Silicon Nanowire Array-Based Surface-Enhanced Raman Scattering Sensor For Mercury Ion Detection

With the rapid development of economy, heavy metal pollution has become a worldwide serious environmental problem. Especially, the pollution of mercury ion(Hg2+) has caused serious damage to the ecological environment and human health. Up to now, numerous well established strategies, such as resonance scattering spectral assay, atomic absorption spectroscopy and atomic emission spectroscopy, have been intensively developed for Hg2+ ions detection. It is worth pointing out that even a small amount of Hg2+ may result in severe damage to human health through food chains, which is due to long-term bioaccumulation of Hg2+ in the human body. Therefore, it is still very necessary to develop new sensors for mercury ion detection with high sensitivity, specificity and reproducibility.Surface-enhanced Raman scattering(SERS) has been widely used in analysis application due to a lot of merits. Gold or silver nanoparticles decorated silicon nanomaterials, such as silver nanoparticles decorated silicon wafer(Ag NPs@Si wafer) and gold nanoparticles decorated silicon nanowire array(Au NPs@Si NWAr), have been demonstrated to be SERS-active substrates, which have been widely used for DNA and cell detection. It is worth pointing out that there exists scanty information about the above-mentioned silicon based SERS substrates for mercury ion detection up to present.In this study, we employ gold nanoparticles(Au NPs) decorated silicon nanowire array(Si NWAr) as SERS substrate to construct high-performance sensing platform, enabling ultrasensitive detection of trace mercury ion with short assay time(~4 min) and 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 Hg2+ ions, due to the formation of thymine(T)-Hg2+-T. As a result, Hg2+ ions with low concentration of 1 p M(0.2 ppt) can be readily discriminated, much lower than those(~n M) reported by conventional analytical strategies. Water samples spiked with various Hg2+ concentrations are further tested, exhibiting a good linear relationship between the normalized Raman intensities and the logarithmic concentrations of Hg2+ ranging from 1 p M to 100 n M, with a correlation coefficient R2=0.998. In addition, such SERS sensor features excellent selectivity, facilely distinguishing Hg2+ ions from ten kinds of interfering metal ions. Moreover, this presented SERS sensor possesses good recyclability, preserving adaptable reproducibility during 5-time cyclic detection of Hg2+. Furthermore, unknown Hg2+ concentration in river water can be readily determined through our sensing strategy in accurate and reliable manners, with the RSD value of ~9.0%.In summary, we have developed a kind of silicon-based SERS sensors. The presented sensor is suitable for trace mercury ion detection taking advantage of its high sensitivity, strong specificity and excellent reproducibility.