Nanowell Arrays Construction And SEF On FL Of Ag Nanoparticle Array

Polystyrene nano-particles of varied sizes (200,500, 1000nm) were synthesized by emulsion method. An ordered monolayer or multilayer polystyrene nanoparticles array template can be spontaneously formed because of energetic movement and gravitation, that is self-assembly .By chemically deposition, Ag, Au, Cu inverse opal structures were generated on the PS template. Macro-porous SiO₂ was produced by sol dipping as well as capillary effect. The influences of temperature, concentration, and diameter of nanparticles on templating process were examined. As an effective SERS base material, Ag nano-well array of different diameters resulted in different enhancement impact on PATP molecule adsorbed onto the nanowells. The larger nanowell causes the larger enhancement.Homogeneous silver nanoparticles were prepared by reducing saturated Ag2o solution with H₂.At the same reaction concentration, the size of Ag nano-particles changes with the reaction time. In our experiments, 4h and 8h nanopaticles were produced and employed in following FL experiments .By self-assembled onto the polyvinyl-pyridine modified glass slide, monolayer Ag nanoparticle arrays were obtained. Absorption spectra of the assemblies demonstrated that the interaction between silver nanoparticles resulted in large shifts of dipolar surface plasmon resonance, whereas only slight effect was observed for quadrupolar surface plasmon resonance. It illustrates there may exist somewhat close relativity between enhancement of electric field in nearby particles and dipolar interaction. Also the UV absorption spectra of different density, that is of different assembly time, there is big blue shift between the origin absorption place and the saturation absorption place. Assemblies of different assembly time Ag nanoarrays and their influence on FL enhancement were investigated.SEF experiments were carried out on these well assembled nanoparticle arrays. To observe large EM enhancement of fluorescence it is desirable to excite the fluorescein molecules by light the energy of which is close to surface plasmon resonance from Ag absorption spectra, the optimum excite wavelength in our experiments is 450nm. The size of nanopaticles influence SEF too. The distance of nanopaticles and the space between FL and nanoparticles contribute to the results as well. Our research shows that when the size increases, the signal swells, and when particle density raises, a larger enhancement was gained. But the relativity is not direct ratio between the density and FL signal. And after saturation, the signal of FL spectrum declines largely. In a word, the enhancement effect on FL strongly depends on the SPR of the metal nanoparticles.