Green Synthesis of Nitrogen-Doped Carbon Dots from Cassava Pulp for Formalin Detection

Cassava (Manihot esculenta) is an agricultural plant produced in a high amount. It’s processing for flour leads to excessive amounts of waste, such as inedible pulps, to be left over, which can be difficult to dispose of. Advantageously, cassava pulps are rich in carbon, being comprised of over 56% starch. In this study, cassava pulp was used to create nitrogen-doped carbon dots (N-CDs) through hydrothermal carbonization. These N-CDs were employed as sensors to detect formalin using a silver mirror reaction. When formaldehyde (FA) was added, it caused fluorescence quenching and a significant color change, with an absorbance peak at 406 nm, due to the formation of silver nanoparticles. Using UV-Vis absorption and fluorescence spectroscopy, N-CDs in the presence of Ag⁺ and Tollen’s reagent demonstrated remarkable sensitivity for FA with detection limits of 96.5 µg/L and 83.6 µg/L, respectively. Additionally, N-CDs showed good selectivity for FA compared to other analytes. It was shown that N-CDs derived from cassava pulp have the potential to be an effective and environmentally friendly FA detection method.