Study On The Luminescent Properties Of Gold Nanoparticle-enhanced Illuminant-based Photonic Crystals

In recent years,photonic crystal luminescent materials doped with luminescent centers have attracted considerable attention due to their potential applications in lasers,optical fibers,solar cells,biosensors and displays.However,the luminescence efficiency of some luminescent centers are low,which limits their practical application.Therefore,people try to enhance the emission intensity of the luminescent center by some methods.In this experiment,the surface plasmon resonance effect of the noble metal nanoparticles is mainly used to enhance the luminescence of the rare earth ions,and the energy transfer efficiency is enhanced by the metal nanoparticles and the photonic bandgap,thus the luminescence of the luminescent centers was enhanced.The SiO₂ inverse opal photonic crystalsd doped with rare earth ions were prepared by the selfassembly technique combined with a sol-gel method,and the visible and near-infrared?NIR?emission properties have been investigated.The Yb³⁺ single-doped SiO₂ inverse opal exhibits the near infrared emission peak located at 976 nm under the excitation of 256 nm,which is attributed to the Yb³⁺-O^2-charge transfer state.For the SiO₂:Er³⁺,Yb³⁺ inverse opals,the 976 nn of Yb³⁺ and 1534 nm of Er³⁺ NIR were observed upon the 256,378 and 520 nm excitation,respectively.The 976 nm NIR mechanism of Yb³⁺ was investigated in the SiO₂:Yb³⁺inverse opal upon the 378 and 520 nm excitations.A novel mechanism was present to demonstrate the origin of 976 nm NIR of Yb³⁺.Additionally,the suppression of the cooperative upconversion?UC?emission of two Yb³⁺ ions was observed in the SiO₂:Yb³⁺ inverse opal due to the photon trap caused by photonic band gap.The cooperative upconversion?UC?of SiO₂:Yb was investigated.Additionally,the suppression of the cooperative UC emission of two Yb³⁺ ions in the Yb³⁺ single-doped SiO₂ inverse opal was observed due to the photon trap caused by photonic band gap.The SiO₂:Tb³⁺ and SiO₂:Yb³⁺,Tb³⁺ inverse opal photonic crystals containing gold nanoparticles were prepared.The influence of Au nanaoparticles on the down shifting emission and up-conversion luminescence properties have been investigated,respectively.The enhancement mechanism was discussed and demonstrated.The enhancement of down shifting emission is attributed to the increasing of radiative decay rates of Tb³⁺ induced by surface plasmon effects of Au nanoparticles.The enhancement of upconversion emission of SiO₂:Yb³⁺,Tb³⁺ inverse opals is from the population increasing of 5D4 luminescent level of Tb³⁺ions induced by surface plasmon effects of Au nanoparticlesThe SiO₂:Tb inverse opals with and without Au nanoparticles were prepared,and the organic rhodamine-B?RhB?dyes were filled into the voids of SiO₂:Tb inverse opals.Non-radiative and radiative energy transfer processes from the SiO₂:Tb inverse opals to the RhB were observed.The influence of Au nanoparticles and photonic band gap on the energy transfer from SiO₂:Tb inverse opals to the RhB was investigated.The Au nanoparticles enhanced energy transfer was observed due to the surface plasmon resonance effects of the Au nanoparticles.When the emission peaks from the SiO₂:Tb inverse opal is overlapped with the photonic band gap,the emission suppression of the SiO₂:Tb inverse opal as well the emission enhancement of the RhB dyes were obtained,which is attributed to improved energy transfer caused by the photonic band gap.The steady state rate equations were used to explain enhancement of energy transfer caused by the photonic band gap.