Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031, China.
J Am Chem Soc. 2011 Jun 8;133(22):8424-7. doi: 10.1021/ja2015873. Epub 2011 May 12.
To detect trace trinitrotoluene (TNT) explosives deposited on various surfaces instantly and on-site still remains a challenge for homeland security needs against terrorism. This work demonstrates a new concept and its utility for visual detection of TNT particulates on various package materials. The concept takes advantages of the superior fluorescent properties of quantum dots (QDs) for visual signal output via ratiometric fluorescence, the feasibility of surface grafting of QDs for chemical recognition of TNT, and the ease of operation of the fingerprint lifting technique. Two differently sized CdTe QDs emitting red and green fluorescences, respectively, have been hybridized by embedding the red-emitting one in silica nanoparticles and covalently linking the green-emitting one to the silica surface, respectively, to form a dual-emissive fluorescent hybrid nanoparticle. The fluorescence of red QDs in the silica nanoparticles stays constant, whereas the green QDs functionalized with polyamine can selectively bind TNT by the formation of Meisenheimer complex, leading to the green fluorescence quenching due to resonance energy transfer. The variations of the two fluorescence intensity ratios display continuous color changes from yellow-green to red upon exposure to different amounts of TNT. By immobilization of the probes on a piece of filter paper, a fingerprint lifting technique has been innovated to visualize trace TNT particulates on various surfaces by the appearance of a different color against a yellow-green background under a UV lamp. This method shows high selectivity and sensitivity with a detection limit as low as 5 ng/mm(2) on a manila envelope and the attribute of being seen with the naked eye.
用于即时、现场检测各种表面上痕量三硝基甲苯（TNT）爆炸物，仍然是应对恐怖主义的国土安全需求的一项挑战。本工作展示了一种新概念及其在各种包装材料上用于 TNT 微粒可视化检测的实用性。该概念利用量子点（QD）的荧光性能优势，通过比率荧光进行视觉信号输出，利用 QD 的表面接枝用于 TNT 的化学识别，以及利用指纹提取技术的简便操作。两种不同尺寸的分别发射红光和绿光的 CdTe QD，分别通过将发射红光的 QD 嵌入到硅纳米粒子中，并将发射绿光的 QD 共价连接到硅纳米粒子表面，形成双发射荧光杂化纳米粒子。硅纳米粒子中的红色 QD 的荧光保持不变，而用聚胺功能化的绿色 QD 可以通过形成 Meisenheimer 络合物选择性地与 TNT 结合，由于共振能量转移导致绿色荧光猝灭。两种荧光强度比值的变化显示，在暴露于不同量的 TNT 时，颜色从黄绿光连续变化到红色。通过将探针固定在滤纸上，创新了一种指纹提取技术，在紫外灯下，在黄绿光背景下，各种表面上的痕量 TNT 微粒会呈现出不同的颜色，从而可以可视化。该方法具有很高的选择性和灵敏度，在马尼拉信封上的检测限低至 5ng/mm(2)，并且可以用肉眼看到。
