Detection of trace mercury ions in water with a bovine-serum-albumin-modified Au@SiNWA surface-enhanced-Raman-scattering sensor

Abstract

Accurate detection of mercury ions (Hg²⁺) in water is of great importance for environmental protection. Here, a surface-enhanced Raman scattering (SERS) sensor using bovine-serum-albumin-modified gold-silicon nanowire arrays (Au@SiNWAs) is used to detect the ions. The SiNWAs were grown via chemical etching; the addition of modified gold particles on the surface formed Au@SiNWAs to increase the surface activity. The Raman enhancement factor was as large as ∼2.52 × 10⁵, which was also confirmed with finite-difference time-domain simulations. The detection limit for Hg²⁺ ions in water was as low as ∼10⁻¹² M, which is much lower than that stipulated by the United States Environmental Protection Agency's maximum residue requirements for drinking water. Furthermore, the SERS intensity was linear with the log of the Hg²⁺ concentration between 1 pM and 100 nM, with a correlation coefficient of 0.992. There was no significant interference when other metal ions were present, which shows the excellent selectivity of the SERS sensor. Unknown Hg²⁺ concentrations in water can be readily determined in an accurate and reliable manner, with a relative standard deviation of ∼9.21%.