Gold nanorods enhanced resonance Rayleigh scattering for detection of Hg2+ by in-situ mixing with single-stranded DNA

Abstract

A resonance Rayleigh scattering (RRS) method for determination of Hg2+ concentration using positively charged gold nanorods (GNRs) and thymine-rich single-stranded DNA (ssDNA) was developed. Hg2+ can induce a conformation change of ssDNA from a random coil to a hairpin structure via thymine–Hg2+–thymine coordination. Hairpin shaped DNA possesses a high density of negative charges, therefore it caused in a drastic aggregation of GNRs. This resulted in an enhancement of RRS intensity. In this work, a change in RRS intensity proportional to the concentration of Hg2+ was monitored by spectrofluorometer at excitation and RRS wavelengths of 550 nm (λex = λRRS). This method offered a detection limit of 0.23 nM, which is lower than the maximum mercury contaminant level specified by the US Environmental Protection Agency. Good precision of analysis was obtained (3.1% relative standard deviation). Furthermore, the method was simple, involving in-situ mixing and sensing in a one-pot solution. Detection was accomplished in 5 min. This makes the method advantageous in terms of convenience and rapidity of analysis. The developed method was successfully applied for detection of Hg2+ in tap water samples. Recoveries were found in range of 100.6–119.0%.