CeO2@SiO2 Core-Shell Nanostructure-Supported CuO as High-Temperature-Tolerant Catalysts for CO Oxidation.

Supported CuO-CeO2 catalysts have been extensively studied for their outstanding catalytic activity in CO oxidation. Unfortunately, they are prone to sintering and deactivation when exposed to high-temperature automotive exhausts. Herein, taking advantage of the heat-resistant SiO2 microspheres, we fabricated a series of core-shell-structured yCuO- xCeO2@SiO2 ( x is the weight ratio of CeO2-SiO2 and y is the weight ratio of Cu-(CeO2@SiO2)) composite catalysts. All the small CeO2 particles were bound to the SiO2 spheres, forming an xCeO2@SiO2 structure, on the surface of which a certain amount of CuO was well-dispersed. The 5CuO-50CeO2@SiO2 catalyst exhibited good activity, with the full conversion of CO achieved at around 130 °C, and no obvious deactivation was observed in the stability test. Importantly, the interaction between CuO and CeO2@SiO2 enhanced its durability at high temperatures. Even at 800 °C and with a space velocity of 800 000 mL·gcat-1·h-1, CO conversion could be maintained at 90%, which is prospectively applied in a real CO elimination system. The result of the temperature-programmed reduction in hydrogen demonstrated that this special core-shell-structured 5CuO-50CeO2@SiO2 catalyst improved the reduction ability of the CuO species. In situ diffuse reflectance infrared Fourier transform spectroscopy measurements further confirmed that CO molecules preferred to be adsorbed on Cu(I) species to form reactive CO-Cu(I) that enhanced the reactivity of the 5CuO-50CeO2@SiO2 catalyst.

7-O-geranylquercetin-induced autophagy contributes to apoptosis via ROS generation in human non-small cell lung cancer cells.

AIMS: To investigate the antitumor effects of 7-O-geranylquercetin (GQ), a novel O-alkylated derivative of quercetin, against non-small cell lung cancer (NSCLC) cell lines A549 and NCI-H1975 and the corresponding mechanisms. MAIN METHODS: Cell viability was assessed using MTT assay. The expression of proteins involved in apoptosis and autophagy was measured using western blotting. Besides, apoptosis was determined with DAPI staining, Annexin V-PI staining and transmission electron microscopy (TEM) assay, and autophagy was observed with TEM assay. Cell cycle and reactive oxygen species (ROS) level were detected using flow cytometry. KEY FINDINGS: GQ inhibited viability of A549 and NCI-H1975 cells in a dose- and time-dependent manner without apparent cytotoxicity to normal human lung fibroblast cells. GQ down-regulated the expression of apoptosis-related proteins pro-caspase 3 and Bcl-2, and up-regulated the expression of cleaved-PARP and Bax in A549 and NCI-H1975 cells. Meanwhile, GQ-induced cell apoptosis could be attenuated by caspase inhibitor Z-VAD-FMK. Besides, GQ induced autophagosome formation in A549 and NCI-H1975 cells, promoted the expression of autophagy-related proteins LC3-II and Beclin 1, and suppressed the expression of p62. Autophagy inhibition with chloroquine or Beclin 1 siRNA could effectively inhibit GQ-induced apoptosis. Furthermore, GQ treatment increased the generation of ROS, and ROS inhibitor N-acetylcysteine could reverse GQ-induced autophagy and apoptosis. Taken together, GQ could induce apoptosis and autophagy via ROS generation in A549 and NCI-H1975 cells, and GQ-induced autophagy contributed to apoptosis. SIGNIFICANCE: Our findings highlight that GQ is a promising anticancer agent for the treatment of lung cancer.

Catalytically active ceria-supported cobalt-manganese oxide nanocatalysts for oxidation of carbon monoxide.

A low-concentration cobalt (∼6 at%) and manganese (∼3 at%) bimetallic oxide catalyst supported on ceria nanorods (CoMnOx/CeO2), as well as its related single metal oxide counterparts (CoOx/CeO2 and MnOx/CeO2) was synthesized via a deposition-precipitation approach. The fresh samples after air-calcination at 400 °C were tested under the reaction conditions of CO oxidation, and showed the following order of reactivity: CoMnOx/CeO2 > CoOx/CeO2 > MnOx/CeO2. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data identified that the structure of the CeO2 support was maintained during deposition of metal (Co, Mn) ions while the corresponding vis-Raman spectra verified that more oxygen vacancies were created after deposition-precipitation than those in pure ceria nanorods. Aberration-corrected, high-angle, annular dark-field scanning transmission electron microscopy (HAADF-STEM) images with the help of electron energy loss spectroscopy (EELS) analyses determined two types of cobalt species, i.e. ultra-fine clusters (<2 nm) and smaller nanocrystals (up to 5 nm) in CoOx/CeO2 while only bigger nanostructures (∼10 nm) of cobalt-manganese oxides in CoMnOx/CeO2. X-ray absorption fine structure (XAFS) measurements demonstrated the presence of a cubic Co3O4 phase in all the cobalt-based catalysts. The fitting results of the extended X-ray absorption fine structure (EXAFS) indicated that the introduction of the secondary metal (Mn) oxide significantly enhanced the two-dimensional growth of cobalt oxide nanostructures on the surface of CeO2. Therefore, the enhanced activity of CO oxidation reaction over the bimetallic cobalt-manganese oxide nanocatalyst can be attributed to the higher crystallinity of the Co3O4 phase in this work.