Role of pH, Organic Additive, and Chelating Agent in Gel Synthesis and Fluorescent Properties of Porous Monolithic Alumina

This work demonstrates the synthesis of porous monolithic alpha-alumina by a modified polyacrylamide gel route at different reaction parameters. Various Al2O3 phases are synthesized by a modified polyacrylamide gel route using different organic additives and solutions with different pH values (3, 7, and 11). After calcination at 1150 degrees C, the pure alpha-Al2O3 is obtained at pH = 3 and 7 while there is still theta-Al2O3 at pH = 11. The organic additive has nothing to do with the purity of alpha-Al2O3 phase. The scanning electron microscopic images indicate that the pore size and morphology of the samples depend on the choice of organic additive and pH value. The photoluminescence spectra show that two emission peaks located at 330 and 368 nm are observed when the excitation wavelength is 228 nm. Interestingly, the intensity of emission peak at 368 nm decreases with the decrease of full width at half-maximum or pore size.