Photoacoustic and upconversion signal variation in In2O3: Er3+/Yb3+phosphor co-doped with Mg2+/Zn2+ions under 980 nm excitation for multifunctional applications

The Er3+/Yb3+ doped In2O3 phosphor samples were synthesized by combustion method and then prepared samples were annealed at 800-1400 degrees C for 2 h for improvement of crystal phase and photoluminescence (PL) properties. The maximum upconversion (UC) emission intensity is achieved for the material annealed at 1300 degrees C for 2 h. The phase was confirmed by X-ray diffraction (XRD) and surface morphological structures of the sample were measured by field emission scanning electron microscope (FE-SEM) & transmission electron microscopy (TEM). The dia-valent dopant ions Mg2+ and Zn2+ were added into the optimum sample for enhancement of UC emission intensity. Then, frequency photoacoustic (PA) and UC spectra were recorded varying pump power through 980 nm diode laser source. Then the effects of dia-valent ions on radiative (happen due to photon) and non-radiative (happen due to phonon) emission properties of phosphors were checked simultaneously. The maximum PA signal is obtained for the 938-974 nm wavelength range and it directs its precious prospective for photo-thermal therapy (PTT) application. Finally, the authors demonstrated promising applications of the phosphor in fingerprint detection and as security ink for anti-counterfeiting purposes.