Synthesis and study of fluorescence properties of Cu nanoparticles

Cu nanoparticles have been synthesized by employing a novel electro-exploding wire (EEW) technique. These nanoparticles exist in the face-centred cubic (fcc) phase and their size is ∼6 nm. Further, the nanoparticles are characterized by disappearance of plasmons and show distinct resonant absorption at ∼222, 244, 280, 336 nm. A fluorescence peak at ∼296 nm has been observed at excitation wavelength in the ranges 200–240 and 250–280 nm. Position of the fluorescence peak remains fixed irrespective of the excitation wavelength used. Further, with increase in the concentration of the Cu nanoparticles in the range 0.5 × 10¹⁷–6.45 × 10¹⁸ atoms/cc, the intensity of the fluorescence peak, at ∼296 nm, increases. In concomitant with these, resonant absorptions are observed at ∼213 and ∼269 nm, evident from the fluorescence excitation spectrum which allows us to give a description of the electronic levels operating in this system. Fluorescence emission of the Cu nanoparticles is attributed to electronic transitions from excited states to 3d levels.