Investigation Of Localized Surface Plasmon Based Optical Sensing Properties Of Noble Metal Nanoparticles

On the basis of the susceptible properties of LSPR to the refractive index of their surrounding mediums of noble metallic nanostructures,they have been broadly applied in LSPR based optical nano-sensors and nano-detections.Motivated by the current status of exploring the key parameter controlling nanoparticles' sensing/detecting properties,in this work,with the help of discrete dipole approximation,the optical sensing properties of Au and Ag nanoparticles are investigated with the aim to get the dominant parameter governing their refractive index sensitivities.The contents are as what follows:1.The extinction spectra of individual Ag nanodisks,dimeric Ag nanodisks and spheric Ag polymers are calculated,hence their corresponding LSPR wavelengths are obtained.Their refractive index sensitivities are calculated,too.The effects of shape,size and near-field coupling on their refractive index sensitivities are also discussed.An accurate and easy-to-use equation has been proposed to calculate the refractive index sensitivities of noble metallic nanostructures,which agrees well with the DDA simulated and experimental results.2.The extinction spectra of dimeric Au nanospheres are calculated;hence the corresponding LSPR wavelengths are obtained for variable gap distances of the two components of the dimer.The corresponding refractive index sensitivities and fractional refractive index sensitivities are calculated as a function of the above gap distances and normalized dimeric sizes(gap distance divided by component nanosphere' diameter),respectively.The effects of plasmonic coupling between the two components on the refractive index sensitivities and their fractional results are discussed.3.The extinction spectra of individual Au nanorods with different aspect ratios are calculated.The changing tendency of their LSPR wavelengths versus their aspect ratios has been achieved.The distinct responses of optical refractive index sensitivity of Au nanorods to aspect ratio in visible and near infrared regions are discussed.Combining with the concepts of full width at half maximum(FWHM)and figure of merit(FOM),the refractive index(RI)sensitivity properties of Au nanorods are optimized,which provides the optimal LSPR wavelength and aspect ratio.The results of this thesis are important not only from the point of fundamental view,but also hold great promise for future designing and fabricating LSPR based sensing/detection substrates and elements.