Sulfur vacancy-rich (α/ß-CdS)/SiO2 photocatalysts for enhanced visible-light-driven photocatalytic degradation of rhodamine B.

The development of highly efficient photocatalysts for visible-light-driven degradation of organic pollution is of great interest for wastewater purification. In this work, a sulfur vacancy-rich (α/ß-CdS)/SiO2 (α: hexagonal & ß: cubic) photocatalyst with a high catalytic activity was novelly synthesized on a nano-SiO2 carrier by the reaction of Cd2+ with a CS2 storage material (CS2SM) as sulfur source and crystalline modifiers. The dispersion of α/ß-CdS on the nano-SiO2 carrier significantly enhanced the visible-light-driven catalytic activity of (α/ß-CdS)/SiO2 photocatalyst, and 93.37 % rhodamine B (RhB) conversion was determined over 50 mg (α/ß-CdS)/SiO2 photocatalyst for 30 mL 400 mg/L RhB solution at light intensity of 150 mW/cm2 and 298.15 K. After five cycle tests, the (α/ß-CdS)/SiO2 photocatalyst still owned excellent visible-light-driven catalytic degradation stability (>90 %). The characterizations of morphology, functional groups, and photo-electrochemistry of (α/ß-CdS)/SiO2 photocatalyst demonstrated that nano-SiO2 as a carrier played meaningful role in dispersing α/ß-CdS and reducing agglomeration, thus increasing the active site of photocatalytic degradation reaction, and the presence of α/ß hetero-phase junctions and sulfur vacancies allows the rapid separation of photo-generated carriers and inhibits photo-generated electron-holes recombination. Meanwhile, the electron paramagnetic resonance (EPR) and free radical masking test have also proved that the main active species is ·O2- for the oxidation of RhB. Therefore, the work is providing a new reference to the visible-light-driven degradation of wastewater with high RhB concentration at room temperature.

Novel Core-Shell (ε-MnO2/CeO2)@CeO2 Composite Catalyst with a Synergistic Effect for Efficient Formaldehyde Oxidation.

A novel core-shell (ε-MnO2/CeO2)@CeO2 composite catalyst with a synergistic effect was prepared by hydrothermal reaction and thermal decomposition and its application to high-efficiency oxidation removal of formaldehyde (HCHO) was systemically investigated. The (MnCO3/CeO2)@CeO2 precursor was prepared first by the one-pot hydrothermal reaction of Mn2+ and Ce3+ solutions with a CO2-storage material (CO2SM) without any external templates or surfactants required. The thermal decomposition of the precursor afforded the core-shell (ε-MnO2/CeO2)@CeO2 composite catalyst with excellent catalytic performance. HCHO in the feed gas (180 ppm HCHO, 21% O2, N2 balanced) at a gas hourly space velocity of 100 L/(gcat h) is 100% converted over the catalyst at 80 °C. The conversion rate remains above 95% in 72 h and above 73.8% in 140 h, suggesting the strong stability of the catalyst at high gas flow rates and relatively low temperatures. The synergistic mechanism of the catalyst was explored by X-ray diffraction, Raman, Brunauer-Emmett-Teller, transmission electron microscopy, and X-ray photoelectron spectroscopy. The number of defects in the catalyst and the strength of the Mn-O bond in ε-MnO2 can be tuned by adjusting the synthesis conditions. More oxygen vacancies on the surface of CeO2 can make the synergistic effect of the catalyst stronger, which significantly improves the lattice oxygen (Olatt) activity on the surface of ε-MnO2. Our work has provided new insights into the preparation of the desired composite catalysts with excellent performances.

Epitaxial Growth of Rectangle Shape MoS2 with Highly Aligned Orientation on Twofold Symmetry a-Plane Sapphire.

Research on transition metal dichalcogenides (TMDs) has been accelerated by the development of large-scale synthesis based on chemical vapor deposition (CVD) growth. However, in most cases, CVD-grown TMDs are composed of randomly oriented grains, and thus contain many distorted grain boundaries (GBs), which seriously degrade their electrical and photoelectrical properties. Here, the epitaxial growth of highly aligned MoS2 grains is reported on a twofold symmetry a-plane sapphire substrate. The obtained MoS2 grains have an unusual rectangle shape with perfect orientation alignment along the [1-100] crystallographic direction of a-plane sapphire. It is found that the growth temperature plays a key role in its orientation alignment and morphology evolution, and high temperature is beneficial to the initial MoS2 seeds rotate to the favorable orientation configurations. In addition, the photoluminescence quenching of the well-aligned MoS2 grains indicates a strong MoS2 -substrate interaction which induces the anisotropic growth of MoS2 , and thus brings the formation of rectangle shape grains. Moreover, the well-aligned MoS2 grains splice together without GB formation, and thus that has negligible effect on its electrical transport properties. The progress achieved in this work could promote the controlled synthesis of large-area TMDs single crystal film and the scalable fabrication of high-performance electronic devices.

P-N depleted bulk BiOBr/α-Fe2O3 heterojunctions applied for unbiased solar water splitting.

P-N depleted bulk BiOBr/α-Fe2O3 heterojunction (DBH) nanostructures with the growth of (001) BiOBr facets were prepared via a simple hydrothermal method. BiOBr possesses an average thickness of around 50 nm and shows preferential exposure of the (001) facets. α-Fe2O3 nanoparticles, with an average diameter of 5 nm, are attached on the surface of BiOBr as 20-50 nm clusters with an intimate contact interface. Such DBH nanostructures show high hydrogen evolution, and 193 mmol g-1 of H2 is produced with DBH containing 1 wt% Pt, which is 6.3 times higher than that of α-Fe2O3 nanoparticles. The structural features of DBH are considered to be important to obtain attractive properties in photocatalytic water splitting.

Enhanced photocurrent by the co-sensitization of ZnO with dye and CuInSe nanocrystals.

ZnO nanocrystals with a particle size of 20-30 nm have been synthesised for the first time using a template-free method. Chalcopyrite Cu0.28In1.72Se2.72 nanocrystals (5-10 nm) were directly anchored on ZnO nanocrystals by a vacuum one-pot-nanocasting process without any long ligands. We further investigated Cu0.28In1.72Se2.72 quantum dots and dye bilayer-sensitized solar cells, which exhibited power conversion efficiency of 57.4% higher than the single-dye-sensitized solar cells.

Facile patterning of upconversion NaYF4:Yb,Er nanoparticles.

Different kinds of highly ordered patterns of NaYF(4):Yb,Er nanoparticles on gold substrates were fabricated using a simple method combining micro-contact printing and "breath figures" techniques. Ordered arrays of water droplets were first formed in the hydrophilic regions of patterned self-assembled monolayers (SAMs). This was subsequently submerged in a chloroform solution of NaYF(4):Yb,Er nanoparticles. The particles were spontaneously assembled at the interface of chloroform/water droplet surface, leading to different kinds of uniform patterns after solvent evaporation. The structures of NaYF(4):Yb,Er particles patterns depended on the dimension of the substrate, the concentration of the NaYF(4):Yb,Er nanoparticles and the water condensation process.

Improving the anti-tumor effect of genistein with a biocompatible superparamagnetic drug delivery system.

The practical application of genistein as a low toxicity chemotherapeutic drug is hindered by many of its in vivo properties. To overcome these obstacles, a new multifunctional drug delivery system is developed, which is based on covalently attaching genistein onto Fe3O4 nanoparticles coated by cross-linked carboxymethylated chitosan (CMCH). The structure of the Fe3O4-CMCH-genistein nano-conjugate was confirmed by transmission electron micrographs (TEM), X-ray diffraction (XRD) and Fourier-transfer infrared (FT-IR) spectroscopy. The nano-conjugate shows good water solubility and superparamagnetic properties with a saturation magnetization of 55.1 emu/g. The effects of free genistein and FeO4-CMCH-genistein nano-conjugate on the proliferation and apoptosis of gastric cancer cell line SGC-7901 were investigated by MTT assay and flow cytometry (FACS). MTT results indicate that the Fe3O4-CMCH-genistein nano-conjugate exhibits a significantly enhanced inhibition effect to the SGC-7901 cancer cells than the free genistein. FACS data suggests that the inhibition on cell proliferation of the nano-conjugate is related with an induced apoptosis process. This drug delivery system is promising for future multifunctional chemotherapeutic application that combines drug release and magnetic hyperthermia therapy.

Shell-Controlled Photoluminescence in CdSe/CNT Nanohybrids.

A new type of nanohybrids containing carbon nanotubes (CNTs) and CdSe quantum dots (QDs) was prepared using an electrostatic self-assembly method. The CdSe QDs were capped by various mercaptocarboxylic acids, including thioglycolic acid (TGA), dihydrolipoic acid (DHLA) and mercaptoundecanoic acid (MUA), which provide shell thicknesses of ~5.2, 10.6 and 15.2 Å, respectively. The surface-modified CdSe QDs are then self-assembled onto aridine orange-modified CNTs via electrostatic interaction to give CdSe/CNT nanohybrids. The photoluminescence (PL) efficiencies of the obtained nanohybrids increase significantly with the increase of the shell thickness, which is attributed to a distance-dependent photo-induced charge-transfer mechanism. This work demonstrates a simple mean for fine tuning the PL properties of the CdSe/CNT nanohybrids and gains new insights to the photo-induced charge transfer in such nanostructures.