基于银纳米材料的银离子的超灵敏比色法测定

Highly Sensitive Colorimetric Detection on Silver(Ⅰ) Ion Based on Silver Nanoparticles

合成了柠檬酸三钠修饰的银纳米粒子.碘离子作为亲和试剂容易通过其孤对电子与银纳米粒子表面的空轨道结合,并使得结合了碘离子的银纳米粒子发生聚集,导致银纳米粒子吸光度的改变及溶液颜色的变化.基于此,建立了银离子的超灵敏比色测定方法.该方法对银离子的线性范围为1.5～1 000 nmol/L,检出限为0.8 nmol/L.其它常见金属离子在浓度为2.0μmol/L时,几乎不能引起银纳米粒子颜色和吸光度的变化,方法具有较好的选择性.并通过高分辨透射电镜、动态光散射、共振光散射等技术研究了体系的测定机理.该方法用于实际样品中银离子的测定,结果满意.

Well-dispersed citrate-capped silver nanoparticles were synthesized in aqueous solution by reducing silver（Ⅰ） nitrate with sodium borohydride.As a nucleophilic agent,iodide ion could be easily adsorbed on the surface of silver nanoparticles through donating its electron pair on the unoccupied orbital of silver nanoparticles.Due to the low solubility constant（Ksp =8.52 × 10-17） of AgI,the addition of silver（Ⅰ） ion could induce the aggregation and color change of silver nanoparticles by forming AgI on the surface of iodide ion adsorbed silver nanoparticles.Based on this phenomenon,a highly sensitive colorimetric detection of silver（Ⅰ） ion was developed.Silver（Ⅰ） ion could be detected at 2.0 nmol/L by naked-eye.The linear range was 1.5-1 000.0 nmol/L,and the detection limit was 0.8 nmol/L when silver （Ⅰ） ion was detected by absorption spectrometric method.The common metal ions could not induce color change and absorption variation of iodide ion adsorbed silver nanoparticles even at the concentration of 2.0 μmol/L,indicating acceptable selectivity of the method to silver（Ⅰ） ion.High resolution transmission electron microscopy,dynamic light scattering and reason light scattering were used to investigate the detection mechanism of the system.All these characterization techniques confirmed the aggregation of silver nanoparticles when iodide ion and silver （Ⅰ） ion were added due to the loss of the negative charges of silver nanoparticles after the formation of neutral AgI.The developed method was used to detect silver（Ⅰ） ion in tap water and lake water by the standard addition methods with satisfactory results.