石墨烯在可穿戴设备上的应用

Graphene coated with nanoparticles has been used to make wearable light sensors that measure the human pulse and blood oxygen levels from ambient light passing through tissue, offering a potential platform for health-care monitoring.

No.1

What they have do?

Polat et al. depositing light-sensitive quantum dots made of the semiconductor lead(ii) sulfide (PbS) onto the graphene layer. When illuminated, the quantum dots generate pairs of charged particles: negatively charged electrons and positively charged holes (quasiparticles associated with the absence of an electron in an atomic lattice). The electrons stay trapped in the quantum dots, but the holes are transferred into the graphene layer and increase its electrical conductivity, producing a measurable electrical signal. The authors used this behaviour to construct light sensors from the quantum-dot-coated graphene.

The researchers observed that the responsivity (the electrical output per optical input) of their devices was remarkably large. The high responsivity is attributable to the fact that the holes in the graphene layer are recycled by the quantum dots, effectively increasing the number of charge carriers generated per absorbed photon in the devices — the devices are said to exhibit a photoconductive gain.

——Polat, E. O. et al. Sci. Adv. 5, eaaw7846 (2019).

No.2

Supplementary

The effectiveness of the most common wearable devices is hindered by the physical specifications of their components: although the device is often embedded in a flexible soft shell, the main parts, such as the sensors and electronics, are still rigid. Now, writing in Science Advances, Polat et al. report a class of truly flexible, transparent wearable device that is based on graphene covered with a layer of semiconducting nanoparticles known as quantum dots. Impressively, the devices measure various vital signs using only ambient light as a signal.