Preparation Of Gold Nanomaterial And Application For Detection Of Metal Ions

Gold nanomaterials with the unique physical and chemical properties have beenwidely used in various fields. In this paper, gold nanorod and nanoparticles wereresearched for their preparation and application.First, a method preparing the gold nanorod based on the in situ growth method isresearched in the paper.The reducing agent sodium borohydride is directly put into thegrowth solution, and then gold nanorods are formed. The aim is to simplify the seedcrystal method, which confines the normal two steps-the preparation of the seed crystal,and the production of the gold nanorod to the singles step. Also the dosage of thechlorine gold acid （HAuCl4）, cetyl three methyl brominated ammonium （CTAB）,ascorbic acid （AA）, nitric acid silver （AgNO3） and sodium borohydride reagent（NaBH4）, reaction temperature, reaction time on the effect of the gold nanorodpreparation are discussed at the same time. Conditions are optimized on preparation ofthe gold nanorod to get one with good uniformity and reproducibility.Second, based on the special physical chemical reaction between Hg and Au, anew method about the determination of Hg²⁺is established by use of gold nanorod. First,in this method strong reducing agent-sodium borohydride is used to reduce the Hg²⁺in the test sample into Hg. After the gold nanorod addition, Hg deposition onto goldnanorod at both ends and react, with the variety of the longitudinal maximumabsorption the same as that of the Hg²⁺concentration in the visible spectrum area. Thenthe Hg²⁺is determined. The method has very high selectivity, with the measurementrange from0.5to10ug/L, detection limit as0.25u g/L.Third， Dye-adsorbed nanogold possesses two specific absorption peaks ofnanogold and dye in visible spectral region. The characteristic spectrum is related to thedye structure, pH and metal ion. Through selecting different dyes （RB, MG, MB） andpH （6.6,7.2,7.8）, we fabricated a sensor array with a series of characteristic spectra.The serial characteristic spectra could be changed when the sensor array interacts withHg²⁺ M2(+Pb²⁺、Cd²⁺、Mn²⁺、Zn²⁺), generating a corresponded visible spectral pattern.The sensor array was screened by Principal Component Analysis （PCA）, the resultshows that we can recognize Hg²⁺low to0.20μM （1%）in the Hg²⁺ M²⁺mixtures byan optimized sensor array consisted of3sensors （NG-RB, NG-MG, NG-MB in pH7.8）. Forth，Based on the study of nanogold-dye sensor array for pattern recognition ofHg²⁺,using the sensor array of nanogold combined with different dyes （RB, MG, MB） inpH6.6,7.2,7.8for differentiating eight metal ions which areHg²⁺,Cu²⁺,Ni²⁺,Pb²⁺,Zn²⁺,Cd²⁺,Fe²⁺andMn²⁺.The sensor array was screened by PrincipalComponent Analysis （PCA）,the result shows that we can differentiate the eight metalions by an optimized sensor array consisted of3sensors （NG-RB, NG-MG, NG-MB inpH7.8）.