Carbon nanodots (also called carbon quantum dots) are a topic I have talked about before. They are tiny particles of carbon, often less that five nanometers in diameter, with some form of protective layer galvanising the particles to prevent any chemical reaction. They have many desirable properties that make them worthy of development: biocompatible, non toxic, mild fluorescence, immune to light bleaching and can be easily dispersed in a solvent. But the important property today of these dots is that they very poorly absorb large wavelength electromagnetic radiation, only developing a very weak absorption band.
This is easily their primary limitation. Only being able to apply their optical properties over the blue and ultraviolet regions of the spectrum. By reacting normal carbon nanodots with citric acid at 160°C and then freeze drying the products led to a new variety of nanodots which were shown to have incredible absorption characteristics in the visible and infra red regions. It is theorised that the reaction alters the function group surrounding the dot giving it the different quality or perhaps a gained surface charge. Either way these new carbon nanodots could easily be used in medical scans now that high energy electromagnetic radiation is not needed to produce an energy spectrum.