Stable and Highly Reactive Decorated Sub-Micron Silica@Anatase Core@Shell Composite

ELIAS P FERREIRA-NETO; JEAN MINAR SANTA CRUZ YABARRENA; JAVIER S. ACUÑA; VITOR PIRES MARTINEZ; MERCEDES PERULLINI1, MERCEDES RIVERO2, MATÍAS JOBBÁGY1, ALEJANDRO MENTABERRY2 AND SARA ALDABE BILMES1; SAJJAD ULLAH; PASA, ANDRÉ ; MARÍA LUZ MARTÍNEZ RICCI; UBIRAJARA PEREIRA RODRIGUES-FILHO,

Hawai

Congreso; THE EMN Meeting on Titanium-Oxides 2016; 2016

Silica-titania nanocomposites are promising materials for the development of photocatalytic self cleaning coatings capable of promoting oxidative degradation of environmentally and aesthetically undesirable pollutants. In order to enable such applications, it is important to develop methods for the immobilization of powdered photocatalysts as thin films on different substrates. In this study we report the preparation of photocatalytic sub-micron SiO2@TiO2 core@shell particles and its remarkable thermal stability. The SiO2@TiO2 particles were prepared by adsorption from several ispropanol/ethanol molar ratio and followed by controlled hydrolysis of titanium isopropoxide on the surface of silica submicron particles. Furthermore, the influence of isopropanol/ethanol solvent ratio (I/E ratio) on the properties of the prepared photocatalysts was observed. A soft hydrothermal treatment was applied to induce TiO2 crystallization. Raman and powder XRD analysis confirmed the selective formation of anatase. TEM and FEG-SEM EDS confirmed the 5-7nm wide anatase forming a porous shell on the surface of the silica particles. The core@shell structure. Both experimental data and optical simulations showed that due to the size of the complete particle, the general optical response of the system is regulated by Rayleigh scattering, exhibiting a red-shift of the extinction spectra as shell-thickness increases. The SiO2@TiO2configuration lead to efficient light harvesting by increasing the optical path inside the core@shell particles. Improved photoactivity and good recyclability of SiO2@TiO2 was demonstrated compared to unsupported TiO2. Together with BET surface area measurements, direct assessment of the density of photocatalytic sites probed by electron paramagnetic resonance assisted by hydrogen peroxide molecular probe measurements was used to provide insight into the enhanced photocatalytic activity of CSNs, which is also understood as a consequence of Rayleigh scattering, relative enhancement of the adsorption of organic molecules on the core@shell photocatalyst surface and increased optical path inside the SiO2@TiO2 particles[1]. All these aspects are directly influenced by the core@shell configuration of SiO2@TiO2 samples. TiO2 loading on silica can be tuned by changing I/E ratio, ethanol rich solvent (low I/E) leads to more controlled TiO2 deposition. The core@shell thermal stability was also studied by in situ Synchroton Powder X-Ray Diffraction with temperature range spanning from 400 to 1000°C and ex situ X-ray Diffraction from room to 12000C. Both measurements prove the phase stability of the anatase up to 12000C, and slight size increase of the particle at 1000°C. Heating at 6000C leads to improve the photocatalytic activity. Aiming to produce visible light photocatalyst we have set up an adapted photoassisted deposition methodology for Prussian Blue[2] on the surface of the core@shell system resulting on photochromic behavior and visible light sensitive improvement of the photocalysis. 1.Ullah, S.et al, Applied Catalysis B: Environmental 179 (2015) 333?343. 2.2. Uchida, H., Sasaki, T., Ogura, K., Journal of Molecular Catalysis 93 (1994), 269-277. Acknowledgements: The research was funded by grants #2011/08120-0 and # 2013/24948-3 from São Paulo Research Foun-dation (FAPESP) and grant 308,653/2010-6 from the National Council f Scientific and Technological Development (CNPq). A.Bilmes and M.L. Martínez Ricci acknowledge financial support from Agencia Nacional de Promoción Científica y Tecnológica, ANPCYT-PICT-2010-0985/PICT2012-1167. S. Ullah is thankful to The World Academy of Science and CNPq for PhD fellowship. Elia P. Ferreira-Neto thanks FAPESP for PhD fellowship (grant # 2013/24948-3)