Facile Preparation of Macroporous Structures Assembled from Branched Cu₂O Crystals

Experimental

CuCl2· 2H2O (99%, Aldrich), polyethylene glycol (PEG, Mw 20,000, Aldrich), D-(+)-glucose (ACS reagent, Aldrich), and N,N,N′,N′-tetramethyl ethylenediamine (TMEDA, 98%, TCI) were used as received. The microwave-assisted method used here for the preparation of the Cu2O products is similar to that of our previous study.18 In a typical preparation of a Cu2O product, 10 mL of a 4.16 mM aqueous D-(+)-glucose solution and 0.2 g PEG were added to 139.9 mL of a 1.19 mM CuCl2·2H2O aqueous solution with stirring at room temperature for 30 min. Then, 0.0622 mL TMEDA was added to the solution. The total volume of the aqueous solution was fixed at 150 mL. In this case, the final reactant concentrations of CuCl2·2H2O, D-(+)-glucose, TMEDA, and PEG were 1.11 mM, 0.277 mM, 2.77 mM, and 66.0 mM, respectively. To investigate the variation in the branched shapes of the Cu2O products, four different concentrations of CuCl2·2H2O (1.11 mM, 2.22 mM, 4.44 mM, and 13.3 mM) were used while keeping the relative reactant concentrations constant. The final mixed solution was placed into a commercial microwave oven (Magic MWO-230KD, 2.45 GHz, 800 W). When we examined the effects of varying the CuCl2·2H2O concentration on the shapes of the Cu2O products, the microwave irradiation time was set at 240 s. Powder forms of the Cu2O products were obtained by using a centrifuge at 4000 rpm for 10 min. The Cu2O products were then washed several times with ethanol and water, and then dried at 60 °C for 12 h in a drying oven.

The crystal structures of the Cu2O products were characterized by using powder X-ray diffraction (XRD, PANalytical, X’Pert-proMPD). The morphologies of the Cu2O products were examined by performing scanning electron microscopy (SEM, Hitachi S-4300) and high-resolution transmission electron microscopy (HRTEM, JEOL JEM-3010).