Fluorescent carbazole dendrimers for the detection of nitroaliphatic taggants and accelerants
作者:Andrew J. Clulow、Paul L. Burn、Paul Meredith、Paul E. Shaw
DOI:10.1039/c2jm32072j
日期:——
The detection of explosive taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB) and accelerant nitromethane (NM) by oxidative quenching of dendrimer fluorescence is examined. Two fluorescent dendrimers incorporating a 3,6-disubstituted-9-n-hexylcarbazole-based core and first-generation biphenyl-based dendrons linked directly or with acetylene bridges are reported. The dendrimers display good photoluminescence (PL) quantum yields in both solution and thin films and appropriate excited state energies for oxidation by the nitroaliphatic analytes. The dendrimer natural excited state lifetimes in solution of 6.8 and 7.4 ns were found to be significantly longer than previously reported fluorescent conjugated polymers and dendrimers for sensing applications. Steady-state PL quenching measurements in solution revealed the highest quenching efficiencies for the detection of nitroaliphatics reported to date of 59 ± 1 M−1 for DMNB and 78 ± 1 M−1 for NM. Furthermore, PL lifetime quenching measurements confirmed that the dendrimers were quenched by a predominantly collisional quenching mechanism. As such, the unprecedented quenching efficiencies with nitroaliphatics in solution are due to the combination of the long excited state lifetimes of the dendrimers and efficient collisional quenching. The fluorescence of dendrimer thin films was also reversibly quenched by exposure to pulses of sub-saturation concentrations of analyte vapours. However, in the thin film case the sensitivity towards DMNB was found to be greater than NM, highlighting the disparity between solution and thin film fluorescence quenching measurements.
研究了通过树枝状聚合物荧光的氧化淬灭来检测爆炸性标记剂 2,3-二甲基-2,3-二硝基丁烷 (DMNB) 和助燃剂硝基甲烷 (NM)。报告中介绍了两种荧光树枝状聚合物,它们包含一个以 3,6-二取代-9-正己基咔唑为核心的树枝状聚合物和直接或通过乙炔桥连接的第一代联苯树枝状聚合物。这些树枝状聚合物在溶液和薄膜中均显示出良好的光致发光量子产率,并具有适当的激发态能量,可被硝基脂肪族分析物氧化。研究发现,树枝状聚合物在溶液中的自然激发态寿命分别为 6.8 和 7.4 ns,明显长于之前报道的用于传感应用的荧光共轭聚合物和树枝状聚合物。溶液中的稳态聚光淬灭测量显示,迄今所报道的用于检测硝基脂蛋白的淬灭效率最高,DMNB 为 59 ± 1 M-1,NM 为 78 ± 1 M-1。此外,聚光寿命淬灭测量证实,树枝状聚合物主要通过碰撞淬灭机制进行淬灭。因此,溶液中硝基脂质体前所未有的淬灭效率是树枝状聚合物激发态寿命长和高效碰撞淬灭相结合的结果。将树枝状聚合物薄膜暴露在亚饱和浓度的分析蒸汽脉冲中,也能可逆地淬灭其荧光。然而,在薄膜的情况下,发现对 DMNB 的灵敏度高于 NM,这凸显了溶液和薄膜荧光淬灭测量之间的差异。