Application Of Gold Nanoparticles In Heavy Metal Ions And Pharmaceutical Molecule Detection

Owing to the unique properties in optics, electricity, magnetics, and catalysis, gold nanoparticles have been widely applied in the fields of environment, food, medicine, catalysis, and so on. In this dissertation, based on the high extinction coefficients and distance-dependent optical properties of citrate-stablized gold nanoparticles, we study the application of gold nanoparticles in determination of heavy metal ions in environment and medicine. The main contents are listed as follows:1、Detection of mercury (Ⅱ)(Hg2+). The citrate-stabilized gold nanoparticles (AuNPs) can aggregate in tris buffer, but riboflavin can protect AuNPs against tris-induced aggregation. Upon the addition of Hg2+, AuNPs can aggregate in tris again, which is because Hg2+could strongly combine with riboflavin to form a coordination complex, and the release of riboflavin from AuNPs leads to the aggregation again. A simple and sensitive detection method of Hg2+is developed based on Hg2+-induced aggregation of riboflavin-stablized AuNPs in tris. The method enables the detection of Hg2+over the concentration range of0.02-0.8μM with the linear equation of A656/A522=0.0195+1.7202cHg2+, the correlation coefficient (r) of0.9943and the limit of determination (LOD) of14nM.2、Detection of silver ions (Ag+). Imidazole has two nitrogen atoms referred to as the pyrrole nitrogen and the pyridine nitrogen. Imidazole can attach onto the surface of the AuNPs through the coordination of pyridine nitrogen and AuNPs, and AuNPs can aggregate through the hydrogen bonding interaction between the pyrrole nitrogen. However, when imidazole was firstly treated with Ag+followed by mixing with AuNPs, AuNPs can disperse well. Based on Ag+prevent the aggregation of AuNPs induced by imidazole, we develop a quantitative method for Ag+detection. The method enables the detection of Ag+over the concentration range of0.1-1.4μM with the linear equation of A520=0.3312+0.1086cAg+, the correlation coefficient (r) of0.9986and the limit of determination (LOD) of19nM. To test the present method, synthetic samples containing various metal ions were determined, and the recoveries are between89.08% and105.99%.3、Detection of captopril. The addition of enough salt can easily induce the aggregation of the citrate-stabilized AuNPs due to the charge shielding effect of salt. However, upon the addition of captopril, AuNPs can disperse well in the same salt conditions. This is attributed to the fact that the thiol groups in captopril molecules can covalently bind to the surface of the AuNPs through Au-S bond, meanwhile, the carboxyl groups in captopril molecules deprotonate to form-COO-at pH9.91, thus the negative charge of the AuNPs increases and the electrostatic repulsion among the AuNPs increases. Based on the phenomenon of AuNPs change from aggregation to dispersion state, we develop a quantitative method for captopril detection by UV-vis absorption spectra. Captopril in the range of0.04-1.2μM could be sensitively detected with the limit of determination (LOD) of20nM. With the present method, detection of captopril tablet was made with the recovery of97.4%～100.2%.