Tuning of emission from copper-doped ZnSe quantum dots

In this paper, different concentrations of copper-doped zinc selenide quantum dots (Cu:ZnSe QDs) were synthesized and compared with differently sized (2.0-3.7 nm) Cu:ZnSe QDs by keeping the concentration of Cu fixed at 5%. In both cases a high-temperature wet chemical route was employed for synthesis. As the concentration of Cu increased from 2.5% to 12.5% in the solution, a clear redshift was observed in the absorption spectrum, which is an indication that Cu ions have been incorporated into the host lattice. In order to identify the state in which the Cu ions are present, electron paramagnetic resonance (EPR) studies were carried out on the samples. The EPR spectra reveal a resonance signal which is characteristic of Cu2+ ions. With an increase in concentration of Cu ions it is found that the g(perpendicular to) component increases. Photoluminescence emission and excitation studies revealed both band-edge and Cu-related emission, further strengthening the incorporation of Cu ions in the host lattice.