Boosting luminescence and MRI evolution via regulation of GdPO4:5%Eu3+ morphologies by H3PO4

Abstract

A series of GdPO4:5%Eu3+ micro/nanomaterials with different morphologies and crystal structures were successfully prepared by the one-step solvothermal method using only the gadolinium source, the phosphoric acid source and ethanol as solvents, without any surfactants or templates, without further calcination and by adjusting only the ratio of phosphoric acid and gadolinium sources. They all have good dispersion and homogeneity. The morphology of the products was mainly regulated by the ratio of H3PO4 to Gd(NO3)3·6H2O, with ratios of 2:1, 8:1, 16:1, 24:1, 32:1, 40:1 and 48:1 mL/g resulting in the formation of square, pillow, star, carambola, hollow cylinder, drum and jujube shaped GdPO4:5%Eu3+ micro/nanomaterials, respectively. Ratios of 2:1–24:1 and 32:1–48:1 allow for the direct solvothermal synthesis of monoclinic and hexagonal phase gadolinium phosphate, simultaneously. In addition to their crystal structure and morphology, chemical bonding, thermal stability and specific surface area, their luminescence properties and magnetic resonance imaging (MRI) tracing properties have also been studied in comparison. Interestingly, the GdPO4:5%Eu3+ micro/nanoparticles in the carambola shape had a higher photoluminescence intensity and relaxation rate of 0.7709 mM−1 s−1 (r1) among all the morphologies. The possible mechanisms by which various morphologies of GdPO4:5%Eu3+ were prepared in different ratios were analyzed, and the reasons for their effects on the fluorescence and MRI tracer properties were further investigated. This study is of reference significance for the simple-regulated synthesis of rare earth inorganic gadolinium-containing micro/nanomaterials and provides a reliable guarantee for the expansion of their multifunctional applications in UV–Vis luminescence and MRI tracing for implants.