Optical Properties and Fabrication of Cuprous Oxide Nanoparticles by Microemulsion Method

Well-crystallized cuprous oxide (Cu(2)O) nanoparticles were successfully fabricated using a microemulsion (ME) method. A solution containing copper (I) element for hydrolysis reaction in small water droplets was obtained using copper (I) acetate as the raw material with the appropriate addition of chelating agents (n-propylamine or benzylamine). A transparent yellowish suspension containing Cu(2)O nanoparticles (ME-Cu(2)O suspension) was prepared at room temperature, using cyclohexane or benzene as a hydrophobic solvent. The average sizes of the Cu(2)O nanoparticles obtained in this case were estimated to be 3.9 and 6.2 nm, respectively. Cu(2)O thin film (average size = 24.6 nm) and a hybrid composite of Cu(2)O nanoparticles with a polymer matrix (average size = 5.5 nm) were also prepared from a ME-Cu(2)O suspension. Optical absorption study revealed that direct band gaps of the Cu(2)O thin film (2.50 eV) and the hybrid composite (2.65 eV) were much greater than that of bulk Cu(2)O (2.17 eV), as a result of quantum size effect in Cu(2)O. The photoluminescence of the obtained Cu(2)O nanoparticles was measured at 12 K. The present study provides a new promising method to fabricate well-crystallized Cu(2)O nanoparticles of single nanometer sizes.