Green synthesis of gold nanoparticles using Sargassum carpophyllum extract and its application in visual detection of melamine

Small-sized gold nanoparticles (AuNPs) were prepared in the extract of Sargassum carpophyllum which had protective and reductive effects. The method is green, clean, and simple. The Gold nanoparticles prepared by using Sargassum carpophyllum extract (SAuNPs) have good biocompatibility and are suitable for biosensors, tumor hyperthermia and food safety testing. The aim of this work is to explore a green way to prepare the wine red nanoparticles without any adapters and to detect melamine (Mel) visually in real milk samples. The precursor of AuNPs used was HAuCl4. In the visual detection of melamine, the results showed that the color of SAuNPs changed from wine red to purple and then to blue black with the increase of melamine concentration. Meanwhile, UV–vis analysis showed that when the concentration of melamine was in the range of 1.8–2.6 μM, the absorbance ratio (A650/A520) was positively correlated with the concentration of melamine (R2 = 0.998), and the detection limit was 1.82 μM. This method has been successfully applied to the determination of Mel in milk samples with satisfactory results.