Synthesis and characterization of silica/silver multilayer nanoparticles and their application in surface enhanced spectroscopy

This research is focused on determining the most effective silver shell growth method formultilayered metallic nanoparticles, and determining the plausibility of using embedded[Ru(bpy)3]2+ as an internal standard for surface enhanced Raman spectroscopy. In the surfacestudy, silica particles were functionalized with (3-aminopropyl)trimethoxysilane followed by avariety of seeding techniques to complete the silver shell. This study revealed that the optimumsynthesis method prior to the hydrogen reduction of the silver shell utilized a tin treatmentfollowed by a silver (I) oxide soak, resulting in the best surface coverage. Likewise extinctionanalysis revealed that this type of particle absorbs the most light, which likely is important forsurface enhanced spectroscopy.In the second part of the study, a procedure is reported for the synthesis of multilayeredmetallic nanoparticles with a dye molecule ([Ru(bpy)3]2+) embedded in the dielectric layerseparating the two silver layers. Raman spectroscopy was used to prove the success ofembedding the dye molecule into the spacer layer. Fluorescence, extinction, absorption, andscattering data were used to determine that, as the shell is synthesized, it begins to absorb moreof the excitation light. This absorption is a problem because [Ru(bpy)3]2+ has a low quantumyield of only 7.2% and the signal is easily extinguished as the shell becomes thicker. Finally, the particles with the embedded dye molecule were used for a preliminary test to determine theirusefulness as an internal standard for surface enhanced Raman scattering. This preliminarystudy revealed that it is possible to detect [Ru(bpy)3]2+ using the 457.9 nm laser and use a632.8 nm laser line to detect a 500 nM crystal violet solution. 500 nM is below the detection ofcrystal violet only using Raman spectroscopy