Solvothermal synthesis of copper cadmium sulphide (CuCdS2) nanoparticles and its structural, optical and morphological properties

Copper cadmium sulphide (CuCdS2) nanoparticles via solvothermal syntheses in ethylene glycol (EG) optimized with different reaction times at a constant temperature of 180 degrees C. The optimized reaction time was adopted to syntheses CuCdS2 particles with oleic acid (OLA) and water (WT). X-ray diffraction patterns confirmed that, all the synthesized CuCdS2 nanoparticles possessed hexagonal structure despite the use of different solvents, however, the high intensity plane was found to be varied. Crystallinity of the nanoparticles was improved with reaction time and the calculated crystallite size increased from 12 to 27 nm. The estimated crystallite sizes of CuCdS2 nanoparticles synthesized with OLA and WT were higher than EG mediated synthesis. Raman analyses confirmed the vibrational modes attributed to the CuCdS2 nanoparticles. UV-visible absorption spectra showed that the nanoparticles had a wide range of absorption up to mid-visible region. Absorption enhancement in the near infrared region is ascribed to localized surface plasmon resonance. Band gap values of the synthesized nanoparticles found to be reduced from 2.05 eV to 1.87 eV as the gradual incorporation of copper. Photoluminescence spectra exhibit emissions in blue and green bands which confirmed the presence of defects in CuCdS2 nanoparticles. Electron microscopy images revealed that morphologies of the nanoparticles are modified into nanorods from spherical shape. In addition, improvement in the crystallinity was further confirmed using selected area diffraction pattern. Passivation by OLA lead the nanoparticles to attain plate like morphology, however, WT nanoparticles had diverse morphology. The growth process was slower in EG than OLA and WT which lead to orient in low surface energy plane. The plausible mechanism involved in the formation and evolution of CuCdS2 nanoparticles is discussed.