Microwave-enhanced catalytic degradation of 4-chlorophenol over nickel oxides under low temperature.

Microwave-enhance catalytic degradation (MECD) of 4-chlorophenol (4-CP) using nickel oxide was studied. A mix-valenced nickel oxide was obtained from nickel nitrate aqueous solution through a precipitation with sodium hydroxide and an oxidation by sodium hypochlorite (assigned as PO). Then, the as-prepared PO was irradiated under microwave irradiation to fabricate a high active mix-valenced nickel oxide (assigned as POM). Further, pure nanosized nickel oxide was obtained from the POM by calcination at 300, 400 and 500 degrees C (labeled as C300, C400 and C500, respectively). They were characterized by X-ray (XRD), infrared spectroscopy (IR) and temperature-programmed reduction (TPR). Their catalytic activities towards the degradation of 4-CP on the efficiency of the degradation were further investigated under continuous bubbling of air through the liquid-phase and quantitative evaluation by high pressure liquid chromatography (HPLC). Also, the effects of temperature, pH and kinds of catalysts on the efficiency of the degradation have been investigated. The results showed that the 4-CP was degraded completely by MECD method within 20 min under pH 7, T=40 degrees C and C=200 g dm(-3) over POM catalyst. The relative activity was affected significantly with the oxidation state of nickel.

Hierarchical copper-decorated nickel nanocatalysts supported on La2O3 for low-temperature steam reforming of ethanol.

Copper/nickel nanocatalysts with a unique morphology were prepared by thermal reduction of a perovskite LaNix Cu1-x O3 precursor (x=1, 0.9, and 0.7). During thermal reduction, copper was first reduced and reacted with lanthanum to form metastable Cu5 La and Cu13 La. When the thermal reduction temperature was increased, the perovskite decomposed to Ni and La2 O3 , CuLa alloys disappeared, and Cu deposits on Ni nanoparticles were generated, thereby forming Cu/Ni nanocatalysts with hierarchical structures. Nanosized nickel, decorated with copper and supported on La2 O3 , could be produced at 520-550 °C. The steam reforming of ethanol was used as a model reaction to demonstrate the catalytic capability of the materials formed. The hierarchical structure of the Cu/Ni/La2 O3 catalysts confers synergetic effects that greatly favor the dehydrogenation of ethanol and which break the C-C bond to produce a higher yield of hydrogen at a low reaction temperature, whereas La2 O3 provides the required stability during the reaction. The reaction at 290 °C achieved almost 100 % conversion with a hydrogen yield reaching 2.21 molH2 mol(-1) EtOH thus indicating that this special structural feature can achieve high activity for the SRE at low temperatures. The proposed synthesis of nanocatalysts appears to be a good way to generate oxide-supported hierarchically structured nanoparticles that can also be applied to other reactions catalyzed by a heterogeneous metal oxide system.

Novel Ag/Au/Pt trimetallic nanocages used with surface-enhanced Raman scattering for trace fluorescent dye detection.

Trimetallic nanostructures have received considerable attention in recent years, due to their widespread use in photonics, catalysis, and surface-enhanced Raman scattering (SERS) detection. Nanoparticles consisting of multiple (n≥ 3) noble metal components, synthesized under controlled conditions, show better SERS-active stability than mono- or bimetallic nanoparticles. In this work, a simple and novel protocol was used for the synthesis of hollow or porous Ag/Au/Pt trimetallic nanocages, based on a galvanic replacement reaction and co-reduction of the corresponding ions. The nanocages were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction. It was also demonstrated that the Ag/Au/Pt trimetallic nanocages were both extremely SERS-active and stable. Our results show that Rhodamine 3B, used as a fluorescent marker, could be detected over a wide concentration range from 10-15 to 10-8 M, with the lower limit of detection being 10-15 M.

Self-focusing Au@SiO2 nanorods with rhodamine 6G as highly sensitive SERS substrate for carcinoembryonic antigen detection.

A highly sensitive self-focusing surface-enhanced Raman scattering (SERS) methodology has been developed using Au@SiO2 core-shell nanorods for carcinoembryonic antigen (CEA) detection. The SERS enhancement factor was evaluated for anisotropic Au@SiO2 nanorods with silica shells of various thicknesses, upon which Rhodamine 6G (R6G) dye was applied as a reporter molecule for the quantitative determination of CEA. The highest R6G signal was attained with a silica layer of 1-2 nm thickness. The self-focusing character originates from the antibody-antigen interaction, which facilitates the SERS probes assembly and significantly increases the detection sensitivity of the CEA. Our results show that the SERS technique is able to detect CEA within a wide concentration range. With an extremely low limit of detection (LOD) of 0.86 fg mL-1, the Au@SiO2 nanoprobes potentially enable the early diagnosis of cancer. Our work offers a low-cost route to the fabrication of sensing devices able to be used for monitoring cancer progression in natural matrices, such as blood.