Construction Of Metal Nanocluster Based Composite Fluorescence Sensing Material And Its Detection Performance Of Heavy Metal Ions

Water is an extremely important resource for life on Earth.Due to excessive population growth,human activities,and rapid industrialization,water resources have been severely damaged.Heavy metals exist in the environment,food and organisms in different concentrations and chemical states,posing serious hazards to human health and the environment.These heavy metals enter ecosystems through agricultural runoff and industrial emissions.Different treatment methods have different effects on the removal and detection of heavy metals in the water environment.Therefore,the development of robust,eco-friendly,and economically feasible processing methods to detect heavy metals in ecosystems is very important for environmental protection.Part I:First,copper nanoclusters（CuNCs）emitting orange-red fluorescence were prepared using D-penicillamine as a stabilizer,which was compounded with polyvinyl alcohol/polyethylene glycol（PVA/PEG）by magnetic stirring.At room temperature,the fluorescent nanocomposite film doped with copper nanoclusters（CuNCs/PVA/PEG）was obtained by standing on the PTFE mold for 24 h.It was found that the fluorescence intensity of CuNCs/PVA/PEG decreased gradually with the increase of Cr（VI）concentration when CuNCs/PVA/PEG was exposed to Cr（VI）ion aqueous solution at p H7.3,and the fluorescence intensity of CuNCs/PVA/PEG decreased gradually under sunlight.The color of the fluorescent nanocomposite film also changed with the addition of Cr（VI）ions,from milky white to reddish-brown;under the irradiation of 365 nm UV lamp,the fluorescence was quenched,and changed from orange-red to colorless.Based on this characteristic,the specific detection of Cr（VI）ions in water environment can be realized.This fluorescent nanocomposite film shows different fluorescence intensities in different p H solutions.When the fluorescent nanocomposite film is exposed to a solution of p H 1-8,under the irradiation of a 365 nm UV lamp,it shows a bright orange-red fluorescence,but when the p H value of the solution is greater than 9,the fluorescence of the film is quenched,the fluorescent color of the film changes from orange-red to black.At the same time,when observed in sunlight,the color of the fluorescent nanocomposite film changed from milky white to black-brown.Part II:First,carbon quantum dots（CQDs）emitting blue fluorescence were prepared using citric acid as carbon source and ethylenediamine as nitrogen source.Then,the CQDs were etched by adding ethyl orthosilicate（TEOS）,urea and ethanol to obtain Silica-coated carbon quantum dots（CQDs@Si O₂）,finally,composited with water-phase nano-copper clusters using a magnetic stirrer to obtain a silica-coated carbon quantum dot/copper nanocluster double fluorescent composite（CQDs@Si O₂/CuNCs）,and applied it to the detection of heavy metal ions in the water environment,it was found that the material can realize the specific detection of mercury ions.The fluorescence color of CQDs@Si O₂/CuNCs fluorescent nanocomposites changed from purple to blue,thus realizing the fluorescence detection of Hg²⁺,and the detection limit of Hg²⁺in aqueous solution could be as low as 1μM.