Research On Detection Of Gold Nanoparticles Using Photothermal Heterodyne Imaging

Gold nanoparticles(GNPs)have excellent optical properties,easy modification and low toxicity.They are often used as biomicroscopic imaging labels in the fields of photothermal therapy of tumors and biosensors.Traditional microscopic imaging methods have some shortcomings,such as complex sample preparation,weak fluorescence signal or large interference of background signal.Therefore,it is very important to find a kind of micro-imaging technology which can achieve stable imaging and reduce the interference of background signal for the detection of gold nanoparticles.Therefore,it is very important to find a technology which can achieve stable imaging of non-fluorescent materials and micro-imaging of nanoscale objects.Photothermal Heterodyne Imaging(PHI)is a new far-field microscopic imaging technology,which utilizes the photothermal characteristics of the object,is less affected by background scattering and the size of the object being measured,and can realize the microscopic imaging of non-fluorescent objects.In this paper,the theory and experiments of PHI for GNPs are studied.The theory and simulations of PHI signal of single GNP under modulated laser are studied,and the influencing factors of PHI are studied.On this basis,a PHI system is designed and built,and the experimens of PHI of GNPs are carried out.The resolution of PHI and the influence factors of PHI signal are analyzed.Firstly,the theoretical models of PHI signal(point heat source model,polarization electromagnetic field model,frequency shift electromagnetic field model)of NPs under modulated laser are established,and the influencing factors of PHI signal are analyzed theoretically.The effects of various experimental parameters(NPs size,surrounding medium,heat and probe laser parameters)on the PHI signal of gold nanoparticles are analyzed by finite element simulation.Secondly,this paper designs and builds a PHI system,including hardware and software systems.According to the principle of PHI,the optical path is designed,including excitation module,detection module,position scanning module and signal detection module.The software of PHI system is designed,including the data processing and PHI signal acquiring,data post-processing and scanning control of two-bit piezoelectric mobile station.The test sample is prepared to meet the requirements of imaging detection.Finally,the PHI experiments of gold nanoparticles is carried out.The influence of experimental parameters on the PHI signal of gold nanoparticles and the resolution analysis of PHI are studied.The microscopic imaging of single 60 and 100 nm GNPs is realized,and the effects of different particle sizes on the PHI signal were analyzed by experiments.The PHI of GNP clusters is carried out,and the relationship between the PHI signals of multiple gold nanoparticles and the number of particles is analyzed.The single nanoparticles and nanoparticle clusters were distinguished.