Carbon Dots: A Modular Activity to Teach Fluorescence and Nanotechnology at Multiple Levels.

In recent years, nanomaterials have entered our daily lives via consumer products; thus, it has become increasingly important to implement activities to introduce these novel materials into chemistry curricula. Here we introduce a newly developed fluorescent nanomaterial, carbon dots, as a more environmentally friendly alternative to heavy-metal semiconductor quantum dots to be used as a model nanomaterial for experiments at multiple educational levels ranging from high school to upper-division college laboratories. These dots, which are polymeric in nature, can be made from a variety of carbon precursors and a cross-linker such as ethylenediamine. The synthesis, which involves heating in a conventional microwave, is quick and straightforward and can be carried out in typical high school chemistry laboratories. The resulting solution is fluorescent without further purification. To increase the complexity for entry-level college students, absorption and emission spectra of the carbon dot solution can be collected as an introduction to spectroscopy. In more advanced undergraduate lab courses, the quantum yield can be determined with a standard reference fluorescent material such as quinine sulfate. Atomic force microscopy or transmission electron microscopy images can also be collected to illustrate the morphology of these particles where such specialty instruments are accessible.