A rapid Surface-Enhanced Raman scattering method for the determination of trace Hg2+ with tapered optical fiber probe

Abstract

Surface-enhanced Raman scattering (SERS) offers a route for trace detection of mercury ions (Hg2+) owing to its great enhancement near the surface of the substrate. However, most of the methods are inconvenient due to the long reaction time and the strict measurement conditions. Based on a reaction between silver nanoparticles (AgNPs) and mercury ions, a simple but effective method is proposed in this paper. In the experimental research, a tapered optical fiber (TOF) modified with AgNPs is employed as a sensing probe and Rhodamine 6G (R6G) is taken as the Raman reporter. The SERS substrate is consumed by the Hg2+, causing a spectrum decrease. In the Hg2+ concentration range of 10−12 M to 10−4 M, the spectra evolution is detected using a mobile Raman spectrometer. By analyzing the decrease of the Raman peak after a 5-minutes interval, the concentration of Hg2+ can be quantified. A limit of detection of 5.15 × 10−13 M is achieved, which is much below the maximum Hg2+ content of drinkable water specified by USEPA (10−8 M). Verification tests were performed with the inductively coupled plasma-mass spectrometry (ICP-MS), the results showed that the proposed SERS method is effective for real samples detection. In addition, the reproductivity and the selectivity are experimentally confirmed. With this reliable, rapid, ultrasensitive and accurate method, trace Hg2+ could be detected in many applications.