We highlight the recent developments in functional nanomaterials with unique enzyme-like characteristics for sensing applications.

Carbon dots (CDs) are a new class of luminescent carbon nanomaterials possessing small size, excellent water solubility, low toxicity, tunable light-emitting properties and good biocompatibility, which display bright prospects in catalysis, drug delivery, bioimaging, biosensing and energy conservation and storage. In the past several years, great achievements on the synthetic strategies, characterization techniques, unique optical properties and novel applications of a large variety of CDs have been realized. In this review, the brilliant optical properties of CDs-based nanomaterials via a series of spectroscopic techniques are summarized. After a brief introduction of the characteristic of CDs, we will focus on the optical properties of the CDs, including photoluminescence (PL), near-infrared (NIR) fluorescence, surface-enhanced Raman scattering (SERS), phosphorescence, chemiluminescence (CL), electrochemical luminescence (ECL), and chirality. The correlation between the structure of CDs and their optical properties has been discussed. In addition, some challenges and future prospects in the field of the optical properties of CDs have been highlighted. With the rapid development of their superior optical properties, it is anticipated that CDs will be applicable in a large number of research fields.