The ternary SiO2 Gd2O3 Eu2O3 system was synthesized by TEOS hydrolysis in an aqueous medium via a sol gel route. Thermal analysis showed that gel dehydration occurred mainly in the low temperature region and was associated with the removal of physically adsorbed and weakly bound water. The apparent activation energy was 30 34 kJ/mol for the ternary gels and about 40 kJ/mol for the SiO2 gel, indicating predominantly physical water binding. The calcined samples exhibited characteristic Eu3+ red emission, with the strongest band at 612 nm corresponding to the ⁵D₀→⁷F₂ transition. The maximum luminescence intensity was obtained for the SiO2 Gd2O3 Eu2O3 composition of 92:5:3 after calcination at 1000 °C, while further rare earth oxide addition caused concentration quenching. The optimal excitation wavelength was 393 nm. The same 92:5:3 sample calcined at 700 °C showed the highest methylene blue adsorption capacity of 108.32 mg/g, which decreased to 79.08 mg/g after calcination at 1000 °C. These results show that the luminescence and adsorption properties of SiO2 Gd2O3 Eu2O3 materials can be tuned by controlling the composition, calcination temperature, and acid base state of the surface.