Ultrasensitive sliver nanorods array SERS sensor for mercury ions

• An excellent SERS sensor for Hg2+ is prepared on a Ag NRs array SERS substrate.
• The LOD of the SERS sensor for Hg2+ is low to 0.16 pM.
• The SERS sensor owns a specific and linear response to Hg2+ from 1 pM to 1 μM.
• The SERS sensor is able to sensitively detect trace Hg2+ in tap water and lake water.

With years of outrageous mercury emissions, there is an urgent need to develop convenient and sensitive methods for detecting mercury ions in response to increasingly serious mercury pollution in water. In the present work, a portable, ultrasensitive SERS sensor is proposed and utilized for detecting trace mercury ions in water. The SERS sensor is prepared on an excellent sliver nanorods array SERS substrate by immobilizing T-component oligonucleotide probes labeled with dye on the 3′-end and –SH on the 5′-end. The SERS sensor responses to the specific chemical bonding between thymine and mercury ions, which causes the previous flexible single strand of oligonucleotide probe changing into rigid and upright double chain structure. Such change in the structure drives the dyes far away from the excellent SERS substrate and results in a SERS signal attenuation of the dye. Therefore, by monitoring the decay of SERS signal of the dye, mercury ions in water can be detected qualitatively and quantitatively. The experimental results indicate that the proposed optimal SERS sensor owns a linear response with wide detecting range from 1 pM to 1 μM, and a detection limit of 0.16 pM is obtained. In addition, the SERS sensor demonstrates good specificity for Hg2+, which can accurately identify trace mercury ions from a mixture of ten kinds of other ions. The SERS sensor has been further executed to analyze the trace mercury ions in tap water and lake water respectively, and good recovery rates are obtained for sensing both kinds of water. With its high selectivity and good portability, the ultrasensitive SERS sensor is expected to be a promising candidate for discriminating mercury ions in the fields of environmental monitoring and food safety.