Colorimetric detection of iron (II) using 4-mercaptobenzoic acid and 3,3′,5,5′-tetramethylbenzidine modified silver nanoparticles

In this work, a novel method for the colorimetric detection of iron (II) by using modified silver nanoparticles was developed. In the detection system, AgNPs were modified with 4-mercaptobenzoic acid (4-MBA) and 3,3′,5,5′-tetramethylbenzidine (TMB) to form 4-MBA-TMB-AgNPs. The presence of iron (II) caused the aggregation of 4-MBA-TMB-AgNPs through metal-ligand coordination, accompanied by solution color changing from gray-white to purple. Several factors including the ratio of the two modifiers and pH value were optimized. Under optimal conditions, this method showed a good linear from 1.00 × 10−6 M to 2.00 × 10−4 M with a correlation coefficient (R2) of 0.9966 and the detection limit was as low as 1.00 μM. The method has a great potential for the rapid detection of iron (II) in environmental samples. Particularly, this was successfully applied to the determination of the iron (II) in tap and lake water samples.