Three birds, one stone: Disinfecting and turning waste medical masks into valuable carbon dots for sodium hydrosulfite and Fe3+ detection enabled by a simple hydrothermal treatment

Disposable medical masks are widely used to prevent respiratory infections due to their ability to block virus particles from entering the human body. The coronavirus disease 2019 (COVID-19) pandemic highlighted the importance of medical masks, leading to their widespread use around the world. However, a large number of disposable medical masks have been discarded, some carrying viruses, which have posed a grave threat to the environment and people's health, as well as wasting resources. In this study, a simple hydrothermal method was used for the disinfection of waste medical masks under high-temperature conditions as well as for their transformation into high-value-added carbon dots (CDs, a new type of carbon nanomaterial) with blue-emissive fluorescence, without high energy consumption or environmental pollution. Moreover, the mask-derived CDs (m-CDs) could not only be used as fluorescent probes for sensing sodium hydrosulfite (Na 2 S 2 O 4 ), which is widely used in the food and textile industries but is seriously harmful to human health, but also be used for detecting Fe 3+ which is harmful to the environment and human health due to its wide use in industries.