Sonochemical synthesis of green emitting Ca2SiO4:Er3+ nanopowders: Promising applications in optical thermometry and radiation dosimeter

The Er3+-activated Ca2SiO4 nanopowders were fabricated via sonochemical method using Epigallocatechin gallate as a bio-surfactant. The X-ray diffraction results reveal that the prepared nanopowders consist of a single phase monoclinic structure. The energy band gap of the prepared samples was estimated and found in the range 4.95-5.18 eV. The photoluminescence emission spectra exhibit intense peaks centered at similar to 517, 551, 613 and 662 nm, which were attributed to H-2(11/2) -> I-4(15/2), S-4(3/2 )-> I-4(15/2), F-4(9/2) -> I-4(15/2) and F-4(9/2(1) )-> I-4(15/2) transitions of Er3+ ions, respectively. The photoluminescence emission intensity increases up to 5 mol % of Er3+ concentration and later diminishes. The decrement of emission intensity with increasing Er3+ concentration was related to a self-quenching of the concentration. The cause behind the concentration quenching was proposed as a dipole-dipole interaction among Er3+ ions. Photometric characterizations of Er3+-doped Ca2SiO4 nanopowders exhibit green light emission with high color purity indicates the present nanopowders were quite useful in the fabrication of cool light emitting diodes. The sensor sensitivity of the Ca2SiO4:Er3+ (5 mol %) nanopowders was found to be - 0.0624 K-1 at lower temperature 303 K, suggesting suitability for the optical thermometry application. Further, thermoluminescence properties of the prepared samples were extensively investigated. The activation energy and frequency factor of the prepared nanopowders were estimated and obtained values were good agreement with standard thermoluminescence materials, which specify the suitability of the prepared nanopowders in dosimetry applications. The aforementioned results confirm the synthesized nanopowders exhibit excellent photometric, sensor sensitivity and thermoluminescence properties signifying suitability in solid state lighting, optical thermometry and dosimetry applications.