Synthesis of CdS-Fe₃O₄ magnetic nanoparticle for organic catalysis

Abstract

This research focuses on developing CdS quantum dots (CdS QDs) with superparamagnetic property to be used as a heterogeneous photocatalyst in thioacid-mediated amide formation and exploring the most suitable means to synthesize CdS magnetic quantum dots (CdS MQDs) with high photocatalytic activity. CdS QDs were synthesized using hydrothermal method and various CdS MQDs were obtained, but only two types of CdS MQDs were well characterized and tested, namely CdS-Fe₃O₄ MQDs and CdS-SiO₂/Fe₃O₄ MQDs. These two types of MQDs were synthesized by growing CdS QDs on the surface of the preformed magnetic nanoparticles using hydrothermal method. TEM was used to study the morphology of CdS QDs and CdS-Fe₃O₄ MQDs, and the results showed that CdS-Fe₃O₄ MQDs formed a nanonetwork structure instead of the expected core-shell structures. UV/vis spectroscopy and fluorescence spectroscopy were used to study their optical properties. CdS-Fe₃O₄ MQDs showed low fluorescence intensity when excited with 440 nm light; on the other hand, CdS-SiO₂/Fe₃O₄ MQDs still retain high fluorescence, almost identical to bare CdS QDs. When used as a photocatalyst in the reaction between Potassium thioacetate and p-anisidine, CdS-Fe₃O₄ and CdS QDs cannot be compared together due to the difference in catalyst amount. However, CdS-SiO₂/Fe₃O₄ MQDs gave higher quantity of product compared to the bare CdS QDs, 70% and 24% respectively, when present in the reaction in low quantity (0.07 wt%). The results showed that with some more experiments, these methods could be used to synthesize CdS magnetic quantum dots with photocatalytic property.