Coumarin fluorometry to quantitatively detectable OH radicals in ultrasound aqueous medium

Abstract

When ultrasound (US) was exposed to aqueous coumarin solution in air atmosphere, the UV–visible and fluorescence spectra of the probe were measured at different US exposure times. The US exposure was carried out at 43kHz and 500kHz with different out-put power. It was found that the 500kHz US produced umbelliferone fluorescence, while the 43kHz US had no fluorescence. In addition, the coumarin absorbance at 270nm maximum was decreased with in cases of the US exposure time. In contrary, the fluorescent intensity of umbelliferone at 460nm increased with increasing of US exposure time. This exhibited that the coumarin probe was converted to umbelliferone by the US exposure, when the 500kHz US was operated. This was facted that the coumarin framework was caused with addition of OH groups which was generated by the 500kHz US. Therefore, the umbelliferone fluorescent became a probe to estimate OH radical in US medium. Furthermore, the chemo-fluorometry showed that the emission maximum of the formed umbelliferone could probe the bulk pHs in the US aqueous medium.