Fabrication And Application Of Self-assembled Plasmonic Crystals

Plasmonics,focusing on light and plasmonic resonance,has been a popular research field of emerging nanophotonics.It can control the interaction between light and material at the nanoscale via metal micro/nano structures,which have good performance in the spatial resolution and energy conversion efficiency.Plasmonic crystals studied in this thesis,an important branch of plasmonics,have periodic metal nanostructures.Compared with nonperiodic structures,plasmonic crystals can ensure the reproducibility of results due to the ordered and uniform structure.Plasmonic enhancement of these structures can be designed and controlled well,which makes them be widely applied as biosensors.Meanwhile,the interaction between incident light and free electron on the surface of metal could produce stable,non-photobleach color.Therefore,plasmonic crystals could be applied in the field of display,solar cell and optical storage.In this dissertation,plasmonic crystals have been fabricated through high-efficiency self-assembly and metal coating,then they were applied for the detection of microorganism and in the field of plasmonic display.The detailed work is listed as follow:1.A method based on filtration self-assembly and electroless plating was proposed for the preparation of plasmonic crystals.Firstly,3D ordered structure was prepared via filtration self-assembly and was coated with silver through electroless plating.This method is easy-operation and low-cost.The plasmonic crystals prepared with this method contains many nanoscale pores and can be used as filter membrane for biological detection and analysis.Secondly,Finite Difference Time Domain(FDTD)simulation was proceeded for the calculation of the intensity and distribution of electric field,which indicated the "hot spots" were located in the gap of nanoparticles,which could contribute to the interaction between substrate and samples.Finally,the results of Raman detection showed that enhancement factor of the plasmonic substrate was at the level of 107.2.Plasmonic crystals prepared with the method mentioned above were utilized for the SERS detection of microorganism.Firstly,we used plasmonic crystals to detect the Surface Enhanced Raman Scattering(SERS)spectra of electricigens.The results showed that through the "filtrate and measure" method,not only the electricigens Geobacter sp.and Shewanella sp.could be discriminated with species specificity,but also Geobacter sp.and pilus-mutated Geobacter sp.strains with minimal sample volume.Besides,we discriminated different nosiheptide sources via SERS signals of Streptomyces spores detected with plasmonic crystals substrate.In comparison to traditional Gram staining method and silver-plated nylon filter membrane,the plasmonic crystals substrate showed good sensitivity and efficiency in the discrimination of nosiheptide prepared with active pharmaceutical ingredients and biological fermentation.The whole detection process was completed with a sample volume of only 5μL in less than 5 min.3.A low-cost,stable and universal method was proposed for the transfer printing fabrication of ordered micro/nano structures.Ordered monolayer structu-re was fabricated through transfer printing of monolayer nanoparticles onto the polydopamine modified substrates and the monolayer nanoparticles were prepared with liquid-air interface self-assembly.This method solved the problem of instability in the process of transfer printing.The results showed that this method is universal and promising and we have explored the preparation of self-assembled ordered structure on the flat surface,cambered surface,rigid surface,flexible surface,inorganic surface and organic surface.The ordered micro/nano structures prepared with this method can be modified with metal layer via electroplate or metal evaporation.Then the obtained plasmonic crystals can be applied in the biological detection,display and energy.Large-area ordered micro/nano structures can be prepared with this method and it has established the foundation for the widely application of plasmonic crystals.4.The method for the preparation of plasmonic crystals patterns was proposed based on the self-assembly and transfer printing.The results showed that we can fabricate stable plasmonic crystals patterns with the help of template on the rigid and flexible substrates.The analysis of optical characteristic indicated that the display color of plasmonic crystals was angle-dependent.But compared with colloidal photonic crystals,the color was brighter under vertical incidence.Based on the results mentioned above,the plasmonic display can be applied in the sensor detection through the responsiveness of substrate.