In this work, chitin microspheres (NCM) having a nanofibrous architecture were constructed using a "bottom-up" fabrication pathway. The chitin chains rapidly self-assembled into nanofibers in NaOH/urea aqueous solution by a thermally induced method and subsequently formed weaved microspheres. The diameter of the chitin nanofibers and the size of the NCM were tunable by controlling the temperature and the processing parameters to be in the range from 26 to 55 nm and 3 to 130 μm, respectively. As a result of the nanofibrous surface and the inherent biocompatibility of chitin, cells could adhere to the chitin microspheres and showed a high attachment efficiency, indicating the great potential of the NCM for 3D cell microcarriers.

Novel nanocomposite hydrogels composed of polyelectrolytes alginate and chitin whiskers with biocompatibility were successfully fabricated based on the pH-induced charge shifting behavior of chitin whiskers. The chitin whiskers with mean length and width of 300 and 20 nm were uniformly dispersed in negatively charged sodium alginate aqueous solution, leading to the formation of the homogeneous nanocomposite hydrogels. The experimental results indicated that their mechanical properties were significantly improved compared to alginate hydrogel and the swelling trends were inhibited as a result of the strong electrostatic interactions between the chitin whiskers and alginate. The nanocomposite hydrogels exhibited certain crystallinity and hierarchical structure with nanoscale chitin whiskers, similar to the structure of the native extracellular matrix. Moreover, the nanocomposite hydrogels were successfully applied as bone scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs and scanning electronic microscope (SEM) images revealed that the addition of chitin whiskers into the nanocomposite hydrogels markedly promoted the cell adhesion and proliferation of the osteoblast cells. The biocompatible nanocomposite hydrogels have potential application in bone tissue engineering.

Nitrogen-doped ZnO bundle-like nanoparticles were prepared by heating ZnOHF precursor at different temperatures under an ammonia atmosphere. ZnOHF gradually transformed to N-ZnO with the increase of the heating temperature, and the as-prepared N-ZnO nanoparticles preserved the original morphologies of ZnOHF at moderate heating temperature. The N-ZnO nanoparticles demonstrated drastically enhanced absorption in the visible region compared with the commercial ZnO and N-ZnO derived from commercial ZnO. Theoretical calculations indicated that the contribution of nitrogen to the top of the valence band (VB) of ZnO plays the major role of extending the absorption of ZnO to the visible region. The as-prepared N-ZnO showed high photocatalytic activity for the visible-light-induced water oxidation, and the activity can be further greatly enhanced by loading IrO2 cocatalyst. To our knowledge, this is the first report of realizing photocatalytic water oxidation on non-metal-doped ZnO under visible light without applied bias, thus adding new value to the band gap engineering of benchmark ZnO for efficient solar energy utilization.

A new type of graphitic C3N4-based composite photocatalysts was designed and prepared by co-loading PEDOT as a hole transport pathway and Pt as an electron trap on C3N4. The as-prepared C3N4-PEDOT-Pt composites showed drastically enhanced activity for visible light-driven photocatalytic H2 production compared to those of C3N4-PEDOT and C3N4-Pt, possibly due to the spatial separation of the reduction and oxidation reaction sites.

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