Design of green emitting CaZrO3:Tb3+ nanophosphor: Luminescence based platform for real-time ultrasensitive detection of latent fingerprints and anti-counterfeiting applications

Abstract

Rare earth doped phosphors are widely applied to the numerous fields, such as luminescent paints, white-light emitting devices, photovoltaics, security inks, etc., owing to their inherent properties, such as sharp emission profiles, substantial stoke shifts, and long luminescence life time. Here, green emitting CaZrO3:Tb3+ (x = 1–11 mol %) nanophosphors have been successfully prepared by solution combustion route using Cordia myxa (lasura) leaves extract as fuel. The powder X-ray diffraction patterns shows orthorhombic crystal structure. Surface morphology of the samples showed porous and flakes type with large void spaces. Photoluminescence spectra exhibits a series of sharp peaks in the wavelength range of 475–650 nm, which ascribed to 5D4→7F6-3 transitions of the Tb3+ ions. The Commission Internationale de I'Eclairage chromaticity coordinates are evaluated from the photoluminescence emission spectra and exhibited co-ordinates (0.32, 0.40) located within the plane green region of the diagram. Highest color purity was achieved for 5 mol % of Tb3+ ions doped CaZrO3 nanophosphors with an average correlated color temperature value ~6025 K. Thermoluminescence properties of the prepared nanophosphors exposed with ultraviolet light exhibit two glow peaks at ~166 and 328 °C. A linear and sub-linear responses of the thermoluminescence intensity after ultraviolet light exposure on samples confirms that the samples are more suitable for dosimetry applications. Latent fingerprints are developed using optimized CaZrO3:Tb3+(5 mol %) nanophosphor exhibit high sensitivity and selectivity, high contrast and low background interference on different surfaces. More importantly, the single information encryption strategy was designed and used for high-level anti-counterfeiting. The results clearly indicate that the optimized nanophosphor has great potential for real time applications in white light emitting diodes, dosimetry and advanced forensic applications.