The Construction Of A Ratiometric Fluorescence Sensing System And Its Application In Rapid Detection

Fluorescence analysis is widely used in the field of environmental pollutants detection,biomedicine and immunoassay for their high sensitivity and fast analysis speed.In fluorescent sensing,the ratiometric fluorescent system utilizes the change of the peak intensity ratio of two wavelengths as a basis to qualitative or quantitative analysis of the analyte,thus it can effectively reduce the interference in the environment.In this paper,based on fluorescent nanomaterials as signal source,and highly selective ratiometric fluorescence systems were constructed by chemical modification and molecular imprinting techniques for the detection of mercury ions and bovine hemoglobin（BHb）.The main research contents are as follows:（1）Dithiothreitol modified carbon dots-gold nanoclusters for the sensitive detection of mercury ions(Hg²⁺)HAuCl₄ was used as the raw material and glutathione（GSH）was employed as the reducing agent to obtain a gold seed solution under heating and refluxing conditions.And then,glucose was dissolved in the as-prepared gold seed solution to generate the carbon-gold nanoclusters under microwave conditions.Finally,the carbon-gold nanoclusters were chemically modified with DTT.Due to the existence of thiol groups at both ends of DTT,one end was anchored on the surface of carbon-gold clusters,the other end was responsible to attract Hg²⁺.When Hg²⁺appeared,the formed metal bonds between Hg²⁺(5d¹⁰)and Au⁺(5d¹⁰)would lead to the fluorescence of gold clusters was quenched,while the fluorescence of carbon dots remained almost unchanged.With the increase of Hg²⁺concentration,the fluorescence color of carbon-gold nanoclusters displayed a change from red to blue with a linear range of 0.05-1μM.The developed system was used for the detection of Hg²⁺in lake water and tap water.The obtained recovery value was between 95.9-104%,indicating that it has a broad application prospect in the actual water sample detection.（2）A molecular imprinting based ratiometric fluorescent system for the visual detection of bovine hemoglobin（BHb）Sol-gel method was chosen to synthesize core-shell molecular imprinted polymer（MIP）.In the preparation process,silica（SiO₂）was acted as support material,green quantum dots（QD）played the role of as fluorescent signal source and auxiliary functional monomer,and BHb was template molecule.Then,during the detection process,the red QD embedded with SiO₂（QD@SiO₂）was mixed with MIP to construct the dual-emission fluorescence sensor for analyzing BHb.At the presence of BHb,the fluorescence intensity of green QD decreased continuously due to photo-induced electron transfer（PET）,while the fluorescence intensity of red QD@SiO₂ was almost constant,resulting in the fluorescence color changed from initial green to red.The linear range of developed ratiometric fluorescent system was 0.050-3.0μM,with the detection limit of 9.6 nM and imprinting factor of 6.8.These results show that the sensor has good selectivity and sensitivity for determination of BHb.In addition,a satisfactory recovery was obtained by spiked calibration of cow urine,with a range of95.7-102%.This convenient and sensitive ratio fluorescent system construction method provides an effective approach to detect other target analytes.