Carbon nanodots: Synthesis, characterization, and bioanalytical applications

Abstract

Carbon dots (CDs) are a new class of carbon-rich nanoparticles with exciting physicochemical properties that make them an interesting material for bioanalytical applications. Since their first description in 2004, several preparation techniques have been developed and described in literature, either starting from carbon raw materials (e.g., soot, graphite) or molecular precursors (e.g., carbohydrates, citric acid). The resulting particles are typically only a few nanometers in size, and their surfaces are decorated with functional groups that are rich in oxygen. The presence of oxygenated functionalities on the surface renders the particles dispersible in water. Carbon dots contain a fraction of carbon atoms that are sp2 hybridized with delocalized electrons on the surface – the basis for the particles’ characteristic photoluminescence. The wavelength of the emitted light is dependent on the wavelength of the excitation source and shows remarkable photostability. Carbon dots are also readily excited in the NIR but still emit visible light (upconverted photoluminescence) which provides significant advantages for in vivo imaging. Nowadays CDs are considered as emerging tools in luminescence-based bioanalytics with their full potential yet to be discovered.