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 ZnGa 2 O 4 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 4T 2 and 2E states of Cr3+. Strong crystal field strength was estimated from the spectroscopic data for the Cr3+ ion in ZnGa 2 O 4 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 4T 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. • Urea assisted hydrothermal method was used to prepare the samples. • Cr3+ experience a strong crystal field in ZnGa 2 O 4 host. • With increase of temperature the FWHM of emission band increases but the PL peak intensity and lifetime decreases. • Lifetime based optical thermometry was done by exciting the sample at UV as well as blue and orange light. • The present nanophosphor is found to be a promising material for bioimaging and optical thermometry application. [ABSTRACT FROM AUTHOR]