Study and application of a novel probe using twisted intramolecular charge transfer fluorescence

This paper reports the investigation of the twisted intramolecular charge transfer (TICT) of 4-(diethylamino)benzoic acid (DEABA) in aqueous β-cyclodextrin (β-CD) and methylated β-cyclodextrin (β-MCD) solution by studying the typical TICT dual fluorescence and makes a comparison between the TICT behavior of DEABA and 4-(dimethylamino)benzoic acid (DMABA). In pure water, DEABA and DMABA emit only locally excited (LE) fluorescence, and the TICT fluorescence band is developed with the addition of β-Cd or β-MCD. Both LE and TICT fluorescence bands are continuously enhanced upon an increase of β-CD or β-MCD concentration. The microenvironmental change of β-CD caused by methylation can be indicated with DEABA. The ratio of TICT to LE fluorescence intensities resulting from excitation at 280 nm decreased markedly with increasing the size of the alcohol molecules or the concentration of methanol, ethanol, propanol and butanol. The ratio is unaffected by the intensity of the source which affects absolute intensities and can be used to quantify alcohol concentrations. This possibility has been tested for the determination of single alcohol in synthetic water samples.