Synthesis of zinc sulfide nanoparticles using microemulsion generated by hydrodynamic cavitation method

Abstract

Zinc Sulfite (ZnS) nanoparticles have attracted attention of researchers as a promising material for semiconductor fabrication. Their optical properties are strongly size-dependent and related to production methodology. A microemulsion technique is simple and requires less energy to produce ZnS nanoparticles. However, this technique usually results in ZnS with a wide size distribution. In this work, microemulsion technique and hydrodynamic cavitation have been effectively combined for synthesis of ZnS nanoparticles with controllable and uniform size distribution. The microemulsion system which consists of water, cyclohexane, hexanol and Triton X-100 surfactant has been prepared by incorporating hydrodynamic cavitation. Experimental results number of passages, cavitation number (Cv) and water to surfactant molar ratio (W0) exert significant effects on rheological properties and size distribution of microemulsion. Increasing number of passages from 300 to 1,500 passages could decrease average size of microemulsion due to higher breakage frequency, as number of passes represents energy dissipation in the system. Higher Cv led to reduction in microemulsion size, which was derived from high intensity turbulence, as confirmed by CFD modeling. Investigation on role of W0 on density, viscosity and surface tension of microemulsions revealed that all properties significantly increased with higher water content. Moreover, average size also increased and size distribution of microemulsion became broader. Difference in microemulsion size would be achieved by adjusting Cv and W0, resulting in growth of ZnS nanoparticles with different size inside reverse micelles. Based on HRTEM analyses, the obtained ZnS nanoparticles exhibited spheroidal morphology and the smallest average size could be achieved at Cv of 1.8 and W0 of 7. XRD analysis confirmed the successful formation of ZnS with cubic crystalline configuration. In summary, microemulsion method enhanced by hydrodynamic cavitation exhibits its potential in synthesis of ZnS nanoparticles with controllable size and narrow size distribution, which could be promising material in many applications.