Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Near-Infrared Emitting Dual-Stimuli-Responsive Carbon Dots from Endogenous Bile Pigments



Parinaz Fathi, Parikshit Moitra, Madeleine M. McDonald, Mandy Esch, Dipanjan Pan


Careful selection of carbon dot precursors and surface modification techniques has allowed for the development of carbon dots with strong near-infrared fluorescence emission. However, the rational selection of tetrapyrrolic carbon dot precursors to obtain stimuli-responsive behavior in addition to strong fluorescence contrast is unexplored. In this work, the first synthesis of carbon nanoparticles derived from endogenous bile pigments bilirubin (BR-CDots) and biliverdin (BV-CDots), which lends them with enzymatically and photolytically switchable spectroscopic characteristics, is reported. Water-dispersible carbon dots with strong fluorescent contrast are obtained without the need for surface modifications post-synthesis. Interestingly, BV- and BR-CDots retain their stimuli-responsive behaviors intrinsic to their precursors post- synthesis. After exposure to bilirubin oxidase or UV irradiation, BR-CDots shift their UV and fluorescence characteristics to be more similar tolike that of BV-CDots. Similarly, after exposure to biliverdin reductase, BV-CDots shift their UV and fluorescence spectral characteristics to be like more silimiar to that of BR-CDots. BR-CDots are additionally found to provide strong near-infrared fluorescence contrast and high biocompatibility. This work demonstrates the use of rationally selected carbon sources for obtaining near-infrared fluorescence and stimuli-responsive switching behavior in carbon dots.


Fathi, P. , Moitra, P. , McDonald, M. , Esch, M. and Pan, D. (2021), Near-Infrared Emitting Dual-Stimuli-Responsive Carbon Dots from Endogenous Bile Pigments, Nanoscale, [online],, (Accessed May 25, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 12, 2021, Updated October 14, 2021