Xingrui Wang

Preparation of aligned porous gelatin scaffolds by unidirectional freeze-drying method

Porous gelatin scaffolds with microtubule orientation structure were manufactured by unidirectional freeze-drying technology, and their porous structure was characterized by scanning electron microscopy. Scaffolds with tunable pore size and high porosity up to 98% were obtained by adjusting the concentration of the gelatin solution and crosslinking agent during the preparation process. All the porous gelatin scaffolds exhibited oriented microtubule pores, with width and length from 50 to 100 microm and 100 to 500 microm, respectively. Meanwhile, the properties of the scaffolds, such as porosity, water adsorption ability and compressive strength, were studied. In vitro enzymatic degradation results showed that the absolute weight loss of the gelatin scaffolds exhibited an increasing trend from low to high gelatin concentration used to prepare gelatin scaffolds; in vitro cell culture results indicated that the porous gelatin scaffolds were non-toxic to cartilage cells, since the cells spread and grew well.

Cost-Effective Reduced Graphene Oxide-Coated Polyurethane Sponge As a Highly Efficient and Reusable Oil-Absorbent

Reduced graphene oxide coated polyurethane (rGPU) sponges were fabricated by a facile method. The structure and properties of these rGPU sponges were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray diffraction, and scanning electron microscopy. The rGPU sponges are hydrophobic and oleophilic and show extremely high absorption for organic liquids. For all the organic liquids tested, the absorption capacities were higher than 80 g g(-1) and 160 g g(-1) (the highest value) was achieved for chloroform. In addition, the absorption capacity of the rGPU sponge did not deteriorate after it was reused 50 times, so the rGPU sponge has excellent recyclability.

An environmentally friendly method for the fabrication of reduced graphene oxide foam with a super oil absorption capacity

Three kinds of graphene oxide (GO) foams were fabricated using different freezing methods (unidirectional freezing drying (UDF), non-directional freezing drying, and air freezing drying), and the corresponding reduced graphene oxide (RGO) foams were prepared by their thermal reduction of those GO foams. These RGO foams were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The absorption process and the factors that influence the absorption capacity were investigated. The RGO foams are hydrophobic and showed extremely high absorbing abilities for organic liquids. The absorption capacity of the RGO foams made by UDF was higher than 100 g g(-1) for all the oils tested (gasoline, diesel oil, pump oil, lubricating oil and olive oil) and had the highest value of about 122 g g(-1) for olive oil. The oil absorption capacity of the GO foams was lower than that of the RGO foams, but for olive oil, the absorption capacity was still high than 70 g g(-1), which is higher than that of most oil absorbents.

Graphene oxide reduced and modified by soft nanoparticles and its catalysis of the Knoevenagel condensation

An approach to prepare reduced graphene oxide (RGO) was developed using soft nanoparticles, amino-terminated poly(amidoanime) (PAMAM) dendrimers, as both a reducing agent and a stabilizing agent. Several factors that affect the reduction of graphene oxide (GO), including the PAMAM generation, the ratio of PAMAM/GO, the pH, and the reduction temperature were investigated. The reduced graphene oxide was characterized with UV-visible absorption spectroscopy, Raman spectroscopy, X-ray diffraction spectroscopy, thermo-gravimetric analysis, X-ray photoelectron spectroscopy and transmission electron microscopy. The PAMAM dendrimers efficiently reduced GO in a short time, and their adsorption onto the RGO nanosheets allows RGO to stably disperse in water and organic solvents, such as N,N-dimethyl formamide and dimethyl sulfoxide. PAMAM modified RGO can catalyze the Knoevenagel condensation with yields up to 99%, and thus is a very active organocatalyst.

Reduction of graphene oxide with L-lysine to prepare reduced graphene oxide stabilized with polysaccharide polyelectrolyte

An environmentally friendly approach to reduce graphene oxide (GO) with L-lysine (L-Lys) was developed by using carboxymethyl starch (CMS) as a stabilizing agent and a stable suspension of reduced graphene oxide (RGO) was obtained. UV visible absorption spectroscopy was used to monitor the deoxygenating process and the factors that affect the GO reduction, such as the ratio of GO/L-Lys, the temperature and pH were optimized. The reduction of the GO was verified by Fourier transform infrared spectroscopy, X-ray diffraction, thermo-gravimetric analysis, Raman spectroscopy and X-ray photoelectron spectroscopy. Ordered porous RGO/CMS foams were prepared by a unidirectional freeze-drying method (UFDM) and used as absorbents for copper ions. Since L-Lys and CMS are natural and edible chemicals, this approach provides a green method to produce stable RGO from GO on a large scale. The nontoxic biodegradable RGO/CMS foams show potential applications for metal ions removal from wastewater.

Graphene oxide supported Au?Ag alloy nanoparticles with different shapes and their high catalytic activities

A simple method was developed to fabricate Au-Ag nanoparticle/graphene oxide nanocomposites (Au-Ag/GO) by using simultaneous redox reactions between AgNO3, HAuCl4 and GO. The Au-Ag/GO was characterized by x-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive x-ray spectroscopy. The GO nanosheets acted as the reducing agent and the support for the Au-Ag alloy nanoparticles. In addition, Au-Ag alloy nanoparticles with different shapes including core-shell-like, dendrimer-like and flower-like were obtained by simply modifying the concentration of the reactants and the reaction temperature. With no reducing or stabilizing agents added, the Au-Ag/GO nanocomposites show superior catalytic performance for the reduction of 4-nitrophenol and for the aerobic homocoupling of phenylboronic acid.