Domestic pressure cooker as inexpensive hydrothermal vessel: Demonstrated utility for eco-friendly synthesis of non-toxic carbon dots

We report on a simple and eco-friendly approach that employs a domestic pressure cooker as an inexpensive hydrothermal reactor for the batch synthesis of water-soluble, photoluminescent nanoscale carbon dots derived from benign and cheap commercial starting materials. The resulting carbon nanodots, which consist primarily of hydrophile-decorated amorphous carbon and boast bright, stable, excitation wavelength-dependent fluorescence, were shown to be viable cellular imaging agents for mice embryonic fibroblast cells, displaying little or no cytotoxicity for carbon dot concentrations up to 0.667 mg/mL. In addition, the carbon dots proved useful as nanoprobes for the fluorescence-based detection of environmentally-relevant heavy metal ions such as Cu2+, displaying detection limits below 6μM, sufficient to determine potable water safety (20μM is the limit for safe drinking water set by the U.S. Environmental Protection Agency). More generally, these results highlight the utility of a household pressure cooker as a cost-effective hydrothermal vessel relevant to nanocarbon synthesis, opening up other possibilities for nanosynthesis, particularly in resource-limited settings, educational venues, and the classroom itself.