Polymer/Au Composite Plasmonic Micro/Nanostructures

Surface plasmon resonance(SPR)is an important property of noble metallic nanostructures.Briefly,SPR is the collective oscillation of electrons at the metal surface driven by the incident electromagnetic waves.Owing to their absorption and transformation of electromagnetic wave energy,metallic nanostructures display a serious of special properties.The most intuitive one is that they display special colors which can be tuned by changing their surrounding refractive index.In addition,the confinement and enhancement of electromagnetic field will occur around the noble metallic nanostructures in the microscopic scale invisible to the naked eye.These properties make metal plasmonic nanostructures have important applications in many fields,including refractive index sensing,bio-sensing,photothermal conversion,photothermal therapy,enhanced spectroscopy and so on.In practical applications,the performance of noble metal plasmonic nanostructures highly depends on their materials,sizes,morphologies and other parameters.By adjusting these parameters,people can obtain a sharper resonance spectrum,a stronger Raman enhancement effect,or a higher photothermal conversion,so as to obtain a better performance in various applications.For this reason,people have developed a variety of preparation methods,from the most basic noble metallic nanoparticles,to the assembly of nanoparticles,or two-dimensional and three-dimensional noble metal nanostructure arrays,to obtain a series of parameters adjustable noble metal plasmonic nanostructures.The development of new methods with low-cost,adjustable parameters,suitable for large-area preparation has always been a hot field.For this purpose,we choose the polymer with easy morphology control and surface modification to composite with noble metallic nanoparticles,and prepare polymer/gold composite plasmonic nanostructure with precise morphology parameters control,so as to achieve the modulation of plasma resonance spectrum and systematically study the relations between the morphology parameters and the plasmonic spectra.The specific contents are as follows:In the second chapter,we combined the colloidal lithography technology and the self-assembly of gold nanoparticles to prepare the size adjustable gold nanoring arrays,which can in turn tune the plasmon resonance spectra.The polymer segment arrays with hexagonal arrangement can be easily obtained by colloidal lithography,and the height and diameter of the polymer segments can be adjusted.By adjusting the size of polymer nanopillar arrays,we have successfully prepared gold nanoring arrays with controllable constant lattices in the range of 1000-2000 nm,diameters in the range of 250-800 nm and heights in the range of 200-1200 nm.We found that with the increase of the diameters of the gold rings,the dipole resonance positions of the gold ring gradually red-shift in the 1250-2250 nm band.With the increase of the height of the gold ring,the anti-symmetric dipole resonances in the1500-2000 nm range will gradually red-shift,accompanied by the enhancement of the peak intensity,while the symmetric dipole resonances in the 2500-4000 nm range will gradually blue-shift.Therefore,we have successfully achieved the adjustment of the plasmonic resonance spectra.In addition,we have also successfully prepared the gold nanocone arrays,which shows that this method can compound the gold nanoparticles and polymer structures with arbitrary morphologies,showing the strong preparation ability of this method.In the third chapter,we fabricated Au nanoring/polymer/Au asymmetric optical cavities by combining colloidal lithography and wet transfer technology.Wet transfer technology ensures the flatness of the cavities and the consistency of the optical signal.The cavity has both the plasmon resonance mode of gold rings and the Fabry-Perot resonance mode.By spin coating different concentrations of polymer,we have successfully obtained the resonance cavities with dielectric layer thicknesses varying from 0 to 1000 nm.We find that with the increase of the thicknesses of the dielectric layer,more high-order Fabry-Perot resonance modes are excited,and the highest order can reach 8.The absorption of Fabry-Perot resonance of the same order is gradually red shifted,and the red-shift of lower order resonance is larger than that of higher order resonance.And we find that the Fabry-Perot resonance absorption positions of our asymmetric resonator is slightly red-shifted compared with that of the perfect Fabry-Perot cavity,which is due to the absorption of light by the plasmonic resonance of gold nanorings.In addition,different incident angles can also change the resonance spectra,and the resonance spectra shift is consistent with the Bragg's law.In the fourth chapter,we combined the electrospinning technology of polymer and the self-assembly of gold nanoparticles to prepare the interfacial photothermal materials for solar-driven seawater desalination.Polymer nanofibers provided a large number of attachment sites for gold nanoparticles.Their three-dimensional microstructure not only enhances the light absorption of gold nanoparticles,but also facilitates the transportation of water and steam.Under the light power of 3.4 kW m^-2,the photo thermal conversion efficiency can reach 77%.Because of the introduction of polymer,it also has the advantages of light weight and flexibility.Through the test of simulated seawater desalination,we found that the water salinity after photothermal distillation is three orders of magnitude smaller than that of simulated seawater,indicating that this material has a good prospect of photothermal application.