Surface-enhancement Raman scattering sensing strategy for discriminating trace mercuric ion (II) from real water...

It is of essential importance to precisely probe mercury(II) (Hg(2+)) ions for environment-protection analysis and detection. To date, there still remain major challenges for accurate, specific, and reliable detection of Hg(2+) ions at subppt level. We herein employ gold nanoparticles (AuNPs) decorated silicon nanowire array (SiNWAr) as active surface-enhanced Raman scattering (SERS) substrates to construct a high-performance sensing platform assisted by DNA technology, enabling ultrasensitive detection of trace Hg(2+) in ∼64 min and with low sample consumption (∼30 μL). Typically, strong SERS signals could be detected when the single-stranded DNA structure converts to the hairpin structure in the presence of Hg(2+) ions, due to the formation of thymine (T)-Hg(2+)-T. As a result, Hg(2+) ions with a low concentration of 1 pM (0.2 ppt) can be readily discriminated, much lower than those (∼nM) reported for conventional analytical strategies. Water samples spiked with various Hg(2+) concentrations are further tested, exhibiting a good linear relationship between the normalized Raman intensities and the logarithmic concentrations of Hg(2+) ranging from 1 pM to 100 nM, with a correlation coefficient of R(2) = 0.998. In addition, such SERS sensor features excellent selectivity, facilely distinguishing Hg(2+) ions from various interfering substances. Moreover, this presented SERS sensor possesses good recyclability, preserving adaptable reproducibility during 5-time cyclic detection of Hg(2+). Furthermore, unknown Hg(2+) concentration in river water can be readily determined through our sensing strategy in accurate and reliable manners, with the RSD value of ∼9%.