Fundamental Research On Nano Core-capped Structure As A Near Infrared Photothermal Probe

Noble metal nanoparticles exhibit unique optical properties,such as strong scattering and absorption of light owning to their localized surface plasmon resonance?LSPR?effects.Due to these properties,noble metal nanoparticles are widely used in biochemical sensing,surface fluorescence enhancement,molecular imaging,biomedical treatment and other fields.The studies show that absorption plays a dominant role in extinction when the size of the noble metal nanoparticles is less than 100 nm.The absorbed light energy of noble metal nanoparticles can be quickly converted into thermal energy,resulting in the temperature of nanoparticles and its surrounding medium environment increases rapidly,and achieving nanoscale thermal manipulation.In recent years,the photothermal effects of noble metal nanoparticles have a large number of applications in photothermal therapy,photothermal imaging,nanomedicine,and fingerprint analysis,which are becoming a focus for scientists.Non-spherical symmetric core-capped structure not only have strong polarization-dependent properties,but also have abundant adjustable structural parameters to flexibly manipulate the absorption lines in the near-infrared region,so that they have a potential application as a photothermal probe.However,most of the current studies only report the qualitative change process or only obtain empirical data.The quantitative analysis for the rise of actual temperature and their spatial distribution are still lack of relevant research,which hinders the devices design and optimization to some extent.The optical and photothermal properties of non-spherical symmetric SiO₂@Au core-capped nanoparticles were systematically studied in this paper based on Lumerical three-dimensional finite-difference time-domain method and finite-element multiphysics simulation software COMSOL.The main contents are listed below:?1?The extinction characteristics and near field distribution of SiO₂@Au core-capped nanoparticles were calculated with different excitation polarizations,and compared with the electromagnetic properties of SiO₂@Au core-shell nanoparticles.?2?The effects between LSPR peak absorption wavelength and the area of absorption cross section were obtained of SiO₂@Au core-capped nanoparticles with structural parameters,including the shell thickness,core diameter,core-shell ratio,metal surface coverage.?3?SiO₂@Au core-capped nanoparticles were prepared by template deposition and ultrasonic lift-off method.The morphology and optical properties were measured and analyzed by the transmission electron microscopy and ultraviolet-visible near-infrared spectrophotometer.?4?The temperature distribution of SiO₂@Au core-capped nanoparticles under the combined action of absorption characteristics and structural parameters were calculated.The studies in this paper show that non-spherical symmetric core-capped nanoparticles are selective for the polarization state of excitation light,which exhibit different optical properties in the direction parallel to the symmetry axis of the particle and perpendicular to its symmetry axis;the LSPR peak wavelength of SiO₂@Au core-capped nanoparticles can be widely moved in the visible to near-infrared range by slightly changing the structural parameters;the temperature of SiO₂@Au core-capped nanoparticles can be adjusted efficiently in the near infrared band by rotating the polarization and changing the structural parameters.