Jincheng Liu

Graphene oxide–CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation

Graphene oxide (GO)-CdS composites were synthesized via a novel two-phase mixing method successfully. CdS nanoparticles were uniformly self-assembled on GO sheets at water/toluene interface. The photocatalytic degradation (photodegradation) and disinfection activities of GO-CdS composites were investigated thoroughly. The results show that GO-CdS composites exhibit higher efficiency in photodegradation of various water pollutants than pure CdS nanoparticles under visible light irradiation. In addition, the interactions between GO sheets and CdS nanoparticles inhibit the photo-corrosion of CdS and leaching of Cd(2+). Only 3.5 wt% Cd(2+) of GO-CdS was leached out after photodegradation, while 38.6 wt% Cd(2+) of CdS was lost into aqueous solution. Furthermore, the disinfection activity of GO-CdS composites was investigated for the first time. Nearly 100% of both Gram-negative Escherichia coli (E. coli) and Gram-positive Bacillus subtilis (B. subtilis) were killed within 25 min under visible light irradiation. The excellent performances of GO-CdS composites can be attributed to that (1) effective charge transfer from CdS to GO reduces the recombination rate of photo-generated electron-hole pairs; (2) uniform deposition of CdS on GO sheets eliminates aggregation of CdS nanoparticles; and (3) the strong interactions between GO and CdS enhancing the durability of GO-CdS composites. Finally, the mechanism behind these excellent performances was verified by transient photocurrent measurement and further confirmed by ESR technique as well as employing a radical scavenging species - dimethyl sulfoxide (DMSO).

Graphene oxide enwrapped Ag3PO4 composite: towards a highly efficient and stable visible-light-induced photocatalyst for water purification.

A novel graphene oxide (GO) enwrapped Ag3PO4 (GO–Ag3PO4) composite as a visible-light-induced photocatalyst has been fabricated through an ion-exchange method of CH3COOAg and Na2HPO4 in the presence of GO sheets. Scanning electron microscope and X-ray diffraction analysis confirmed that Ag3PO4 particles have been enwrapped by GO sheets. The UV-vis spectra curve of the GO–Ag3PO4 composite showed strong absorbance in the visible light regions. The photocatalytic activity of the composite was evaluated by the degradation of organic dye (AO7) and phenol under visible-light irradiation. The results indicated that this novel GO–Ag3PO4 composite exhibited significantly higher photocatalytic activities and improved stability under visible-light irradiation, compared with bare Ag3PO4. Moreover, the GO–Ag3PO4 composite showed both excellent intrinsic antibacterial and visible-light-induced photocatalytic disinfection activities toward E. coli cells. The possible mechanism for the enhanced photocatalytic properties and antibacterial activity of the GO–Ag3PO4 composite was also discussed. Our finding paves a way to design highly efficient and stable visible-light-induced photocatalysts for the removal of organic pollutants and pathogenic bacteria for water purification.

High quality graphene oxide-CdS-Pt nanocomposites for efficient photocatalytic hydrogen evolution†

Graphene oxide–CdS–Pt (GO–CdS–Pt) nanocomposites with different amounts of Pt nanoparticles were successfully synthesized via the formic acid reduction process followed by a two-phase mixing method. The morphology, crystal phase and optical properties of obtained composites were well characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis spectroscopy, Fourier transform IR spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic activity of GO–CdS–Pt composites for hydrogen generation was investigated. The results show that the GO–CdS–Pt composite containing 0.5 at% of Pt exhibits the highest hydrogen evolution rate of 123 mL h−1 g−1 with strong photostability, which is about 2.5 times higher than that of GO–CdS and 10.3 times higher than that of CdS. The increased photocatalytic hydrogen generation efficiency is attributed to the effective charge separation and decreased anti-recombination with the addition of GO and Pt, as well as the low overpotential of Pt for water splitting. Our findings pave a way to design multi-component graphene-based composites for highly efficient H2 generation and other applications.

Facile synthesis of monodispersed silver nanoparticles on graphene oxide sheets with enhanced antibacterial activity

Graphene oxide–Ag nanoparticle (GO–Ag) composites were synthesized through a facile two-phase (toluene–water) process. Transmission Electron Microscopy and X-ray diffraction analysis revealed that the Ag nanoparticles anchored on GO sheets were spherical in shape and highly monodispersed with uniform size of 6 nm. The antibacterial activity of GO–Ag composites was investigated against gram-negative bacteria Escherichia coli (E. coli) and showed a remarkably enhanced antibacterial activity compared with the original Ag nanoparticles, suggesting that the as-prepared nanocomposites may be used as effective antibacterial materials.

Multifunctional graphene oxide-TiO2-Ag nanocomposites for high performance water disinfection and decontamination under solar irradiation

Multifunctional nanocomposites (GO-TiO2-Ag) integrating 2D GO sheets, 1D TiO2 nanorods and 0D Ag nanoparticles were synthesized via a facile two-phase method and characterized by various analytical techniques including TEM, EDS and XRD. The GO-TiO2-Ag nanocomposites demonstrate remarkably enhanced photocatalytic activities in degrading AO 7 and phenol under solar irradiation compared with GO-TiO2 and GO-Ag. They also exhibit excellent intrinsic antibacterial activity toward Escherichia coli, as well as significantly enhanced photo-biocidal capability over GO-TiO2 and GO-Ag. Through systematically investigating the influence of Ag content in the nanocomposites for their photocatalytic activities, it indicates that the optimal Ag content in the GO-TiO2-Ag nanocomposites varies for dye degradation and for phenol/bacterial degradation with different mechanisms. The superior photocatalytic activities under solar irradiation and the easy recovery make the GO-TiO2-Ag nanocomposites a good promising candidate for water purification.

Porous calcium phosphate ceramics prepared by coating polyurethane foams with calcium phosphate cements

Porous calcium phosphates have important biomedical applications such as bone defect fillers, tissue engineering scaffolds and drug delivery systems. While a number of methods to produce the porous calcium phosphate ceramics have been reported, this study aimed to develop a new fabrication method. The new method involved the use of polyurethane foams to produce highly porous calcium phosphate cements (CPCs). By firing the porous CPCs at 1200 °C, the polyurethane foams were burnt off and the CPCs prepared at room temperature were converted into sintered porous hydroxyapatite (HA)-based calcium phosphate ceramics. The sintered porous calcium phosphate ceramics could then be coated with a layer of the CPC at room temperature, resulting in high porosity, high pore interconnectivity and controlled pore size.

High-quality reduced graphene oxide-nanocrystalline platinum hybrid materials prepared by simultaneous co-reduction of graphene oxide and chloroplatinic acid.

Reduced graphene oxide-nanocrystalline platinum (RGO-Pt) hybrid materials were synthesized by simultaneous co-reduction of graphene oxide (GO) and chloroplatinic acid with sodium citrate in water at 80°C, of pH 7 and 10. The resultant RGO-Pt hybrid materials were characterized using transmission electron microscopy (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Platinum (Pt) nanoparticles were anchored randomly onto the reduced GO (RGO) sheets with average mean diameters of 1.76 (pH 7) and 1.93 nm (pH 10). The significant Pt diffraction peaks and the decreased intensity of (002) peak in the XRD patterns of RGO-Pt hybrid materials confirmed that the Pt nanoparticles were anchored onto the RGO sheets and intercalated into the stacked RGO layers at these two pH values. The Pt loadings for the hybrid materials were determined as 36.83 (pH 7) and 49.18% (pH 10) by mass using XPS analysis. With the assistance of oleylamine, the resultant RGO-Pt hybrid materials were soluble in the nonpolar organic solvents, and the dispersion could remain stable for several months.

Ag loaded WO3 nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation

Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO3 nanoplates using a photo-reduction method to generate WO3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO3 and WO3/Ag composites was conducted under visible light irradiation. The results show that WO3/Ag composites performed much better than pure WO3 where the highest removal rate was 96.2% in 5h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2h under visible light irradiation for all three WO3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.

A novel strategy to fabricate inorganic nanofibrous membranes for water treatment: use of functionalized graphene oxide as a cross linker

A novel type of nanofibrous membrane was assembled using hierarchical K-OMS-2/GO-SO3H heterojunctions, and the membrane exhibited excellent permeability and selectivity in a dead-end microfiltration process.