NUS Engineers have developed a cost-effective and scalable strategy for designing tiny semiconductor particles known as transition metal dichalcogenide quantum dots (TMD QDs) which can potentially generate cancer-killing properties. The team is also looking to optimize TMD QDs for applications such as the next generation TV and electronic device screens, advanced electronics components and even solar cells.
Current synthesis of TMD nano materials rely on a top-down approach where TMD mineral ores are collected and broken down from millimetre to nanometre scale via physical or chemical means. This method, while effective in synthesizing TMD nano materials with precision, is low in scalability and costly as separating the fragments of nano materials by size requires multiple purification processes. Using the same method to produce TMD QDs of a consistent size is also extremely difficult due to their minute size.
To overcome this challenge, a team of engineers from the Department of Chemical and Biomolecular Engineering at NUS Faculty of Engineering developed a novel bottom-up synthesis strategy that can consistently construct TMD QDs of a specific size, a cheaper and more scalable method than the conventional top-down approach. The TMD QDs are synthesized by reacting transition metal oxides or chlorides with chalogen precursors under mild aqueous and room temperature conditions. Using the bottom-up approach, the team successfully synthesized a small library of seven TMD QDs and were able to alter their electronic and optical properties accordingly.
The team of NUS engineers then synthesized MoS2 QDs to demonstrate proof-of-concept biomedical applications. Through their experiments, the team showed that the defect properties of MoS2 QDs can be engineered with precision using the bottom-up approach to generate varying levels of oxidative stress, and can therefore be used for photo-dynamic therapy, an emerging cancer therapy.
Photo-dynamic therapy currently utilises photosensitive organic compounds that produce oxidative stress to kill cancer cells. These organic compounds can remain in the body for a few days and patients receiving this kind of photo-dynamic therapy are advised against unnecessary exposure to bright light. TMD QDs such as MoS2 QDs may offer a safer alternative to these organic compounds as some transition metals like Mo are themselves essential minerals and can be quickly metabolized after the photo-dynamic treatment.
The potential of TMD QDs, however, goes far beyond just biomedical applications. Moving forward, the team is working on expanding its library of TMD QDs using the bottom-up strategy, and to optimise them for other applications such as the next generation TV and electronic device screens, advanced electronics components and even solar cells.