[Nanosilver sensitized fluorescence and second-order scattering of Tb (III)-norfloxacin and its application]

Norfloxacin (NFLX) can form complex with Tb(III) ion, and the intramolecular energy transfer from NFLX to Tb (III) takes place when excited. And thus the characteristic fluorescence of Tb (III) ion is enhanced and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb (III)-NFLX complex with the excitation wavelength of 272 rnm. When the silver nanoparticles were added to the Tb (III)-NFLX binary system, the luminescence intensity at 545 nm greatly increased. And the relative intensity is proportional to the amount of NFLX. Based on this phenomenon, a novel method for the determination of NFLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The calibration graphs for NFLX are linear in the range of 6.0 x 10(-9)-1.0 x 10(-5) mol x L(-1), and the detection limit is 4.4 x 10(-9) x mol x L(-1). This method was applied satisfactorily to the determination o f NFLX in capsule and eye drop samples. The experimental results showed that it is the certain size and certain concentration of silver nanoparticles that can greatly enhance the fluorescence-SOS intensity.