Fluorescence on and off sensing platform based on europium nanosheets for the detection of DPA and Cu ions.

With the development of society, the modern environment has put forward higher requirements for analysis and detection. This work proposes a new strategy for the construction of fluorescent sensors based on rare-earth nanosheets. Organic/inorganic composites were obtained by the intercalation of 4,4'-stilbene dicarboxylic acid (SDC) into layered europium hydroxide, and then the composites were exfoliated to form nanosheets. Taking advantage of the fluorescence emission characteristics of SDC and Eu, a ratiometric fluorescent nanoprobe was constructed, which realized the detection of dipicolinic acid (DPA) and Cu in the same system. With the addition of DPA, the blue emission of SDC gradually decreased and the red emission of Eu gradually increased, when Cu was added, the emission of SDC and Eu were gradually weakened. The experimental results showed that the ratio of fluorescence emission intensity (I/I) of the probe had a positive linear relationship with the concentration of DPA, and a negative linear relationship with the concentration of Cu, thus realizing the high sensitivity detection of DPA and a wide detection range of Cu. In addition, this sensor also exhibits potential visual detection possibilities. This is a multifunctional fluorescent probe that provides a novel and efficient method for the detection of DPA and Cu, which broadens the application field of rare-earth nanosheets.