In Situ Microfluidic SERS Chip for Ultrasensitive Hg Sensing Based on I-Functionalized Silver Aggregates

Mercury(II) ions are causing serious environmental pollution and health damage. Developing a simple, rapid, and sensitive sensor for Hg detection is of great significance. Herein, we demonstrate an I-functionalized surface-enhanced Raman scattering (SERS) substrate for rapid and sensitive Hg sensing on a highly integrated microfluidic platform. Based on the combination reaction between I and Hg, the Hg sensing is achieved via the SERS intensity "turn-off" strategy, where HgI precipitation is formed on an SERS substrate interface, dissociating the Raman reporters that coadsorbed with I. Owing to the strong binding constant between I and Hg, our I-functionalized substrate demonstrates a very fast sensing response (∼150 s). Through reliable in situ SERS detection, a robust calibration curve between the "turn-off" signal and "lg" is obtained in a broad concentration range of 10 to 10 M. Additionally, the detectable Hg concentration can be as low as 1 fM. The good selectivity toward Hg is also verified by testing about a dozen common metal ions in water, such as K, Na, Ca, Mg, and so forth. Furthermore, we apply the SERS sensor for real tap and lake water sample detection, and good recoveries of 113, 97, and 107% are obtained. With its advantages of high integration, simple preparation, fast response, high sensitivity, and reliability, the proposed I-functionalized SERS sensor microfluidic chip can be a promising platform for real-time and on-site Hg detection in natural water.