Zero-Dimensional Quantum Materials for the Next Generation of Highly-Selective Chemical Sensors

Summary

Heavy metals are a major public health concern and their on-site detection in water supplies is not well served by existing lab techniques. We develop a new multi-modal platform comprising functionalized quantum dots of two-dimensional materials (2D-QDs) for the sensing of four highly-toxic heavy metal pollutants (arsenic, cadmium, lead and mercury). The zero-dimensional nature of quantum dots brings essential properties necessary for fluorescence-based chemical sensing of heavy metals in the field. We focus on one type of 2D material, molybdenum disulfide (MoS₂), which is a direct band gap semiconductor when produced as a monolayer. To fabricate and functionalize the 2D-QDs, we expose flakes of MoS₂ suspended in a solution to a pulsed laser. This technique allows us to simultaneously functionalize the 2D-QDs, so that they become sensitive to a specific pollutant metal, and control their fluorescence wavelength, so that 2D-QDs functionalized for different target metals will produce distinguishable optical signals. By combining multiple types of functionalized 2D-QDs into a single solution capable of simultaneously identifying various heavy metals, we expect to advance a range of applications that require a field-deployable solution. These include for example, rapid contaminant point source identification, and water analysis of heavy metals in developing countries where conventional equipment is too costly.

Figure 1. Functionalized quantum dots of a 2D material are being developed for fluorescence-based chemical sensing of toxic heavy metal pollutants.