Structural and optical characterization of Ni-doped CdS quantum dots

Ni-doped CdS quantum dots have been prepared by chemical precipitation technique. The X-diffraction results indicated that the particle size of Ni-doped CdS nanoparticles is smaller than that of undoped CdS and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.7-4 nm. The compositional analysis results show that Cd, Ni, and S are present in the samples. HRTEM studies reveal that the average particle size of undoped and Ni-doped CdS quantum dots is 2 and 3 nm, respectively. Raman spectra shows that 1LO, 2LO, and 3LO peaks of the Ni-doped CdS samples are slightly red shifted when compared to that of undoped CdS. The absorption edge of Ni-doped CdS nanoparticles is found to shift towards the higher-wavelength (red shift) side when compared to that of undoped CdS and the band gap is observed to lie in the range of 3.79-3.95 eV. This band gap is higher than that of the bulk CdS and is due to quantum confinement effect present in CdS nanoparticles.