Aqueous synthesis and characterization of CdS, CdS:Zn2+ and CdS:Cu2+ quantum dots

CdS quantum dots of different sizes ∼3–5 nm were prepared using aqueous solutions of CdSO4 and Na2S2O3 at 303 K with thioglycerol as stabilizing agent and catalyst. The broad X-ray diffraction pattern and SAED pattern with bright circular spots and clear lattice fringes in the high-resolution TEM image indicate cubic phase of the nanocrystals. Band gap changes from the bulk value of 2.4 to 3.16 eV in the nanoparticles indicating quantum size effect. The photoluminescence (PL) spectrum is blue-shifted to 528 nm. The PL emission band is blue/red-shifted on doping with Zn2+/Cu2+. In the case of Cu2+, the PL intensity is found to be maximum at 10 wt% doping and almost completely quenched at 15 wt% doping. On doping with Zn2+, the intensity and blue-shift of PL are found to be maximum at 2 and 6 wt% doping, respectively.