Investigation On Laser-induced Welding And Giant Photoluminescence Enhancement Of Au Nanoparticles

In view of their unique properties,gold nanoparticles are widely used in many fields.In particular,the plasma localized enhancement effect of gold nanoparticles,enables enhance thousands of times of local light field between nanoparticles by plasma coupling.The local field enhancement can be used to amplify the optical response of materials surrounding the gold nanoparticle.However,the low fluorescence quantum yield of gold nanoparticles restricts their further application.In order to improve the quantum yield of fluorescence emission of gold nanoparticles,the most common method at present is aggregation.That is,the photoluminescence(PL)of gold nanoparticles can be enhanced by forming a gold nanoparticle dimer or multimer.Our research is that continuous laser irradiation was used to enhance the fluorescence of gold nanoparticles.Based on the photothermal effect produced by laser irradiation of gold nanospheres,the surface of gold nanoparticles can be fused by focused continuous laser irradiation,and then adjacent gold nanoparticles can be fused.During the melting and fusion process,the irregular and sharp surface formed will greatly enhance the localization enhancement effect of the plasmon,thereby increasing the quantum yield of fluorescence.Compared to femtosecond laser-induced two-photon fluorescence,single-photon fluorescence using continuous laser-enhanced gold nanoparticles has more important applications in biological imaging and medical diagnosis.Our main works are as follows:The PL enhancement effect and welding of gold nanorods was studied.The enhancement effect and enhancement kinetics of gold nanospheres during continuous wave laser irradiation have been investigated,where the effects of laser wavelength,power density and size on PL enhancement have been studied.The PL spectral profiles during their PL enhancement were also measured.The morphology characterization of multiple gold nanoparticles,after continuous wave lasers irradiation,confirmed the shape change during PL enhancement.At last,we proposed a mechanism to explore all the observed experimental results.The PL enhancement effect and welding of gold nanorods was studied.Firstly,the statistical distribution of PL enhancement under different conditions was studied.Secondly,the enhancement effect and enhancement time of gold nanorods with laser wavelength,power density,diameter of rod and length nanorods were obtained.Finally,we explored the possible reasons for the changes in different enhancement effects.