Investigation on spectroscopic properties and temperature dependent photoluminescence of NIR emitting Cr3+ doped zinc gallate long persistent nanophosphor

In the present context, detailed spectroscopic analysis of Cr3+ doped ZnGa2O4 has been reported. Hydrothermal method was adopted for the formation of nanoparticles. XRD patterns revealed the cubic phase with good crystallinity. The PL emission spectra showed a broadband NIR emission with a sharp peak from the T-4(2) and E-2 states of Cr3+. Strong crystal field strength was estimated from the spectroscopic data for the Cr(3+)ion in ZnGa2O4 host. The material also showed long afterglow property. With increase of temperature, the FWHMs of the emission band were found to be increased and the average lifetimes were decreased because of the increasing population of the T-4(2) state. Further, the system was utilized for optical temperature sensing using lifetime based technique and maximum sensitivity was obtained as 0.018 K-1. UV, as well as blue and orange light was found to be suitable to be used as excitation sources for temperature sensing measurement. The possibility of the present nanophosphor to emit a long persistent signal in first biological window and the significant temperature dependent photoluminescence property allows it to be considered as a promising material in bioimaging application as well as for temperature sensing in biotechnological applications.