GaPO4–EuPO4 System in NanoSize Dimensions: An Investigation Based on Luminescence and 31P Magic Angle Spinning Nuclear Magnetic Resonance Techniques

Abstract

GaPO4 nanoparticles having hexagonal structure with different amounts of Eu3+ ions were prepared at 130°C based on precipitation method in glycerol medium. The interaction between GaPO4 nanoparticles and Eu3+ ions has been investigated using Eu3+ luminescence and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) techniques. Based on these studies, it is established that Eu3+ ions up to 2.5 at.% replace the protons of the hydroxyl groups attached on Ga3+ ions present on the surface of the nanoparticles and above 2.5 at.%, a separate EuPO4 phase is formed. The anisotropy parameters derived from the side band intensities of the 31P MAS NMR patterns from these samples confirmed the surface ion exchange at low Eu3+ concentration (2.5 at.%) and EuPO4 phase formation at high Eu3+ concentration (5 at.% and more). The increase in anisotropy at high Eu3+ contents has been attributed to the presence of paramagnetic EuPO4 phase.