Building Transition Metal Quantum Dots From The Bottom Up

Engineers at NUS have developed a strategy for designing quantum dots that could be used in cancer therapy as well as next-generation television screens.

AsianScientist (Jan. 31, 2019) – A research group at the National University of Singapore (NUS) has developed quantum dots made of nanomaterials structurally resembling graphene. They published their findings in the journal Nature Communications.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) nanomaterials such as molybdenite (MoS2), which possess a similar structure as graphene. TMDs have a wide range of potential applications in biomedicine, sensors, catalysts, photodetectors and energy storage devices. TMD quantum dots (QDs) further accentuate the optical and electronic properties of TMDs and are highly exploitable for catalytic and biomedical applications. However, TMD QDs are hardly used because of the difficulty of manufacturing them.

In the present study, engineers from the NUS developed a cost-effective and scalable strategy to synthesize TMD QDs. Taking a bottom-up approach, the researchers reacted transition metal oxides (such as MoS2) or chlorides with precursors from group 16 of the periodic table, or chalogens, under mild aqueous and room temperature conditions. They successfully synthesized a small library of seven TMD QDs and were able to alter their electronic and optical properties accordingly.

“Using the bottom-up approach to synthesize TMD QDs is like constructing a building from scratch using concrete, steel and glass component; it gives us full control over the design and features of the building,” said Associate Professor David Leong of NUS who led the study.

“Similarly, this bottom-up approach allows us to vary the ratio of transition metal ions and chalcogen ions in the reaction to synthesize the TMD QDs with the properties we desire. In addition, through our bottom-up approach, we are able to synthesize new TMD QDs that are not found naturally. They may have new properties that can lead to newer applications,” he added.

The researchers explained that their TMD QDs can generate varying levels of oxidative stress, and can therefore be used for photodynamic therapy, an emerging cancer therapy.

Photodynamic therapy currently utilizes 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 photodynamic 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 photodynamic treatment. We will conduct further tests to verify this,” said Leong.

The potential of TMD QDs, however, goes beyond just biomedical applications. Moving forward, the team is working on expanding its library of TMD QDs and optimize them for other applications such as next-generation television and electronic device screens, advanced electronics components and solar cells.


The article can be found at: Ding et al. (2019) Defect Engineered Bioactive Transition Metals Dichalcogenides Quantum Dots.

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Source: National University of Singapore; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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