加納 博文

This study reports a direct route for deposition of Pd nanoclusters on single-walled carbon nanohorns (SWNHs) in a one step reaction involving chemical reduction of metal ions in the presence of a polymer- stabilizer. The applied strategy provides small Pd nanoclusters with an average diameter of similar to2.3 nm robustly attached to the nanotubular carbon. The attachment is mediated by the polymer (poly(vinylpyrrolidone), PVP) used to stabilize the nanoclusters.

A mechanochemical intercalation approach which applies a simple mechanical milling to induce intercalation reaction was applied to introduce controlled amount of tetraethoxylsilane (TEOS) into surfactant-preexpanded graphite oxide, and the relationships between the intercalation structure, the porosities of the calcined products, and the Si addition were examined. It was found that a small added amount of TEOS produced a more expanded ordered layer structure with the interlayer distance and silicon content increasing with the amount of TEOS added, although a large amount of added TEOS easily induces layer delamination, resulting in a less ordered structure. The silica structure in the composite is changed from a disordered structure having enhanced bond strain to a condensed silica network when the amount of TEOS added increases. The porosities of the final calcined samples increase with the increase of silicon content but then decrease slightly after reaching a maximum where silicon content starts to become constant, indicating that both silicon content and the composition state of silica particles and carbon layers play important roles in porosity formation.

Nanoporous metallic platinum with a high specific surface area of 91 m(2)/g was synthesized by a templating method using nonporous silica nanoparticles. The templating reaction is constituted of four steps: (1) a coating reaction of a Pt compound on the silica surface; (2) reduction of the Pt compound; (3) dissolution of the silica by alkaline treatment; (4) removal of residual carbon in the nanoporous platinum by heat treatment. Thus, nanoporous metallic platinum, stabilized by a small amount of carbon, can successfully be obtained by a relatively convenient synthetic process. This material can be a promising model material for development of new scientific fields concerned with electromagnetic properties and a functional material applicable to fuel cell or catalytic reactions. (C) 2004 Elsevier B.V. All rights reserved.

The temperature dependencies of in situ small-angle X-ray scattering (SAXS) of water adsorbed and of adsorption isotherm of water in hydrophobic carbon nanopores were measured over the temperature range of 293 to 328 K. The structures of water nanoclusters adsorbed in the nanopores were determined with the density fluctuation analysis of in situ SAXS data. The difference of the density fluctuations between adsorption and desorption was ascribed to the water structural difference. The structural transitions of the water nanoclusters were observed around 318 K for adsorption and 308 K for desorption.

Resorcinol-formaldehyde aerogels and carbon aerogels of different mesoporosities have been used as templates for preparing bimodal zeolites of mesopores. Samples were thoroughly characterized with X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, N-2 adsorption at 77 K, as well as FT-IR spectroscopy and Si-29 nuclear magnetic resonance spectroscopy. The mesoporous ZSM-5 zeolites have additional mesopores of 9-25 nm in widths and 0.07-0.2 cm(3)/g in volumes, besides their perfect inherent micropores. Experimental results show the mesoporous systems of the finally obtained zeolites can be influenced by proper preparation of resorcinol-formaldehyde aerogels and carbon aerogels through solution chemistry. Consequently, zeolites of tunable mesoporosities can be prepared with this unique methodology.

Mesoporous zeolite A has been synthesized by using a template method with resorcinol-formaldehyde aerogels having three-dimensional mesopores. It was characterized with X-ray powder diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and nitrogen adsorption/desorption. The pore size distribution calculated from the nitrogen adsorption isotherm is a bimodal distribution with micropores and mesopores. Field emission scanning electron micrograph observations confirm the presence of mesopores.

The addition of the mesoporosity to activated carbon fibers (ACF) (A10) using a reactivation process was investigated. The A10 samples were reactivated with Na2HPO4, Ca(NO3)2, and K 2CO3. The porosity change of the samples were investigated using N2 adsorption at 77K using a volumetric method. It was found that the use of Na2HPO4 and Ca(NO3)2 had added mesoporosity to pitch-based ACF without destroying of the original microporosity. The results show that the reactivation can be controlled to produce optimum pore structures of micropores and mesopores.

A novel nanoporous C/SiO2 Composite was synthesized using graphite precursor by a soft chemical method and its adsorption properties were characterized by nonane, water, and nitrogen adsorption. It was found that only one part of micropores can strongly confine nonane molecules, indicating a wide micropore size distribution. Water adsorption leads to disappearance of one part of micropores, possibly due to closing of pores by dissociative adsorption of water on defective sites. Fractal analysis of the original and the differential nitrogen adsorption isotherms indicate that micropores have a rougher surface and mesopore a flatter surface, suggesting that micropores are surrounded by silica particles and mesopores involve the flat carbon layers.

Nanopore formation in silica, in which nanoparticles of metal compounds were embedded, was studied using analytical techniques such as SEM, XRD, XRF, XPS and nitrogen adsorption. Such metal compound nanoparticles formed between primary silica particles, providing micropores and mesopores caused by the formation of Si-O-M bonds (M = Al, Ni). Acid treatment dissolved the metal compound nanoparticles and destroyed the Si-O-M bonds, thereby increasing the micropore volume. The mesopore volume of the aluminiurn system increased on acid treatment, whereas that of the nickel system decreased.

The structure of RbBr aqueous solution confined in the interstitial nanospaces of single-wall carbon nanohorn (SWNH) assemblies was elucidated by using extended x-ray absorption fine structure (EXAFS) technique. The decrease of hydration number around a Rb ion is clearly observed. The EXAFS analysis indicates that the highly distorted and dehydrated structure around ions of aqueous solution confined in the nanospace (nanosolution: NSN) to form quasi one-dimensional structure in the interstitial nanospaces of SWNH assemblies. This unique hydration structures formed in nanospaces of SWNH is quite different from that not only of the bulk aqueous solution, but also confined in the slit-shaped nanospaces of activated carbon fiber (ACF). © Physica Scripta 2005.

Resorcinol-formaldehyde aerogels and carbon aerogels of different mesoporosities were used as templates for preparing ZSM-5 of tunable mesoporosities. All nitrogen adsorption isotherms of mesoporous ZSM-5 zeolites prepared from resorcinol-formaldehyde aerogels and carbon aerogels templating had a steep uptake below P/P0 = 0.02 and clear hysteresis loop above P/P0 =∼ 0.6 suggesting the co-existence of micropores and mesopores. The mesoporous ZSM-5 zeolites had mesopores of 9-25 nm in widths and 0.07-0.2 mL/g in volumes from nitrogen adsorption data analysis. Field emission scanning electron micrograph observations confirmed the presence of mesopores. The mesoporous systems of the finally obtained zeolites could be influenced by proper preparation of resorcinol-formaldehyde aerogels and carbon aerogels through solution chemistry. This is an abstract of a paper presented at the AIChE 2004 Annual Meeting (Austin, TX 11/7-12/2004).

The use of resorcinol-formaldehyde (RF) aerogels and carbon aerogels of different mesoporosities as templates for preparing ZSM-5 of tunable mesoporosities was analyzed. RF gels were derived from the sol-gel polymerization of resorcinol and formaldehyde with a slight amount of sodium carbonate as a basic catalyst. The crystal structure of ZSM-5 and mesoporous ZSM-5 were examined using x-ray diffraction (XRD) and Fourier transform infrared (FT-IR) absorption spectroscopy. Results show that the mesoporous systems of the zeolites can be influenced by proper preparation of RF aerogels and carbon aerogels through solution chemistry.

Hydrogen adsorption isotherms in single-wall carbon nanohorns (SWNHs) have been measured at 20 K. The pore volume from hydrogen adsorption is compared with that from nitrogen adsorption at 77 K to determine the density of confined hydrogen in the internal space of SWNHs; it indicates that the average density of confined hydrogen inside SWNHs at 20 K is higher than that of liquid hydrogen in the bulk and nearly approaches the density of solid hydrogen at the triple point. The surface area from hydrogen adsorption using the BET theory is anomalously large compared with that for nitrogen; however, an alternative method (modified BET theory), in which an assumption is made that the energy of a molecule in the second layer is larger than that in the liquid, gives a reasonable surface area, especially when the adsorbed hydrogen in the first layer is assumed to be in a solid state. In the modified BET model, a packing constraint of the second layer due to the cylindrical geometry of SWNH is also taken into account. The solidlike behaviors of adsorbed hydrogen would be attributed to quantum effects, which give a strongly attractive pore situation for the hydrogen-SWNH system.

The pore-wall chemistry of activated carbon fiber (ACF) was controlled by heating in Ar and H-2. The ACF structures were characterized from various levels, and interaction of water vapor with the micropores of ACF was directly measured by calorimetry. Two kinds of pitch-based ACFs with different pore widths (w) (P5, w = 0.7 nm, and P20, w = 1.0 nm) were used. P20 was treated at 1273 K in a gas flow of Ar or H-2 for 1 h to modify its surface properties. Adsorption isotherms of water on the two ACFs at 303 K showed different features, which are possibly caused by the pore width difference. The surface modification by the heat treatment of P20 changed its pore structure, leading to different water adsorption behavior. The mechanisms of water adsorption and desorption can be discussed through the differential or integral heat of water adsorption or desorption. Water adsorbs on the functional groups located at the surface of P20 with an adsorption heat comparable to the heat of condensation at relatively low P/P-0, causing the cluster formation of water molecules. The removal of such functional groups by heat treatment decreases the adsorption heat at low pressure. The differential heat abruptly increases at filling in all cases, indicating a structural formation of water from a clustered form to a highly ordered form.

The stabilities of water molecules in carbon slit-shaped nanospaces have been studied using the potential calculation for possible water clusters (H2O)n) of n = 2-12. The adsorption isotherm of water on a graphite slit pore (w = 1.1 nm) with no surface functional groups at 303 K was calculated with GCMC simulation using TIP-5P and 10-4-3 Steele potential functions; this simulated isotherm has a vertical uptake at P/P-0 = 0.5. The cluster growth along the vertical adsorption uptake was evidenced through the snapshot of GCMC simulation. The simulated adsorption isotherm agreed well with the experimental isotherm of water on an activated carbon fiber (ACF) having uniform slit pores. Thus, H2O molecules are adsorbed in hydrophobic carbon nanopores without surface functional groups through cluster formation. The isosteric heat of adsorption of clusters of (H2O)(n=8-10) obtained from the GCMC simulation coincided well with the experimental value. The radial distribution function of the clusters from the GCMC simulation is close to the structure of ice I-h. Therefore water molecules can gain an explicit hydrophobicity through clusterization in nanopores.

The changes in microporous structure and surface properties of pitch-based activated carbon fibers upon air oxidation were examined by high-resolution N-2 adsorption and various physicochemical methods such as DTA, DRIFT, XPS, and chemical titration/analysis. It was found that air oxidation below 673 K slightly modifies the microporous structure together with a minor replacement of surface -C-O groups by -C=O groups. However, oxidation above 773 K gradually increases the specific surface area and the average width of micropores by producing micropores with larger widths and greatly induces the formation of surface functional groups, especially the -COOH group. A slight change in microporosities has an evident effect on CH4 storage property. (C) 2004 Elsevier Inc. All rights reserved.

Magnesium oxide/hydroxide was deposited on pitch-based activated carbon fibers which were previously oxidized in air at different temperatures, and the changes in carbon oxidation activity, microporosity, and CH4 adsorptivity of the parent carbons due to Mg deposition were examined. DTA results, chemical analysis, and DRIFT spectra indicate that Mg species are mainly supported on the -COOH groups of the parent carbons, which serve as the catalysts to improve the oxidation activity of carbon. Mg deposition either increases or decreases the specific surface area, pore volume, and average micropore width of the parent carbon depending on the preoxidation temperatures. Mg deposition does not simply enhance CH4 adsorptivity: the complex changes are due to the differences in the supporting states of Mg species and slight modifications in micropore structure. (C) 2004 Elsevier Inc. All rights reserved.

Well-crystalline ZSM-5 and zeolite Y having uniform mesopores were synthesized with template route method using carbon aerogels of different mesoporosities. These mesoporous zeolites were characterized with X-ray diffraction, FT-IR spectroscopy, field emission scanning electron microscopy, and N-2 adsorption. ZSM-5 having mesopore volume of 0.2-1 cm(3) g(-1) was obtained. Mesoporous ZSM-5 synthesized by heating at 423 K for 96 h was well-crystal line, which had mesopores of 11 nm in width. Mesoporous zeolite Y was well-crystalline, of which mesopore volume and width were 1.37 cm(3) g(-1) and 10 nm, respectively. (C) 2004 Elsevier B.V. All rights reserved.

Single wall carbon nanohorns (SWNHs) were fluorinated to form more attractive nanohorns that have characteristic structural and adsorptive properties. Nitrogen adsorption, XPS, and TEM studies elucidated the surface states and the morphologies of fluorinated SWNHs (F-SWNHs). The XPS results of F-SWNHs showed that the nature of C-F bonds changed from semi-ionic to covalent with an increase in the fluorination temperature. The N-2 adsorption isotherm indicated that the total amount of N-2 adsorption on SWNHs fluorinated at 303 and 373 K was smaller than that of pristine SWNHs. After fluorination at 473 K, nanoorder windows were produced on the sidewalls of SWNHs without a change in the shape of each horn and aggregate. Therefore, the SWNHs fluorinated at 473 K can adsorb N-2 molecules on the internal surfaces of nanohorns through the nanowindows.

A new technique of superwide pressure range adsorption (SWPA) isotherm measurement of N-2 from P/P-0 = 10(-9) to 1 at 77 K was developed. The superwide pressure range adsorption isotherms of N-2 on activated carbon fiber, molecular sieve carbon, and carbon black were compared with those of their ordinary pressure range isotherms and the simulated isotherms calculated with grand canonical Monte Carlo technique. The SWPA measurement can show the adsorption uptake below P/P-0 = 10(-6), which is assigned to the adsorption in ultramicropores of pore width < 0.7 nm. The SWPA method shows the presence of ultramicropores even for nonporous carbon black, which has been believed to be nonporous from the ordinary adsorption measurement. Thus, the SWPA method can elucidate the ultramicropore structures of less-crystalline materials.

Single wall carbon nanohorns (SWNHs) were treated in vacuum at different temperatures of 473 to 1073 K. The nanostructural change due to the heat-treatment vas studied by adsorption of N-2 at 77 K and H2O at 303 K. The determined particle density showed that gas is not adsorbed in internal pores, but in interstitial pores. The high temperature treatment (HTT) in vacuo changed water adsorption, but it gave almost no influence on N-2 adsorption. The maximum nanopore volume from H2O adsorption was observed at 673 K, indicating the interstitial nanopore change due to a local orientational change of SWNH particles. (C) 2004 Elsevier B.V. All rights reserved.

We propose a new methodology projected for the estimation of the adsorption energy distribution from the monolayer part of a single nitrogen adsorption isotherm determined at 77 K based on the lattice density functional theory (DFT) via the Aranovich-Donohue formalism. At first sight, the presented approach is computationally more difficult than a classical one. However, it is more flexible and comprehensible. Next, we developed a numerical program and used it for the estimation of the adsorption energy distribution from the experimental data on carbon black samples. The main nitrogen molecule-carbon black surface interaction energy can be estimated as approximate to7-8 kJ/mol, but the heterogeneity of the investigated materials differs significantly. Furthermore, we compare the results obtained from the lattice DFT via the Aranovich-Donohue formalism with the solution of the integral equation with the kernel represented by the classical monolayer localized Fowler-Guggenheim isotherm equation. The similarity between these two independent approaches is observed. The proposed methodology can be used for the investigation of the energetic heterogeneity of not only the carbonaceous materials but also the other "flat-surfaced" solids.

The interaction of water with hydrophobic surfaces is quite important in a variety of chemical and biochemical phenomena. The coexistence of water and oil can be realized by introduction of surfactants. In the case of water vapor adsorption on graphitic nanopores, plenty of water can be adsorbed in graphitic nanopores without surfactants, although the graphitic surface is not hydrophilic. Why are water molecules adsorbed in hydrophobic nanopores remarkably? This work can give an explicit insight to water adsorption in hydrophobic graphite nanopores using experimental and theoretical approaches. Water molecules are associated with each other to form the cluster of 1 nm in size, leading to a significant stabilization of the cluster in the graphitic nanopores. This mechanism can be widely applied to interfacial phenomena relating to coexistence of water and nanostructural materials of hydrophobicity.

Exfoliated carbon fibres (ECFs) were prepared from preheated mesophase pitch-based carbon fibre by electrochemical treatment. The nitrogen adsorption isotherms on ECFs were measured at 77 K. All the nitrogen adsorption isotherms were transformed into αs-plots using the standard adsorption isotherms for carbon blacks of different crystallinities and the GCMC simulation isotherm. Using the standard isotherm of well-crystallized carbon black, the αs-plot for the ECF prepared from carbon fibre preheated at 3273 K was almost linear, while αs-plots obtained using the standard isotherm of well-crystallized carbon black and the simulated form had have a downward and an upward deviation, respectively. The α s-plots of carbon samples having similar nanoscale crystallite sizes were close to each other, showing that αs-plot analysis was effective for determining the average surface irregularity structure in the nanoscale range.

Three kinds of activated carbon fibre (ACF) having different shapes were observed by scanning electron microscopy. Their cross-sectional morphologies were Y-shaped, asterisk-shaped and circular. The micropore structures of these ACF samples were determined by as-plots from the nitrogen adsorption isotherms at 77 K. Analysis of the as-plots showed that despite these ACFs having a non-circular cross-section, they retained their uniform microporosity similar to that of a conventional ACF with a circular cross-section.

The cluster structures of supercritical CH4 confined in slit-shaped carbon micropores was investigated using in situ small-angle X-ray scattering (SAXS) and the cluster analysis for grand canonical Monte Carlo (GCMC) simulation. The pore size distribution of micropores was determined from the fitting of the GCMC-simulated adsorption isotherm to the experimental one for high-pressure CH4; the pore size distributions of two kinds of activated carbon fibers (ACFs) were very narrow, and their average widths are 0.6 and 1.1 nm. The density fluctuation changes with fractional filling from in situ SAXS and GCMC simulation evidenced explicitly the formation of clusters of high concentration in the micropores. CH4 molecules in smaller pores of 0.6 nm form highly concentrated clusters even in low fractional filling. Fewer clusters are formed in the case of wider pores of 1.1 run.

Adsorptions of N-2, H2O, and organic vapors including CH2Cl2, CCl4, c-C6H12, C6H6, n-C6H14, and n-C9H20 on a silica-pillared layered manganese oxide (SiHMnO) and nonane-preadsorbed SiHMnO were examined. It is found that SiHMnO has a microporosity with a wide pore width distribution showing different pore wall affinities. Micropores with smaller width preferentially accommodate the nonane preadsorbate while the surface hydrophilicity of pore wall leads to an easier detachment of the adsorbed nonane molecules. H2O adsorption influences both the porosity and the surface properties by accelerating a sufficient hydrolysis of the remained TEOS molecules in SiHMnO. Examinations using Dubinin-Radeshkevich (DR) equation and isosteric heat of adsorption of organic molecules provide evidences that the wall surface of micropores with smaller and larger width have less affinity toward nonpolar and polar organic vapors, respectively. (C) 2003 Elsevier Inc. All rights reserved.

Recently developed two lattice density functional theory (DFT) models are verified experimentally. For this purpose the experimental nitrogen isotherms on carbon blacks at 77 K (M4040 and M32B) were carefully measured by the volumetric apparatus. Moreover, the additional nitrogen data on Sterling FT and SAO carbon blacks were taken from the literature and analyzed. The main goal of this study is the evaluation of the adsorption energy distribution function (and differential adsorption enthalpy at zero coverage) by the new powerful tool based on the lattice DFT formalism proposed by Do and Do and Aranovich and Donohue. New algorithms are proposed for this purpose. The quantitative agreement between these two independent approaches is recognized. The presented in this study new heterogeneous lattice DFT model seems to be very promising one in the investigation of flat surfaces heterogeneity effects. (C) 2004 Elsevier Ltd. All rights reserved.

The hydration structure of RbBr electrolytic solutions confined in slit-shaped nanospaces of carbon was determined with the extended X-ray absorption fine structure (EXAFS) technique and related analysis. The nitrogen adsorption isotherms at 77 K were measured to evaluate the porosity of RbBr-deposited carbon samples. The EXAFS results indicate that the electrolytic solution confined in hydrophobic nanospaces has a restricted hydration structure depending on the average pore width of the nanospaces. Also the asymmetric-field effect of slit-pore geometry on the formation of unique hydration structures of ions in nanospaces was unveiled with the analysis of EXAFS spectra. A marked decrease of the hydration number around a Rb ion was observed in slit-shaped nanospaces, indicating the compressed hydration structure around a Rb ion restricted in slit-shaped nanospaces. The distorted hydration structure around a Br ion in the slit-shaped pore of 0.7 nm was formed to increase the hydration number, though partially dehydrated structure can be formed in a 1.1 nm pore. The cluster-mediated ordered structure of water molecules can play an important role in forming a dehydrated structure around a Br ion confined in the 1.1-nm pore.

The reduced partition function ratios (RPFRs) of Li+(Solv)(n) (in which Solv = H2O, H2S, and CH3OH) clusters with different values were calculated, to investigate the solvent effect of the isotopic effect of the lithium. Structures of three solvated clusters-Li+(H2O)(n), Li+(H2S)(n), and Li+(CH3OH)(n)-were optimized by an ab initio molecular orbital method, and their RPFRs were calculated by frequency analysis. The RPFR of the solution was estimated by the extrapolation of the cluster values. The most-stable isomers of all three clusters for n greater than or equal to 4 have four solvent molecules in their first shell. The RPFR is dependent mainly on the number of solvent molecules in the first shell, and the size dependence of the RPFR plateaus at n = 4. The extrapolation of these values can be regarded as the RPFR in the solutions. The RPFRs are similar to1.07 for Li+(H2O)(n) and Li+(CH3OH), and are similar to1.03 for Li+(H2S)(n). The smaller RPFR of Li+(H2S)(n) is attributed to the smaller binding energy of the Li-S bond, which is weaker than that of the Li-O bond. The present results suggest the possibility of ionophores with S atoms (such as thioether, etc.) for lithium isotopic separation.

Zeolite Y of mesoporous channels has been synthesized using novel mesoporous carbon aerogels as template. It was characterized with X-ray powder diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis, and nitrogen adsorption/desorption. The pore size distribution with N-2 adsorption shows the presence of mesopores and micropores whose average pore widths are ca. 10 and 0.75 nm, and pore volumes are 1.37 and 0.21 cm(3) g(-1), respectively. FE-SEM observation supports the presence of mesopores.

A novel nanoporous carbon-silica composite with medium hydrophilicity is synthesized by a series of methods consisting of preexpansion of the interlayer of graphite oxide (GO) by surfactant intercalation, the intercalation of tetraethoxylsilane (TEOS) and its hydrolysis in the interlayer, followed by post carbonization to form a robust bridged/pillared network. High-resolution N-2 adsorption results show that carbonization at 823 K gives a composite having the highest specific surface area of more than 1000 m(2)/g with both microporosity and mesoporosity. Varieties of analytical results using DRIFT, NMR, XPS, and RAALAN spectra indicate that this composite contains small graphene sheets in its structure and its silicon components are silica particles with +4 valence. Morphology observation, thermal desorption, and other properties suggest the important roles of dispersion of GO in aqueous solution, preexpansion of GO interlayer, interlayer hydrolysis of TEOS molecules, and the carbonization condition in the formation mechanism of this nanoporous composite.

A ZSM-5 monolith of uniform mesopores(meso-ZSM-5) was synthesized with the template method using carbon aerogel of uniform mesopores of great pore volume. The pore size distribution determined by N2 adsorption showed the presence of mesopores with an average pore width of 11 nm and micropores with an average pore width of 0.51 nm. Field emission scanning electron micrograph observation revealed the presence of uniform mesopores. X-ray diffraction and FT-IR provided evidence that the synthesized meso-ZSM-5 monolith has a highly crystalline ZSM-5 structure. Copyright © 2003 American Chemical Society.

A synthetic route for preparing nanostructured nickel using poly(vinyl alcohol) (PVA) as a polymer precursor was described. The used of PVA was significant for the formation of the metallic nickel colloids. As such, the nickel species can be readily doped into a PVA polymer matrix in aqueous solutions. Moreover, another major advantage of the use of PVA was that the PVA can be removed almost completely by burning off.

The hydration structure of RbBr electrolytic solution confined in carbon nanospaces was determined with EXAFS technique and related analyses. The analytical results indicate that the electrolytes confined in hydrophobic nanospaces have an incomplete dehydration structure, because of an intensive restriction and cluster formation of adsorbed water molecules in the nanospaces.

A mesoporous ZSM-5 monolith several millimetres in size has been synthesized employing the template method and using a carbon aerogel with uniform mesopores. Measurement of the pore-size distribution using nitrogen adsorption showed a bimodal pore system of mesopores and micropores whose average pore widths were 8 nm and 0.51 nm, and whose volumes were 0.09 cm(3)/g and 0.34 cm(3)/g, respectively.

Towards the goal of nanoscale molecular systems, littlework has been undertaken on ionic solutions at the nanoscale ('nanosolution', NSN). Functional nanoporous materials can be applied to confine, and thereby allow study of molecular assemblies and NSNs; electrically neutral hydrophobic pores reveal a particularly marked confinement effect. This article summarizes the properties and structures of molecules confined within nanospaces and the pioneering work on the distorted and partially dehydrated structures of NSNs.

The exact physical adsorption amounts of supercritical hydrogen on the single-wall carbon nanohorn (SWNH) assemblies were determined at 77, 196, and 303 K. There are two physical adsorption sites of interstitial and internal spaces on SWNH assemblies. The interaction potential depths of interstitial and internal spaces are -1000 and -600 K, respectively. However, both hydrogen densities in interstitial and internal spaces were about 70 g L-1 at 77 K at 5 MPa, though the hydrogen densities in interstitial and internal spaces were 15 and 10 g L-1 at 303 K and 6.5 MPa. The similar enhancement in the internal spaces was observed even at 196 K. The additional stabilization by the strong fluid-fluid interaction due to the cluster formation in the internal spaces. On the other hand, hydrogen molecules adsorbed in the interstitial spaces cannot form the stable cluster owing to the space limitation. The enthalpy of adsorption supports the presence of the stable cluster of hydrogen adsorbed in the internal spaces below 303 K.

Hydration structures of "nanosolutions" around both cation and anion for rubidium bromide confined in nanospaces (pore width = 1.1 nm) of activated carbon fiber were determined with EXAFS measurements and related analysis. The analytical results indicate that the ionic solutions confined in hydrophobic nanospaces tend to form an incomplete dehydration structure, because of the spatial restriction by the nanospace and capturing water molecules in the ordered structure. Copyright © 2002 American Chemical Society.

HiPco single-walled carbon nanotubes (HPNTs) containing Fe were purified by a one-step process with HCl-washing (D-method) and a two-step process with HCl-washing after air oxidation (GD-method). The HPNT samples before and after purification were characterized using the N2 adsorption at 77 K, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The TGA results showed a decreased Fe content after purification. In addition, the XPS results provided evidence that oxygen-based functional groups were introduced to the nanotube surface by both purification methods. The purification treatments also altered the N2 adsorption isotherms from type II to type IV this accompanied the development of microporosity. Thus, purification considerably affects the surface chemistry and pore structures of HPNT aggregates. The effects of purification on the adsorption properties of HPNT aggregates with regard to CH3OH and C2H5OH vapors were examined at 303 K. The purification greatly enhanced the adsorptivity for CH3OH and C2H5OH vapors at 303 K under a low relative pressure. We associated this with the enhanced microporosity and the oxygen-based functional groups introduced on the surface.

A novel nanoporous composite containing micrographitic carbon layers is synthesized by preliminarily expanding the interlayer of an oxidized product of graphite using surfactant, followed by Si bridging/pillaring, and carbonization.

CO2 is almost vertically adsorbed and desorbed at 0.0106-0.0073 relative pressure at 273 K, respectively, on the preevacuated Cu-complex. crystals which have no open micropores from the crystallographic structures. These vertical adsorption and desorption steps are named gate effects. Here, guest water molecules are evolved during the pre-evacuation at 373 K and the crystal structure with X-ray diffraction examination does not change due to pre-evacuation. The X-ray diffraction patterns also show no change before and after the steps. The adsorption/desorption gate effects and the remarkable hysteresis are explained in terms of the molecular valve model stemming from the reorientation of the bending vibration of the hydrogen bonding. This model can explain the observed hysteresis in the gate effect; the spring constant difference of the molecular valve for desorption and adsorption is estimated to be a similar order to that of the hydrogen bond in bulk ice. (C) 2002 Elsevier Science B.V All rights reserved.