(248aj) La- and Cr- Doped SrTiO3 Nanoparticles for Photocatalytic Pollutant Degradation

The most heterogeneous photocatalysts are presented by nanostructured titanium dioxide (anatase), which is associated with the amorphous phases characterized by a large amount of surface defects, existence of which facilitates an effective separation of charge carriers. It was shown recently that chromium and lanthanum doped SrTiO₃ perovskites exhibit high photocatalytic activity [1]. The goal of this work was to synthesize nanostructured La- and Cr- doped strontium perovskites SrTi_(1−x)La_xO₃ and SrTi_(1−x)Cr_xO₃ at (x=0.01-0.2) by using Solution Combustion Synthesis (SCS) approach [2] and examine their photocatalytic absorption properties. Doped perovskites with metal atoms contains more interstitial defects altering the cubic crystal lattice. Consequently, these materials experienced a shift in the absorption of incoming EM waves, causing the band gap to widen or become more narrow depending on the effects of the defects. Moreover, oxygen vacancies are fairly common in SrTiO₃ crystals that induce free electrons in the conduction band of the material, making it more electron/hole pairs by photo-excitation. These vacancies can be produced using SCS by altering reaction processes at the moderate temperatures. Perovskite nanostructured particles may decrease the concentration of NO_x pollutants and cigarette smoke in air, as well as volatile automobile emissions. When exposed to UV or visible light, these nanoparticles can oxidize organic pollutants into nontoxic substances, such as CO₂ and water, and can disinfect a variety of bacteria and viruses in secondary wastewater treatment. The synthesis of high purity nanocrystalline powders (<100 nm) is the key to improve the performance of perovskite-based ceramics for both electronic and catalytic applications.  The reactants mixture contained Sr- and La- nitrate precursors, butyl titanate Ti(CH₃(CH₂)₃O and glycine were used to produce nanostructured La- and Cr- doped strontium perovskites SrTi_(1−x)La_xO₃ and SrTi_(1−x)Cr_xO₃ at (x=0.01-0.2) by using Solution Combustion Synthesis. The main parameter affecting the process, product particle size distribution and photocatalytic properties is the ratio of metal nitrates and glycine. Increasing glycine concentration amplified combustion temperature which lead to growth particle size of photocatalysts. The SrTiO₃ had an absorption maximum at approximately 395 nm that agrees with the value of 387 nm in the literature. The spectra of SrTi_0.9LaO₃exhibit absorption in visible light region with the maximum peak at 644 nm.

REFERENCES

1. S. Tonda, S. Kumar, O. Anjaneyulu, and V. Shanker, Phys Chem Chem Phys, 2014, 16, 43 23819-28.

2. K.S. Martirosyan, and A.S. Mukasyan, Combustion Synthesis of Nanomaterials, In Dekker Encyclopedia of Nanoscience and Nanotechnology, Third Edition. CRC Press: New York, (2014) 983–1001.