Pengpeng Chen

Fabrication of hydrogel of hydroxypropyl cellulose (HPC) composited with graphene oxide and its application for methylene blue removal

Novel environmental friendly hydroxypropyl cellulose (HPC) hydrogels were fabricated upon compositing with graphene oxide (GO) in this work. In order to promote a more homogeneous dispersion of GO sheets in HPC, GO was firstly modified with HPC chains through esterification. The morphology and chemical structure of the functionalized HPC-GO were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, X-ray diffraction, and thermo-gravimetric analysis. Then scanning electronic microscope was employed to compare the morphologies of the HPC and HPC-GO/HPC hydrogels. The obtained HPC-GO/HPC hydrogels exhibited excellent adsorption performance toward methylene blue. Simulation of the practical use by preparing simple adsorption columns made from in situ formation of HPC-based hydrogels had given a visible observation of the significant adsorption effect brought by the incorporation of HPC-GO sheets. Adsorption kinetics were then imitated by Lagergren pseudo-first-order and pseudo-second-order models. Adsorption isotherms were imitated by Langmuir isotherm and Freundlich isotherm.

Greatly improved mechanical and thermal properties of chitosan by carboxyl-functionalized MoS2 nanosheets

In this work, molybdenum disulfide (MoS2) nanosheets were employed to enhance the mechanical and thermal properties of chitosan (CS), which was one of the most promising biomaterials. In order to promote a homogeneous dispersion of MoS2 and improved interface interactions between CS and fillers, carboxyl functionalization was subjected to the exfoliated MoS2 nanosheets by chemical conjugation with thioglycolic acid before compositing with CS. Afterward, the CS/MoS2–g–COOH composite films were prepared by a simple solution blending method. Micromorphology characterizations showed that MoS2–g–COOH nanosheets dispersed much better than unmodified MoS2 nanosheets, which was considered to be quite beneficial for the enhanced properties of CS nanocomposites. DMA results indicated that the mechanical properties of CS were improved by incorporating with MoS2–g–COOH nanosheets compared with neat CS and unmodified MoS2-filled CS. The thermal stability of CS/MoS2–g–COOH was also improved. This work demonstrated a promising route to prepare MoS2-based polymer nanocomposites with excellent performances.

CuS/MoS2 nanocomposite with high solar photocatalytic activity

Two-dimensional CuS/MoS2 heterostructure with high photocatalytic activity had been successfully obtained by a simple combination of wet chemical method and hydrothermal process. CuS nanosheets had been successfully grown on the two-dimensional MoS2 nanosheets uniformly and tightly. The obtained heterostructures were well characterized through X-ray diffraction patterns, transmission electron microscopy, Fourier transform infrared spectra, ultraviolet–visible diffuse-reflectance spectra, and Zeta potential measurement. Photocatalytic performance of the CuS/MoS2 nanocomposite was evaluated toward the decomposition of methylene blue solution under natural light. The as-prepared nanocomposite showed remarkably enhanced photocatalytic activity compared with pure CuS and MoS2. This could be attributed to the enhanced dyestuff absorption and charge transport after the conjugation between CuS and MoS2.

Novel synthesis of silver/reduced graphene oxide nanocomposite and its high catalytic activity towards hydrogenation of 4-nitrophenol

A novel synthesis method was reported for the preparation of silver/reduced graphene oxide (Ag/RGO) nanocomposites via reducing AgNO3 in a macroscopic RGO aerogel directly through a convenient impregnation process. The as-prepared RGO-supported Ag nanocrystal exhibited high activity in the catalytic hydrogenation of 4-nitrophenol.

Weak acid–base interaction induced assembly for the formation of rambutan-like poly(styrene-alt-maleic anhydride)/silica composite microspheres

To investigate the effect of surface functionality on the morphology of polymer/silica composite, poly(styrene-alt-maleic anhydride) (SMA) spheres prepared via precipitation polymerization method was employed. In water/ethanol solution, diethanolamine (DEA) was used to catalyze the hydrolysis reaction of tetraethoxysilane (TEOS), and rambutan-like poly(styrene-alt-maleic anhydride)/silica (SMA/SiO2) microspheres were synthesized through in situ sol–gel process. The obtained structure and morphology were characterized by FTIR, NMR, TEM, SEM, and TGA. The results showed that the hydrolyzed SMA chains on the surface was crucial to the nucleation and growth of silica, and the morphologies of SMA/SiO2 composite microspheres can be controlled by the amount of DEA and the ratio of SMA/TEOS. In addition, the SMA/SiO2 microspheres were used to prepare hierarchical structure of SMA/SiO2/Ag particles, which were utilized for the construction of surface-enhanced Raman scattering substrate (SERS).

Sodium alginate-assisted exfoliation of MoS2 and its reinforcement in polymer nanocomposites

In this work, molybdenum disulfide (MoS2) nanosheets were facilely prepared by direct exfoliation of MoS2 in aqueous media with the assistance of sodium alginate (SA). Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectra results showed that the raw MoS2 was successfully exfoliated into few-layer MoS2 nanosheets (SA-MoS2). FTIR and thermal gravimetric analysis (TGA) investigations showed that the obtained MoS2 nanosheets were modified by SA after exfoliation and improved dispersion in water were achieved. The obtained SA-MoS2 nanosheets were employed to reinforce the water-soluble polymer SA. No obvious macroscopic phase separation could be found from the SA/SA-MoS2 films. Dynamic mechanical analysis (DMA) results showed that almost 9 times enhancement for the storage modulus of SA was achieved with the incorporation of only 0.5wt% of SA-MoS2, and the thermal stability of SA was also found improved with the addition of SA-MoS2 according to the thermal gravimetric analysis TGA results.

Ibuprofen-loaded micelles based on star-shaped erythritol-core PLLA-PEG copolymer: effect of molecular weights of PEG

Amphiphilic star-shaped copolymers based on star-shaped poly(L-lactide) (s-PLLA) and poly(ethylene glycol) (PEG) (s-PLLA-PEG) were synthesized with variable molecular weights (Mw) of PEG, and the relationship between the PEG block molecular weight of s-PLLA-PEG copolymers and their micelle properties were investigated. The structure and Mw of s-PLLA-PEG were characterized with 1H NMR, GPC, DSC, and XRD. The ibuprofen (IBU)-loaded s-PLLA-PEG micelles were prepared by dialysis method. The effects of PEG block molecular weight on the morphology, particle size, zeta potential, drug loading content (LC), drug encapsulation efficiency (EE), and in vitro drug release behavior of prepared micelles were investigated. Results indicated that the average diameters, LC, and EE of IBU-loaded s-PLLA-PEG micelles increased with increasing the Mw of PEG in s-PLLA-PEG copolymers. The in vitro study showed that the IBU accumulative release can be depressed by increasing the Mw of the s-PLLA-PEG, and the release profiles of IBU from s-PLLA-PEG followed the Baker-Lonsdale model equation. The results suggest that structural tailoring of PEG length from s-PLLA-PEG copolymers could provide a new strategy for designing drug carriers of high efficiency.

Effective reinforcement of amino-functionalized molybdenum disulfide on epoxy-based composites via strengthened interfacial interaction

The effects of amino-functionalized molybdenum disulfide (f-MoS2) on the curing activity and mechanical properties of epoxy-based composites were evaluated. The f-MoS2 was prepared through the mild reaction between mercapto-ethylamine and the exfoliated MoS2. Benefiting from the universal binding ability of amino groups, good dispersion of f-MoS2 in epoxy matrix was achieved. Studies of the curing behavior of epoxy composites showed that the curing temperature and heat release during the curing process of epoxy composites with MoS2 was lower than that of neat epoxy and composites with MoS2, indicating a decreased activation energy. The f-MoS2 containing amino groups on its surface was revealed can react with epoxy matrix and enhance the curing reactions like a co-curing agent of amine-type curing agent. The mechanical properties and thermal stability of the epoxy were both enhanced by f-MoS2. The storage modulus of the EP/f-MoS2 composites was about 60% higher than that of EP/MoS2 composites, which was attributed to the improved dispersion of f-MoS2 in matrix and the strengthened interfacial interactions between f-MoS2 with epoxy than that of the neat MoS2.

Fabrication of polyacrylate core–shell nanoparticles via spray drying method

Fine polyacrylate particles are thought to be environmental plastisols for car industry. However, these particles are mainly dried through demulsification of the latexes, which is not reproducible and hard to be scaled up. In this work, a spray drying method had been applied to the plastisols-used acrylate latex. By adjusting the core/shell ratio, spray drying process of the latex was fully studied. Scanning electronic microscopy observation of the nanoparticles before and after spray drying indicated that the core–shell structures could be well preserved and particles were well separated by spray drying if the shell was thick enough. Otherwise, the particles fused into each other and core–shell structures were destroyed. Polyacrylate plastisols were developed using diisononylphthalate as a plasticizer, and plastigels were obtained after heat treatment of the sols. Results showed that the shell thickness also had a great influence on the storage stability of the plastisols and mechanical properties of the plastigels.Graphical Abstract