Enhanced Luminescence Of Rare Earth Eu And Tb Based On Coupled LSPR Structure

Rare earth materials are widely used in optical communication,bioluminescence imaging,laser,and other fields due to their narrow emission bandwidth,large Stokes shift,long emission lifetime,and good photostability.However,the photon absorption cross section of lanthanide ions is small,and the luminous efficiency is low.The effective improvement luminescence properties of lanthanide doped materials has always been a challenge in many applications.The plasmonic nanoparticles with local surface plasmon resonance（LSPR）effect leads to the enhancement of local electric field.The local electromagnetic field further excite more ions to the excited state and improve the excitation efficiency.Meanwhile,the emission process of lanthanide ions can be affected by Purcell effect.However,the maximum enhancement reported so far is limited,leaving a wide gap between theoretical and practical applications.And the way of regulating the luminescence by a single metal nanoparticle is relatively simple.Plasmonic coupling structure has become an excellent platform to further improve the luminescence of rare earth materials because of its great enhanced local field and Purcell effect.In this thesis,different plasmonic coupling structures are explored to enhance the luminescence of lanthanide Eu and Tb co-doped films.And the mechanisms are analyzed systematically.The main content of this thesis are as follows:1.The Ag film substrate was prepared by laser molecular beam epitaxy system.And different thickness of PMMA space layers were prepared on Ag nanoparticles（NPs）film substrate by spin coating method.The impact of the space layer/Ag NPs film LSPR structure on the luminescence of lanthanide Eu（dbm）₃phen films was researched.It is found that space layer/Ag NPs film LSPR structure can enhance the luminescence of Eu（dbm）₃phen films.With the increasing of thickness,the photoluminescence intensity of Eu（dbm）₃phen films first increases and then decreases.The maximum luminous intensity of Eu（dbm）₃phen film is obtained when the thickness of the space layer is 22 nm,and the maximum enhancement factor is 4.5 times and 2 times compared with pure Eu（dbm）₃phen film and Eu（dbm）₃phen film on Ag NPs film substrate,respectively.The FDTD modulation results show that excitation process of Eu（dbm）₃phen film is mainly regulated by Ag NPs film substrate.With the introduction of space layer,the distance between the Ag NPs film substrate and the Eu（dbm）3phen film is changed,reducing the luminescence quenching caused by the non-radiative process due to the close distance,and further improves the luminescence intensity of the Eu（dbm）₃phen film.2.The nano gap coupled structure of Au nanorod/space layer/Ag NPs film was further designed to explore the modulation on the luminescence of lanthanide Eu（dbm）₃phen film.It is indicated that the maximum luminescence enhancement factor of the Au nanorod/space layer/Ag NPs film nano gap coupled structure is 53.5 times compared with the pure Eu（dbm）₃phen film.Large luminescence enhancement can be achieved in a wide concentration range by adjusting the concentration of Au nanorods,.The lifetime of Eu（dbm）₃phen films under nano gap coupled structure is sharply shortened from 662.25μs to 310.3μs.The results show that the mechanism of luminescence enhancement is divided into three aspects:the excitation process of Eu（dbm）₃phen film is mainly modulated by Ag NPs film substrate,the luminescence quenching is suppressed with the introduction of space layer,the emission process of Eu（dbm）₃phen film is regulated by Au nanorods due to the matching between the LSPR of the Au nanorod and the emission spectrum of the Eu（dbm）₃phen film.3.The impact of Au nanorod-PVA film coupled structure on luminescence and energy transfer of lanthanide Tb（TMHD）₃/Eu（dbm）₃phen co-doped films were studied.Compared with the pure Tb（TMHD）₃/Eu（dbm）₃phen co-doped films,the Au nanorod-PVA film coated coupled structure improves the energy transfer efficiency and luminescence intensity.The maximum luminescence enhancement factors of the Au nanorod-PVA film coupled structure are 37.2 times under excitation of 292 nm and 71 times under excitation of 360nm.It is demonstrated that the presence of Au nanorod-PVA film coupled structure can reduce the luminescence quenching due to the close distance.In addition,the interaction between Tb（TMHD）₃/Eu（dbm）₃phen co-doped films and Au nanorod-PVA film coupled structure leads to the change of the proportion and relative strength of red and green emission bands,and the emission color can be adjusted from green to red.