Role of Diethylene Glycol in the Glycothermal Synthesis of Highly Dispersed Colloidal YAG:Ce³⁺ Nanoparticles

Diethylene glycol (DEG)-assisted glycothermal synthesis can yield highly dispersed crystalline YAG (Y₃Al₅O₁₂) colloidal nanoparticles (NPs). However, the role of the DEG is still unclear. Herein, we have investigated the influence of volume fraction of the cosolvent DEG and metal precursor concentration on phase composition and dispersion property of the glycothermally synthesized cerium(III)-doped YAG NPs. The addition of DEG can significantly improve the solubility of Al(ⁱOPr)₃ in glycol solvents, which in turn ensures a better contact between dissolved Al³⁺ ions and lanthanide ions. This prevents the formation of much larger boehmite or glycol derivative of boehmite particles from the undissolved Al precursor. With an appropriate Al molar concentration and a DEG to Al molar ratio, colloidal cerium-doped YAG NPs with a hydrodynamic diameter of about 10 nm can be obtained with nearly 100% yield by weight. The computational prediction suggests that colloidal YAG NPs can strongly associate with DEG ligands. The resulting NPs exhibit enhanced dispersion, likely due to the increased polarity and additional hydrogen bonding sites introduced by the DEG ligands. The implementation of DEG had a limited effect on the optical properties of the synthesized NPs, as long as it did not excessively compromise the crystalline integrity.