Titanium 4 isopropoxide ti oc3h7 4

All reagents were of analytical grade and were applied in this study without further purification: titanium (IV) isopropoxide (Ti(OC₃H₇)₄, Sigma Aldrich, St. Louis, MO, USA, 98.0%), zinc acetate ((CH₃CO₂)₂Zn, Sigma Aldrich, St. Louis, MO, USA, 99.99%), isopropyl alcohol (C₃H₈O, Sigma Aldrich, St. Louis, MO, USA, ≥99.5%), hydrochloric acid (HCl, Sigma Aldrich, St. Louis, MO, USA, 37.0%), sodium hydroxide (NaOH, Sigma Aldrich, St. Louis, MO, USA, ≥85.0%), potassium cyanide (KCN, Sigma Aldrich, St. Louis, MO, USA, ≥97.0%), picric acid ((O₂N)₃C₆H₂OH, Sigma Aldrich, St. Louis, MO, USA, ≥99.0%), sodium carbonate (Na₂CO₃, Sigma Aldrich, St. Louis, MO, USA, ≥99.0%), hydrogen peroxide (H₂O₂, Sigma Aldrich, St. Louis, MO, USA, 35%), silver nitrate (AgNO₃, Sigma Aldrich, St. Louis, MO, USA, >99.8%), nitric acid (HNO₃, Sigma Aldrich, St. Louis, MO, USA, 69%), sodium metasilicate nonahydrate (Na₂O₃Si·9H₂O, Sigma Aldrich, St. Louis, MO, USA, ≥98.0%), sodium aluminate (Sigma Aldrich, St. Louis, MO, USA, ≥98.0%), Al(Al₂O₃): 50–56%, Na(as Na₂O): 37–45%).

Pure CaTiO₃ (CTO) perovskite nanoparticles were prepared by the sol-gel method. In this synthesis, titanium (IV) isopropoxide Ti(OC₃H₇)₄ (97% Sigma-Aldrich, St. Louis, MO, USA ), calcium (II) nitrate tetrahydrate Ca(NO₃)₂∙4H₂O (99% Sigma-Aldrich, St. Louis, MO, USA), 2-propanol (EMSURE®, Merk, Darmstadt, Germany), and citric acid monohydrate C₆H₈O₇∙H₂O (≥99% Sigma-Aldrich, St. Louis, MO, USA), were used as starting materials. All the chemicals were of analytical grade and no further purification was performed. The synthesis steps are the following (Figure 1): a) Ti(OC₃H₇)₄, Ca(NO₃)₂∙4H₂O and citric acid were weighed accurately according to the stoichiometric composition, and dissolved separately in 2-propanol, under vigorous stirring for 30 min; b) once the solution of Ca(NO₃)₂∙4H₂O was added drop by drop to the solution of Ti(OC₃H₇)₄), the solution of citric acid was likewise added drop by drop to obtain a CTO precursor solution; c) this last solution was stirred vigorously for 30 min at room temperature while deionized water was slowly added until the gel was formed; d) then, the gel was dried at 50 °C for 96 h. The resultant powder (xerogel) was ground in an agate mortar for 5 min and finally calcined at 600 °C over 1 h in air to obtain CTO powder.

All chemicals (analytical grade) were utilized in this research without additional purification: titanium (IV) isopropoxide (Ti(OC₃H₇)₄, Sigma Aldrich, St. Louis, MO, USA, 98.0%), zinc acetate ((CH₃CO₂)₂Zn, Sigma Aldrich, 99.99%), isopropyl alcohol (C₃H₈O, Sigma Aldrich, ≥99.5%), hydrochloric acid (HCl, Sigma Aldrich, 37.0%), sodium hydroxide (NaOH, Sigma Aldrich, ≥85.0%), hydrogen peroxide (H₂O₂, Sigma Aldrich, 35%), sodium metasilicate nonahydrate (Na₂O₃Si·9H₂O, Sigma Aldrich, ≥98.0%), kaolin (Sigma Aldrich), sodium dodecyl sulfate (CH₃(CH₂)₁₁OSO₃Na, Sigma Aldrich, ≥99.0%), poly(ethylene glycol) (H(OCH₂CH₂)_nOH, Sigma Aldrich).