| With the excessive increase of population,the development of science and technology and industrialization,the natural environment has been greatly damaged.Heavy metals exist widely in social and natural environments in various forms and states,causing serious impact on the environment and our global village.A large number of heavy metals have been polluted by agricultural pollutants and industrial waste gases.Using different technical means,the heavy metal pollutants in water can be effectively eliminated and detected.In order to effectively protect our environment,an efficient,safe and economical technical means has been developed to accurately detect and control heavy metal pollution in the ecosystem.As new fluorescent materials,photoluminescent carbon dots and nanoclusters have broad application prospects and have attracted much attention due to their attractive characteristics.However,there are still some difficulties and obstacles in the development of its composite materials.The development of effective fluorescence signal amplification schemes based on carbon dots and copper nanoclusters is challenging,so it is very important to develop new fluorescent nanocomposites.The main research content of this paper is as follows:In the first part of the work,using o-phenylenediamine as carbon source and phosphoric acid as passivating agent,the carbon dots(CDs)emitting red fluorescence was prepared,and then diatomite was added.The carbon dots/Diatomite nanocomposite(CDs/Diatomite)with signal amplification ability and higher fluorescence quantum yield was successfully prepared by one-step hydrothermal method.The CDs/Diatomite nanocomposites were characterized by SEM,FT-IR,XRD,Raman,UV-Vis and fluorescence techniques.The obtained CDs/Diatomite nanocomposites have good water dispersion and stable photoluminescence.The results showed that the fluorescence quantum yield of CDs increased from 10.1% to 32.3% after diatomaceous earth coating.CDs/Diatomite nanocomposites have selective and sensitive fluorescence quenching behavior for hexavalent chromium ions in aqueous solution,and significantly improve the sensitivity to hexavalent chromium ions.With the increasing of Cr(VI)concentration,the detection limit of Cr(VI)ions in CDs/Diatomite nanocomposites reached 0.15 μM,and its fluorescence color changed from red to dark black under the irradiation of 365 nm UV lamp.In addition,in order to enhance its visualization and convenience,a Cr(VI)test paper is also developed,which can expand the application effect of CDs/Diatomite nanocomposites in environmental detection and other aspects.In this part of the work.Firstly,copper nanoclusters(Cu NCs)were prepared using D-penicillamine as the preparation system,which were doped into the pores of Diatomite based on quantum limited effect,and the copper nanoclusters/Diatomite nanocomposites with enhanced fluorescence and higher fluorescence quantum yield were obtained.The prepared Cu NCs/Diatomite nanocomposites emit red fluorescence at a wavelength of 650 nm under the excitation of 340 nm light.The fluorescence nanocomposites based on Cu NCs can not only enhance the fluorescence emission intensity of copper nanoclusters,but also the quenching efficiency was enhanced.In addition,in order to increase its convenience and visualization,the composite of polyvinyl alcohol(PVA)and Cu NCs/Diatomite nanocomposite material,at room temperature,static 12 h,successfully obtained red photoluminescent fluorescent nanocomposite film(Cu NCs/Diatomite/PVA).By experiments,we found that Cu NCs/Diatomite/PVA composite film reacts with Cr(VI).With the continuous addition of Cr(VI),the fluorescence intensity of Cu NCs/Diatomite/PVA composite film slowly decreases.Under the UV lamp,we can see that the red fluorescence is significantly weakened until the fluorescence quenching.Through these phenomena,specific monitoring of Cr(VI)in water environment can be detected.The color of Cu NCs/Diatomite/PVA changes from milky white to brownish yellow under sunlight. |
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