Carbon dots (CDs) are optically active carbon-based nanomaterials. These nanomaterials can change their light emission properties in response to various external stimuli such as pH, temperature, pressure, and light. The CD’s remarkable stimuli-responsive smart material properties have recently stimulated massive research interest for their exploitation to develop various sensor platforms. Herein, an effort has been made to review the major advances made on CDs, focusing mainly on its smart material attributes and linked applications. Since the CD’s material properties are largely linked to their synthesis approaches, various synthesis methods, including surface passivation and functionalization of CDs and the mechanisms reported so far in their photophysical properties, are also delineated in this review. Finally, the challenges of using CDs and the scope for their further improvement as an optical signal transducer to expand their application horizon for developing analytical platforms have been discussed.

The natural protein-based enzymes, despite their various advantages, possess some drawbacks that impede their commercial applications. These led to the introduction of artificial enzymes. Over the last few decades, different nanomaterials have been included in the list of artificial enzymes. With their high stability and low cost, nanomaterial-based artificial enzymes are emerging as potential candidates for enzyme mimics. So far, nanozymes have been mostly found to possess oxidase-like, peroxidase-like, catalase-like, and superoxide dismutase-like activity. These nanomaterials with enzyme-like activity have been explored for developing various processes and products in different fields. However, some challenges need to be addressed for improving the catalytic activity of the nanozymes for their practical applications.