We report here two different simple, one‐pot, and low cost chemical synthetic routes for the preparation of Cu2O nanocrystals: (a) thermal decomposition of copper–organic precursors copper(II) acetate or copper(II) acetylacetonate in long chain organic solvents oleyl alcohol and trioctylamine, respectively, at 170 °C and (b) a surfactant‐free solvothermal approach involving the reaction of copper(II) acetylacetonate in acetone at 140 °C. The structure and morphology of the nanocrystals have been characterized in detail by XRD, FTIR spectroscopy, Raman spectroscopy, and high‐resolution transmission electron microscopy (HRTEM). The optical properties of the nanocrystals have been explored by diffuse‐reflectance spectroscopy (DRS) and a blueshift of the optical band gap of the nanocrystals is observed owing to size effects. Based on the FTIR, GC–MS, and 13C{1H} NMR studies of post‐reaction solutions, different formation mechanisms for the Cu2O nanocrystals, which depend on the synthetic approach, have been proposed. Oleyl alcohol and trioctylamine play dual roles as solvents and mild reductants and reduce CuII species to CuI species during the course of the thermal decomposition reactions. The solvothermal reaction of copper(II) acetylacetonate in acetone possibly proceeds by acetylacetone‐mediated reduction of Cu2+ to Cu+ in the absence of any reducing agent. The potential of Cu2O nanocrystals as photocatalytic materials for hydrogen generation from water/methanol (2:1) mixtures under UV/Vis irradiation has also been evaluated. The results show that all the nanocystalline Cu2O samples generate H2.
MCM-48 samples containing uranium (U−MCM-48) to the extent of 1 to 6 wt % were
synthesized hydrothermally and characterized using powder XRD, 29Si MAS NMR, FTIR
spectroscopy, DR UV−Vis spectroscopy, N2 sorption, and TEM techniques. These analyses
confirmed the formation of an ordered cubic-phase MCM-48 mesomaterial where the uranium
existed in the hexavalent state forming a local uranate type structure. A part of the uranyl
groups were found to be incorporated in the framework positions, while the rest were
anchored on to the wall of the host silica matrix. Also, the U−MCM-48 samples exhibited
an enlargement of the cubic cell unit as well as an increase in the degree of cross-linking,
as revealed by XRD and MAS NMR results. The samples exhibited N2 sorption isotherms of
type IV and an increase was observed in the pore diameter as a result of uranium
incorporation. TEM investigation revealed that although U−MCM-48 samples were of cubic
symmetry similar to that of Si−MCM-48, some distortion in the pore structure was clearly
noticeable. Furthermore, in case of the samples with U loading of ∼6 wt %, formation of
nanocrystallites of α-U3O8 was also detected after calcination and such samples consisted
of a multiple-size pore system.
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