Magnetic iron oxide/mesoporous silica nanocomposites consisting of iron oxide nanoparticles embedded within mesoporous silica (MCM-41) and modified with aminopropyl functional groups were prepared for application to Cr(III) adsorption followed by magnetic recovery of the nanocomposite materials from aqueous solution. The composite materials were extensively characterized using physicochemical techniques, such as powder X-ray diffraction, thermogravimetric and elemental analysis, nitrogen adsorption, and zeta potential measurements. For aqueous Cr(III) at pH 5.4, the iron oxide/mesoporous silica nanocomposite exhibited a superior equilibrium adsorption capacity of 0.71 mmol/g, relative to 0.17 mmol/g for unmodified mesoporous silica. The aminopropyl-functionalized iron oxide/mesoporous silica nanocomposites displayed an equilibrium adsorption capacity of 2.08 mmol/g, the highest adsorption capacity for Cr(III) of all the materials evaluated in this study. Energy-dispersive spectroscopy (EDS) with transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) experiments provided insight into the chemical nature of the adsorbed chromium species.

A comprehensive study of aspirin loading and release from MCM-41 and amine functionalized MCM-41 was conducted. Two different functionalization methods, co-condensation and postsynthesis modification, were utilized and compared. All of the MCM-41 samples were thoroughly characterized before and after aspirin loading by powder X-ray diffraction, nitrogen adsorption isotherms, and thermogravimetric analysis to determine the structure and physicochemical properties such as surface area, pore volume, and functional group loading. Molecular level details about the aspirin−MCM-41 interactions were revealed through FTIR and 13 C solidstate NMR experiments. For the aminopropyl-functionalized MCM-41, the carboxylic acid group of aspirin associates with the amine group of the functionalized MCM-41. In all of the samples, an interaction between the aspirin phenyl group and the mesoporous silica host was hypothesized based on shifts in the phenyl group 13 C NMR resonances. Molecular dynamics simulations supported the NMR observations in that the phenyl group of the aspirin was determined to be oriented parallel to the pore wall. The release data indicated that both the distribution and loading of the amine functional groups in MCM-41 influenced the release properties of aspirin.

M esoporous silica materials find use in many applications such as catalysis, separations, drug delivery, and gas adsorption wherein a large pore volume is desirable. 1−4 High pore volumes can be achieved by swelling traditional surfactant templates, 5−8 by employing larger templates such as block copolymers 9,10 or sacrificial nanoparticles, 11,12 or through interface-directed syntheses. 13−20 For example, Stucky and coworkers demonstrated structural control over silica materials at two size scales by utilizing phase boundaries at the micelle level and at a bulk oil−water interface. 13 Oil−water interfaces were also used in the biphasic stratification synthesis of dendritic mesoporous silicas. 19 Further, solid−liquid interfaces between 3DOM carbon materials and water resulted in uniform silica nanoparticles with large pores. 20 Despite novel structures and pore swelling strategies, pore volumes of mesoporous silica nanoparticles have seldom topped 2.0 cm 3 g −1 . 21−23 In addition, swollen or hollow structures can suffer from other disadvantages. Some literature describes small micro-or mesopores on the shell portion of a particle, 14,24 and many schemes result in thin silica walls, 25,26 all of which are prone to breakage and aggregation.Herein, we report the development of a new mesoporous silica nanoparticle structure with extremely high pore volume and an open pore structure. These nanoparticles, which are formed from combinations of surfactant swelling strategies, stirring, and sonication, demonstrate pore volumes of up to 4.5 cm 3 g −1 while maintaining the high surface areas of traditional mesoporous silica (>1000 m 2 g −1 ). In addition, these structures demonstrate thermal stability and mechanical sturdiness. We propose that this new structure is formed through micellar aggregation during silica condensation.These ultraporous mesostructured nanoparticles (UMN) were synthesized with cetyltrimethylammonium bromide (CTAB) as a surfactant, dimethylhexadecylamine (DMHA) as a cosurfactant, and decane as an oil phase (exact combinations are shown in Table 1). Prior to silica condensation from tetraethylorthosilicate (TEOS), CTAB, DMHA, and decane mixtures were stirred and then sonicated for 90 min. The prepared suspension was equilibrated at 50 °C. After TEOS condensation, the synthesized material was dialyzed and centrifuged at 66 000 × g multiple times for purification.The textural properties of UMN are shown in Figure 1, Table 1, and Supporting Information Table S1 and Figures S1−S3. The difference in transmission electron microscopy (TEM) mass contrast between the center and edges of each particle suggests either a hollow or lacy interior silica network (Figure 1a). Image analysis of UMN-3, the structure with the highest pore volume, revealed average particle diameters of 71.3 ± 13.4

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The anti-inflammatory drug, aspirin, was loaded into three zeolite HY hosts with silica to alumina ratios (SiO 2 /Al 2 O 3 ) of 5, 30, and 60. The aspirin loading in the zeolite HY samples as measured by thermogravimetric analysis decreased from 106, to 78, to 69 mg aspirin/g zeolite with increasing SiO 2 /Al 2 O 3 . The surface areas and pore volumes, measured using nitrogen adsorption−desorption experiments, indicated that the aspirin was loaded into the internal pore surface of these materials. The Fourier transform infrared and 27 Al and 13 C magic angle spinning nuclear magnetic resonance spectra of the aspirin-loaded materials provided molecular level information about aspirin− zeolite interactions. Quantum calculations at both Hartree−Fock and density functional theory levels of theory were conducted in order to understand the nature of intermolecular interactions between the zeolite host and the aspirin. The release of the aspirin from HY was dependent on the hydrophobicity of the zeolite host with more hydrophobic zeolites (higher SiO 2 /Al 2 O 3 ) releasing the aspirin less readily.