An "OR-AND" logic gate based multifunctional colorimetric sensor for the discrimination of Pb2+ and Cd2.

Abstract

Pb2+ and Cd2+ are the most ubiquitous heavy metal ion pollutants, and they have aroused much attention due to their irreversible and significant damage to human organ. In this work, a new fluorescein-based "OR-AND" logic gate colorimetric probe 3',6'-bis((tert-butyldiphenylsilyl)oxy)-2-(2-((2-hydroxyphenyl)imino)ethylidene)aminspiro[isoindoline-1,9'-xanthen]-3-one (FP) was designed and synthesized via attaching 2-(2-((2-hydroxyphenyl)imino)ethylidene)amino and tert-butyldiphenylsilyl to fluorescein as the specific identification groups. This sensor can rapidly and sensitively discriminate Pb2+ and Cd2+ by utilizing F- as an auxiliary reagent. When Pb2+ or Cd2+ was added into the FP solution, the absorption band at 533nm increased and the peak at 374nm decreased, the color changed from colorless to pale-purple, resulting in a ratiometric spectral change. However, adding fluoride ion to the FP solution containing Pb2+ or Cd2+ resulted in a distinct phenomenon in which the pale purple color fades out to colorless for a Pb2+-containing solution and deepen to dark purple for a Cd2+-containing solution, which is attributable to the different coordination mechanisms. In aqueous solution, the detection limits of FP can reach 0.42μM for Pb2+ and 0.53μM for Cd2+. The probe exhibited rapid responses for these analytes. Moreover, FP was successfully used to rapidly detect trace amounts of hazardous Pb2+ and Cd2+ in tap water with good relative recovery and the relative standard deviations (RSD) were 1.8% for Pb2+ and 0.3% for Cd2+, providing a novel approach for detecting Pb2+ and Cd2+ in practical application.