2,4-Dihydroxypyrimidine-5-carboxylic acid (Uracil-5-carboxylic acid) has been used for the visual sensing of melamine (at parts-per-billion (ppb) level) by a highly sensitive analytical method based on Au nanoparticles. It has been used to synthesize N1-alkylated uracil derivatives.Has been used for the visual sensing of melamine. 2,4-Dihydroxypyrimidine-5-carboxylic acid (Uracil-5-carboxylic acid) has been used for the visual sensing of melamine (at parts-per-billion (ppb) level) by a highly sensitive analytical method based on Au nanoparticles. It has been used to synthesize N1-alkylated uracil derivatives. Has been used for the visual sensing of melamine.