Mesopore slit-shaped

Recent reports describe the use of various porous carbon materials for protein adsorption. For example, Hyeon and coworkers summarized the recent development of porous carbon materials in their review [163], where the successful use of mesoporous carbons as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for protein immobilization are described. Gogotsi and coworkers synthesized novel mesoporous carbon materials using ternary MAX-phase carbides that can be optimized for efficient adsorption of large inflammatory proteins [164]. The synthesized carbons possess tunable pore size with a large volume of slit-shaped mesopores. They demonstrated that not only micropores (0.4—2 nm) but also mesopores (2-50 nm) can be tuned in a controlled way by extraction of metals from carbides, providing a mechanism for the optimization of adsorption systems for selective adsorption of a large variety of biomolecules. Furthermore, Vinu and coworkers have successfully developed the synthesis of... 

By size of pore one can mean the diameter of an equivalent cylindrical or the distance between the sides of a slit-shaped pore (i.e., in general a diameter of the largest circle that can be inscribed in a flat cross section of a pore of arbitrary form). The basis of this classification is that each of the size ranges corresponds to characteristic adsorption effect that is manifested in the isotherm of adsorption [53,115], In micropores, the interaction potential is significantly higher than in wider pores, owing to the proximity of the walls. This explains that such pores become totally full with adsorbate at low relative pressures. In mesopores, one will observe formation of mono- and then multilayer molecular film forming over the walls. After formation of a multilayer molecular film,... 

The sample used by Naono et al. (1982) was a non-porous one (based on a t-plot) (Fig. 14.8) with a BET surface area of 22 m g . It developed a maximum surface area of 178 m g at 200 °C due to the formation of a system of slit-shaped pores ca. one nm wide (see Fig. 14.2 c). During this process, a contraction of ca. 30% occurred along [100] and [010], but not along [001], i.e. not along the tunnels. With increasing temperature, the pores widened to mesopores and irregular macropores. The surface area of the hematite that finally formed at 500 °C was only 23 m g . ... 

We have an excellent activated carbon of fiber morphology, so called activated carbon fiber ACF[3]. This ACF has considerably uniform slit-shaped micropores without mesopores, showing characteristic adsorption properties. The pore size distribution of ACF is very narrow compared with that of traditional granular activated carbon. Then, ACF has an aspect similar to the regular mesoporous silica in particular in carbon science. Consequently, we can understand more an unresolved problem such as adsorption of supercritical gas using ACF as an microporous adsorbent. 

Type H3 hysteresis loop, which does not level off near the saturation vapor pressure, is characteristic of the mesoporous materials being comprised of agglomerates of plate-like particles with slit-shaped pores.79,86 Type H4 loop, which features parallel and almost horizontal branches, is attributable to the adsorption/ desorption in narrow slit-like pores. However, Type H4 loop was recently reported for MCM-41 being comprised of particles with internal voids of irregular shape and broad PSD,90 and also... 

The adsorbents normally applied are in general porous. The classification of the different pore widths of porous adsorbents was carried out by the International Union of Pure and Applied Chemistry (IUPAC) [1], IUPAC classified these materials as microporous, with pore diameters between 0.3 and 2nm, mesoporous with pore diameters between 2 and 50nm, and macroporous with pore diameters greater than 50 nm [1], The pore width, Dp, is defined as equal to the diameter in the case of cylindricalshaped pores, and as the distance between opposite walls in the case of slit-shaped pores. 

A sample of microcrystalline nordstrandite was found to be somewhat mesoporous by Aldcroft and Bye (1967). The nitrogen hysteresis loop was Type H3, which indicated the existence of slit-shaped pores between the crystallites. The BET-nitrogen area of 34 m2 g 1 appeared to represent the external area of the crystallites. 

Lawrence and co-workers (L41,L43,L44) concluded from sorption data using Nj and butane that the microstructure partly collapses during normal drying. This agrees with Parrott s (P37,P36) conclusion, noted earlier. Pastes that had been rapidly dried were likely to be closest in structure to undried pastes the sorption results indicated that their structures were dominated by platey particles or lamellae that formed slit-shaped mesopores and micro-... 

Therefore, these results indicate that Cr-K10 has, at least in part, a pillared structure. The results for Cr-PB indicate (Fig. 1 and Table 1) that this material has a micro-porous structure with some contribution of mesopores (shape of Nj adsorption-desorption isotherm) and a narrow pore volume distribution with a maximum at a pore radius of 2.1 nm. All Cr-PILC studied exhibit hysteresis loop of type H4 [11] which can be attributed to solids with a slit-shaped porous structure. Heat treatment results only in a small decrease of the BET surface area for both Cr-KIO and Cr-PB (Table 1). Sulfidation does not influence significantly the porous texture of both Cr-PILC as well [12]. 

Microporous solid selected in this study is alumina pillared montmorillonite (Al-PILM) which exhibits well-defined slit-shaped micropores. Four mesoporous solids are examined Two silica MCM-41 samples prepared with quaternary ammonium surfactants dodecyltrimethylammonium bromide (the main carbon chain of the ammonium has 12 carbon atoms. Cl2) and cetyltrimethylammonium bromide. They are labeled as MCM-41 (Cl2) and MCM-41 (Cl6), respectively. The other two are commercial porous silicas (Kieselgel 60 and silica gel 40 A from Aldrich). 

As expected, the initial part of the tts-plot for sample B in Figure 2 is similar to that for A, but in this case there is a third stage of pore filling. This is due to capillary condensation in mesopores, which according to the corrected Kelvin equation would have an effective pore width in the range 3 - 7 nm. The results of the micropore structure analysis for sample B are summarised in Table 2 and the mesopore size analysis by the BJH method in Table 3 (assuming a slit-shaped mesopore configuration). 

The isotherm of the parent SBA-15 (not shown) was of type fV with possessing a HI hysteresis loop [8], characterized by adsorption and desorption branches nearly parallel to the abscissa at high relative pressure. Similarly to SBA-15, sample WO also shows an isotherm of type fV with a HI hysteresis loop, indicating that it contains mesopores with a narrow radius distribution [8]. With increasing water content in the glycerol, the slope of the adsorption and desorption branches at high relative pressure (P/Po > 0.8) increases, which might indicate the formation of slit-shaped pores [8]. While for samples WIO and W15 still type IV isotherms are observed, indicative for mesoporous materials, the isotherms of samples W30 and W40 are intermediates between type IV and type I, the latter indicative for the presence of micropores [8]. 

They so called BJH (Barret-Joyer-Halenda) and DH (Dollimore-Heal) methods have been widely used for such calculations. However, in other articles, only a simple Fortran program for the DH method is shown. (This program can be easily used for the analysis of the mesopore size distribution). The thickness correction is done by the Dollimore-Heal equation. One can calculate the mesopore size distribution for cylindrical or slit-shaped mesopores with this program. Therefore, the adsorption branch provides more reliable results. However, the adsorption branch gives a wide distribution compared to the desorption branch due to gradual uptake. Theoretical studies on these points are still done [133]. 

In this case, the hydrogen adsorption was very low. Thus, weakly polar or nonpolar adsorbates (especially with plane molecules as benzene), which tend to be adsorbed in slit-shaped nanopores, are rather negative co-adsorbates for hydrogen in contrast to water which locates at the edges of carbon sheets around O-containing functionalities in narrow mesopores that results in the formation of secondary nanoporosity. Thus, clustered adsorption of water provides enhancement of effective nanoporosity appropriate for hydrogen adsorption. 

Carbonization of organics used in this study was carried out at a sufficiently low temperature ( 870 K). This condition leads to formation of the carbon layers whose graphene clusters have sizes that do not exceed 2 nm (Fenelonov 1995). Consequently, formation of partly graphitized areas on the carbon surface is hardly probable, and the up-field shifts of the H NMR signal for the adsorbed water may be due to location of water molecules in narrow mesopores partially filled by carbon deposits because this displacement does not exceed 5 ppm (in slit-shaped nanopores this shift could be larger see Chapter 3). 

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