Study On The Near-field Enhancement And Far-field Properties Of LSPR Of Al Nanoparticles

Metal nanoparticles are widely used in the fields of surface-enhanced Raman scattering and semiconductor luminescence because of their unique localized surface plasmon resonance(LSPR)characteristics,so it is of great importance to study the LSPR properties of metal nanoparticles.Gold and silver are widely studied plasmon photonic metal materials,but gold and silver can only achieve plasmon resonance in near infrared and visible wavelengths,along with ultraviolet-related devices in water purification treatment,air purification treatment,photocatalysis and white light lighting and other fields play a more and more important role,now we need a kind of metal material which can appear local surface plasmon resonance in ultraviolet band.Al has excellent LSPR properties in the ultraviolet band,and it is the most effective metal that can be coupled with ultraviolet light to produce localized surface plasmon resonance.At present,there is a lack of systematic research on the influence of the size of Al nanoparticles and the surrounding medium environment on the localized surface plasmon characteristics in the ultraviolet band.In this paper,Al nanoparticles which can produce local surface plasmon resonance in ultraviolet band are taken as the research object.The near-field local enhancement and far-field properties of square cylindrical Al nanostructures are simulated and analyzed by using finite-difference time-domain method(FDTD).Firstly,the research background and development of plasmon photonics are briefly introduced,and the metal Al nanomaterials which can realize plasmon resonance in ultraviolet band are introduced.Secondly,the basic principle of time-domain finite difference method is introduced,and the full-field scattering field light source and perfectly matched layer boundary conditions used in this paper are summarized.The effects of the size parameters of cubic cylindrical Al nanoparticles on the nearfield and far-field properties of LSPR were simulated by finite-difference time-domain method,and the effects of changing the dielectric environment around metal nanoparticles on their LSPR properties were simulated and analyzed.The following contents are the main contents and results of this paper:(1)In this paper,through the simulation calculation of FDTD,the effect of the shape structure and size parameters of the metal Al nanoparticles on the LSPR characteristics of the metal nanoparticles is systematically studied.Two aspects of the near-field local enhancement feature are analyzed.The plasmon extinction coefficient spectra of Al nanoparticles with different sizes were obtained through simulation analysis;the near-field local electric field distribution at different LSPR wavelengths corresponding to different sizes was obtained through simulation calculations.The extinction coefficient spectra of Al nanoparticles with different sizes were obtained by simulation analysis,and the local electric field distribution of near field at LSPR wavelengths corresponding to different sizes was obtained by simulation calculation.(2)The influence of the surrounding dielectric environment on the LSPR characteristics of square cylindrical Al nanoparticles was simulated by FDTD,and the simulation model was selected as the size of Al nanoparticles with the strongest extinction intensity and the best local electric field enhancement in the near field.The extinction coefficient spectra of Al nanoparticles with different oxide thickness were obtained by simulation,and the electric field distribution of Al nanoparticles in the presence of single Al nanoparticles and oxide layer was obtained by simulation.(3)The effect of substrate on metal nanoparticles is further identified based on the mixing theory and the analysis of the near-field distribution of Al nanoparticles.The existence of substrate not only changes the dielectric environment around metal nanoparticles and improves the effective refractive index of the environment,but also provides an effective way for the coupling and hybridization between different modes of localized surface plasmon(LSP).