential healthy and commercial value, and developing of various bioderived food-grade particles for use in fabrication of Pickering emulsion has attracted great attentions. Herein, the bio-originated sodium caseinate-lysozyme (Cas-Lyz) complex particles were firstly designed to be used as a novel interfacial emulsifier for Pickering emulsions. Pickering emulsions of various food oils were all successfully stabilized by the Cas-Lyz particles without addition of any synthetic surfactants, while the fluorescence microscopy and SEM characterizations clearly evidenced Cas-Lyz particles were attached on the surface of emulsion droplets. Additionally, the Cas-Lyz particles stabilized emulsion can also be used to encapsulate the ß-carotene-loaded soybean oil, suggestion a potential method to carry lipophilic bioactive ingredients in an aqueous formulation for food, cosmetic and medical industry. At last, we present a Pickering emulsion strategy that utilizes biocompatible, edible and body temperature-responsive lard oil as the core material in microcapsules, which can achieve hermetic sealing and physiological temperature-triggered release of model nutraceutical ingredient (ß-carotene).

Water-in-water emulsions stabilized by self-assembled chitosan colloidal particles.

Dextran (Dex) and poly(ethylene glycol) (PEG)-based aqueous emulsions were stabilized using the self-assembled chitosan colloidal particles (CS CPs). Besides, the effects of pH, CS CPs concentration, polymer concentration, volume ratio of PEG solution to Dex solution, temperature, homogenizing speed and homogenizing time on the property of the W/W emulsions were investigated, respectively. In order to enhance the stability of the PEG-Dex emulsion, sodium tripolyphosphate was used to cross-link the CS CPs at the interface of emulsion droplets, which resulted in the stability duration for >1 year. Finally, the CS CPs were used as a support to immobilize urease and bovine serum albumin and a stabilizer to prepare W/W emulsion, which were then adopted as a catalysis system and as a spinning solution to fabricate drug-loaded nanofiber. This strategy potentially provides a new opportunity to encapsulate the active molecules at the water-water interface, and enrich the types of usable active molecules in the encapsulation in the W/W emulsions.

One-pot low temperature synthesis of monodisperse silver nanoparticles.

A facile one-pot route for the synthesis of monodisperse Ag nanocrystals with a narrow size distribution is described. Uniform Ag nanoparticles with the size of around 12 nm were obtained by reduction of AgNO3 in the presence of oleylamine and polymer polyvinylpyrrolidone (PVP) at low temperature. It is found that temperature has a significant effect on the sizes and the size distributions of the nanoparticles. Because irregular Ag nanoparticles are produced easily due to Ostwald ripening or kinetic control at both high temperature and low temperature, respectively, uniform nanocrystals can be obtained at an appropriate temperature (70 degrees C).

A molecularly imprinted biosensor based on water-compatible and electroactive polymeric nanoparticles for lysozyme detection.

A molecularly imprinted biosensor for lysozyme based on the polymer nanoparticles self-assembled from water-soluble and electroactive poly (γ-glutamic acid) modified with 3-aminothiophene copolymer were prepared. The water-soluble copolymer made imprinting of lysozyme in aqueous solution possible and thus facilitated improvement of the activity of LYS. Subsequent electro-polymerization not only locked the recognition site between copolymer and lysozyme but also created a conductive polymer network, which can enhance the electron transfer rate and increase the conductivity of the film. The prepared molecularly imprinted biosensor exhibited a wide linear range from 1 × 10-10 to 1 × 10-5 mg mL-1, and satisfactory selectivity, stability, repeatability for lysozyme detection.

O-N-S Self-Doped Hierarchical Porous Carbon Synthesized from Lotus Leaves with High Performance for Dye Adsorption.

Three-dimensional porous carbon was fabricated using lotus leaves as a renewable precursor. The as-synthesized carbon had a high surface area (3601 m2/g), suitable O-N-S self-doping, and three-dimensional (3D) architecture with interconnected micro/meso/macropores, together with proper pore size distribution. Consequently, these admirable features endowed porous carbon as a superadsorbent for dye removal with ultrahigh adsorption capacity for rhodamine B (9444.39 mg/g) and reliable cyclability (>97% capacitance retention after 10 cycles). The adsorption of dye onto the as-prepared carbon was a spontaneous endothermic process and followed the pseudo-second-order kinetic model and the Langmuir isotherm model. The π-π stacking, hydrogen bond, and acid-base interactions were proposed to mainly account for the combination of the adsorbate and the adsorbent. Overall, these values indicated the high-performance biomass-derived carbon as a dye adsorbent and may boost the large-scale production and application of 3D hierarchical porous carbon with heteroatom doping in the field of wastewater treatment.

Formation of bowl-shaped nanoparticles by self-assembly of cinnamic acid-modified dextran.

The self-assembly of amphiphilic copolymers has attracted much attention because of their various morphologies and potential applications. Bowl-shaped nanoparticles could apply in many aspects due to their interior cavity, specific concave structure and high surface area. In this study, dextran (Dex) was hydrophobic modified by cinnamic acid (CINN) via esterification reaction between the hydroxyl group of Dex and the carboxyl group of CINN. The modification degree of CINN could be achieved by changing the feed ratios between Dex, CINN and the coupling agent. The cinnamic acid-modified dextran (Dex-CINN) composed of Dex as hydrophilic segment and CINN as hydrophobic segment could self-assemble into bowl-shaped nanoparticles with a single dimple on the surface. Furthermore, the size of the dimples could be controlled by changing the modification degree of CINN, concentration of Dex-CINN and the rate of water addition. The morphologies of bowl-shaped nanoparticles were characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM).