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

ELIAS P. FERREIRA-NETO; VITOR PIRES MARTINEZ; SAJJAD ULLAH; JEAN MINAR SANTA CRUZ YABARRENA; SARA A. BILMES; MARTINEZ RICCI, MARIA LUZ; JAVIER S. ACUÑA; ANDRE A. PASA; UBIRAJARA PEREIRA RODRIGUES-FILHO

hawaii

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

Silica-titania nanocomposites are promisingmaterials for the development ofphotocatalytic self cleaning coatings capableof promoting oxidative degradation ofenvironmentally and aesthetically undesirablepollutants. In order to enable suchapplications, it is important to developmethods for the immobilization of powderedphotocatalysts as thin films on different substrates.In this study we report the preparation ofphotocatalytic sub-micron SiO2@TiO2core@shell particles and its remarkablethermal stability. The SiO2@TiO2 particles wereprepared by adsorption from severalispropanol/ethanol molar ratio and followed bycontrolled hydrolysis of titanium isopropoxide onthe surface of silica submicron particles.Furthermore, the influence of isopropanol/ethanolsolvent ratio (I/E ratio) on the properties of theprepared photocatalysts was observed. A softhydrothermal treatment was applied to induceTiO2 crystallization.Raman and powder XRD analysis confirmed theselective formation of anatase. TEM andFEG-SEM EDS confirmed the 5-7nm wideanatase forming a porous shell on thesurface of the silica particles. Thecore@shell structure. Both experimental dataand optical simulations showed that dueto the size of the complete particle, thegeneral optical response of the system is regulatedby Rayleigh scattering, exhibiting a red-shift ofthe extinction spectra as shell-thicknessincreases. The SiO2@TiO2configuration leads THE EMN Meeting on Titanium-Oxides 2016 PROGRAM & ABSTRACTAbstractΦ5to efficient light harvesting by increasingthe optical path inside the core@shellparticles. Improved photoactivity and goodrecyclability of SiO2@TiO2 was demonstratedcompared to unsupported TiO2.Together with BET surface area measurements,direct assessment of the density of photocatalyticsites probed by electron paramagnetic resonanceassisted by hydrogen peroxide molecular probemeasurements was used to provide insight into theenhanced photocatalytic activity of CSNs, which isalso understood as a consequence of Rayleighscattering, relative enhancement of the adsorptionof organic molecules on the core@shellphotocatalyst surface and increased optical pathinside the SiO2@TiO2 particles[1]. All these aspectsare directly influenced by the core@shellconfiguration of SiO2@TiO2 samples. TiO2 loadingon silica can be tuned by changing I/E ratio, ethanolrich solvent (low I/E) leads to more controlled TiO2deposition. The core@shell thermal stability wasalso studied by in situ Synchroton Powder X-RayDiffraction with temperature range spanning from400 to 10000C and ex situ X-ray Diffraction fromroom to 12000C. Both measurements prove thephase stability of the anatase up to 12000C, andslight size increase of the particle at 10000C.Heating at 6000C leads to improve thephotocatalytic activity. Aiming to produce visiblelight photocatalyst we have set up an adaptedphotoassisted deposition methodology for PrussianBlue[2] on the surface of the core@shell systemresulting on photochromic behavior and visiblelight sensitive improvement of the photocalysis.