Nguyen et al. (2026) synthesize nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs) from rice straw waste biomass as a precursor, and use these as a fluorescence-quenching probe for the selective detection of Hg2+ in water samples. The use of rice straw as a zero-waste, green synthesis precursor is highlighted as an environmental sustainability contribution.
Key numbers
Limit of detection (LOD): 0.148 mM (approximately 29.7 µg/L, or ~30 ppb) for Hg2+. This LOD is above the WHO drinking water guideline for mercury (6 µg/L) and significantly above food-matrix regulatory levels, making this approach a screening-level rather than compliance-level tool for water.
Validated in water matrices only. No food matrix validation.
Methods (brief)
N,S-CQDs synthesized hydrothermally from rice straw and a nitrogen/sulfur source. Fluorescence quenching mechanism in the presence of Hg2+. Simple synthesis route; green chemistry appeal. LOD of 0.148 mM (~30 ppb) is not competitive with ICP-MS for food or regulated water testing, but demonstrates the rice-straw-to-sensor concept.
Implications
Testing: The LOD is too high for most food or drinking-water regulatory applications. This paper is primarily a materials chemistry contribution rather than a method ready for food monitoring. Of note for the wiki’s synthesis of low-cost sensor approaches to Hg detection.