Nonlinear Optical Properties Of Au/Ag Alloyed Nanoboxes Under The Excitation Of Long-wavelength Femtosecond Laser And Their Applications In Bioimaging

In recent years, nanobiophotonics has attracted more and more attention with the fast development of nanotechnology and biophotonics. Among various nanomaterials, metal nanoparticles have demonstrated distinct advantages and great potentials in many kinds of applications. In this thesis, we focus on a kind of asymmetrical metal nanoparticles:Au/Ag alloyed nanoboxes (ANB). We would research the synthesis and surface modification of ANB, the nonlinear optical properties of ANB under different femtosecond (fs) lasers and the applications of ANB in bioimaging.Firstly, we introduce the detailed synthesis process of ANB and its basic optical properties. Two chemical methods to control the LSPR peak wavelength of ANB are stated; Then the surface modification methods of ANB are illustrated, including CTAB-PSS-PAH coating, PEG coating and silica coating. The coating process and results are testified by UV-Vis spectrophotometer, TEM and Zeta potential testing;Secondly, the abundant nonlinear optical signals of ANB under the excitation of different fs lasers are researched, including second harmonic generation (SHG), third harmonic generation (THG), two-photon luminescence (2PL) and three-photon luminescence (3PL). Further research shows that the existence of the LSPR effect of the ANB did generate the enhancement of its THG/SHG signals, which can be called "LSPR induced THG/SHG".Thirdly, zebrafish embryos are set as the model to research the biocompatibility of Ag nanospheres, Ag nanoplates, naked ANB and PEG-coated ANB. The first three materials are found to cause embryos deformation or even death while PEG-coated ANB have negligible toxicity to the zebrafish embryos even at extra-high concentration. These results prove that PEG-coated ANB has good biocompatibility in biological applications.Fourthly, we apply ANB in some different biological models for nonlinear bioimaging. For example, under the excitation of a 1260 nm fs laser, the ANB with the LSPR wavelength at 630 nm are applied in SHG bioimaigng of cells and mouse ear blood vessel; what’s more, ANB are applied in 3PL bioimaging under the excitation of a 1550 nm fs laser with a confocal microscope. Long-time scanning of cells stained with ANB confirms that the photo-thermal effect of ANB has negligible influence on cells. Ex vivo imaging of mouse tumor tissues stained with ANB shows that ANB could accumulate in mouse tumor, which means ANB have great potential in in vivo tumor imaging and therapy. In addition, the 3PL of ANB is utilized to obtain the images of mouse ear blood vessels and deep brain blood vessels; Finally, the distribution of ANB in zebrafish embryos is investigated based on the 3PL imaging with a 1550 nm fs laser and a confocal microscope;...