Tm; Yb:ZnTiO near infrared to blue upconversion phosphors for anti-counterfeit applications.

Tm; Yb:ZnTiO samples have been synthesized using a solid state reaction route. The phase, lattice parameters, crystallite size has been examined using X-ray Diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). An intense peak of Yb codoped samples is observed near ∼957 nm due to the F → F transition in diffuse reflectance spectra (DRS), which confirms the presence of Yb ion in the prepared compound. The optical band gap of Yb codoped samples has been calculated using Kubelka-Munk function. The Raman spectra corresponds to incorporation of Tm/Yb at the octahedral and tetrahedral site of the spinel host. The emission spectra recorded by using 370 nm excitation wavelength shows intense blue colour band corresponding to the G → H transition of Tm ion. The upconversion (UC) emission spectra recorded by using 980 nm laser excitation source shows emission bands due to the G → H, G → F and H → H transitions of Tm ion in the host matrix lying in the blue, red and NIR regions respectively. There is effective enhancement of about ∼35 times in the blue UC emission intensity with incorporation of Yb at 3% doping concentration in the prepared sample. The anti-counterfeit application of the optimized upconverting phosphor has been successfully demonstrated.