Synthesis of Hollow Silica Nanoparticle Aggregates from Asymmetric Methyltrimethoxysilane Using a Modified SBA-15 Method

Abstract

This work presents the synthesis and characterization of hollow silica particles that were fabricated with the asymmetric methyltrimethoxysilane (MTMS) as the only silica precursor, by using a modified SBA-15 synthesis method, for the first time. The MTMS concentration was varied in the range from 0.300 to 0.900 M. The hollow silica nanoparticulate material characteristics were compared to those of SBA-15 silica made by using tetraethyl orthosilicate. The hollow silica nanoparticle aggregates (named as MS-Asym) showed varied nanoparticle shapes from irregular to close to spherical, with multiple hollow pores as characterized by SEM and TEM. This result is very different from SBA-15, which has a ropelike shape. X-ray diffraction data showed that the MS-Asym silica samples were disordered compared to the ordered SBA-15. Nitrogen sorption measurements suggested that the SBA-15 is mainly mesoporous, whereas MS-Asym has a combined microporous and mesoporous structure. Furthermore, attenuated total reflectance−Fourier transform infrared spectroscopy spectra infer a different polymerization mechanism occurs for MS-Asym compared to that of SBA-15 silica.

Bottom-Up Synthesis of Multicompartmentalized Microreactors for Continuous Flow Catalysis

“…Binary siliceous precursors of trimethoxysilane (TMS) and methyltrimethoxysilane (MTMS) were employed for growing a porous shell around the IL droplets through an interfacial sol−gel process since TMS was found to be easily hydrolyzed under mild conditions to enhance the robustness of the shell, 33 and MTMS can in situ hydrophobize the formed shell. 34 After growing a silica shell around the droplets through interfacial cross-linking, primary capsules were obtained as subcompartments of the final MLMs. Noticeably, we found that control of the amount and ratio of siliceous precursors were very crucial for the construction of free-flowing primary capsules (Figure S4).…”

Guanine‐La complex supported onto SBA‐15: A novel efficient heterogeneous mesoporous nanocatalyst for one‐pot, multi‐component Tandem Knoevenagel condensation–Michael addition–cyclization Reactions

“…shows the low‐angle XRD pattern of La@guanine@SBA‐15. The lattice parameter on SBA‐15 which can be indexed as the (100), (110), (200) reflections corresponds to p6mm space group of the two‐dimensional hexagonal lattice . Decreasing in the diffraction intensity of these three peaks for the catalyst indicated successful formation of La complex in the SBA‐15 hexagonal channels.…”

“…Also, it was found that the position of the d 100 peak in the catalyst shifted to lower values, which are due to the shrinking pore size, and reduced the order of homogeneity of the pores in comparison to SBA‐15. This may correspond to the re‐condensation reactions of the silica with lanthanum nanoparticles in the pore channel …”

“…[14,58] F I G U R E 1 FT-IR spectra of 100), (110), (200) reflections corresponds to p6mm space group of the twodimensional hexagonal lattice. [47,65,66] Decreasing in the diffraction intensity of these three peaks for the catalyst indicated successful formation of La complex in the SBA-15 hexagonal channels. Thus far, only one well-resolved peak at 2θ ≈ 1.20 (d 100 ) can be recognized and the (d 110 ) and (d 200 ) reflections disappeared.…”

“…This may correspond to the recondensation reactions of the silica with lanthanum nanoparticles in the pore channel. [46,62,[65][66][67] Moreover, energy dispersive X-ray spectroscopy (EDS) analysis of La@guanine@SBA-15 is carried out to indicate the adsorption of La 3+ on SBA-15 surface. These results are presented in Figure 3.…”