Evaluating Pore Sizes in Mesoporous Materials:  A Simplified Standard Adsorption Method and a Simplified Broekhoff−de Boer Method

Atomic layer deposition (ALD) enables the conformal coating of porous materials, making the technique suitable for pore size tuning at the atomic level, e.g., for applications in catalysis, gas separation and sensing. It is, however, not straightforward to obtain information about the conformality of ALD coatings deposited in pores with diameters in the low mesoporous regime (<10 nm). In this work, it is demonstrated that in situ synchrotron based grazing incidence small angle X-ray scattering (GISAXS) can provide valuable information on the change in density and internal surface area during ALD of TiO 2 in a porous titania film with small mesopores (3-8 nm). The results are shown to be in good agreement with in situ X-ray fluorescence data representing the evolution of the amount of Ti atoms deposited in the porous film. Analysis of both datasets indicates that the minimum pore diameter that can be achieved by ALD is determined by the size of the Ti-precursor molecule.

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“…4(b)). 31 The average size of these "bottlenecks" was ca. 3 nm, as deduced from the desorption branch using Kelvin's equation.…”

Section: Resultsmentioning

confidence: 99%

Atomic layer deposition-based tuning of the pore size in mesoporous thin films studied by in situ grazing incidence small angle X-ray scattering

et al. 2014

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“…The total pore volume was calculated from the N 2 amount adsorbed at maximum p/p 0 () 0.99). The pore size distribution was calculated according to the Broekhoff-de Boer (BdB) method using a spherical model; 26 i.e., cavity and entrance pore sizes were determined from the adsorption and desorption branches, respectively. X-ray photoelectron spectra (XPS) were recorded on a Kratos Axis Ultra instrument using a monochromatic Al KR X-ray source.…”

Section: Synthesis Of Nonfunctionalized Andmentioning

confidence: 99%

Functionalized Mesoporous Silica with Very Large Pores for Cellulase Immobilization

et al. 2010

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Organo-functionalized FDU-12 type silicas exhibiting large pore sizes and ordered mesoporous structures were synthesized at low reaction (15°C) and high hydrothermal (160°C) temperatures via the co-condensation of tetraethoxysilane (TEOS) with a suite of organosilanes, i.e., 3-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane (MPTMS), vinyltrimethoxysilane (VTMS), and phenyltrimethoxysilane (PTMS), in the presence of structure directing micelles formed using the surfactant pluronic F127 and the pore enlarging reagent trimethylbenzene (TMB). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) confirmed that all synthesized materials possessed a face-centered cubic mesostructure (space group Fm3 j m), while nitrogen sorption analyses showed that the synthesized materials had extra large pores with cavity sizes of up to 25.4 nm and entrance sizes of up to 10.8 nm. X-ray photoelectron spectroscopy (XPS) and 13 C solid-state magic-angle spinning nuclear magnetic resonance ( 13 C-MAS NMR) measurements verified the incorporation of the different organosilanes into the silica network and more importantly on the inner and outer surfaces of the materials. As-obtained mesoporous silicas were tested in protein immobilization studies using bovine serum albumin and the cellulose-hydrolyzing enzyme cellulase, which in itself is a mixture of three large enzymes. Enzyme immobilization efficiency, activity, and stability varied significantly with organic functionality due to size exclusion effects at pore entries, electrostatic and hydrophobic interactions between the organo-functionalized surfaces and the enzymes, and conformational changes of the enzymes which can occur on some of the material surfaces. As a result, phenyl (PTMS)-and thiol (MPTMS)-functionalized FDU-12 mesoporous silicas had a very low adsorption capacity of proteins because of their small pore sizes. Amino (APTES)-functionalized FDU-12 mesoporous silica showed the highest adsorption amount of proteins yet the lowest activity of immobilized cellulase. Cellulase immobilization on vinyl (VTMS)-functionalized FDU-12 mesoporous silica appeared to be the most promising approach, since it occurred with high efficiency, maintained enzyme activity, and provided temporal enzyme stability.

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“…The SEM samples were prepared by placing SBA-16 powder on double-sided carbon adhesive tape mounted on the sample holder and then coated with a thin layer of gold in order to minimize charging effects. Transmission electron microscopy (TEM) was [17] over the relative pressure (P/P 0 ) range of 0.05 -0.2, the pore-size distribution was determined using the Broekhoff-de Boer (BdB) method [18] applied to the adsorption branch. Finally the total pore volume was calculated from the amount of adsorbed N 2 at P/P 0 = 0.99, and the microporous volume was determined using the t-plot method.…”

Section: Characterizationmentioning

confidence: 99%

Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system

Ballem

Córdoba

Odén

2010

Microporous and Mesoporous Materials

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Spherical particles of mesoporous silica SBA-16 with cubic Im3m structure were synthesized at low pH using Pluronic F127 as template and TEOS as silica source. The diameter of the spherical particles can be controlled in the range of 0.5 -8 µm by varying synthesis temperature between 1 °C up to 40 °C. A sharp transition from large particle sizes at approximately 20 °C to smaller ones is observed when the temperature is increased. It is suggested that this morphology transition is due to a change in hydrolysis and condensation rate of the silica source and as a result the assembly of F127 micelles will differ. The SBA-16 samples were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Nitrogen adsorption techniques.

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Evaluating Pore Sizes in Mesoporous Materials: A Simplified Standard Adsorption Method and a Simplified Broekhoff−de Boer Method

Cited by 457 publications

References 43 publications

Atomic layer deposition-based tuning of the pore size in mesoporous thin films studied by in situ grazing incidence small angle X-ray scattering

Atomic layer deposition-based tuning of the pore size in mesoporous thin films studied by in situ grazing incidence small angle X-ray scattering

Functionalized Mesoporous Silica with Very Large Pores for Cellulase Immobilization

Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system

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