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Based On Nonlinear Scattering And Super-resolution Imaging Of Plasmonic Core-shell Nanoparticles

Posted on:2022-04-19Degree:MasterType:Thesis
Country:ChinaCandidate:X C ZhongFull Text:PDF
GTID:2481306734466034Subject:Optical communication and optical sensing
Abstract/Summary:PDF Full Text Request
With the rapid development of social science and technology,optical microscopes have gone through the development process of ordinary optical microscopes with limited diffraction,fluorescence super-resolution microscopes that break the diffraction limit,and then to label-free non-fluorescent super-resolution optical microscopes.The non-fluorescent super-resolution imaging based on the nonlinear scattering of local plason nanoparticles is a hot research area and has been successfully applied to the imaging of biological cells.However,it has been found in research that gold nanoparticles have serious local thermal effects,aggregation and coupling between particles are prone to occur,and high temperature melting at high power is likely to affect practical applications.In this study,we proposed the strategy of Au@Si O2spherical shell particles,in order to improve the above-mentioned shortcomings of gold nanoparticles,and studied the mechanism of the nonlinear saturation scattering of gold nanoparticles based on the photothermal effect and explored the application of Au@Si O2in super-resolution imaging.The specific content is as follows:In this paper,it takes Au spherical nanoparticles with diameter D=70nm as the core,and uses different packaging methods to study plasmonic gold nanoparticles.Firstly,70nm Au spherical nanoparticles were encapsulated on glass slides with oil and spin-on glass(SOG),named 70nm Au oil and 70nm Au SOG.Secondly,a silicon dioxide(Si O2)shell layer with thicknesses of 10.0nm,23.0nm,and 40.0nm was chemically synthesized on the surface of 70nm Au spherical nanoparticles to form three kinds of Au@Si O2spherical shell particles with different thicknesses,which are respectively encapsulated on glass slides with oil and named70nm Au@Si O2shell 10.0nm,70nm Au@Si O2shell 23.0nm,70nm Au@Si O2shell 40.0nm.1.In this study,through the above-mentioned packaging method,using the difference in thermal conductivity of oil,Si O2,and SOG,five local microenvironments with different thermal conductivity are provided for 70nm Au spherical nanoparticles,which are 70nm Au oil,70nm Au@Si O2shell 10.0nm,70nm Au@Si O2shell 23.0nm,70nm Au@Si O2shell 40.0nm and 70nm Au SOG respectively.Their thermal conductivity are respectivelyKoil=0.30W/(m·k),KSiO2-10.0nm=0.38W/(m·k),KSi O2-23.0nm=0.47W/(m·k),KSiO2-40.0nm=0.62W/(m·k),KSO G=1.0W/(m·k).In the experiment,the temperature of 70nm Au spherical nanoparticles was locally adjusted by the difference in thermal conductivity.Using a 532nm CW laser for irradiation,the saturated scattering behavior of D=70nm Au spherical nanoparticles was studied under a confocal microscope.The experimental results show that the incident light power required when the 70nm Au spherical nanoparticles are scattered in the above five local microenvironments are0.25MW/cm2,0.30MW/cm2,0.40MW/cm2,0.55MW/cm2and 1.0MW/cm2respectively.It can be seen that the smaller the thermal conductivity of the local microenvironment,the higher the temperature of the gold nucleus in the environment,and the lower the power required to achieve scattering saturation.This indicates that the scattering saturation behavior of plasmonic gold nanoparticles is related to the temperature.2.Using the DLT(Drude-Lorentz-Temperature)model,it theoretically calculate the change of the dielectric constant of gold with temperature,and import the dielectric constant parameters of gold at different temperatures into the FDTD,and theoretically simulate the change of the cross section scattering and absorption of gold at the temperature of 300K?1100K.Reading the value of the scattering and absorption cross section at 532nm,the results showed that with the increase of temperature,the scattering cross section decreased from 0.68×10-14m2to 0.33×10-14m2,a decrease of 50%;the absorption cross section decreased from 1.3×10-14m2to 1.1×10-14m2,the decrease of 15%.At the same time,using the dielectric constant as an intermediate variable,the temperature rise curves of gold nanoparticles in five local microenvironments are calculated.The calculation results show that as the incident light power increaseing,the particles heat up the fastest in oil and the slowest in SOG,the Au@Si O2particles in the middle.Finally,the nonlinear saturated scattering behavior of 70nm Au in five local microenvironments is simulated,and the simulation results are consistent with the experimental results,which proves that the nonlinear saturated scattering behavior of gold nanoparticles is thermo-optical effect.The mechanism of the effect is the result of a decrease in the scattering cross section caused by temperature.3.The optical switching behavior of 70nm Au in different local microenvironments was studied.On the basis of the confocal microscope,two laser beams of 532nm and 561nm were used to irradiate nanoparticles at the same time.Keeping the 561nm laser unchanged at low power,the variation of the scattering intensity of 70nm Au at 561nm is observed with the increase of the 532nm laser intensity.The experiment found that with the increase of 532nm laser power,the scattering intensity at 561nm gradually decreased.The results show that the modulation effect of 70nm Au oil is the best,reaching a modulation depth of 90%at 0.6MW/cm2;while 70nm Au@Si O2shell 10.0nm and 70nm Au@Si O2shell 40.0nm need to be 0.8MW/cm2and 1.3MW/cm2respectively reached 90%modulation depth.In SOG,the modulation effect is the worst,and only 30%modulation depth can be achieved at 1.6MW/cm2.Using the 70nm Au optical switching effect,it can be applied to the field of super-resolution imaging.4.The photothermal stability and super-resolution imaging results of 70nm Au bare gold particles and 70nm Au@Si O2shell 40.0nm spherical shell particles are compared.70nm Au melted at 3.25MW/cm2power,while 70nm Au@Si O2shell 40.0nm spherical shell particles remained intact,which proved that the local heat dissipation of the particles can be effectively improved by wrapping the Si O2layer,reducing heat accumulation,and avoiding the melting of gold cores.Combining the STED optical path method to perform super-resolution imaging of a single nanoparticle,it is found that 70nm Au@Si O2shell 40.0nm spherical shell particles compress the FWHM to an astonishing 52nm at a suppression power of 1.3MW/cm2,which is better than the super-resolution result of 70nm Au.At the same time,the super-resolution imaging of the combination of particles with different spacing is compared.When the gap between two 70nm Au particles is less than 82nm,it cannot be distinguished in the STED optical system;while for two 70nm Au@Si O2shell 40.0nm the spherical shell particles can achieve a resolution of gap=5nm.It shows that the Au@Si O2spherical shell particles are compared with the Au bare gold particles,which not only improves the super-resolution result,but also can effectively avoid the influence of the coupling between the particles on the imaging through the Si O2layer.
Keywords/Search Tags:Non-fluorescent super-resolution microscopy, Nonlinear saturation scattering, Core-shell particles, Photothermal effect
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