It was found that the CTA+/SiO2 molar ratios of M-1, M-2, and M-3 were 0.16, 0.14, and 0.13, respectively, which were in the range of 0.1 to 0.2, a value previously found for a well-organized hexagonal mesophase [25]. From this chemical analysis, it appeared that six to eight SiO− groups compensated one CTA+ organic cation. The TG curves of three as-synthesized samples had a similar shape with slight difference in the percentage https://www.selleckchem.com/products/apr-246-prima-1met.html of weight loss (please refer to Additional file 1: Figure S1). In the first stage,
the weight loss of approximately 6% at below 130°C was attributed to desorption of water. In the second (weight loss of 33% to 38% at 130°C to 340°C) and third (weight loss of approximately 4% at 340°C to 550°C) stages, the weight losses were due to the thermal decomposition of organic template via Hofmann elimination [28]. In the fourth stage, at the temperature above 500°C, the weight loss was caused by the condensation
of silanol groups to form siloxane bonds [29]. From the TG results, it can be summarized that the MCM-41 nanoporous silica synthesized from three subsequent cycles contained almost the same amount of template (total weight loss of 36 to 41 wt.% in the range of 120°C to 500°C), demonstrating that the consumption of the organic template during the formation of MCM-41 was almost constant in each step of the multi-cycle https://www.selleckchem.com/products/3-methyladenine.html synthesis. The N2 adsorption-desorption isotherms
for the MCM-41 nanoporous materials were of type IV with type H1 hybrid loop [30] in accordance with IUPAC classification (Figure 5). A sharp adsorption-desorption step at P/P o range of 0.3 to 0.35 was observed for all the solids due to pore filling of uniform pores of hexagonal lattice. Table 3 showed that M-1, M-2, and M-3 had high surface areas (above 500 m2·g−1) and pore volumes (above 0.60 cm3·g−1), which could be explained by their high degree of ordering. Among the three samples, the M-2 and M-3 possessed higher Pregnenolone pore volume over M-1. The difference in the total pore volume of these samples was attributed to the varied packing of the nanoporous silica particles [25]. The pore size distribution of the primary nanopores based on BJH calculation method for M-1, M-2, and M-3 was measured (inset of Figure 5). All samples showed a narrow pore distribution wherein M-3 offered the largest pore size (highest peak centered at 2.72 nm) among the three synthesized samples, and M-1 had the smallest pore size (approximately 2.62 nm). Figure 5 Nitrogen adsorption-desorption isotherms and BJH pore diameter distribution (inset) of MCM-41 meso-ordered materials synthesized from three subsequent cycles: (a) M-1, (b) M-2 and (c) M-3. Solid symbols denoted adsorption, and open symbols denoted desorption.
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