Paper matrix based array for rapid and sensitive optical detection of mercury ions using silver enhancement

The authors describe a nitrocellulose membrane based paper matrix array for detection of mercury(II) with high throughput and repeatability. A thymine-rich signal reporting ssDNA probe labeled with gold nanoparticles (AuNPs) was designed, and detection is based on the strong T-Hg-T interaction which leads to a significant color change. In addition, catalytic signal amplification is accomplished by silver staining in order to enhance coloration. The method has a detection limit as low 0.5 ppt. This is at least 500-fold better than that of existing methods. By using an array, multiple sets of duplicate detections can be carried out simultaneously and in parallel. This improves the efficiency and accuracy of the assay. The method shows remarkable specificity since the signal of other competing metal ions is negligible compared to that of mercury(II) even at 100-fold higher concentration. The protocol was successfully applied to the determination of Hg(II) in spiked tap water and lake water samples. In our perception, this assay is a most promising tool for optical determination f ultra-low levels of Hg(II).