Fluorescein-based Logic-gated Probes For Detection Of Heavy Metals And Fluoride Ions

The development of modern industry has caused a series of environmental pollution problems,of which heavy metal pollution is particularly serious.Since waste gas and water were emitted into the atmosphere,river and soil,they will eventually enter the human body through the food chain.However,various functions of human will be damaged and eventually lead to illness or even death,as long as these heavy metals accumulate in excess in human body.In addition,fluoride ions,as the smallest anions,are very difficult to detect,and their excessive ingestion can also cause human illness.Therefore,the rapid and sensitive detection of heavy metals and fluoride ions has become a popular research.At present,the detection of different analytes in complicated environment usually require multiple probes or most probes can only detect one substance,but the two fluorescein-based logic-gated probes prepared in this paper can avoid these disadvantages and simultaneously detect heavy metals and fluoride ions,which provide new ideas for monitoring heavy metal cations and anions.The specific work contents are as follows:1. In this study,we have designed and synthesized a novel“AND”logic-gated fluorescence probe,1-（3′,6′-bis（（tertbutyldiphenylsilyl）oxy）-3-oxospiro（isoindoline-1,9′-xanthen）-2-yl）-3-phenylthiourea（FPSi）,for the rapid（3 min）simultaneous detection of F^-and Hg²⁺in DMSO/H₂O solution（7:3,v/v）.The FPSi probe was constructed by attaching tert-butyldiphenylsilyl and thiosemicarbazide(as the specific identification groups for F^-and Hg²⁺)to the skeleton of fluorescein,respectively.FPSi produced no fluorescence response towards the addition of F^-or Hg²⁺separately.However,when the probe was exposed to a solution containing both F^-and Hg²⁺,there was a significant yellow-green fluorescence.FPSi demonstrated an excellent selectivity towards both F^-and Hg²⁺in the presence of interfering substances.The results of TOF-MS-EI analysis indicated that the response of FPSi towards F^-and Hg²⁺was mainly aroused by the F^-promoted cleavage of Si–O bond,and Hg²⁺triggered an irreversible desulfurization reaction leading to the spiral ring opening.Furthermore,the FPSi probe has been successfully used to detect F^-and Hg²⁺ions in tap water and cropland soil,which has a certain basis for achieving the detection of complex samples.2. We still use fluorescein as the base and modify it to prepare an“OR-AND”logic-gated colorimetric sensor.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 533 nm increased and the peak at 374 nm 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⁺and0.53μM for Cd²⁺.The reaction mechanism was verified by mass spectrometry.Moreover,FP was successfully used to rapidly detect trace amounts of hazardous Pb²⁺and Cd²⁺in tap water with good relative recovery,providing a novel approach for detecting Pb²⁺and Cd²⁺in practical application.It is a new method for the simultaneous detection of multiple substances.