The effect of annealing on band gap and optical properties of CdS/CdS-TiO 2 nanoparticles

In this paper, we studied the effect of annealing of CdS nanoparticles that were prepared using chemical precipitation technique. The synthesized material were characterized using TEM and it was found the size of the CdS nanoparticles were ∼5 nm. The prepared nanoparticles were annealed using hot air oven at 120°C and microwave oven at 900 W for different amount of time in order to check the effect of annealing. It was found that the annealing of the nanoparticles has increased the optical absorbance and reduced the band gap of the material. Interestingly, microwave annealing enhanced the optical absorbance compared to the annealing using oven and the band gap of the material was found to be less in case of 60s microwave assisted annealing compared to the 3 hr hot-air oven treatment. Moreover, the time requirement for microwave annealing was significantly less than that of hot air oven annealing for obtaining similar optical characteristics. The study was also performed for CdS-TiO 2 nanocomposites and a similar trend in band gap reduction was observed. This study of annealing will be helpful in tuning the band gap of the CdS and CdS-TiO 2 nanocomposites for different optoelectronic applications.