Additionnally, STO nanoparticles we

Additionnally, STO nanoparticles were synthesized via sol-precipitation followed by hydrothermal treatment. Two solutions, designated A and B, containing the Sr and Ti precursors, respectively, were prepared. Solution A was prepared by dissolving 2.4313 g of Sr(OH)2·8H2O (Alfa Aesar, 99%) in 50 mL of 1 M acetic acid yielding a clear transparent solution with pH ∼4. Solution B was prepared by adding 1.00 mL of TiCl4 (Acros Organics, 99.9%) to 20 mL of absolute ethanol yielding a light yellow transparent solution with pH ∼1. Solution B was added to solution A under moderate stirring resulting in a clear transparent solution with pH ∼1; the Sr:Ti molar ratio in this solution was equal to 1. Coprecipitation of SrTiO3 was then induced by adding 5 g of NaOH pellets (Mallinckrodt Chemicals, 99%) to the above precursor solution while maintaining stirring. Upon dissolution of the NaOH pellets, the solution became progressively cloudy; a continuous increase of viscosity was observed until a white opaque gel was formed. After vigorous stirring, the gel lost rigidity and a highly viscous suspension with pH ∼14 was obtained, which was stirred moderately for 10 min. The suspension was loaded into a 125 mL Teflon-lined autoclave and heated at 240 °C for 24 h. The autoclave was subsequently allowed to cool to room temperature. The solution was filtered and the product (white powder) washed thoroughly with double-deionized water, and air-dried at 80 °C for 24 h.