CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids

Cupric oxide (CuO) nanoparticles with an average size of 6 nm have been successfully prepared by an alcothermal method. The prepared CuO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) and UV-visible absorption spectroscopy. A strong sharp emission under UV excitation is reported from the prepared CuO nanoparticles. The results show that the CuO nanoparticles have high dispersion and narrow size distribution. The fluorescence emission spectra display an intense sharp emission at 365 nm and weak broad intensity emission at 470 nm. Picosecond fluorescence measurements of the nanoparticles suggest bi-exponential function giving time constants of τ1 (330 ps, 94.21%) and τ2 (4.69 ns, 5.79%). In neutral and alkaline solutions, Zeta potential values of CuO nanoparticles are negative, due to the adsorption of COO- group via the coordination of bidentate. At low pH the zeta potential value is positive due to the increased potential of H+ ions in solution. Comparative UV-visible absorption experiments with the model amino acid compounds of positive and negative charges as arginine and aspartic acid, respectively confirmed the negative surface of CuO nanoparticles. The results should be extremely useful for understanding the mode of the interaction with biological systems. This binding process also affects the particle's behavior inside the body.