Multiresponsive polysiloxane bearing photochromic spirobenzopyran for sensing pH changes and Fe3+ ions and sequential sensing of Ag+ and Hg2+ ions

A spiropyran-appended polysiloxane ( SP-Si ) was synthesized and characterized. The photochromic SP-Si has good thermal stability and exhibits high fatigue resistance to light. SP-Si acts as a dual colorimetric and spectroscopic probe for determining multi-scale pH over a wide range of 1∼14, and for detection of Ag + and Fe 3+ ions. Based on the transformation from colorless SP-Si solution without absorption at 440   nm to brown SP-Si /Ag + showing extremely strong absorption at 440   nm by addition of Ag + ions and subsequent transformation from brown to colorless SP-Si /Ag + /Hg 2+ with very weak absorption at 440   nm after addition of 1 equivalent of Hg 2+ ions, SP-Si /Ag + system serves as a dual colorimetric and spectroscopic probe for highly selective and sensitive detection of Hg 2+ ions. The detection is not interfered by common competitive metal ions such as Na + , K + , Li + , Ni 2+ , Fe 2+ , Zn 2+ , Co 2+ , Sr 2+ , Cu 2+ , Al 3+ , Ce 3+ and Cr 3+ . Applicability of SP-Si for real water sample analysis has been proved.