Determination of mercury(ii) ions in aqueous solution using silver nanorods as a probe

Abstract

We report here the selective and sensitive determination of Hg²⁺ in aqueous solution using the aggregation and re-aggregation of silver nanorods (SNRs) in the presence of dithiothreitol (DTT). The SNRs covalently bound with the thiol groups at the ends of the DTT molecule, leading to the aggregation of the SNRs. However, the aggregation of the SNRs was prevented by the addition of Hg²⁺. The thiol group of DTT has a strong binding affinity with Hg²⁺ that helps to prevent the aggregation of SNRs. UV-visible spectrophotometry and transmission electron microscopy confirmed the aggregation and re-aggregation of SNRs with DTT and Hg²⁺. The absorption ratio (A/A₀) of the SNRs at λ₅₈₅ nm decreased after reaction with DTT and increased with the addition of Hg²⁺. The changes in the absorption ratio of the SNRs at λ₅₈₅ was directly proportional to the concentration of Hg²⁺ in the range 1–100 pM. The developed method had good linearity (y = 0.001x + 0.899; R² = 0.968) under the optimized conditions with a limit of detection of 0.15 pM. The method was validated in real samples such as tap and lake water and could be used for the environmental sensing of Hg²⁺.