Screen printing of upconversion NaYF4:Yb3+/Eu3+ with Li+ doped for anti-counterfeiting application

Li ions affect the upconversion efficiency by changing the local crystal field of the luminescent center. Herein, in order to improve the upconversion efficiency of NaYF4:Yb3+/Eu3+, a series of NaYF4:Yb3+/Eu3+micro-particles with different Li+doping concentrations were synthesized by the hydrothermal synthesis method, respectively.Firstly, the structure and morphology of NaYF4:Yb3+/Eu3+upconversion micro-particles(UCMPs) with different doping concentrations were analyzed by X-ray diffraction and a scanning electron microscope(SEM). SEM results show that the UCMPs are not only highly crystallized, but also have hexagons with different Li+concentrations of NaYF4:Yb3+/Eu3+. X-ray diffraction shows that the crystal field around Eu3+changes with the increase of Li+concentration. Then, the fluorescence spectrum of NaYF4:Yb3+/Eu3+was studied under the irradiation of a 980 nm laser. The results show that the fluorescence intensity of NaYF4:Yb3+/Eu3+with2% Li+is the strongest, which is twice the intensity of NaYF4:Yb3+/Eu3+without Li+. Finally, the fluorescence imaging analysis of NaYF4:Yb3+/Eu3+with 2% Li+concentration was carried out. The UCMPs are used to screen printing to evaluate the imaging effect on different sample surfaces. The results show NaYF4:Yb3+/Eu3+(with 2% Li+) has great application prospects in anti-counterfeiting recognition.

Spectroscopic properties of Er^(3+)-doped fluoroindate glasses

The optical and thermal properties of a new class of fluoroindate glass with different erbium contents were investigated via Raman,transmission,and fluorescence spectroscopies,fluorescence decay curve analysis,and differential scanning calorimetry.The strength parameters of the samples were calculated using the Judd-Ofelt theory.The mid-infrared luminescence properties of erbium-doped fluoroindate glasses were studied,and a strong emission at 2.7μm was obtained.Compared with the traditional ZBLAN glass,this glass has excellent emission properties,especially a longer fluorescence lifetime(7.09 ms)and larger emission cross-section(6.95×10^(-21) cm^(2))at 2.7μm.The results indicate that fluoroindate glass is an attractive host for mid-infrared lasers and as a gain medium for optical amplifier applications.