Synthesis Of Biomolecules Protected Silver Nanoclusters And Their Analysis Applications

Ag NCs as a new class of fluorophores possess advantages such as low cost synthesis, chemically active, easily modified surface and good water-solubility, so Ag NCs as the excellent fluorescent probes have caused extensive research interests. In the thesis, kinds of biological molecules were used as protective agents or ligands for synthesis of luminescent Ag NCs with different functions. And based on the fluorescence quenching mechanism, several detection methods for the detection of metal ions and biothiols were presented.Chapter 1:We reviewed the research development on synthesis, optical properties and applications of Ag NCs.Chapter 2:A novel ssDNA owning hairpin structure with a plurality of cytosine bases C loop was designed. And the high quantum yield, red fluorescent DNA/Ag NCs was synthesized with the C-containing loop hairpin DNA as a template. In the presence of Hg2+ the fluorescence of DNA/Ag NCs could be quenched dramatically, thus we established a high selective and sensitive detection method for Hg2+. The method allowed a linear range from 1.0×10-10 mol/L to 1.2×10-8 mol/L for the determination of Hg2+, and the detection limit was 1.0×10-10 mol/L (S/N=3). The ordinary exploration using UV-vis spectra indicated that the fluorescence quenching may generate from the metallophilicity 5d10(Hg2+)-4d10(Ag+) reaction.Chapter 3:We synthesized the blue fluorescent GSH@Ag NCs by one step ultrasound method using common sulfhydryl small molecules----glutathione (GSH) as a protective agent and ligand. And the Ag NCs were characterized through transmission electron microscopy (TEM), UV-vis absorption and fluorescence spectra. It was found that the fluorescence could be quenched efficiently in the presence of Fe3+, therefore a high sensitive detection method for Fe3+ was established. The method owns a good response to Fe3+ in the linear range of 5×10-7mol/L-2×10-5 mol/L with a detection limit 1.2×10-7 mol/L (S/N = 3), and this method was applied to the detection of iron ion content in human serum samples successfully. When introducing a complexing agent EDTA, the fluorescence of Fe3+-GSH@Ag NCs system could be recovered. This could not only provide new understanding for the reaction between Fe3+ and GSH @ Ag NCs but also demonstrate that the GSH @ Ag NCs are potential for developing an off/on novel reversible fluorescent probe.Chapter 4:Red fluorescent BSA-Ag NCs were synthesized with bovine serum albumin (BSA) as a protecting agent. Small molecular biothiols, such as cystine (Cys), homocysteine (Hcy) and glutathione (GSH) could cuase the fluorescence quenching, which may be due to the affinity interaction between sulfhydryl and silver. The BSA-Ag NCs could be used as the fluorescent nano-probe for the establishment of novel detection method for analysis of biological thiols. The linear ranges for Cys, Hcy and GSH were 2.0×10-6 mol/L-9.0×10-5 mol/L,2.0×10-6 mol/L-1.2×10-4 mol/L and 1.0×10-5 mol/L 8.0×10-5 mol/L, respectively. The detection limits (when S/N=3) were 8.1×10-7 mol/L for Cys,1.0×10-6 mol/L for Hcy and 1.1×10-6 mol/L for GSH. Our proposed method was successfully applied to the determination of thiols contents in human plasma and the recovery was 94.83-105.24%. It is potentially applicable to BSA-Ag NCs in a chemical or biosensing system.Chapter 5:We summarized the rearch results about the fluorescent Ag NCs as nano-probes for applications in metal ion and biothiols analysis and detection aspects, and the future possible work steps were speculated.