Size controlled synthesis of highly dispersed anatase/rutile nanoparticles with photocatalytic activity toward salicylic acid degradation

Abstract

TiO 2 nanocrystals supported in SBA-15 pores were prepared by a simple route of successive cycles of impregnation of SBA-15 with titanium(IV) di-(n-propoxy)-di-(2-ethylhexanoate) followed by thermal treatment. Anatase and rutile phases were identified by XRD in the materials obtained after cycles 1, 3, 5, 7 and 10. Raman scattering combined with XRD and TEM shows that titania is in a nanometric regime. Increases in the size of the titania nanocrystals, as well as increases in the TiO 2 content in the final material (XRF), occur after successive cycles. SAXS and N 2 sorption indicate that the nanocrystals are formed inside the SBA-15 mesopores, which remain unblocked even after 10 cycles. UV-Vis (DRS) spectroscopy indicates important changes in electronic properties. The ability of SBA-15-supported titania nanocrystals to photodegrade salicylic acid was tested. There is a clear relation between the TiO 2 nanoparticle size and the photocatalytic activity. Among all samples tested, the best result was obtained for the materials with the highest band-gaps and with the smallest sized titania.

Size-Controlled Synthesis of Anatase in a Mesoporous Silica, SBA-15

“…There are many efforts to increase the TiO 2 content in the PMSs for controlling the photocatalytic performances. ,,,− Landau et al reported a high TiO 2 content (64 mass % TiO 2 ), which was obtained by impregnation repeated twice using the high concentration of tetrabutyl orthotitanate (80 mass %) solution in n -decane . The crystal size of anatase was determined to be 5.5 nm, which was consistent with the BJH pore diameter of the used SBA-15 (6 nm).…”

“…The TiO 2 contents reported so far were not consistent with the decrease of the pore volume, indicating the different contribution of the externally formed anatase and anatase in the mesopore. The higher TiO 2 contents have been achieved by the repeated infiltration; ,,,− however, it was difficult to avoid the formation of the anatase particles on the external surface of mesoporous silicas. Here, by using neat TTIP without solvents, the high TiO 2 content (62 mass %) in the hybrid was obtained by a single infiltration step.…”

“…To control the catalytic functions, the state, the size, and the shape of the TiO 2 particles as well as their location in the mesopore are key factors. The TiO 2 species have been immobilized in PMSs as isolated molecular species and oxide nanoparticles in the silica wall and on the mesopore using several molecular precursors and with varied synthetic conditions (both direct synthesis and postsynthetic immobilization); − however, the size and shape of the TiO 2 particles as well as their location (on the external surface or in the mesopore) are still difficult to be controlled precisely. Although the size-controlled synthesis of TiO 2 particles has been a topic of interest in materials chemistry to adapt the wide range of applications of TiO 2 and to optimize the performances of materials, − the size-controlled synthesis of TiO 2 using PMSs as a template is still challenging.…”

Estudo de vórtice magnético em nanopartículas para aplicações em hipertermia magnética

“…No processo de impregnação desenvolvido no trabalho usamos um composto metalorgânico que, a princípio, quando exposto a altas temperaturas em atmosfera oxidante perde a cadeia orgânica, restando apenas o óxido do metal correspondente. No entanto, dada a morfologia cilíndrica da partícula foi possível implementar a impregnação por metalorgânico [112,113] em algo mais elaborado.…”