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Investigation Of The Refractive Index Sensitivity Responses Of LSPR Sensors Of Individual Noble Metal Nanoparticles

Posted on:2017-05-20Degree:MasterType:Thesis
Country:ChinaCandidate:M L HuangFull Text:PDF
GTID:2311330503995655Subject:Condensed matter physics
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Plasmonic sensor of noble mental nanoparticles is an advanced label-free biosensing technique, which attributes to the high sensitivities of their localized surface plasmon resonsnaces to the bulk and local refractive index(RI) of their surrounding mediums. Such sensitivities are associated closely with the nanoparticle's shape, size, composition, and etc. They have been widely used in biological, medical, and chemical sensing and detections, and have been one of the research focuses in nano optics. Yet, it is crucial to undress the the linear or nonlinear response of such sensitivities to the corresponding RI, which is fundamentally important for their potential technical applications. Accordingly, by MiePlot software(based on Mie theory) and DDA(Discrete dipole approximation) method, we have calculated the absorption, extinction, and scattering spectra of noble metal nanospheres, nanocylinders, nanocubes, nano elliptical pillars, nano triangular prisms, and nano diamond pillars, respectively, in this thesis, and then investigated the responses of their LSPR peak wavelengths to the RI of surrounding mediums.The main research work and results of the thesis are listed as below:1) The optical(including scatteing, absoption and extinction) spectra of individual noble Au/Ag/Cu nanospheres with different radius are calculated by MiePlot software. Their dipolar LSPR peak positions ?LSPR are are revealed to red shift nonlinearly with the RI of their surrounding mediums, while their sensitivity factors red shift linearly with the RI, respectively. Their underlying mechanism are illuminated well based on Rayleigh approximation and the dipolar resonance condition. The responses of their ?LSPR to the local RI are discussed as well.2) The optical(including scatteing, absoption and extinction) spectra of individual Au/Ag nanodiscs are numerically calculated by using DDA method, whose heights are kept to be 12 nm with varying radius of 8nm, 10 nm, 15 nm, 20 nm, 25 nm, and 30 nm. The aspect ratio effect of the nanodiscs are demonstrated to not destroy the nanolinear and linear responses of their dipolar LSPR peak positions ?LSPR and sensitivities factors to the RI of their surrounding mediums, respectively. Their ?LSPR and sensitivities factors are demonstated to quadraticly increase with their aspect ratios. Their underlying mechanism are explained in terms of Rayleigh approximation and the dipolar resonance condition.3) The optical(including scatteing, absoption and extinction) spectra of individual Au/Ag nanoelliptical pillars, nano triangular prisms, nano diamond pillars, and nano cubes are calculated by DDA, respectively, while keeping their heights and volumes the same. The quadratic responses of their dipolar LSPR peak positions of ?LSPR to their RI of surrounding mediums are investigated. Their shape factors effect are discussed as well.The above results demonsrate that the responses of ?LSPR of different noble metal sensors are quadratic in nature, regardless of the shape of the concerned nanoparticles. This is believed to be fundamentally important, and is able to provide data for future designing corresponding miniaturized plasmonic sensors.
Keywords/Search Tags:Localized surface plasmon resonance(LSPR), LSPR based sensors, Rerfactive index sensitivity, Sensitivity factor, Mie scattering theory, Discrete dipole approximation, Noble metal nanoparticles, optical spectra
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