ABSTRACT
A highly sensitive fluorescent probe TZ based on a novel Schiff's base was prepared for detection of Mg2+. It was constituted by introducing dansyl chloride and 2-hydroxy-1-naphthaldehyde through amino and hydrazide groups on p-aminobenzoyl hydrazide. The recognition mechanism of the fluorescent probe TZ for Mg2+was studied by electrospray ionization mass spectrometry (ESI-MS), UV-vis and fluorescence spectra. UV-vis spectra showed that the probe TZ had a characteristic absorption peak of naphthalene aldehyde at 386. 5 nm,and a new absorption peak at 411 nm was observed after coordination between TZ with Mg2+. A sharp isobestic point was obtained at 400 nm. Fluorescence spectra showed that the emission wavelength was red-shifted to 400 nm upon the addition of Mg2+into probe TZ. The fluorescence intensity was enhanced by 10 times at the emission wavelength of 468 nm and the quantum yield of 0.57 was obtained. Moreover,chemical bond energy transfer was found when 2-hydroxy-1-naphthaldehyde was coordinated with Mg2+. When the other metal ions (Li+,Na+,K+,Zn2+,Ca2+, Mn2+, Cd2+, Pb2+, Ag+, etc.) were added into TZ, no significant change of fluorescence intensity was observed. It indicated that TZ had high selectivity to Mg2+. Furthermore, the recognition of TZ to Mg2+was not interfered by other competing metal ions. ESI-MS titration and Job's plot analysis confirmed that 1: 1 complexation stoichiometry between TZ and Mg2+was obtained. The lowest detection limit was up to 0.13 μmol/L.