Nitrogen-Enriched Carbon Nanofiber Aerogels Derived from Marine Chitin for Energy Storage and Environmental Remediation

Nitrogen-enriched (N-enriched) carbon nanofiber aerogels (NCNAs) with an ultrafine nanofiber network structure were designed and prepared by using chitin nanofiber aerogels as the precursor. Because of the uniform nanofibrous architecture and nitrogen-rich composition of chitin nanofiber aerogels, the NCNAs exhibited large specific surface area (490–1597 m² g^–1) and a high nitrogen content (2.07–7.65%). As a consequence, supercapacitor electrodes prepared from NCNA-900 showed specific capacitances as high as 221 F g^–1 at the current density of 1.0 A g^–1 and good capacitance retention of 92% over 8000 cycles in a 6.0 mol L^–1 KOH electrolyte without further activation. Moreover, the NCNA-900 could also be applied as an effective adsorbent for dye adsorption, such as Congo red (496 mg g^–1) and Rhodanine B (489 mg g^–1). In view of an excellent electrochemical performance and high adsorption capacities for dyes as well as cost-effective and eco-friendly approaches, NCNAs derived from marine chitin show great potential for application in energy storage and environmental remediation

Three-Dimensional Nanoporous Cellulose Gels as a Flexible Reinforcement Matrix for Polymer Nanocomposites

With the world’s focus on utilization of sustainable natural resources, the conversion of wood and plant fibers into cellulose nanowhiskers/nanofibers is essential for application of cellulose in polymer nanocomposites. Here, we present a novel fabrication method of polymer nanocomposites by in-situ polymerization of monomers in three-dimensionally nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solution. The NCG have interconnected nanofibrillar cellulose network structure, resulting in high mechanical strength and size stability. Polymerization of the monomer gave P­(MMA/BMA)/NCG, P­(MMA/BA)/NCG nanocomposites with a volume fraction of NCG ranging from 15% to 78%. SEM, TEM, and XRD analyses show that the NCG are finely distributed and preserved well in the nanocomposites after polymerization. DMA analysis demonstrates a significant improvement in tensile storage modulus <i>E</i>′ above the glass transition temperature; for instance, at 95 °C, <i>E</i>′ is increased by over 4 orders of magnitude from 0.03 MPa of the P­(MMA/BMA) up to 350 MPa of nanocomposites containing 15% v/v NCG. This reinforcement effect can be explained by the percolation model. The nanocomposites also show remarkable improvement in solvent resistance (swelling ratio of 1.3–2.2 in chloroform, acetone, and toluene), thermal stability (do not melt or decompose up to 300 °C), and low coefficients of thermal expansion (in-plane CTE of 15 ppm·K^–1). These nanocomposites will have great promising applications in flexible display, packing, biomedical implants, and many others

Tough and Cell-Compatible Chitosan Physical Hydrogels for Mouse Bone Mesenchymal Stem Cells in Vitro

Most hydrogels involve synthetic polymers and organic cross-linkers that cannot simultaneously fulfill the mechanical and cell-compatibility requirements of biomedical applications. We prepared a new type of chitosan physical hydrogel with various degrees of deacetylation (<i>DD</i>s) via the heterogeneous deacetylation of nanoporous chitin hydrogels under mild conditions. The <i>DD</i> of the chitosan physical hydrogels ranged from 56 to 99%, and the hydrogels were transparent and mechanically strong because of the extra intra- and intermolecular hydrogen bonding interactions between the amino and hydroxyl groups on the nearby chitosan nanofibrils. The tensile strength and Young’s modulus of the chitosan physical hydrogels were 3.6 and 7.9 MPa, respectively, for a <i>DD</i> of 56% and increased to 12.1 and 92.0 MPa for a <i>DD</i> of 99% in a swelling equilibrium state. In vitro studies demonstrated that mouse bone mesenchymal stem cells (mBMSCs) cultured on chitosan physical hydrogels had better adhesion and proliferation than those cultured on chitin hydrogels. In particular, the chitosan physical hydrogels promoted the differentiation of the mBMSCs into epidermal cells in vitro. These materials are promising candidates for applications such as stem cell research, cell therapy, and tissue engineering