Upconversion luminescence based temperature sensing properties and anti-counterfeiting applications of GdNbO4:Tm3+/Yb3+ phosphor

Pure monoclinic phase GdNbO4:Tm3+/Yb3+ phosphor was prepared using solid state reaction method for upconversion emission, optical thermometry, latent fingerprints visualization and anti-counterfeiting applications. The prepared phosphor exhibits colour tunability with temperature variation (from blue to almost white) and good suppression of thermal quenching. The temperature sensing characteristic from thermally and non-thermally coupled levels of Tm3+ ion were investigated using the fluorescence intensity ratio (FIR) approach. The result shows that the sensitivity for non-thermally coupled level is about ∼ 45 times higher than thermally coupled level. Latent fingerprint detection on various surfaces and anti-counterfeiting ink application were also shown upon 980 nm laser diode excitation. Above results indicate that the prepared GdNbO4:Tm3+/Yb3+ phosphor have applicability in the field of frequency upconversion, optical thermometry, color tunable devices, latent fingerprint visualization and anti-counterfeiting applications.