Efficient blue-emitting silafluorene–fluorene-conjugated copolymers: selective turn-off/turn-on detection of explosives
作者:Jason C. Sanchez、William C. Trogler
DOI:10.1039/b802623h
日期:——
The synthesis and spectroscopic characterization of a series of new blue-emitting silafluoreneâfluorene copolymers is described. The polymers are synthesized using kinetically controlled hydrosilylation copolymerization of 1,1-dihydridosilafluorene with a series of 9-substituted 2,7-diethynylfluorenes. The polymers contain a trans-only framework with molecular weights in the range of 13â000â20â000, as determined by gel permeation chromatography (GPC) using polystyrene standards, and by 1H NMR spectroscopy using dimethylphenylsilane as an end-capping marker group. The three stereoregular polymers synthesized include a 9,9-dihydridofluorene (PSF1), a 9,9-dimethyl-9H-fluorene (PSF2), and a 9,9â²-spirobifluorene (PSF3) comonomer with the frameworks. These fluorenyl units are conjugated through the silicon center of the silafluorene moiety by bridging vinylene groups. Quantum yields of fluorescence range from 20 to 100% with PSF3 having the highest quantum efficiency. Polymers PSF1-3 emit in the blue region of the spectrum (â¼475 nm), showing good color purity with little change in luminescence properties between the solution and solid-state phases. The polymers were tested for explosives detection properties by a fluorescence-quenching mechanism. Targeted explosives include laboratory prepared TNT, DNT, picric acid, RDX, HMX, PETN, TNG, and Tetryl, as well as production line PETN and C-4. All three polymers exhibit detection of explosive particulates with limits as low as 1 pg cmâ2 for Tetryl. Polymer PSF1 simultaneously acts as a selective fluorescence âturn-onâ sensor for nitrate ester explosives when irradiated with UV light. In the presence of nitrate ester-based explosives such as PETN, PSF1 initially exhibits fluorescence quenching, but continued exposure to UV-light (302 nm), promotes a photochemical reaction forming a luminescent green fluorenone copolymer. This is the first example of a single material acting as both a turn-off and turn-on selective fluorescent sensor for an explosive material.
描述了一系列新型发蓝光硅芴-芴共聚物的合成和光谱表征。该聚合物是通过 1,1-二氢硅芴与一系列 9-取代的 2,7-二乙炔基芴的动力学控制氢化硅烷化共聚来合成的。该聚合物含有仅反式骨架,分子量范围为 13-000-20-000,通过使用聚苯乙烯标准的凝胶渗透色谱 (GPC) 和使用二甲基苯基硅烷作为末端的 1H NMR 光谱测定。封端标记组。合成的三种有规立构聚合物包括 9,9-二氢芴 (PSF1)、9,9-二甲基-9H-芴 (PSF2) 和 9,9-螺二芴 (PSF3) 骨架共聚单体。这些芴基单元通过桥连亚乙烯基通过硅芴部分的硅中心共轭。荧光量子产率范围为20%至100%,其中PSF3具有最高的量子效率。聚合物 PSF1-3 在光谱的蓝色区域 (~475 nm) 发光,显示出良好的色纯度,溶液和固态相之间的发光特性几乎没有变化。通过荧光猝灭机制测试了聚合物的爆炸物检测性能。目标炸药包括实验室制备的 TNT、DNT、苦味酸、RDX、HMX、PETN、TNG 和 Tetryl,以及生产线 PETN 和 C-4。所有三种聚合物均可检测爆炸性颗粒,Tetryl 的检测限值低至 1 pg cm-2。当受到紫外线照射时,聚合物 PSF1 同时充当硝酸酯炸药的选择性荧光“开启”传感器。在存在硝酸酯基爆炸物(例如 PETN)的情况下,PSF1 最初表现出荧光猝灭,但持续暴露于紫外线(302 nm)下,会促进光化学反应,形成发光的绿色芴酮共聚物。这是单一材料充当爆炸材料的关闭和开启选择性荧光传感器的第一个例子。