Such Torin 1 order a drastic reduction in the crystallization time allows the specific surface area and the porosity to retain high values, eventually leading to a better photocatalytic performance: as shown in Figure 5, when the as-synthesized TiO2 spheres are subjected to 10 to 15 min of MW sintering; the methyl orange is almost completely photodegraded after 6 h, this result being remotely accessible for a conventionally sintered powder. Figure 5 Evolution of methyl orange concentration during the photocatalytic test. Conclusions
When conventional electric heating is LOXO-101 nmr applied to consolidate an amorphous powder of hierarchically nanostructured anatase microspheres, an increase in the crystal order is inescapably accompanied by a deleterious decrease in the specific surface and the porosity which dramatically reduces the photoactivity of
this TiO2-based material. To avoid this scenario, microwave sintering has been successfully MLN2238 molecular weight applied as an eco-friendly (energy saving) consolidation alternative: by reducing the heating time to just a few minutes, microwave radiation promotes the fast crystallization of the nanostructured microspheres, allowing the starting anatase powder to achieve a high crystallinity while keeping a high specific surface area and low density. As a straight consequence, the hunting of photons, the absorption of guest species and the photo-induced charge separation is fostered, eventually harvesting an improved photocatalytic performance. Acknowledgements This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) through the projects IPT-120000-2010-033 (GESHTOS), IPT-2011-1113-310000 (NANOBAC), CICYTMAT
2010-16614, MAT2010-18432 and CSD2008-00023. Dr T. Jardiel also acknowledges the JAE-Doc contract of the Spanish National Research Council (CSIC) and the European Science Foundation (ESF). Dr M. Peiteado acknowledges the Ramon y Cajal Program of MINECO for the financial support. References 1. Grätzel M: Photochemical cells. Nature 2001, 414:338–344.CrossRef 2. Wang D, Choi D, Li J, Yang Z, Nie Z, Kou R, Hu D, Wang C, Saraf LV, Zhang J, Aksay IA, Liu J: Self-assembled TiO2-graphene hybrid nanostructures others for enhanced Li-ion insertion. ACS Nano 2009, 3:907–914.CrossRef 3. Kim DH, Seong WM, Park IJ, Yoo E-S, Shin SS, Kim JS, Jung HS, Lee S, Hong KS: Anatase TiO2 nanorod-decoration for highly efficient photoenergy conversion. Nanoscale 2013, 5:11725–11732.CrossRef 4. Hu X, Li G, Yu JC: Design, fabrication, and modification of nanostructured semiconductor materials for environmental and energy applications. Langmuir 2010, 26:3031–3039.CrossRef 5. Calatayud DG, Jardiel T, Peiteado M, Rodríguez CF, Espino Estévez MR, Doña Rodríguez JM, Palomares FJ, Rubio F, Fernández-Hevia D, Caballero AC: Highly photoactive anatase nanoparticles obtained using trifluoroacetic acid as an electron scavenger and morphological control agent. J Mater Chem A 2013, 1:14358.