Reaction-based fluorescent silk probes with high sensitivity and selectivity to Hg2+ and Ag+ ions

Abstract

The detection and removal of heavy metals in the environment is urgent and meaningful. In this work, two types of fluorescent functionalized silks OSP and ASP have been prepared using worm silk as the substrate. These fluorescent silk probes exhibit an obvious fluorescence quenching effect in the presence of Hg²⁺ or Ag⁺, enabling silk to specifically detect Hg²⁺ or Ag⁺. An obvious color response occurs under visible light, from yellow to brown or gray, thereby realizing dual-channel identification of fluorescence and colorimetry. In addition, its sensing mechanism has been studied, and it is found that the probe reacts with metal ions as a reactive response. Compared with the fluorescent probes bearing one CC/CC bond, the probes with two terminal CC/CC bonds are more sensitive. And the excellent recognition ability can make the limit of detection as low as 0.25 μM. This indicates that silk fluorescent probes can be used to detect Hg²⁺ and/or Ag⁺.