Guanglin Sun

Incorporation of homogeneous Co3O4 into a nitrogen-doped carbon aerogel via a facile in situ synthesis method: implications for high performance asymmetric supercapacitors

A novel high-performance electrode material, nitrogen-doped carbon aerogel/cobalt oxide (NCA/Co3O4) material, was prepared by a facile, one step and in situ coating method, followed by a freeze-drying process. The effects of different amounts of Co3O4 on the structural properties, specific surface areas, elemental compositions and electrochemical performance of the composite electrodes were investigated. Consequently, the electrode with 75% mass content of Co3O4 exhibited excellent electrochemical performance, in particular, a high specific capacitance of 616 F g−1 at a current density of 1 A g−1, excellent rate capability (445 F g−1 at 20 A g−1) and outstanding cycle performance. In addition, the asymmetric supercapacitor assembled with NCA/Co3O4-3 and NCA electrodes could be cycled in a high voltage range of 1.5 V and deliver a maximum energy density of 33.43 W h kg−1 at a power density of 375 W kg−1. The enhanced electrochemical performance is attributed to the complementary contributions of the 3D interconnected porous structure and the efficient pseudocapacitance of the uniformly dispersed Co3O4 nanoparticles. The preparation method offers a new fabrication strategy to in situ fabricate carbon-supported metal oxide electrodes for high-performance energy storage applications.

Rational design of uniformly embedded metal oxide nanoparticles into nitrogen-doped carbon aerogel for high-performance asymmetric supercapacitors with a high operating voltage window

We report the design of a high-performance asymmetric supercapacitor (ASC) based on manganese monoxide/carbon aerogel (MnO/NCA) composites as the positive electrode and iron oxide/carbon aerogel (Fe2O3/NCA) composites as the negative electrode. The prepared MnO/NCA hybrid composites display a highly interconnected network structure with ultrathin MnO nanoparticles uniformly embedded into the 3D nitrogen-doped carbon matrix. Because of the synergistic effects of the highly conductive carbon aerogel and highly pseudocapacitive metal oxides, the hybrid MnO/NCA electrode exhibits highly effective surface area, greatly enhanced ion transportation, and excellent electrochemical performance, in comparison with other MnOx-based electrode materials. Matching it with the Fe2O3/NCA cathode, the novel ASC devices can achieve a high voltage window of 2.0 V, delivering a remarkable energy density of 48.67 W h kg−1 at a power density of 1000 W kg−1 and still retains 27.39 W h kg−1 at a high power density of 10 kW kg−1, consequently giving rise to stable cycling performance. These encouraging results will provide a fresh route for the design and fabrication of metal oxide@carbon aerogel materials for application in next-generation storage systems.

Constructing multi-component organic/inorganic composite bacterial cellulose-gelatin/hydroxyapatite double-network scaffold platform for stem cell-mediated bone tissue engineering

Bacterial cellulose/hydroxyapatite (BC/HAp) composite had good bioaffinity but its poor mechanical strength limited its widespread applications in bone tissue engineering (BTE). Bacterial cellulose/gelatin (BC/GEL) double-network (DN) composite had excellent mechanical properties but was seldom used in biomedical fields. In this regard, a multi-component organic/inorganic composite BC-GEL/HAp DN composite was synthesized, which combined the advantages of BC/HAp and BC/GEL. Compared with BC/GEL, the BC-GEL/HAp exhibited rougher surface topography and higher thermal stability. Compression and tensile testing indicated that the mechanical strength of the BC-GEL/HAp was greatly reinforced compared with BC/HAp and was even higher than that of BC/GEL. In vitro cell culture demonstrated that the rat bone marrow-derived mesenchymal stem cells (rBMSCs) cultured on the BC-GEL/HAp showed better adhesion and higher proliferation and differentiation potential than the cells cultured on BC/GEL. We hope the BC-GEL/HAp composite could be used as ideal bone scaffold platform or biomedical membrane in the future.

A novel chitosan-tussah silk fibroin/nano-hydroxyapatite composite bone scaffold platform with tunable mechanical strength in a wide range

Currently, great efforts have been made to enhance the mechanical strength of bone tissue engineering (BTE) scaffolds, which are composed of biopolymeric matrices and inorganic nano-fillers. But the tunability of mechanical strength in a wide range for BTE scaffolds has seldom been investigated in spite of the great importance of this performance. In this work, a chitosan-tussah silk fibroin/hydroxyapatite (CS-TSF/HAp) hydrogel was synthesized by using a novel in situ precipitation method. Through in situ inducing the conformation transition of TSF in the CS-TSF/HAp hydrogel, which could be monitored by XRD, FT-IR, TGA, and DTA, the elastic modulus and fracture strength of the final CS-TSF/HAp composite could be tailored in a wide range without changing its composition, morphology, roughness, and crystal structures. The elastic modulus of the CS-TSF/HAp composite ranged from ∼250 to ∼400MPa while its fracture strength ranged from ∼45 to ∼100MPa. In order to clarify the rationale behind this process, a speculative explanation was provided. In vitro cell culture indicated that MC3T3-E1 cells cultured on the CS-TSF/HAp composite had positive adhesion, proliferation, and differentiation potential. We believed that the CS-TSF/HAp composite could be used as an ideal scaffold platform for cell culture and implantation of bone reconstruction.

Comparisons among Mg, Zn, Sr, and Si doped nano-hydroxyapatite/chitosan composites for load-bearing bone tissue engineering applications

In load-bearing bone tissue engineering (BTE), ionic doping is a promising strategy to make up for the inherent defects of hydroxyapatite (HAp). However, the influence of doped elements on the structures and properties of in vitro mineralized HAp has not been investigated in detail so far. In addition, no systematic investigations have been found comparing the properties of different kinds of element doped HAp-based organic/inorganic composites. In this work, the hydroxyapatite/chitosan composite (CS/HAp) and Mg, Zn, Sr, and Si doped hydroxyapatite/chitosan composites (Mg-CS/HAp, Zn-CS/HAp, Sr-CS/HAp, and Si-CS/HAp) were synthesized by using a facile in situ precipitation method. The impacts of different kinds of doped elements on the crystallinity, crystal morphology, and crystal structure of the mineralized HAp were carefully studied. In addition, we also investigated and compared the surface morphology, surface roughness, thermal stability, mechanical strength, and in vitro cytocompatibility of the five samples in detail. We anticipate that our work could shed new light on the influence of ionic doping on the mineralization of HAp and inspire researchers to prepare an HAp-based organic/inorganic composite load-bearing bone substitute in the future.

Comparisons between gelatin-tussah silk fibroin/hydroxyapatite and gelatin-Bombyx mori silk fibroin/hydroxyapatite nano-composites for bone tissue engineering

In this research, gelatin-tussah silk fibroin/hydroxyapatite (GEL-TSF/HAp), gelatin-Bombyx mori silk fibroin/hydroxyapatite (GEL-BMSF/HAp), and gelatin/hydroxyapatite (GEL/HAp) nano-composites were synthesized by a novel in situ precipitation method. Characterizations, including surface morphology, elemental composition and distribution, structure of the crystalline phase, mechanical strength, thermal stability, and in vitro cytocompatibility, were carried out. Investigations on the crystalline phase showed that rod-like HAp crystallites in the GEL-TSF/HAp composite had a higher aspect ratio than those in the GEL-BMSF/HAp composite and the GEL/HAp composite. In addition, the GEL-TSF/HAp composite also presented better thermal stability than the other two composites revealed by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Mechanical properties testing indicated that the GEL-TSF/HAp composite had a higher elastic modulus at low strain and higher compressive modulus at high strain simultaneously than the other two composites. An in vitro cell culture showed that MG63 osteoblast-like cells on the GEL-TSF/HAp membrane took on higher proliferative potential than those on the GEL-BMSF/HAp membrane. These results indicated that compared to the GEL-BMSF/HAp composite, the GEL-TSF/HAp composite was more suitable for bone tissue engineering (BTE) applications.

One-Pot Template-Free Strategy toward 3D Hierarchical Porous Nitrogen-Doped Carbon Framework in Situ Armored Homogeneous NiO Nanoparticles for High-Performance Asymmetric Supercapacitors

The composites based on graphitic carbon and transitional metal oxides are regarded as one of the most promising electrochemical materials owing to the synergistic combination of the advantages of both superior electrical conductivity and high pseudocapacitance. In this work, a simple one-pot template-free strategy for the preparation of three-dimensional hierarchical porous nitrogen-doped carbon framework in situ armored NiO nanograins (NCF/NiO) by an ammonia-induced method assisted by the pyrolysis of a decomposable salt is reported. Due to such unique architecture and homogeneously dispersed nanoparticles, the as-prepared NCF/NiO-2 hybrid exhibits a large specific surface area (412.3 m2 g-1), a high specific capacitance (1074 F g-1 at 1 A g-1), good rate capability (820 F g-1 at 20 A g-1), and outstanding cycling performance (almost no decay after 5000 cycles). Moreover, the solid-state asymmetric supercapacitor, assembled with NCF/NiO-2 and NCS electrodes, can achieve a high cell potential of 1.6 V and deliver a superior specific capacitance of 113 F g-1 at 1 A g-1 with a maximum energy density of 40.18 W h kg-1 at a power density of 800 W kg-1, consequently, giving rise to stable cycling performance (94.3% retention over 5000 cycles). The prepared devices are shown to power 20 green light-emitting diodes efficiently. These encouraging results open up a wide horizon for developing novel carbon-supported metal oxide electrode materials for high rate energy conversion and storage devices.

Constructing an Anisotropic Triple-Pass Tubular Framework within a Lyophilized Porous Gelatin Scaffold Using Dexamethasone-Loaded Functionalized Whatman Paper To Reinforce Its Mechanical Strength and Promote Osteogenesis

In bone tissue engineering (BTE), most of the currently developed scaffolds still lack the ability to demonstrate high porosity and high mechanical strength simultaneously or the ability to maintain bioactivity and sustained release of loaded biofactors. In this work, we constructed an anisotropic triple-pass tubular framework within a lyophilized porous GEL scaffold using FP, which was prepared by coating DEX-covered Whatman paper (WP) using the silk fibroin (SF) membrane with β-sheet conformation. This novel structural design endowed the functionalized paper frame (FPF)/scaffold implant high porosity, high mechanical strength, and sustained DEX delivery capability. Specifically, its porosity was as high as 88.2%, approximating that of human cancellous bone. The pore diameters of the implant ranged from 50 to 350 μm with an average pore diameter of 127.7 μm, indicating proper pore sizes for successful diffusion of essential nutrients/oxygen and bone tissue-ingrowth. Owing to the construction of double-network-like structure, the FPF/scaffold implant demonstrated excellent mechanical properties both in dry (174.7 MPa in elastic modulus and 14.9 MPa in compressive modulus) and wet states (59.0 MPa in elastic modulus and 3.3 MPa in compressive modulus), indicating its feasibility for in vivo implantation. Besides, the FPF/scaffold implant exhibited long-term DEX releasing behavior (over 50 days) with constant release rate in phosphate buffered saline (PBS). Murine osteoblasts MC3T3-E1 cultured in the porous FPF/scaffold implant had excellent viability. Furthermore, the cells cocultured with the FPF/scaffold implant showed positive proliferation, osteogenic differentiation, and calcium deposition. Twenty-eight days after implantation, extensive osteogenesis was observed in the rats treated with the FPF/scaffold implants. The anisotropic triple-pass tubular framework of the FPF/scaffold implant demonstrates structural similarities to the long bone. Therefore, this novel FPF/scaffold implant could be a better alternative for long bone defect repair.