1：Experimental Design and Method Selection:

The study compares two synthesis methods for Eu3+ doped TiO2 powders: solid-state reaction and hydrothermal-assisted sol-gel process.

2：Sample Selection and Data Sources:

TiO2:Eu3+ (1%) samples were prepared using TiO2 and Eu2O3 for SSR and TIPT precursor mixed with europium (III) nitrate penta-hydrate for HTM-SG.

3：List of Experimental Equipment and Materials:

XRD measurements were performed using a SIEMENS -D8-θ/2θ with a Cu Kα X-ray source. SEM photographs were taken using a MEB-FEG Zeiss electron microscope. Emission measurements were carried out with a Fluoromax 4P Horiba fluorimeter.

4：Experimental Procedures and Operational Workflow:

For SSR, powders were pressed into pellets, heated at various temperatures, and cooled. For HTM-SG, a titania sol was prepared, placed in an autoclave, heated, depressurized, and annealed.

5：Data Analysis Methods:

The photocatalytic decomposition of methylene blue was measured, and the first order apparent rate constant was calculated.