Preparation Of Silver Nanoparticles Composite And Their Applications In The Determination Of Nitrite In Waters

Nitrite exists widely in soil,water and food.It is the most common nitrogenous compound in nature.Studies have shown that excessive absorption of nitrite in the body is harmful to health.Therefore,the detection of nitrite is very important to everyone.Fluorospectrophotometry is widely used as the detection method of nitrite due to its advantages such as high sensitivity,good selectivity,and low detection limit etc.In this thesis,three kinds of organic/inorganic composite nanoparticles of fluorescent probes were constructed by using silver nanoparticles(Ag NPs)as platform,surface modification of cyclodextrin,and inclusion of neutral red(NR)molecules.The nitrite ions in water were detected by fluorescence quenching of diazotization reaction between the neutral red of the composite nanoparticles and nitrite ions.1)Ag NPs were prepared with the size of 22 nm under microwave irradiation and sodium citrate as reducing agent,and then modified by β-cyclodextrin(β-CD).The nanoparticles composite of NR-β-CD@Ag NPs were constructed finally with the inner cavity of β-CD containing NR;The linear range for the determination of nitrite is 0.5 ～ 4.0μg/m L,and the detection limit is 14.1μg/L under acidic conditions;2)Ag NPs prepared with method(1)were modified by Mono-(6-mercapto)-β-cyclodextrin(SH-β-CD),and composite nanoparticle of NR-S-CD@Ag NPs were made with SH-β-CD after encapsulating NR;The linear range for the determination of nitrite is 0.5 ～ 5.0 μg/m L,and the detection limit is 7.04μg/L under acidic conditions;3)β-CD@Ag NPs with the size of 11 nm were prepared with the stabilizer of SH-β-CD and reducing agent of sodium borohydride at the room temperature,and the NR-CD@Ag NPs were obtained with NR;The linear range for the determination of nitrite is 0.1 ～ 1.0μg/m L,and the detection limit is 3.96μg/L.In a conclusion,the results shown that all of the three nanoparticles mentioned above can be used for the detection of nitrite in waters by the fluorescence quenching method;The smaller the size of Ag NPs,the lower the detection limit;Both of the first method and the second method have a wide detection range,and the third has a low detection limit;As fluorescent probes,the three nanoparticles have high sensitivity for detecting nitrite in waters and good anti-interference to other ions,and all of them can be used for qualitative judgment by naked eye observation and quantitative analysis by fluorescence spectrophotometer;Especially,a significant change in color can be observed by the naked eye when the concentration of nitrite in the waters is more than 0.5 μg/m L.Therefore,they are expected to be used for rapid determination of nitrite pollution in the wild waters in the future.