Solvothermal preparation of Cu2O crystalline particles

A solvothermal process has been developed to prepare both the cubic single crystals and the spherical polycrystals of Cu2O by the reduction of CuSO4·5H2O with d-glucose as a reductant in the presence of the different organic additives such as ethylene glycol, polyethylene glycol 200 (PEG-200), polyethylene glycol 400 (PEG-400), polyethylene glycol 10000 (PEG-10000), polyethylene glycol 20000 (PEG-20000) or polyvinyl pyrrolidone (PVP K-30). All the products were characterized using X-ray diffraction and transmission election microscopy. The organic additives were found to play a key role in the formation of the Cu2O crystals and lead to the different microstructures of the resultant Cu2O. Two different mechanisms, diffusion mechanism and aggregation mechanism, were used to explain the formation of single crystals and polycrystals of Cu2O, respectively. When PEG-10000, PEG-20000 or PVP K-30 was added into the reaction system, a diffusion mechanism contributes to the formation of the single crystals of Cu2O, while aggregation mechanism prevails in the polycrystals of Cu2O with EG, PEG-200 or PEG-400. The pH of the mixture was also found to be a key factor in deciding the final products.