•A facile preparation method for NCGA by using CNFs and GO as assembling primitives.•The NCGA electrodes were fabricated without any binder and conductive additive.•The NCGA electrodes show high specific capacitances and prominent cycling stability.Carbon materials derived from various biomasses have aroused forceful interest from scientific community based on their abundant resource, low cost, environment friendly and easy fabrication. Herein, the method has been developed to prepare nitrogen-doped biomass-derived carbon nanofibers/graphene aerogel (NCGA) as the binder-free electrode for supercapacitors. Ethylenediamine (EDA) is select as nitrogen source for its high nitrogen content and strong interaction with graphene oxide (GO) and cellulose nanofibers (CNFs) via hydrothermal self-assembly method to form hybrid hydrogel, and finally converts to NCGA by freeze-drying and carbonization. After carbonization the insulated CNFs converted to high conductivity carbon nanofibers. The NCGA electrode exhibits a high specific capacitance of 289 F g−1 at 5 mV s−1 and high stability of 90.5% capacitance retention ratio after 5000 cycles at 3 A g−1. This novel biomass electrode could be potential candidate for high performance supercapacitors.Download high-res image (204KB)Download full-size image

This paper reported an immobilization of Candida rugosa lipase (CRL) onto PAMAM-dendrimer-grafted magnetic nanoparticles synthesized by a modified solvothermal reduction method. The dendritic magnetic nanoparticles were amply characterized by several instrumental measurements, and the CRL was covalently anchored on the three generation supports with glutaraldehyde as coupling reagent. The amount of immobilized enzyme was up to 150 mg/g support and the factors related with the enzyme activity were investigated. The immobilization of lipase improved their performance in wider ranges of pH and temperature. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with free enzyme and can be reused 10 cycles with the enzymatic activity remained above 90 %. The properties of lipase improved obviously after being immobilized on the dendritic supports. The inactive immobilized lipase could be regenerated with glutaraldehyde and Cu2+, respectively. This synthetic strategy was facile and eco-friendly for applications in lipase immobilization.

This work reports a facile and easily-achieved approach for enzyme immobilization by embedding glucose oxidase (GOx) in magnetic zeolitic imidazolate framework 8 (mZIF-8) via a de novo approach. As a demonstration of the power of such materials, the resulting GOx embedded mZIF-8 (mZIF-8@GOx) was utilized as a colorimetric sensor for rapid detection of glucose. This method was constructed on the basis of metal–organic frameworks (MOFs), which possessed very fascinating peroxidase-like properties, and the cascade reaction for the visual detection of glucose was combined into one step through the mZIF-8@GOx based mimic multi-enzyme system. After characterization by electron microscopy, X-ray diffraction, nitrogen sorption, fourier transform infrared spectroscopy and vibrating sample magnetometry, the as-prepared mZIF-8@GOx was confirmed with the robust core–shell structure, the monodisperse nanoparticle had an average diameter of about 200 nm and displayed superparamagnetism with a saturation magnetization value of 40.5 emu g−1, it also exhibited a large surface area of 396.10 m2 g−1. As a peroxidase mimic, mZIF-8 was verified to be highly stable and of low cost, and showed a strong affinity towards H2O2. Meanwhile, the mZIF-8 embedded GOx also exhibited improved activity, stability and greatly enhanced selectivity in glucose detection. Moreover, the mZIF-8@GOx had excellent recyclability with high activity (88.7% residual activity after 12 times reuse).

A mild and facile method for the construction of robust organic–inorganic hybrid magnetic microcapsules was developed by a hard-template mediated method combined with polydopamine (PDA) and Fe3O4 nanoparticles onto a CaCO3 microparticle template. More specifically, negatively charged Fe3O4 nanoparticles were adsorbed on the surface or into the lumen of porous CaCO3 microparticles through electrostatic interaction and physical absorption. Then, the magnetic sacrificial templates were coated with PDA through the self-polymerization of dopamine to obtain the magnetic PDA–CaCO3 microparticles, which was followed by template removal using EDTA to construct organic–inorganic hybrid magnetic microcapsules. Characterization confirmed that the microcapsules possess a robust hollow structure such that the enzyme inside exists in a free state. The Fe3O4 nanoparticles acted as critical factors in the microcapsules for both recyclable component and tough scaffolds to sustain the microcapsules away from collapsing and folding. Combing the merits of the organic layer and the inorganic component, the microcapsules were applied for the encapsulation of Candida Rugosa Lipase (CRL). The encapsulated CRL was demonstrated to have several advantages, including increased encapsulation efficiency, enzyme activity and long-term storage stability. Hopefully, the as-prepared microbioreactor may provide a facile and generic approach for other biochemical applications.

Superparamagnetic Fe3O4 nanoparticles with diameter about 18 nm were prepared by a solvothermal method. A simple and green method was used to prepare amino-rich magnetic nanoparticles. The magnetic nanoparticles were modified by polyethylenimine (PEI) which is a polycationic polymer when pH < 10. The resulted magnetic nanoparticles were activated by glutaraldehyde to obtain nanoscale support for Candida rugosa Lipase (CRL) immobilization. The CRL was immobilized on the magnetic nanoparticles covalently, as well as via ionic exchange. The structure and magnetic behavior of the magnetic nanoparticles were confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). Then the properties of the immobilized CRL were investigated, and the results showed that the obtained immobilized lipase displayed good reusability and applicability. The immobilized Candida rugosa Lipase (ICRL) presented wider pH tolerance (residual activity > 80% in a pH range from 5.5 to 8.0) than free Candida rugosa Lipase (residual activity decreased rapidly when the pH values were away from 7.0). ICRL showed excellent thermal stability (the relative of ICRL > 90%) after keeping in the water bath at 50 °C for 150 min while free Candida rugosa Lipase (FCRL) was absolutely deactivated. After being reused 10 times, ICRL maintained 60% relative activity.

By the facile adhesion way, the novel composite complex by polydopamine (PDA) and magnetic graphite nanosheets (Fe3O4@GNSs) has been successfully synthesized. The resulting composite was characterized by means of scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, and Raman spectra, X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Meanwhile, the PDA functionalized Fe3O4@GNSs (Fe3O4@GNSs-PDA) was applied for Candida rugosa lipase (CRL) immobilization covalently without any toxic coupling agent. Combining the superior physical properties and chemical stability of Fe3O4@GNSs and the well biocompatibility, functional characteristics of PDA, the Fe3O4@GNSs-PDA composite displayed several advantages, including the high enzyme capacity, enzyme activity and stability and a decrease in enzyme loss. Our work demonstrated that the mussel-inspired Fe3O4@GNSs can be extended to many other applications such as biocatalytic, genetic and industrial.

•Core–shell magnetic polydopamine/alginate biocomposite was synthesized.•The superparamagnetic mPDA/ADA possesses a well-defined structure.•The mPDA/ADA was used for enzyme immobilization without any toxic coupling reagent.•The mPDA/ADA possesses good biocompatibility for enzyme immobilization.•The ICRL shows excellent environmental stability and catalytic activities.A flexible, biocompatible and bioadhesive enzyme immobilizing material, which was synthesized based on the covalent assembly of biomimetic polymer and oxidized polysaccharide on magnetic nanoparticles (NPs), has been developed in this feasibility study. In this work, the bio-inspired polymer, polydopamine (PDA), was used to modify the well-monodispersed Fe3O4 NPs (mPDA NPs) with a controllable thickness via a dip-coating process, then the alginate di-aldehyde (ADA) was covalently assembled on the mPDA NPs and employed as a naturally occurring linking agent for Candida rugosa lipase (CRL) immobilization. The resulting support material was characterized by means of the transmission electron microscope (TEM), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetry (TG) analyser, and vibrating sample magnetometer (VSM). It was verified that the prepared mPDA NPs possessed distinct core–shell structure with uniform size and high saturation magnetization. For further application, the mPDA NPs was utilized in CRL immobilizing procedures and demonstrated can facilitate improving the enzyme activities. The optimum amount of lipase was 200 mg g−1 support, the optimal pH and temperature for the catalyse condition of the immobilized CRL was 7.0 and 40 °C, respectively. Moreover, the immobilized CRL kept the high activity at 77% after 12 times of recycling for batch hydrolysis of olive oil emulsion. This magnetic bioadhesive composite with functionalized properties and adhesion strength presents a general strategy for the immobilization of macromolecules.

In the present study, Au-loaded magnetic metal organic frameworks (MOFs)/graphene multifunctional composite were prepared. The well-dispersed nanoparticles were stabilized with 2D reduced graphene oxide and MOFs, which acts as effective substitutes for more conventional polymer ligands that are used to stabilize nanoparticles in a sol-immobilization procedure. The result shows the multifunctional composite could overcome the drawbacks of MOFs catalysts (chemical instability). This study indicated that the as-prepared Au-loaded magnetic MOFs/graphene multifunctional composite has great potential for using in a wide range of applications.In the present study, Au-loaded magnetic metal organic frameworks (MOFs)/graphene multifunctional composite were prepared. The well dispersed nanoparticles were stabilized with 2D graphene oxide and MOFs, which act as effective substitutes for more conventional polymer ligands that are used to stabilize nanoparticles in a sol-immobilization procedure.Download high-res image (152KB)Download full-size image

A mild and facile method for the construction of robust organic–inorganic hybrid magnetic microcapsules was developed by a hard-template mediated method combined with polydopamine (PDA) and Fe3O4 nanoparticles onto a CaCO3 microparticle template. More specifically, negatively charged Fe3O4 nanoparticles were adsorbed on the surface or into the lumen of porous CaCO3 microparticles through electrostatic interaction and physical absorption. Then, the magnetic sacrificial templates were coated with PDA through the self-polymerization of dopamine to obtain the magnetic PDA–CaCO3 microparticles, which was followed by template removal using EDTA to construct organic–inorganic hybrid magnetic microcapsules. Characterization confirmed that the microcapsules possess a robust hollow structure such that the enzyme inside exists in a free state. The Fe3O4 nanoparticles acted as critical factors in the microcapsules for both recyclable component and tough scaffolds to sustain the microcapsules away from collapsing and folding. Combing the merits of the organic layer and the inorganic component, the microcapsules were applied for the encapsulation of Candida Rugosa Lipase (CRL). The encapsulated CRL was demonstrated to have several advantages, including increased encapsulation efficiency, enzyme activity and long-term storage stability. Hopefully, the as-prepared microbioreactor may provide a facile and generic approach for other biochemical applications.