Construction And Application Of Photosensitive Lanthanide-Doped Upconversion Core-Shell Nanoparticles

Lanthanide-doped upconversion nanoparticles have attracted the attention of researchers for nearly a decade,but how to control their emission properties in real time to expand their application fields has become a current challenge.In response to this problem,in this paper,core-shell light-sensitive nanoparticles were constructed,which realized timely and precise adjustment of its luminescence properties.Combining with the theoretical study of upconversion luminescence dynamics,it promotes its application in advanced anti-counterfeiting and speed sensing.The specific research contents are as follows:1.NaYF₄:Nd³⁺/Yb³⁺@NaYF₄:Yb³⁺/Er³⁺@NaGd F₄:Yb³⁺/Tm³⁺@NaGd F₄:A@NaYF₄(A=Eu³⁺,Tb³⁺,Eu³⁺/Tb³⁺,Ce³⁺/Eu³⁺,Ce³⁺/Tb³⁺,Ce³⁺/Eu³⁺/Tb³⁺),the upconversion core-shell nanoparticles sensitive to excitation light power and various excitation light wavelengths were prepared by co-precipitation method;The steady-state emission spectra of the samples were measured,and the up-conversion emission of Er³⁺/Tm³⁺/Eu³⁺/Tb³⁺and the down-conversion emission of Eu³⁺/Tb³⁺were realized,It is shown that its luminescence characteristics are sensitive to the wavelengths and powers of the three lasers,980 nm,808 nm and 254 nm;the anti-counterfeiting ink is prepared by using the samples,and the designed particles are applied in the anti-counterfeiting aspect.For the first time,an independent structure can realize four This mode of anti-counterfeiting mode（power/980/808/254 nm）has certain application prospects in preventing economic losses.2.An excitation light pulse-sensitive upconversion core-shell nanoparticle was designed:NaGd F₄:Tm³⁺/Yb³⁺@NaYF₄@NaGd F₄:Er³⁺/Yb³⁺;The steady-state emission spectra of the samples were measured,and the upconversion emissions of Er³⁺and Tm³⁺were realized;The time-resolved curve of the emission intensity of the sample was measured,indicating that the"rising edge"of the Er³⁺two-photon and Tm³⁺multi-photon up-conversion processes has different responses to the pulse width of the excitation light;A real-time method to detect the linear velocity of the object using the"rising edge"difference was proposed,and the experimental device for velocimetry was designed,the luminescence color of the sample changes with the variety of velocity was demonstrated,the emission spectrum was measured when the sample passes through the excitation point at different velocities,and the speed was accurately detected at which the particles move through spectral analysis.This work realizes the application of up-conversion nanoparticles in the field of speed sensing for the first time,opens up a new application field,and has certain application value in long-distance accurate speed measurement.3.An excitation light pulse-sensitive upconversion core-shell nanoparticle NaYF₄:Yb³⁺/Ho³⁺/Ce³⁺@NaGd F₄ was prepared.The steady-state emission spectrum of the sample was measured,and the up-conversion emission of Ho³⁺was realized;The time-resolved curve of the emission intensity and emission spectrum of the sample under excitation with different laser pulse widths were measured,which proved that the luminescence characteristics of the sample are sensitive to the excitation light pulse width;The luminescence color of the fluid changes with the flow rate was demonstrated under steady-state laser excitation,and the emission spectra at different flow rates are detected.A method for detecting the fluid velocity using nanoparticles as a probe is proposed,and a device for measuring the velocity is designed,imitating biological arterial blood flow,a fluid circulation system with controllable flow rate was established,and the flow rate was successfully measured through a simple spectral detection device;The two-photon process of Ho³⁺was verified,and the red and green emission intensity ratios of the fluid were analyzed under different powers and flow rates,demonstrating the superiority of this velocimetry method without the need for recalibration of the pump power.A 2D scan of the flow velocity of the fluid demonstrates the powerful ability of this velocimetry method to handle application scenarios with flow changes or spatial velocity gradients.In conclusion,it shows that this nanoprobe and fluid velocity measurement method have good application prospects in the detection of human blood flow velocity.This method of fluid velocity measurement has important implications for the sensor field.