Plasmonic Silver Nanowires Amplified Aggregation-Induced Photon Upconversion And Circular Polarization Of Photon Upconversion

Surface plasmon resonance(SPR)of metallic nanostructures have wide applications in optoelectronic and material science.In recent decades,SPR enhanced fluorescence has attracted much attentions.However,there were few reports on plasmon-enhanced the fluorescence of organic fluorescent nanoparticles,especially on triplet-triplet annihilation-based photon upconversion.Therefore,SPR of silver nanowires enhanced aggregation-induced emission(AIE),the effect of mass ratio between silver nanowires and fluorescent nanoparticles and the mechanism of silver nanowires enhanced AIE have been discussed in this thesis.Subsequently the silver nanowires enhanced the fluorescence of aggregation-induced photon upconversion(iPUC)and how the silver nanowires affect the iPUC have studied.At the same time,we try to introduce chiral environment to achiral acceptor/sensitizer pairs to induce an upconverted circularly polarized luminescence.The main contents of this paper are as follows:(1)A tetraphenylethylene-based AIE molecule BTPA,which employs anthracene as a core,was designed and synthesized.The AIE properties of BTPA were characterized by UV-Vis spectrum,fluorescence spectrum and emission quantum yield.To get homogenous structures,emissive nanoparticles(BTPA-NPs)have been fabricated using surfactant(sodium dodecyl sulfonate,SDS)assisted self-assembly method.And polyvinyl-pyrrolidone(PVP)stabilized AgNWs was synthesized using the same method.After mixing with AgNWs,BTPA-NPs can be affected by SPR of AgNWs.The fluorescence enhancement was detected by fluorescence spectrum,which was also seen directly in the fluorescence microscope.To confirm the mechanism of plasmon-enhanced fluorescence,some measurements were carried out,such as time-decay spectra,quantum yield and UV-Vis spectra.(2)Aggregation-induced photon upconversion nanoparticles(iPUC-NPs)were prepared by doping PtOEP with BTPA-NPs.The photophysical properties of sensitizer,PtOEP,and annihilator,BTPA,were examed by UV-Vis spectra and fluorescence spectra.The enhanced iPUC can be achieved by mixing AgNWs with iPUC-NPs.To our surprise,the enhancement factor of iPUC increased with the increasing of excitation intensity.To further understand the mechanism of the iPUC enhancement caused by AgNWs,time decay of photon upconverted emission and the enhancement factor of photon upconversion as well as phosphorescence at different excitation intensity were carried out.In order to avoid tedious degassing operation,free-standing film has been fabricated by the reprecipitation method for further application in device.Upon excitation the free-standing film with the 532 nm green laser,bright blue emission could be clearly observed in air behind a 532 nm short-pass filter.(3)The acceptor DPAH containing two carbonyl groups was designed and synthesized according to a commercial acceptor DPA.Blending DPA/PtOEP and DPAH/PtOEP with gelator DG/LG,we have discussed the property of upconverted circularly polarized luminescence.The results showed that we could obtained an upconverted circularly polarized luminescence by introducing chiral environment to achiral acceptor/sensitizer pairs.This research opened a road to achieve an upconverted circularly polarized luminescence.