Determination of Lead (II) Concentration Using Iminodiacetic Acid-Modified Silver Nanoparticles by Highly Sensitive SERS Technique

A system for the highly sensitive detection of Pb2+ ions by surface-enhanced Raman scattering (SERS) was designed based on silver nanoparticles (AgNPs) capped with iminodiacetic acid (IDA)/4-mercaptopyridine (4-MPY). In this system, IDA was absorbed on the surface of the AgNPs to induce the coupling of Pb2+ ions for aggregation in the aqueous solution. 4-MPY, which was also attached to the surface of the AgNPs, was used as a Raman reporter. When the concentration of Pb2+ ions increased, a stronger 4-MPY Raman signal was detected. The IDA and 4-MPY concentrations were adjusted to maximize the 4-MPY Raman signal. Under this optimal condition, the concentration of Pb2+ ions had a linear relationship with 4-MPY Raman signal in the range of 1 x 108 to 2 x 106 mol/L (R = 0: 9953). The limit of detection (LOD) of 1.816 nmol/L was obtained, which is significantly lower than the World Health Organization's (WHO) defined limit of 100 mu g/L in drinking water. This system was successfully applied to determine the Pb2+ concentration in a contaminated water sample, which is obtained by adding a trace of Pb2+ ions to drinking mineral water. The results proved that the IDA/4-MPY-modified AgNPs sensing system had a potential application for the Pb2+ measurement with high sensitivity and excellent selectivity.