Self-assembled multidoped cryptomelane hollow microspheres with ultrafi ne particles in the size range of 4-6 nm, and with a very high surface area of 380 m 2 g − 1 have been synthesized. The particle size, morphology, and the surface area of these materials are readily controlled via multiple framework substitutions. The X-ray diffraction and transmission electron microscopy (TEM) results indicate that the as-synthesized multidoped OMS-2 materials are pristine and crystalline, with no segregated metal oxide impurities. These results are corroborated by infrared (IR) and Raman spectroscopy data, which show no segregated amorphous and/or crystalline metal impurities. The fi eld-emission scanning electron microscopy (FESEM) studies confi rm the homogeneous morphology consisting of microspheres that are hollow and constructed by the self-assembly of pseudo-fl akes, whereas energy-dispersive X-ray (EDX) analyses imply that all four metal cations are incorporated into the OMS-2 structure. On the other hand, thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) demonstrate that the as-synthesized multidoped OMS-2 hollow microspheres are more thermally unstable than their single-doped and undoped counterparts. However, the in-situ XRD studies show that the cryptomelane phase of the multidoped OMS-2 hollow microspheres is stable up to about 450 ° C in air. The catalytic activity of these microspheres towards the oxidation of diphenylmethanol is excellent compared to that of undoped OMS-2 materials.

Copper oxides have been widely used as catalysts, gas sensors, adsorbents, and electrode materials. In this work, CuO nanomaterials were synthesized via a facile microwave-assisted hydrothermal process in Cu(CH3COO)2(0.1 M)/urea(0.5 M) and Cu(NO3)2(0.1 M)/urea(0.5 M) aqueous systems at 150 °C for 30 min. The formation processes of copper oxides were investigated, and their catalytic activities were evaluated by the epoxidation of alkenes and the oxidation of CO to CO2. Their electrochemical properties were compared as supercapacitor electrodes using cyclic voltammetry. Experimental results indicated that copper acetate solution could be hydrolyzed to form urchin-like architectured CuO, and the addition of urea accelerated this transformation. CuO nanoparticles were formed and aggregated into spheroidal form (CuO-1) in Cu(CH3COO)2/urea aqueous solution. Cu2(OH)2CO3 was formed as an intermediate, and then thermally decomposed into CuO nanorods (CuO-2) in the Cu(NO3)2/urea aqueous system. The synthesized copper oxide nanomaterials exhibited excellent catalytic activities for the epoxidation of alkenes, the oxidation of CO, and pseudocapacitance behavior in potassium hydroxide solution. The increase of specific surface area promoted the catalytic activities and conversions for olefins and CO. CO was oxidized to CO2 when the applied temperature was higher than 115 °C, and conversion of 100% was obtained at 130 °C. CuO-1 showed higher catalytic activities and capacitance values than those of CuO-2 likely due to the former having a larger specific surface area. This work facilitates the preparation of nanosized CuO materials with excellent catalytic and electrochemical performance.

The catalytic degradation of organic dye (methylene blue, MB) has been studied using green oxidation methods (tertiary-butyl hydrogen peroxide, TBHP, as the oxidant with several doped mixed-valent and regular manganese oxide catalysts in water) at room and higher temperatures. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The most active catalysts were those of Mo(6+)- and V(5+)-doped OMS. Rates of reaction were found to be first-order with respect to the dye. TBHP has been found to enhance the MB decomposition, whereas H(2)O(2) does not. Reactions were studied at pH 3-11. The optimum pH for these reactions was pH 3. Dye-decomposing activity was proportional to the amount of catalyst used, and a significant increase in catalytic activity was observed with increasing temperature. X-ray diffraction (XRD), energy dispersive spectroscopy (EDX), and thermogravimetric analysis (TGA) studies showed that no changes in the catalyst structure occurred after the dye-degradation reaction. The products as analyzed by electrospray ionization mass spectrometry (ESI-MS) showed that MB was successively decomposed through different intermediate species.

The efficacy of dynamic nuclear polarization (DNP) surface-enhanced NMR spectroscopy (SENS) is reviewed for alumina, silica, and ordered mesoporous carbon (OMC) materials, with vastly different surface areas, as a function of the biradical concentration. Importantly, our studies show that the use of a "one-sizefits-all" biradical concentration should be avoided when performing DNP SENS experiments and instead an optimal concentration should be selected as appropriate for the type of material studied as well as its surface area. In general, materials with greater surface areas require higher radical concentrations for best possible DNP performance. This result is explained with the use of a thermodynamic model wherein radical-surface interactions are expected to lead to an increase in the local concentration of the polarizing agent at the surface. We also show, using plane-wave density functional theory calculations, that weak radical-surface interactions are the cause of the poor performance of DNP SENS for carbonaceous materials.

Short reaction times and morphology control in the synthesis of inorganic materials under nonthermal conditions remain a challenge. Herein we report a rapid, self-templating, and nonthermal method based on ultraviolet light to prepare metal oxide hierarchical structures. With this method, the morphology of the metal oxides was controlled readily without using templates.