This nanostructure was investigated by click here specific surface area measurements, and as inferred from the data summarized in Table 1, the decrease in the specific surface area is less pronounced for the sample exposed 10 min to the microwaves (113 m2/g) than for the powder conventionally heated in the electric furnace (82 m2/g), although both powders exhibit a similar crystallinity
by XRD. Figure 3 FESEM micrographs of the Ti sph powder. After being exposed to different thermal treatments, 7 min under MW radiation (a, b), 15 min under MW radiation (c, d) and 1 h of conventional electric heating at 400°C (e, f). Table 1 Specific surface area of the prepared samples Sample selleck chemicals Specific surface area (±1 m2/g) As-synthesized Tisph powder 322 7 min MW heating 232 10 min MW heating 113 15 min MW heating 75 30 min MW heating 65 400°C/1 h conventional heating 82 In addition, the pore structure of the samples was analyzed by N2 adsorption/desorption measurements, the pore size distribution
being calculated by the density functional theory method. The BET isotherms in Figure 4a are in agreement with the observed decrease in the specific surface area after the thermal treatments. Regarding the pore size, a bimodal distribution centred on 2.3 nm is observed for the Tisph as-synthesized powder (Figure 4b); it has a narrow shape IACS-010759 which confirms that the mesoporous microspheres are formed by densely packed primary nanoparticles with uniform agglomeration. On heating, the narrow shape is preserved but with significant differences; while the sample heated on the MW oven keeps the bimodal distribution of pores centred on 2.7 nm (like in the as-synthesized Selleck Ixazomib powder), the sample conventionally heated has increased this value up to 4.3 nm, indicating that the pores have grown substantially in the electric furnace. Figure 4 Nitrogen adsorption-desorption BET isotherms (a) and pore size distribution curves (b). Photocatalytic performance As described in the experimental section, the photocatalytic response of the obtained powders was estimated evaluating the degradation of methyl orange under UV-visible light.
Figure 5 thus illustrates the decrease in the methyl orange concentration as a function of the reaction time for all those powders and, as observed, several interesting conclusions can be surmised. First, a thermal treatment of the TiO2 powder is by all means required. With the as-synthesized spheres, we attain the highest specific surface (Table 1), but merely a 10% to 20% of the starting methyl orange is degraded after the photocatalytic process, this certifying the importance of a certain degree of crystalline order for an effective catalysis. Second, the microwave heating that we propose here is clearly more efficient than the conventional electric heating typically used to improve the crystallinity of the particles.