The 13 nm gold nanoparticles(AuNPs)were synthesized through the reduction of HAuCl4 with sodium citrate,afterwards the para-aminobenzoic acid was assembled on the surface of AuNPs.Under a certain pH value,PABA-AuNPs was induced to aggregate by the addition of cartap,accompanied with the color of AuNPs solution changed from wine red to blue.Thus,a rapid detection method for cartap using PABA-AuNPs as colorimetric probe was proposed.The optimal experiment conditions were equilibrium time=5 min,pH=5.5.Under th...