Xilan Ma

Hierarchical Porous Nitrogen-Doped Carbon Nanosheets Derived from Silk for Ultrahigh-Capacity Battery Anodes and Supercapacitors

Hierarchical porous nitrogen-doped carbon (HPNC) nanosheets (NS) have been prepared via simultaneous activation and graphitization of biomass-derived natural silk. The as-obtained HPNC-NS show favorable features for electrochemical energy storage such as high specific surface area (SBET: 2494 m(2)/g), high volume of hierarchical pores (2.28 cm(3)/g), nanosheet structures, rich N-doping (4.7%), and defects. With respect to the multiple synergistic effects of these features, a lithium-ion battery anode and a two-electrode-based supercapacitor have been prepared. A reversible lithium storage capacity of 1865 mA h/g has been reported, which is the highest for N-doped carbon anode materials to the best of our knowledge. The HPNC-NS supercapacitors electrode in ionic liquid electrolytes exhibit a capacitance of 242 F/g and energy density of 102 W h/kg (48 W h/L), with high cycling life stability (9% loss after 10,000 cycles). Thus, a high-performance Li-ion battery and supercapacitors were successfully assembled for the same electrode material, which was obtained through a one-step and facile large-scale synthesis route. It is promising for next-generation hybrid energy storage and renewable delivery devices.

From Rice Bran to High Energy Density Supercapacitors: A New Route to Control Porous Structure of 3D Carbon

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m2 g−1 with optimized pore volume of 1.21 cm3 g−1 (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g−1 and 100 A g−1 i.e., 265 F g−1 and 182 F g−1 in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg−1 (550 W L−1) and energy density 70 W h kg−1 (32 W h L−1) are achieved on the base of active material loading (~10 mg cm2) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices.

A novel three-dimensional tubular scaffold prepared from silk fibroin by electrospinning

Effects of electrospinning parameters (including voltage, collection distance, solution concentration and flow rate) on the morphology and diameter distribution of regenerated SF (silk fibroin) fiber were investigated. Afterward, SF tubular scaffold composed of homogenous fibers was fabricated at voltage of 18kV, collection distance of 18cm, concentration of 37%, and flow rate of 0.15mL/min. After methanol treatment, SF tubular scaffold showed tensile strength of 3.57MPa and porosity of 80.85%. It is satisfied that our work offers a simple method to fabricate seamless and porous tubular scaffold from SF without any additives and organic solvents. Furthermore, the results suggest that this tubular scaffold shows promising applications in small-diameter vascular graft.

Electrospinning of silk fibroin and collagen for vascular tissue engineering.

Tubular scaffolds of silk fibroin (SF)/collagen (Col) were prepared by electrospinning with the aim to develop a new scaffold for vascular tissue engineering. The effects of the solvent, solution concentration and collagen content on the morphology of the scaffolds were investigated by SEM. FTIR and XRD were used to investigate their structural changes. Although there were morphological and structural differences, the water uptake and the tensile strength of the scaffolds with different collagen content showed no significant difference. This study confirmed the feasibility of the fabrication of SF/Col tubular scaffold by electrospinning from aqueous solution and provided promising tubular scaffold for vascular tissue engineering.

Optimization of macroporous 3-D silk fibroin scaffolds by salt-leaching procedure in organic solvent-free conditions

A novel all-aqueous process is described to form three-dimensional porous silk fibroin (SF) scaffolds, which not only avoided the use of organic solvents or harsh chemicals, but also can form scaffolds with various sizes and in large quantities. The scaffolds show a rough surface on the pores and the pores are highly interconnected. The porosity of the scaffolds, which varied between a large range (67.6~99.3%), can be controlled by the SF concentrations and the salt/fibroin ratio. The results of measurements indicated that this novel process can improve and enforce the transformation in SF structure from a random coil to a β-sheet. Swelling studies showed that the scaffold has excellent properties of hydrophilicity. The cell culture experiments demonstrated that the scaffolds facilitated the human osteosarcoma cells attachment and proliferation in vitro.

Hierarchical LiMn2O4 Hollow Cubes with Exposed {111} Planes as High-Power Cathodes for Lithium-Ion Batteries

Hierarchical LiMn2O4 hollow cubes with exposed {111} planes have been synthesized using cube-shaped MnCO3 precursors, which are fabricated through a facile co-precipitation reaction. Without surface modification, the as-prepared LiMn2O4 exhibits excellent cyclability and superior rate capability. Surprisingly, even over 70% of primal discharge capacity can be maintained for up to 1000 cycles at 50 C, and with only about 72 s of discharge time the as-prepared materials can deliver initial discharge capacity of 96.5 mA h g(-1). What is more, the materials have 98.4% and 90.7% capacity retentions for up to 100 cycles at 5 C under the temperatures of 25 and 60 °C, respectively. The superior electrochemical performance can be attributed to the unique hierarchical and interior hollow structure, exposed {111} planes, and high-quality crystallinity.

Study on the preparation of collagen-modified silk fibroin films and their properties.

Blended films were prepared from a silk fibroin (SF) solution by adding a small amount of type I collagen (<5%). The mechanical properties of the wet films modified by collagen were improved obviously. The elongation at break reached 42%, and the smaller contact angles revealed that modified films had better hydrophilicity. 1% heparin was also added to modify the SF films to further improve the in vitro antithrombogenecity. The internal structure of the modified SF films was investigated with scanning electron microscopy, x-ray diffraction and Fourier transform infrared attenuated total reflection spectroscopy. The result indicates that the addition of a small amount of collagen and heparin did not change their conformation.

Multifunctional iron oxide/silk-fibroin (Fe3O4–SF) composite microspheres for the delivery of cancer therapeutics

In this article, we report novel multifunctional iron oxide/silk-fibroin (Fe3O4–SF) microspheres synthesized by simple salting out process. These microspheres are used as the carriers of doxorubicin hydrochloride (a traditional anti-cancer drug), denoted as DOX–Fe3O4–SF. The results show that the drug loading capacity (LC) is 3.3% and the drug encapsulation efficiency (EE) could reach up to 76%. The DOX-loaded microspheres exhibit sustained and pH-sensitive release patterns. The total DOX release is measured to be about 60% at pH 5.5. More interestingly, RhB-labelled Fe3O4–SF microspheres exhibit a striking endocytosis, selectively accumulating in the cytoplasm compared to the free RhB. The endocytosis of DOX–Fe3O4–SF microspheres results in only ∼10% survival ratio of HeLa cells after 48 h. Furthermore, because of the remarkable biocompatibility of SF, Fe3O4–SF microspheres show no cytotoxicity toward HeLa cells compared to DOX–Fe3O4–SF. The results clearly indicate that Fe3O4–SF microspheres hold significant potential for drug loading and delivery into cancer cells to induce cell death.

Novel Prosthesis Using Silk Fibroin for Small Caliber Vascular

A novel prosthesis using silk fibroin with blending heparin and sulfonated silk fibroin was studied. Anticoagulation activities of heparin/silk fibroin and sulfonated silk fibroin/silk fibroin vascular and mechanical property results showed that heparin/silk fibroin and sulfonated silk fibroin/silk fibroin vascular could meet the requirement of small caliber grafts. This study indicated that silk fibroin could be used for developing tissue engineering biological vascular grafts that could use for human coronary or low extremity artery bypasses.

Preparation of Ni-cysteine Hollow Spheres with Ferromagnetic Property and Good Biocompatibility

In this work, magnetic Ni-cysteine hollow spheres were firstly fabricated by a facile room temperature self-assembly method. The most outstanding advantage of these hollow spheres is that the biocompatibility of amino acid and the magnetic property of metal nickel ions are successfully combined. Their coercivity in the magnetic measurement is 90 Oe at 80 K. This ferromagnetic performance and the satisfying blood compatibility in the anticoagulation test make them show promising applications in biological technique, especially the targeted drug delivery.