Nobel Metal/Semiconductor-enhanced Rare-earth Doped Upconversion Luminescence And Its Application

Rare-earth doped upconversion luminescence nanomaterials with good chemical stability have been widely used in biological imaging,solar cells,optical sensing and other fields.However,the luminescence efficiency of upconversion nanoparticles has been generally limited due to the presence of surface defects.Up to now,some attempts have been employed to improving upconversion luminescence properties,such as the host and doping ions concentration adjustment,core-shell structure construct,local-field modulation and so on.The noble metal nanostructures have attracted much attention through localized surface plasmon resonance(LSPR)effect modulated localized field enhancement for improving upconversion luminescence intensity.Recently,heavily doping semiconductors with wide spectral absorption capacity as an emerging plasmonic material have also successfully enhanced luminescence intensity through induced localized electromagnetic field.Nevertheless,the challenge of effectively improving luminescenve efficiency has been a bottleneck in various single plasmonic mode.So this work has carried out the development of upconversion nanostructure via LSPR effect sensitization.In our work,the Na YF₄:Ln³⁺acted as a model emitter to approach the plasmonic semiconductor,noble metals,and semiconductor-noble metals composite nanostructures.And we further investigated sensitized-upconversion luminescence system and corresponding LSPR modulation mechanism.The main results were shown as follows:1.The upconversion luminescence performance of CeO₂:Yb,Er has been modulated through the LSPR property of W₁₈O₄₉.The core-shell CeO₂:Yb,Er@W₁₈O₄₉was synthesized by solvothermal method.The octahedral CeO₂:Er,Yb nanocrystal exhibited green,red and NIR emission under 980 nm laser diode excitation,and the multiband emissions re-excited higher energy LSPR of W₁₈O₄₉.With the excitation of980 nm,the photocatalytic property of CeO₂:Er,Yb@W₁₈O₄₉ for H₂ evolution from BH₃NH₃,a three-fold increase compared to W₁₈O₄₉,was researched.Furthermore,the application of natural sunlight for the production of H₂ was studied,and an obvious H₂ production enhancement(two-fold)compared to the use of W₁₈O₄₉ was also observed.2.To overcome the limitation of single plasmonic structure on the upconversion luminescence,a new binary composite film composed of a metal domain(Ag nanorices)and a semiconductor domain(W₁₈O₄₉ nanowires)was designed,which exhibited a broad and strong LSPR.The plasmonic coupling in the Ag/W₁₈O₄₉composite film induced remarkable overall upconversion enhancement(938-fold)via the LSPR effect.The investigation indicated that luminescence enhancement mostly have drived from the strong excitation field,and the emission field and plasmonic enery transfer also contributed to this modulated-system.The Na YF₄:Yb,Er/Ag/W₁₈O₄₉ luminescence composite film have been successfully applied in the quantitative and qualitative Rh B molecular detection by LRET and SERS,which was representative molecules detection system.3.From the view of plasmon-enhanced luminescence mechanism,the composite film integrating tunable Au nanorods with plasmonic semiconductor W₁₈O₄₉further realized that a significant enhancement was observed by precisely tuning the L-LSPR wavelength at 980 nm,after optimizing the interaction distance between plasmonic nanostructure and upconversion emitters.The emission field coupling provided an assignable contribution to the luminescence enhancement in this system,although the dominant contribution was still excitation field enhancement.Finally,the composite luminescence film were applied to the qualitative and quantitative detection of fluorescent molecules,which widen the space for solving the problem of fluorescent molecular detection.4.The noble metals with higher carrier density performed more thermal effect than the plasmonic semiconductors,the upconversion luminescence was improved based on Cu_2-xS/Au plasmonic composite film with lower thermal effect.Making great efforts studied the LSPR-induced enhancing mechanism and luminescence quenching effect caused by reverse energy transfer and thermal quenching.A remarkable upconversion luminescence enhancement(1150 folds)was obtained,and plasmon-coupling photocatalyst improved the photocatalytic activity based on“hot electrons”/photothermal/upconversion re-excited comprehensive effect.