Preparation Of Gold Nanoparticles And Their Application In Colorimetric And Fluorescence Analysis

Chapter 1:The development of gold nanomaterials is stated briefly.Summarized the preparation,properties and applications of gold nanoparticles.The research contents are put forward at last.Chapter 2: The Pectinase?PE?protected gold nanoparticles?PE-Au NPs?have been successfully synthesized by PE as a ligand and micro-wave as heating method.PE-Au NPs have good dispersion and the average diameterwas 20.0 ± 1.4 nm.We have constructed Mg²⁺ and Cys colorimetric sensors based on PE-Au NPs under different experimental conditions successfully.Aggregation of PE-Au NPs was induced immediately following the addition of Mg²⁺ ion through electrostatic interaction in pH 4.0 buffer solution,yielding a color change from red to blue.Based on the aggregation,colorimetric detection of Mg²⁺ was proposed.The detection limit for Mg²⁺ was determined to be 4.0 × 10-9 ?M.Cys could also cause the aggregation of PE-Au NPs due to formation of the strong covalent Au-S bond and electrostatic binding under pH 5.0.As the Cys concentration increased,the color of the solutions gradually changed from wine-red to blue as well as the large absorption band shifted from 523 to 650 nm upon PE-Au NPs aggregation.The detection limit was 4.6 n M.Chapter 3: A simple one-pot method was developed in this chapter,employing inexpensive chicken egg white?EW?as a reducing/capping reagent,synthesis of water-soluble and well-dispersed chicken egg white-protected Au nanoclusters?EW@Au NCs?with far-red/near-infrared?FR/NIR?emission.The resultant Au NCs showed strong emission at 667 nm with a quantum yield of 7.23%,and the average diameter was 3.57 ± 0.56 nm.The excellent photostability,large stokes shift?>350 nm?and strong emission of EW@Au NCs make it as a good Hg²⁺ sensor.After ethylenediamine?En?was used as a masking agent,the EW@Au NCs offer highly selective and high sensitivity for determination of Hg²⁺ ion with a detection limit as low as 20 p M,which is 500 times lower than the limit value?10 n M?defined by the U.S.Environmental Protection Agency in drinkable water.Additionally,the applicability of our sensing system is also verified by analysis of Hg²⁺ in tap water and pond water.Chapter 4: Highly orange fluorescent gold nanoclusters?SMBD-Au NCs?have been synthesized by using thiolate SMBD as reducing and stabilizing agents.The SMBD-Au NCs have good dispersion and the particle size was 1.5 + 0.1 nm.Since the H₂ S and pH values could quench the fluorescence of SMBD-Au NCs,a rapid,accurate and sensitive method for the detection of H₂ S and pH were established.The detection of H₂ S has high sensitivity,the detection range is 2.7 ×10-11 8.5×10-4 M,and the detection limit is 0.024 n M.The relative detection mechanism for H₂ S has also been discussed.Moreover the SMBD-Au NCs showed high sensitivity to pH value.The response range was from pH 2.01 to pH 12.00,and the pH sensor based on the Au NCs had good reproducibility.