Construction Of Silica Particle-based Fluorescence Resonance Energy Transfer System And Its Application In Hg²⁺ Ratiometric Detection

In this thesis, according to the principles of Fluorescence Resonance Energy Transfer （FRET）, we chose 7-nitrobenzofurazan （NBD）, quantum dots （QDs） as the donors, rhodamine B as the acceptor. Several classes of FRET systems based on silica nanoparticles or silica films were constructed via some facile methods. Due to the unique structural feature of rhodamine, the presence of Hg2+ in the water induced the ring-opening reaction of the spirolactam rhodamine moieties and lead to the occurrence of the FRET process, affording the system a rationmetric sensor for Hg2+. The main contents and the results of this work are as following:Core/shell silica nanoparticles were prepared by sol-gel method. A hydrophobic ?uorescent dye NBD was covalently embedded in the nanoparticle core and used as the donor; On the other hand, an ethoxysilane-linked spirolactam rhodamine derivative RHB-OET was covalently linked onto the particle surface and used as the mercury ion-recognition element （the probe）. The presence of Hg2+ in the water dispersion of nanoparticles induced the ring-opening reaction of the spirolactam rhodamine moieties ed to the occurrence of the FRET process, affording the nanoparticle system a ratiometric sensor for Hg2+.It has been discussed that : the F?rster R0 ,the effective area for FRET and the ?uorescence lifetime.Multi-layer silica nanoparticles were prepared by sol-gel method. NBD was covalently embedded in the second layer of the particles and the spirolactam rhodamine derivative SRHB-OET was covalently linked onto the particle surfaces, both of them were fixed in the system using the way of cohydrolysis. The presence of Hg2+ in the water dispersion of nanoparticles induced the ring-opening reaction of the spirolactam rhodamine moieties and led to the occurrence of the FRET process, affording the nanoparticle system a ratiometric sensor for Hg2+ . It has been founded that: the thickness of the spacer play an important role in the transfer efficiency and the system can afford higher transfer efficiency （74%）. The nanoparticle sensor can selectively detect the Hg2+ in water with the detection limit of 500 nM. Moreover, the sensor was applicable in a relatively wide pH range （pH 5 to 9） in water. This sensor may provide a new strategy for ratiometric detection of analytes in some environmental and biological applications.The ?uorescence QDs/SiO₂ composite particle were prepared by the reverse microemulsion. The water soluble QDs CdTe was doped in the second layer of the particles by using the APS to dramatically reduced the electrostatic interactions between the negatively charged silica and the CdTe. The spirolactam rhodamine derivative SRHB-OET was covalently linked onto the particle surface using the way of cohydrolysis. The ratiometric fluorescent signal change of the system is based on the FRET process generated by mercury ions in water. Also, the particles have the same superiority as the multi-layer particles because they have the same probe.The multi-layer films were prepared by the spin-coating and grafting. The substrate layer was SiO₂, film by spin-coating the silica sol. The spacer, the donor （NBD） and the acceptor （SRHB-OET） all were grafting to the substrates layer by layer. NBD/Spacer/SRHB-OET constructed the FRET system. Dipping the film into the mercury solutions, the color of the film will changed from green to pink. By this way, a shortcut and simple detection for mercury was applicable.