A nitroaromatic fluorescence sensor from a novel tripyrenyl truxene

A new fluorophore containing a truxene core and three ethynyl pyrene peripheries is successfully synthesized by Sonogashira coupling. This compound exhibits superior emission properties compared to the parent truxene with quantum yields of 71 and 53% in CHCl3 and aqueous THF, respectively. In CHCl3, it shows a selective fluorescence quenching towards 2-nitrophenol with a detection limit of 1.54 ppm. When dissolved in aqueous THF, however, its fluorescence signal is selectively quenched by picric acid with a detection limit of 0.15 ppm. Since the absorption bands of these analytes overlap with the excitation wavelength of the fluorophore, the inner filter effect may be a significant cause of the fluorescent quenching. However, there is no constant correlation between the fraction of photons absorbed by the fluorophore and the emission integrals, therefore, other quenching mechanisms might also play important roles. The Stern-Volmer plots at different temperatures indicate a static or contact quenching of the fluorophore, which could be caused by the pi-pi interaction between the fluorophore and the electron-deficient analytes.