Multi-target Detection Based On Metal Nano-dimer Probe

Recently,Gold nanoparticles with the special local surface plasmon resonance(LSPR)show great potential applications in the biosensing,medical diagnosis and other fields,which is becoming one of the hotspots.On the basis of single gold nanoparticle,a more complex dimer structure which is consisted of two tightly linked nanoparticles can be synthesized.The two gold nanoparticles can interact with each other leading to the strong enhancment of the local field.The scattering and absorption properties of the dimer are obviously stronger than those of the single one.Most of the existing researches of gold nanoparticles are based on their agglomerated structures,which can get the average performance of the probe.In this paper,we use gold nanoparticle dimers as biological molecular probes and propose a method which can extract the multiple gold-dimer from large scattering background.This method can effectively overcomes the interference caused by the biomacromolecule scattering signal in the biological imaging system.What's more,it also can locate multiple targets with high sensitivity at the same time and obtains the information of the multiple single probe.In this paper,the optical properties of the dimer probe are systematically studied by using Finite Difference Time Domain(FDTD)method.The research works in this paper mainly focus on the following aspects: 1)we calculate the extinction properties and near field distribution of the gold nanoparticle dimer with different excitation polarizations and find the single resonant wavelength of the probe at each excitation polarization.2)we obtain the scattering field of the probe along x-axis and y-axis directions respectively by changing the angle between the dimer axis and y-axis and discuss the influence of excitation polarizations on the scattering field,then we used the orthogonal polarization microscopic imaging system which is designed by our group to make the experimental verification.3)we proposed a method to extract the dimers from large scattering background based on the analysis of the gold nanoparticle dimer's scattering properties under the high convergence light.There are two mainly innovation points in this paper as follow: Firstly,we calculate the far field scattering of the gold nanoparticle dimer under a highly focused illumination objective and discuss the influence of the excitation polarization on the far field scattering.It is found that when the excitation polarization is parallel to y-axis,there is strong dependence on the angle between the dimer axis and the excitation polarization for the scattering field component of the probe along x-axis direction.When the angle is equal to 45°,the probe can obtain an optimal signal and the maximum scattering field amplitude can reach 6.71 fold compared to the minimum amplitude.The coupling enhancement of the dimer can be shown by the scattering field of the x component;On the other hand,according to the far-field scattering properties of the dimer probe under a highly focused illumination objective,we proposed a method to extract multi-target from large scattering background.