Research On Construction Of Gold Nanostructures And Their Refractive Index Sensing Properties

Noble metal nanomaterials have attracted great interests since they werediscovered owing to their superior photoelectric properties that are distinct fromanalogous atomic or bulk materials. The special properties are due in large part tolocalized surface plamon resonance (LSPR). Localized surface plasmon resonance iscollective electron oscillations on the surface of conductive nanoparticles that areexcited by appropriate incident light. The LSPR properties depend not only onstructural features of nanoparticles themselves but also on the parameters ofenvironment. It is concluded via previous researches that size, morphology,aggregation, distance of nanoparticles, refractive index and dielectric constant ofenvironment all have an effect on LSPR of nanoparticles. The localized surfaceplasmon extinction would shift in both wavelength and intensity in response to changeof these factors. Thus, metal nanoparticles were widely applied towards surfaceplasmon enhanced spectroscopy, biosensing and a large amount of other fields.Great progresses have been made in controlling of morphology of metalnanomaterials by solution-phase preparation, however solution-phase nanomaterialshave a few inevitable limits in applications. At the same time, a lot of top-down andunconventional fabrication techniques have been invented and widely used, such aselectron beam lithography, focused ion beam lithography, nanosphere lithography,colloid lithography and imprint lithography. Although unconventional lithographytechniques has overcome the high cost and low efficiency in top-down lithographytechniques, they still cannot be used to fabricate nanostructures in a large scale.Herein, we fabricate metal nanostrucutures with different interparticle distancesand different densities of nanoparticles by self-assembly due to static interactionbetween gold nanoparticles and substrates derivatized with aminopropyltrimethoxysilane (APTMS). The sizes of gold nanoparticles can becontrolled with different ratio of reactants. Average inter-particle distance and densityof particles can also be adjusted by deposition time and ionic strength of colloidsolution. Furthermore, Morphology of nanostructures can be influenced by theannealing process at various temperatures. This mehod of fabrication is facile, simpleand of low cost and can be utilized to construct metal nanostructures in a large scale.In studying the refractive index sensing property of above nanostructures, wefound that the RIS property of LSPR extinction peak can be increased with averagesize of nanoparticles and that interparticle distance and density of nanoparticle haveno apparent influence on the RIS properties of LSPR extinction peak. Moreimportantly, refractive index sensitivity can be enhanced by inter-particle couplingeffect remarkably. Although in UV-Vis spectra, the half peak width of the extinctionpeak due to coupling effect is wider than that of the extinction peak due to LSPR, itstill provide crucial guidance and a potential platform for biosensing and otherapplications.