Silicon Substrate Surface Autofluorescence Assembly Of Silver Nanoparticles To Enhance The Effect

Surface Enhanced Fluorescence have been discovered by Drexhage in1970s. Since then researchers at home and abroad have explored the SEF in both theoretical and experimental area, and a series of important results have been found. There are two main research cores in recent researches:exploring the mechanism of surface-enhanced fluorescence enhancement and looking for higher enhancement substrates. Surface-enhanced fluorescence is affected by many factors, so there are varieties of enhanced theories. There are three main theoretical models generally established. They are the theory of Substrate surface fluorescence molecules near the local field enhancement; the theory of Molecules and substrate surface energy transfer and the theory of Fluorescent molecular radiation attenuation rate. Surface enhanced fluorescence effect is caused by various factors; the key to it is whether the surface Plasmon can be excited effectively. At present, people are constantly trying to find better-enhanced substrates. There are several effective enhanced substrates of fluorescence, which are Aluminum and precious metal:Gold, Silver, Copper etc. The precious metals have broad plasma absorption band relatively in visible spectral region, so when the metal nanostructures excited by the light of the same oscillation frequency of surface Plasmon, which will cause the surface plasma oscillation, and saturated absorption, resulting in metal surface to produce strong local electromagnetic field relatively, so that the fluorescence of fluorescent molecules near the surface will be enhanced. Not only metal can enhance the fluorescence of fluorescent molecules, some special surface on non-metallic such as silicon array can also have fluorescence enhancement effect.In the study of surface enhanced fluorescence effects, select an appropriate substrate is crucial. In researches during I wrote this thesis, I chose composite material which is silicon substrate self-assembled with silver nanoparticles (Ag@Si) on it as substrate, the surface morphology of the silver nanoparticles that deposited on silicon substrate surface, which effect the fluorescence molecule Rodeming6G (Rh6G) on the spectrum, and has carried on with theoretical analysis. There are two main parts in this thesis. In the first part, we discussed the fluorescence effect of Rh6G on the surface of the composite structures substrate that silicon self-assembled with silver nanoparticles. The second part shows us the annealing process enhancement effect on the fluorescence of Ag@Si composite structure surface. The first part is about the enhancements effect on Rh6G fluorescence of composite structure that silicon substrate surface self-assembled with silver nanoparticles. Deoxygenating by controlling the depositing time produced uniform distributed silver nanoparticles, can we get Ag@Si Nano-composite structure with different surface morphology, and laser spectroscopy is used to study the phenomenon of fluorescence enhancement of the composite structure of Rh6G molecules on the surface. And we analyzed the effect on fluorescence caused by the surface morphology of the nanometer metal. After comparing with the silver nanoparticles on glass substrate in the same condition, we found that the enhancement fluorescence effect of Rh6G molecules is much better than that on Ag@Si substrate. And after that, we had a cooperation and discussion based on respectively for the local field of metal nanoparticles enhanced characteristics with glass substrate and silicon substrate.The second part is about effect on the enhanced surface fluorescence of Ag@Si composite structure during annealing process. Using Ag@Si composite structures annealed under different temperatures as substrate, we studied the enhancement fluorescence effect of Rh6G molecule on annealed substrate. We have found that after annealing, the substrate can enhancing the fluorescence in certain way, and with the increasing of the temperature of annealing, the fluorescence intensity of the molecule is first increased and then decreased by substrate. We analyzed the substrate’s effect on fluorescence enhancement according to the changes of metal surface plasma between the local field and fluorescent molecules and the changes of distance of metal substrate changed and other factors. We changed silicon substrate into glass substrate with other conditions unchanged and found that annealed glass substrate still shows a obvious positive result, what’s more is that the result is even better than the one used silicon substrate. This significant result proves that the influences are not the same for the structure of metal particles on different substrate during annealing.