The Function of Nano-polystyrene Template and Comb Polycarboxylic Acid Surfactant in Synthesis of ZnS Nanoparticles via Hydrothermal Method

Raspberry-like ZnS nanoparticles were synthesized by hydrothermal method. ZnS particle size varies by controlling the amount of comb polycarboxylic acid surfactant and polystyrene (PS) template. The products were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy, and Fourier transformed infrared spectroscopy. Optical properties were investigated via UV-vis and photoluminescence spectrophotometry. All samples consisted of ZnS cubic phase (sphalerite). The XRD patterns showed that surfactant has a vital effect on crystallite size reduction. In contrast, PS template enhanced the growth rate of ZnS nano- particles. Studies on morphology and particle size showed that increasing the amount of surfactant content causes the ZnS particle size to decrease to nanometric range. Although particle size increased by deposition of ZnS nanoparticles on the surface of PS template, the uniformity of the particles increased considerably. A narrow range of particle size distribution (110-150 nm) was shown in the sample synthesized in the presence of both surfactant (2.2 g/L) and PS template (1 cc of 2.7% w/v). The blue shift of absorption edge in UV-vis spectra with an increase in surfactant content demonstrated the quantum confinement effect of ZnS nanoparticles. The obtained ZnS nanoparticles displayed blue emission peaks at 400 and 425 nm. Furthermore, a schematic model is proposed illustrating ZnS formation on the surface of PS template in the presence of the anionic surfactant.