Constructing A New Platform Based On Gold Nanoclusters For The Specific Optical Detection Of Perfluorooctane Sulfonate

Perfluorooctane sulfonate（PFOS）is widely used in industry due to its excellent surfactant properties and antioxidant properties.However,toxicology has shown that PFOS can cause adverse ecological and human health effects.In recent years,the traditional detection technique for PFOS has been mainly chromatography and mass spectrometry coupling.However,expensive instrumentation and complex operation have limited its application largely.Therefore,it is urgent need to develop simple,rapid and low-cost technique for the detection of PFOS.Recently,optical techniques,such as colorimetric and fluorescence methods,have received particularly attention due to their short response times,good selectivity and high sensitivity.Metal nanoclusters（MNCs）are both excellent luminescent and catalytic materials due to small dimensions,excellent photostability and a unique electronic structure.However,so far,the relatively weak luminescence and almost untunable emission for MNCs have limited the practical applications of them.Therefore,in this study,we designed and synthesized calixarene derivatives to enhance the fluorescence of Au NCs,which are further applied to the determination of PFOS.In addition,a colorimetric platform for the specific detection of PFOS was either designed based on the peroxidase-like activity of Au NCs,which can catalyze the oxidation of TMB by H₂O₂.Firstly,based on mechanism of aggregation-induced emitting enhancement（AIEE）,Au NCs@CMP and calix[4]arene derivatives（C4A-Ds）were used to construct fluorescent probes for the highly sensitive detection of PFOS.For that,a series of C4A-Ds with different interchain lengths and positive charges at the wide rim were designed and synthesized to interact with Au NCs@CMP.The fluorescence emission of Au NCs@CMP was maximally enhanced by lysine-calix[4]arene-propoxy（LC4AP）.Therefore,LC4AP was selected for supramolecular assembly with Au NCs@CMP to construct a fluorescent probe（Au NCs/LC4AP）.Besides,due to the competitive binding of and PFOS and LC4AP,the assembly of Au NCs/LC4AP underwent partial disassembly and fluorescence burst.Thus,a highly sensitive approach for PFOS was achieved in a wide responsive range（0-100μM）,through the fluorescence quenching of Au NCs/LC4AP to PFOS.Furthermore,the method successfully detected PFOS in tap water and soil extracts with high recoveries,demonstrating its potential for the PFOS determination in practice.Secondly,beyond a luminescent material,Au NCs@CMP also have superior peroxidase-like activity which can catalyze the oxidation of TMB by H₂O₂,causing the solution turn to blue.In principle,PFOS can inhibit the oxidation of TMB via binding to the catalytic active site,or by depleting the reactive oxygen species（ROS）in the system.This established a colorimetric platform of Au NCs/TMB/H₂O₂ specifically for PFOS detection.The results showed that the system of Au NCs/TMB/H₂O₂ responded to PFOS over a wide range of 0-50μM,with a low LOD as 150 n M.Further mechanistic studies have shown that the colorimetric response is due to the fact that PFOS consumed part of the reactive oxygen species（ROS）produced in the system,thereby,inhibiting the TMB oxidation.Furthermore,the system was successfully applied to the determination of PFOS in soil extracts or tap water with good recoveries.Thus,it provides a novel colorimetric platform for the specific detection of PFOS in water.The method has the advantages of being rapid,sensitive and highly selective,providing a new option for the detection of PFOS in environments.