Sub-10-nm multicolored gold nanoparticles for colorimetric determination of antibiotics via formation of interlocking rings

A general approach is presented for synthesis of multicolored gold nanoparticles (GNPs) by Au(I)-mediated generation of interlocking rings in proteins and antibiotics. The Au(I) ions are shuttled from proteins to antibiotics, and this causes the formation of interlocking rings. The multicolored GNPs of different sizes were synthesized in the rings by using the rapid nucleation method. To take the unique colors of GNPs, a functional array was designed for the colorimetric determination and discrimination of antibiotics, specifically of amoxicillin, chlortetracycline, erythromycin, spiramycin, neomycin, thiamphenicol, gentamycin and lincomycin. The method is based on the “three color” (RGB) principle. The color response patterns are characteristic for each antibiotic and can be quantitatively differentiated by statistical techniques. The limits of detection (LOD, at S/N = 3) for spiramycin (Sp) have been calculated to be 0.18 μM and 0.10 μM in water and milk, respectively. The good linear range (from 0.3 to 3.5 μM) has been used for the quantitative assay of Sp in a certified reference material.