Calotropis mediated hydrothermal route for the synthesis of Eu3+ activated La(OH)3 and La2O3 red phosphors

The study details a green-mediated hydrothermal route for the synthesis of Eu 3+ activated La(OH) 3 and La 2 O 3 nanophosphors using Calotropis milk latex (CML) as a surfactant. The functionalization of as-formed La (OH) 3 : Eu 3+ (10 ml, 1, 5, 9, 11 mol%), calcined La 2 O 3 : Eu 3+ (2–12 ml, 9 mol%) and La 2 O 3 : Eu 3+ (10 ml, 1–11 mol%) nanophosphors was investigated through PXRD, FTIR, SEM, TEM and photoluminescence (PL) studies. From the surface morphology, it was noticed that the CML/Eu 3+ concentration showed tremendous potential in the self-assembly process and has been utilized as a soft template for the engineering of ordered nanostructures. The energy band gap of calcined La 2 O 3 : Eu 3+ (10 ml, 1–11 mol%) was found to decrease from 4.68 to 3.91 eV. The PL intensities of transitions between different J levels depend on the symmetry of the local environment of Eu 3+ activators. The high ratio of intensity of ( 5 D 0 → 7 F 2 ) and ( 5 D 0 → 7 F 1 ) provides the conclusion that the Eu 3+ ion occupies a site with a low symmetry and without an inversion centre. La (OH) 3 : Eu 3+ (10 ml, 9 mol%) and La 2 O 3 : Eu 3+ (10 ml, 9 mol%) nanophosphors show an intense red emission with CIE coordinates (0.56, 0.43) and (0.58, 0.41) respectively. The correlated color temperature (1893 K, 1786 K) was within the range of vertical daylight. The present study successfully demonstrates biotemplate-mediated green synthesis of hexagonal La(OH) 3 : Eu 3+ and La 2 O 3 : Eu 3+ nanophosphors for display applications.