graphene coated with nanoparticles has been utilized to develop wearable light sensors capable of monitoring the human pulse and blood oxygen levels by detecting ambient light that passes through tissue. this technology presents a promising foundation for health-care monitoring systems.
No.1
What they have done?
Polat and colleagues have coated graphene with light-sensitive quantum dots composed of the semiconductor lead(ii) sulfide (PbS). When these quantum dots are exposed to light, they produce pairs of charged particles, including negatively charged electrons and positively charged holes (quasiparticles indicating the absence of an electron in an atomic lattice). While the electrons remain confined within the quantum dots, the holes migrate to the graphene layer, enhancing its electrical conductivity and generating a detectable electrical signal. Utilizing this mechanism, the researchers have developed light sensors using the quantum-dot-coated graphene.
They noted that the responsivity of these devices, which measures the electrical output relative to the optical input, was significantly high. This high responsivity results from the recycling of holes in the graphene layer by the quantum dots, which effectively amplifies the number of charge carriers produced per absorbed photon, leading to what is known as photoconductive gain in the devices.
——Polat, E. O. et al. Sci. Adv. 5, eaaw7846 (2019).
No.2
Supplementary
The functionality of typical wearable devices is often limited by the rigidity of their core components, such as sensors and electronics, despite being encased in flexible materials. In a breakthrough reported in Science Advances, Polat et al. introduce a new type of fully flexible and transparent wearable device. This device utilizes graphene layered with semiconducting nanoparticles called quantum dots, and remarkably, it can measure vital signs solely by using ambient light as its signal source.
