State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China.
Analyst. 2012 Jul 21;137(14):3286-92. doi: 10.1039/c2an35204d. Epub 2012 Jun 11.
A colorimetric sensor for nitrite ion with high selectivity and sensitivity by unmodified citrate-capped gold nanoparticles (Au NPs) is presented. Recognition of nitrite is developed on the basis of a highly specific diazo reaction between nitrite and phenylenediamine (PDA). PDA caused the Au NPs to aggregate owing to the strong covalent NH-Au bond, with a clear color change of solution from red to blue being visualized. In the presence of phosphoric acid and nitrite, the amines of PDA would readily be converted to diazo bonds, and a red solution was observed after the subsequent addition of Au suspension due to the much less strength of electrostatic interaction between the positive diazo groups and the negative citrate-capped Au NPs. With this colorimetric "light-up" method, <1 ppm of nitrite can be easily detected within 5 min at room temperature without instrumentation. Since the diazo reaction and the colorimetric response are separate, this approach features the use of pristine Au NPs in an assay where acidic environment is a necessity, making it a more convenient and cost-effective method for the sensing of nitrite when compared with those utilizing chemically modified Au NPs.
本文提出了一种利用未经修饰的柠檬酸钠包裹的金纳米粒子（Au NPs）高选择性和高灵敏度的比色传感器来检测亚硝酸根离子。亚硝酸根与苯二胺（PDA）之间的高特异性重氮反应是亚硝酸根识别的基础。由于强共价 NH-Au 键的作用，PDA 会导致 Au NPs 聚集，溶液的颜色从红色变为蓝色，肉眼可见。在存在磷酸和亚硝酸根的情况下，PDA 的胺基很容易转化为重氮键，由于正重氮基团和带负电荷的柠檬酸钠包裹的 Au NPs 之间的静电相互作用强度要小得多，因此在随后加入 Au 悬浮液后，观察到红色溶液。通过这种比色“点亮”方法，在室温下无需仪器即可在 5 分钟内轻松检测到 <1 ppm 的亚硝酸根。由于重氮反应和比色响应是分开的，因此该方法在需要酸性环境的测定中使用原始的 Au NPs，与利用化学修饰的 Au NPs 的方法相比，这使其成为一种更方便、更具成本效益的亚硝酸根检测方法。
