NIR dual-wavelengths excited upconversion photoluminescence of the core–shell luminescent material for anti-counterfeiting recognition

NaGdF4:Yb,Er,Nd@NaGdF4@NaYF4:Yb,Tm core–shell upconversion (UC) luminescent materials were prepared by solvothermal method. With XRD, TEM, XPS and other characterization methods, the composition, morphology and luminescent properties of the prepared UC luminescent materials were characterized. Under the excitation of 980 nm laser and 808 nm laser, the prepared UC luminescent materials can emit blue light and red light respectively. Compared with the uncoated NaGdF4:Yb,Er,Nd materials, the photoluminescence (PL) intensity of the materials with active-shell structure could be enhanced by several times. Furthermore, the influence of Tm3+ doping concentration and other factors on the PL intensity were investigated. Furthermore, the resultant UC luminescent materials were used as the raw material of anti-counterfeiting ink. The anti-counterfeit patterns printed on the glass can emit different colors luminescence under NIR dual-wavelength excitation. The experimental results indicate that the prepared NaGdF4:Yb,Er,Nd@NaGdF4@NaYF4:Yb,Tm UC luminescent materials can be applied as screen-printing materials for anti-counterfeiting recognition labels.