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. •A method for the determination of Fe2+ by 4-mercaptobenzoic acid (4-MBA) and 3,3',5,5'-tetramethylbenzidine (TMB) modified silver nanoparticles is developed;•The colorimetric sensing of Fe2+ has high sensitivity and selectivity;•The method is applied to the determination of Fe2+ in tap water and lake water.