Preparation And Upconversion Luminescence Property Of Laser Sensitized Rare Earth Doped Gd₂O₃

Lanthanide ions doped upconversion fluorescence materials（LUFM）have achieved extensive applications,spanning from data storage,biological imaging,3D displays to solar energy,anticounterfeiting and temperature detection owning to their unique properties such as sharp-band emitting,long fluorescence decay times,low background interference as well as controllable luminescent color.Unfortunately,low luminescent efficiency,poor sensitivity of temperature detection as well as narrow color adjustment range still seriously hinder the application of LUFM.Here,lanthanide doped gadolinium oxide with good physical and chemical stability was researched.The convenient laser sensitization treatment was utilized to enhance the luminescent intensity as well as temperature sensitivity of Yb/Er/Gd₂O₃sample.In addition,the bright white emission and adjustable full-color emission were realized by controlling the energy transfer and cross relaxation process via tuning laser power.Particle agglomeration during heat treatment was studied and the upconversion luminescence intensity was improved by adjusting the morphology of Yb/Er/Gd₂O₃upconversion nanomaterials.Yb/Er/Gd₂O₃upconversion nanoparticles were synthesized through hydrothermal method and coprecipitation method following thermal treatment,and the influence of thermal treatment on morphology was studied.Results indicated that the nanospheres morphology via coprecipitation method well maintained after thermal treatment,and strong upconversion emission was also achieved in Yb/Er/Gd₂O₃nanospheres.Then the content of lanthanide ions was optimized,the concentration quenching between lanthanide ions was effectively avoided,and the content of Er³⁺and Yb³⁺were determined to be as 1%mol and 10 mol%,respectively.High efficiency multi-color upconversion fluorescence was achieved via adjusting the local structure of Yb/Er/Gd₂O₃nanoparticles induced by laser sensitization.In Yb/Er/Gd₂O₃system,local hot spots were generated by laser thermal effect,leading to the enhancement of fluorescence intensity and the expand of color adjustment range.As the laser sensitized power was 1511 m W,the nanospheres size was 309 nm,and the test power was 534 m W,913-fold and 894-fold improvement were realized in terms of the red and green emitting intensity.Structured characterization,spectrum tests and lifetime tests show that the laser-sensitized upconversion emission improvement is due to the increase of energy transfer from Yb³⁺to Er³⁺.Thermally activated upconversion luminescence was constructed to inhibit fluorescence quenching at high temperature and enhance the accuracy and sensitivity of temperature detection.The temperature-dependent luminescence and temperature sensing performance of Yb/Er/Gd₂O₃particles before and after laser treatment were explored.It is found that the Yb/Er/Gd₂O₃sample without laser treatment presented the regular thermal quenching luminescence.In contrast,the laser treated sample showed thermal activated upconversion luminescence,which overcomed the limitation of the regular thermal quenching luminescence temperature detection.In addition,the relative sensitivity of the laser sensitized sample was as high as 4.5%K^-1at 578 K,which was significantly improved compared with Yb/Er/Gd₂O₃particles without laser treatment.Full color upconversion luminescence was realized by regulating the unsteady cross relaxation and energy transfer between rare earth ions.Although tunable color emission was achieved in Yb/Er/Gd₂O₃system,the color regulation range was limited.On basis of this,Tm³⁺with blue light output was introduced in Yb/Er/Gd₂O₃system.By regulating the power,bright white light output and tunable full color upconversion emission were realized in Yb/Er/Tm/Gd₂O₃sample.The relationship between lanthanide ions content and laser sensitized color adjustment were explored.Experimental results indicated that Yb/Er/Tm/Gd₂O₃crystals could realize bright white light emitting as well as wide range of color tune by changing the laser sensitization power and test power in a certain doping range,overcoming the shortcoming of conventional concentration-dependent color adjustment.In addition,the anti-counterfeiting identification was realized through manufacturing different patterns,which lays a foundation for the anti-counterfeiting application of upconversion luminescence materials.