Zhiwei Yang

Effect of Si content on structure and electrochemical performance of ternary nanohybrids integrating Si nanoparticles, N-doped carbon shell, and nitrogen-doped graphene

Hybridizing graphene with silicon (Si) is effective in developing high-performance Si-based anodes. However, the effect of Si content on the structure and electrochemical performance of these nanohybrids has not been extensively studied. Herein, a type of ternary Si/NC/NG nanohybrid with varying Si content was synthesized via a scalable, ecofriendly, and facile solution-mixing and carbonization process. In this nanostructure, Si nanoparticles were sheathed with N-doped carbon (NC) and the NC-wrapped Si nanoparticles were confined by nitrogen (N)-doped graphene (NG). The focus of this work was to determine how the Si content in the ternary nanohybrid affects its structure and electrochemical performance. SEM and TEM observations revealed that all Si nanoparticles were embedded in graphene nanosheets at low Si content while some aggregated and bare Si nanoparticles were observed at high Si content. Despite the simple preparation procedure, the ternary nanohybrid with an optimal Si content (83.9 wt%) delivered a high reversible capacity of 1210 mA h g−1 after 100 cycles at 0.5 A g−1, which outperforms most Si-based anodes in lithium-ion batteries (LIBs) reported so far. The findings presented in this paper represent a new criterion for the design of Si-based anodes with optimized electrochemical performance.

Layer-by-Layer Assembled Bacterial Cellulose/Graphene Oxide Hydrogels with Extremely Enhanced Mechanical Properties

Uniform dispersion of two-dimensional (2D) graphene materials in polymer matrices remains challenging. In this work, a novel layer-by-layer assembly strategy was developed to prepare a sophisticated nanostructure with highly dispersed 2D graphene oxide in a three-dimensional matrix consisting of one-dimensional bacterial cellulose (BC) nanofibers. This method is a breakthrough, with respect to the conventional static culture method for BC that involves multiple in situ layer-by-layer assembly steps at the interface between previously grown BC and the culture medium. In the as-prepared BC/GO nanocomposites, the GO nanosheets are mechanically bundled and chemically bonded with BC nanofibers via hydrogen bonding, forming an intriguing nanostructure. The sophisticated nanostructure of the BC/GO leads to greatly enhanced mechanical properties compared to those of bare BC. This strategy is versatile, facile, scalable, and can be promising for the development of high-performance BC-based nanocomposite hydrogels.

Magnetic Lamellar Nano-Hydroxyapatite as a Vector for Gene Transfection in Three-Dimensional Cell Culture

Compared to two-dimensional (2D) conditions, investigation on gene transfection in three-dimensional (3D) conditions is much less extensive. In this work, lamellar nano-hydroxyapatite (L-HAp) with and without magnetism were used as the vectors and gene transfection in 2D and 3D cell culture was carried out and compared. We found that the transfection efficiency in 3D conditions was much higher than 2D cell culture. Additionally, magnetism enhanced transfection efficiency under both 2D and 3D conditions. The findings presented in this study demonstrated that the magnetic L-HAp could be a promising vector in 3D gene transfection.

Engineering photoluminescent and magnetic lamellar hydroxyapatite by facile one-step Se/Gd dual-doping

The design and synthesis of multifunctional hydroxyapatite (HAp) nanoparticles are important in expanding their clinical applications. Herein we report a novel selenium (Se) and gadolinium (Gd) dual-doped lamellar hydroxyapatite (L-HAp-Se-Gd) produced by facile one-step template-assisted synthesis. The results show that the as-prepared L-HAp-Se-Gd nanoparticles exhibit obvious changes in morphology, dimensions, and crystallinity as compared to bare L-HAp. XRD results reveal that high dopant levels of Se and Gd reduce the degree of ordering of HAp lamellae. It is found that the L-HAp-Se-Gd nanoparticles display Gd content-dependent blue fluorescence under ultraviolet (UV) irradiation and magnetic properties. Cell tests with mouse embryo osteoblast cells (MC3T3-E1) reveal their improved biocompatibility over bare L-HAp due to Se incorporation. These results indicate that L-HAp-Se-Gd nanoparticles have potential in numerous applications such as multifunctional gene delivery and bioimaging.

Sacrificial template method for the synthesis of three-dimensional nanofibrous 58S bioglass scaffold and its in vitro bioactivity and cell responses

Three-dimensional nanofibrous scaffolds that morphologically mimic natural extracellular matrices hold great promises in tissue engineering and regenerative medicine due to their increased cell attachment and differentiation compared with block structure. In this work, for the first time, three-dimensional porous nanofibrous 58S bioglass scaffolds have been fabricated using a sacrificial template method. During the process, a natural three-dimensional nanofibrous bacterial cellulose was used as the sacrificial template on which precursor 58S glass was deposited via a sol-gel route. SEM and TEM results verify that the as-prepared 58S scaffolds can inherit the three-dimensional nanofibrous feature of bacterial cellulose. Pore structure characterizations by nitrogen adsorption-desorption and mercury intrusion porosimetry demonstrate that the 58S scaffolds are highly porous with a porosity of 75.1% and contain both mesopores (39.4 nm) and macropores (60 µm) as well as large BET surface area (127.4 m2 g−1). In vitro cell studies suggest that the 58S scaffold is bioactive and biocompatible with primary mouse osteoblast cells, suggesting that the nanofibrous structure of 58S is able to provide an appropriate environment for cellular functioning. These results strongly suggest that the three-dimensional nanofibrous 58S scaffold has great potential for application in bone tissue engineering and regenerative medicine.