Tetraphenylethene probe based fluorescent silica nanoparticles for the selective detection of nitroaromatic explosives.

A simple and sensitive fluorometric method is developed utilizing aggregation-induced emission probe based silica nanoparticles for the detection of nitroaromatic explosives. A positively charged tetraphenylethene based probe (TPE-C2-2+) is doped into silica nanoparticles exploiting electrostatic interactions to produce TPE–SiO2 nanoparticles with a uniform particle size. The TPE–SiO2 nanoparticles exhibit strong fluorescence emission due to the aggregation-induced emission (AIE) effect of the doped TPE probe. The fluorescence emission of TPE–SiO2 offers quantitative and sensitive response to picric acid (PA), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) which are used as model examples of nitroaromatic compounds. The fluorescence spectroscopy results show that the fluorescence emission of TPE–SiO2 was greatly quenched in the presence of the electron-poor nitroaromatic compounds due to the inner filter effect (IFE) and possibly the contact quenching mechanism. TPE–SiO2 nanoparticles show better sensitivity towards PA and could detect PA down to 0.01 μM with a linear detection range of 0.1–50 μM. The increased chemical stability, efficient high sensitivity and simple synthesis of the TPE–SiO2 nanoparticles demonstrate that they can be used as an excellent fluorescent probe for a wide range of electron-poor compounds, i.e. nitroaromatic compounds. Interference studies show that common interfering species with nitroexplosives such as acids, bases, volatile organic compounds, and salt solutions have a negligible effect during the sensing process.