Surface - Enhanced Fluorescence Effect Of Porous Alumina Films And Precious Metal Nanoparticles Composite Structures

The electromagnetic field distribution on the nanostructure metal substrate surface can be change by interferences of the surface plasmon excited by incident light. As a result, the fluorescence radiation of the fluorescent species located near the surface of the substrate is modulated. Comparing to fluorescent molecules of free, the dramatically increase of its fluorescence radiation efficiency is known as surface-enhanced fluorescence effects. In practicing, as the need of measurement environment in the spectrum detection technology is increasing, surface enhanced fluorescence attracted more and more researchers because of its high sensitivity. With the rapid development of nanotechnology, people are studying the surface enhanced fluorescence effect on the properties of the nanomaterial, adjusting the size of the substrate, modification of surface morphology and other aspects of nanomaterial. Meanwhile, on theoretical exploration, local field enhancement theory, the energy transfer theory, the theory of radiation decay rate is proposed to support the exploring the surface-enhanced fluorescence in experiments.In the study of surface-enhanced fluorescence, one of the most popular field researchers concerning is the substrate processing. Nanowires, nanospheres, nanorods, flower morphology, has been widely applied in the surface enhanced fluorescence effect. Substrate with silver island film, spherical gold plastic, triangular silver plastic, rubber and other rod-shaped gold nanostructures which are produced through redox method, magnetron sputtering method and thermal deposition method have provided good sample platform for the study of surface enhanced fluorescence. However, those substrates mentioned above have some shortcomings in a large area, to enhance the uniformity of the substrate exploration, which have limited their large-scale promotion.As we all know, porous alumina membrane pores having a hexagonal honeycomb structure, with controllable pore size, fine hole distribution, good pore orientation, and the hole is perpendicular to the surface of the substrate. This porous alumina has made a wide range of applications in the surface-enhanced Raman scattering field of study as its highly ordered porous alumina membranes prepared reinforcing substrate. However, researches based on the preparation of porous alumina film substrate are rarely reported on the study of surface-enhanced fluorescence effect.In this paper, the use of porous alumina membrane as template with electrochemical deposition, ion sputtering and other means to prepare a porous alumina membrane and noble metal nanoparticle composite structure, and we also researched its surface enhanced fluorescence effect, access to large area substrates with simple process, which have the advantages of low cost, easy to controlling the morphology, the uniformity and fluorescence enhancement significantly. The main work and conclusions are as follows:1. Preparation of the porous alumina membranes and measurement of fluorescence spectroscopyPorous alumina membranes with distributed hexagonal honeycomb mesh holes uniformly distributed by secondary oxidation were prepared. Morphology characterized by field emission scanning electron microscope. We explored on the influence of surface enhanced fluorescence effects by processing of porous alumina membrane by means of laser spectroscopy. The results showed that the porous alumina membrane without reaming process had a strong enhancement compared to those have got the reaming process. The enhancement factor could be up to 3.8. Analysis showed that the porous alumina membrane without reaming process has a unique three-dimensional surface topography, with larger area surface, which leads to better effect on surface enhanced fluorescence.2. Research on the preparation of porous alumina template modulating Au/Ag composite nano-structured and on the surface fluorescence effect enhancement.With the electrochemical deposition method, the Au/Ag composite nano structured substrate was prepared that modulated by the AAO by depositing gold, silver nanoparticles into the pores of the porous alumina template, sequentially. Rh6G was selected as fluorescent probe molecules in the experiment, and the new substrate surface enhanced fluorescence effects were studied at 532nm laser excitation. The results showed that the prepared substrate has a significant fluorescence enhancement effects, and the data was increased about 8.5 times. With the decreasing of cell density, enhancement factor is growing larger. Discussions about enhanced fluorescence effects of the composite substrate are proposed based on enhanced local field theory, and gold/silver nanoparticles electromagnetic response of angles.3. The research on surface gold and silver nanoparticles modified porous substrate composite structure reinforced aluminum effect.Porous aluminum composite structure is obtained by using ion sputtering method and electrochemical deposition method, respectively. The fluorescence enhancement effects of fluorescence enhancement effects by this subtract is studied. We obtained an average of 2.6-fold fluorescence enhancement factor under the excitation of 532nm laser. The experimental phenomena observed were discussed according to the radiation decay rate increase theory.