Synthesis Of Novel Fluorescent Materials Based On Carbon Dots And Their Detection For Metal Chromium

Fluorescent carbon dots(FCDs),which are a kind of fluorescent probes,show many good properties,such as stable fluorescent property,good water solubility,low toxicity,good biocompatibility and so on.However,they also have some problems,for example,the fluorescence intensity of FCDs is week and the sensitivity of detecting the metal ions is limited.In order to solve the problems above,this paper studied the synthesis and properties of FCDs at first and synthesized different series of fluorescent FCDs materials modified by ?-cyclodextrin and chitosan.The fluorescent materials also were used to detect metal ions in soil.This paper includes the following four parts:(1)The water-soluble FCDs were prepared by hydrothermal method using cotton.The structure and particle size distribution of FCDs were characterized by a series of methods concluding UV-Vis,FT-IR and TEM.The particle size distribution was 2-5nm.The optimum conditions for the preparation of FCDs were: 200?of hydrothermal temperature,15 h of hydrothermal time,1.2g/70 m L of cotton material usage.The paper studied the effects of FCDs concentration,p H and reaction time on the fluorescence spectra of Cr(VI)system.The obtained results showed that the optimum conditions for its interaction with Cr(VI)were: 2.0×10-5g/m L of FCDs concentration,p H=6.5 value of buffer solution,and 20 min of time.Plotting F0/F of Cr(VI)and the fluorescence system of FCDs against the Cr(VI)concentration gave a good straight line and the linear correlation was 0.9979.Based on the results,the paper established FCDs fluorescence analysis method of FCDs for determining quantitative chromium metal.The proposed method has been successfully applied to the determination of Cr(VI)in homemade water samples and soil.The recoveries were 96.70%-99.20% and 97.20%-99.80%,respectively.The results were satisfactory.(2)A novel water-soluble fluorescent material(FCDs-IPDI-CD)was prepared,which used FCDs by hydrothermal method using cellulose,isophorone diisocyanate(IPDI)and ?-cyclodextrin(?-CD)as raw materials.TEM result indicated thatIV FCDs-IPDI-CD was a kind of cavity structure.The water solution was light yellowunder the natural light to illuminate and was bright blue violet light under the ultraviolet light to illuminate.The obtained results showed that the optimum conditions for its interaction with Cr(VI)were: 0.03 g/m L of dosage of FCDs-IPDI-CD,p H=9.5 value of buffer solution,and 20 min of time.Plotting F0/F of Cr(VI)and the fluorescence system of FCDs-IPDI-CD against the Cr(VI)concentration gave a good straight line and the linear correlation was 0.9976.Based on the results,the paper established fluorescence analysis method of FCDs-IPDI-CD for determining quantitative chromium metal.The proposed method has been successfully applied to the determination of Cr(VI)in homemade water samples and soil.The recoveries were 95.80%-99.30% and 93.59%-97.34%,respectively.The results were satisfactory.(3)A novel water-soluble fluorescent carbon dots coated with chitosan material(FCDs/CTS)by hydrothermal method using cellulose and chitosan(CTS)as raw materials.TEM result indicated that FCDs/CTS was near spherical particles scattered and was surrounded by irregular shadows.The water solution was light yellow under the natural light to illuminate and was bright blue violet light under the ultraviolet light to illuminate.The obtained results showed that the optimum conditions for its interaction with Cr(VI)were: 0.02g/m L of FCDs/CTS concentration,p H=8.5 value of buffer solution,and 20 min of time.Plotting F0/F of Cr(VI)and the fluorescence system of FCDs/CTS against the Cr(VI)concentration gave a good straight line and the linear correlation was 0.9970.Based on the results,the paper established fluorescence analysis method of FCDs/CTS for determining quantitative chromium metal.The proposed method has been successfully applied to the determination of Cr(VI)in homemade water samples and soil.The recoveries were 95.60%-99.20%and 93.52%-97.47%,respectively.The results were satisfactory.(4)A novel water-soluble fluorescent material(FCDs-IPDI-CTS)was prepared with FCDs by hydrothermal method using cellulose,IPDI and CTS as raw material.TEM result indicated that FCDs-IPDI-CTS was near spherical particles scattered and was surrounded by irregular shadows.The water solution was light yellow under thenatural light to illuminate and was bright blue violet light under the ultraviolet light to illuminate.The obtained results showed that the optimum conditions for its interaction with Cr(VI)were: 0.01 g/m L of FCDs-IPDI-CTS concentration,p H=10.5 value of buffer solution,and 30 min of time.Plotting F0/F of Cr(VI)and the fluorescence system of FCDs-IPDI-CTS against the Cr(VI)concentration gave a good straight line and the linear correlation was 0.9993.Based on the results,the paper established fluorescence analysis method of FCDs/CTS for determining quantitative chromium metal.The proposed method has been successfully applied to the determination of Cr(VI)in homemade water samples and soil.The recoveries were 96.10%-99.40%and 94.27%-97.58%,respectively.The results were satisfactory.