Visible and fluorescent detection of melamine in raw milk with one-step synthesized silver nanoparticles using carbon dots as the reductant and stabilizer

- Visible and fluorescent detection is developed for melamine detection in raw milk.
- One-step melamine detection is label free and rapid without tedious operation.
- Silver nanoparticles are synthesized using carbon dots as reductant and stabilizer.
- The strategy shows high sensitivity and selectivity for detection of melamine.

Using carbon dots as the reductant and stabilizer, a visible and fluorescent method was developed for melamine detection in raw milk with one-step synthesized silver nanoparticles. In this work, carbon dots (C-dots) were applied to reduce silver ions and stabilize the nanoparticles, resulting in the formation of silver nanoparticles (AgNPs). As a result, the inherent fluorescence emission of C-dots was significantly reduced after the formation of AgNPs. However, in the presence of melamine, silver ions could interact with the nitrogen atoms in amine and triazine groups of melamine. With 0-2 μM melamine, aggregated AgNPs were found after the reduction by C-dots, resulting in color and absorbance changes. With further increase of melamine (2-20 μM), both formation and aggregation of AgNPs were inhibited, and the fluorescence was gradually increased. This optical platform was optimized for melamine detection and then was applied to detecting melamine in raw milk samples. The results for melamine assay based on visible and fluorescent method showed the requisite sensitivity with a low detection limit of 30 nM, as well as high selectivity.

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