Surface Oxidation of Cu(2)O Nanoparticles by Adsorbed Ammonia

Copper-based nanoparticles have been intensively studied owing to their superior antibacterial activity. In this study, cuprous oxide (Cu(2)O) nanoparticles were synthesized using two different methods. In particular, two methods for synthesizing copper oxide from NaOH, namely, with and without the addition of NH(3), were used to adjust the morphology of the nanoparticles. The nanoparticles from the NH(3) and NaOH samples possessed an octahedral morphology. The crystal structure of the samples was confirmed by X-ray diffraction. The size distribution of the NH(3) sample was narrower than that of the NaOH sample. Furthermore, the average size of the NH(3) sample was smaller than that of the NaOH sample. Unexpectedly, the antibacterial activity of the NH(3) sample was found to be lower than that of the NaOH sample. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy revealed that the adsorbed NH(3) caused the surface oxidation of Cu(2)O nanoparticles with azide (N(3)) formation on surface.