Conscious Changes of Carbon Nanotubes Cytotoxicity by Manipulation with Selected Nanofactors.

We discuss eight major challenges in the field of carbon nanomaterial toxicity. Generally, we pick up some of them, and the most important challenge is searching of the qualitative relationships between nanofactors and cytotoxicity. This is important since it can provide the possibility of conscious changes of carbon nanotubes cytotoxicity by manipulation with selected nanofactors.

New insights into the ideal adsorbed solution theory.

The GCMC technique is used for simulation of adsorption of CO2-CH4, CO2-N2 and CH4-N2 mixtures (at 298 K) on six porous carbon models. Next we formulate a new condition of the IAS concept application, showing that our simulated data obey this condition. Calculated deviations between IAS predictions and simulation results increase with the rise in pressure as in the real experiment.

Study of hydration process on silica hydride surfaces by microcalorimetry and water adsorption.

A series of hydrosilated stationary phases were compared with respect to their hydrophilic-hydrophobic properties. The stationary phases were also compared to the bare silica gel used for this synthesis. The investigations were done using microcalorimetric measurements of methanol and acetonitrile heats of immersion.

Determination of accessible silanols groups on silica gel surfaces using microcalorimetric measurements.

The calorimetric measurements of methanol and hexane heats of immersion were carried out on different silica gels. Based on the difference in immersion heats, a methodology for the determination of the number of silanols on the surface is presented. The calculated concentration of residual silanols on the silica gel surface agreed with data found in the literature.

Investigation of silanol activity on the modified silica surfaces using microcalorimetric measurements.

A detailed description of the stationary-bonded phase surface in reversed-phase liquid chromatography (RPLC) is a topic of great interest in separation sciences. For this purpose, the thermal effects connected with solvent adsorption on the series of octadecyl stationary-bonded phases were investigated. Microcalorimetric study of organic solvent heat of immersion of the stationary-phase and chromatographic measurements of the silanol activity were executed.

New phosphorus-containing spherical carbon adsorbents as promising materials in drug adsorption and release.

A simple method of preparation of new high surface area spherical carbon adsorbents is presented. The phosphoric acid activation upon hydrothermally formed spherules was employed to produce carbons having controlled high specific surface area (over 2100m(2)/g), large volumes of pores (1.2cm(3)/g), and high acidity.

Study of solvent adsorption on chemically bonded stationary phases by microcalorimetry and liquid chromatography.

A detailed, molecular-level description of the sorption mechanism in reversed-phase liquid chromatography is of great interest to analytical chemists. For this purpose, solvent adsorption in the octadecyl stationary bonded phase was investigated. Preferential adsorption of solvents from an acetonitrile-water and methanol-water mobile phase was measured on a series of non-end-capped octadecyl bonded phases with different coverage densities of bonded ligands using the minor disturbance method.

The system of carbon tetrachloride and closed carbon nanotubes analyzed by a combination of molecular simulations, analytical modeling, and adsorption calorimetry.

Using the combined techniques of molecular simulation, simple analytical modeling, and adsorption calorimetry, we propose new models describing adsorption onto closed carbon nanotubes. The models are capable of describing the adsorption isotherms and calorimetric enthalpy of carbon tetrachloride adsorption measured on three different closed carbon nanotubes. It is shown that the assumption of the presence of two types of surface centers (high- and low-energy centers) on external tube surfaces is sufficient to describe experimental adsorption and calorimetric enthalpy data.

Carbon surface chemical composition in para-nitrophenol adsorption determined under real oxic and anoxic conditions.

A series of commercial unmodified and modified activated carbons was studied. The surface chemical composition was characterized using X-ray photoelectron spectroscopy and Boehm titration methods. Data on p-nitrophenol (pnp) adsorption isotherms determined under real oxic and anoxic conditions (at 310 K) are presented and described using bimodal Langmuir and lattice density functional theory models.

How realistic is the pore size distribution calculated from adsorption isotherms if activated carbon is composed of fullerene-like fragments?

A plausible model for the structure of non-graphitizing carbon is one which consists of curved, fullerene-like fragments grouped together in a random arrangement. Although this model was proposed several years ago, there have been no attempts to calculate the properties of such a structure. Here, we determine the density, pore size distribution and adsorption properties of a model porous carbon constructed from fullerene-like elements.

Water adsorption on carbons--critical review of the most popular analytical approaches.

The purpose of the current study is to present the state of art in the field of analytical description of water sorption on carbons. We discuss the most important and promising models proposed recently (for example by Mahle; Talu and Meunier; and Malakhov and Volkov) as well as some older theoretical models inspired by the pioneering ideas proposed in the papers of Dubinin, Serpinsky, Barton, D'Arcy, Watt, Do and Do and others. The applicability, advantages, and defects of all these analytical formulas are pointed out and some new approaches in this field are presented.

Thermodynamics of the CMMS approach and carbon surface chemistry in SO2 adsorption.

In this study, we develop the equation describing the enthalpy of adsorption corresponding to the cooperative multimolecular sorption approach proposed by Malakhov and Volkov. For different shapes of adsorption isotherms plotted from this model (and analyzed by Rutherford and Coons), we generated the corresponding enthalpy of adsorption curves. We also discuss other enthalpy plot shapes predicted by the CMMS.

Effect of coverage density and structure of chemically bonded silica stationary phases on the separation of compounds with various properties.

The chemical character, geometry, and architecture of chemically formed surface layers determine interactions between stationary phase, analyte, and mobile phase, and therefore the retention mechanisms (partitioning, adsorption, ion exchange, steric exclusion) of separated analytes. These interactions also depend on the structure and chemical character of the solutes and the composition of the mobile phase. High-molecular-weight fullerenes (C60 and C70) and water-soluble selenium-containing peptides (833 and 2607 Da) were used for the evaluation of laboratory-prepared octadecyl stationary phases with high and low coverage density before and after end-capping.

Simple models of adsorption in nanotubes.

We present two very simple models of adsorption in cylindrical pores. It is assumed that a layer-by-layer mechanism occurs similarly to that in the BET theory. The major assumption is that in the pores having an adsorption space with cylindrical geometry, the surface area of the upper surface (in comparison with the bottom surface) should be diminished in proportion to the radii of a cylinder.

Corrected thermodynamic description of adsorption via formalism of the theory of volume filling of micropores.

Based on the series of benzene adsorption and related enthalpy of adsorption data measured on porous carbons that possess various porous structures, we show that the creation of a solidlike structure in pores depends on the average pore diameter of an adsorbent. Taking into account the solidlike adsorbed phase in the thermodynamic description of the adsorption process via the formalism of the theory of volume filling of micropores (TVFM) leads to very good agreement between the data measured experimentally and those calculated from TVFM. Finally we show that the boundary between solidlike and liquidlike structures of benzene molecules in carbon pores is located around the average pore diameter, close to ca.

Effect of the carbon surface layer chemistry on benzene adsorption from the vapor phase and from dilute aqueous solutions.

We present a complex study of benzene adsorption on chemically modified commercial activated carbons. The porosity of studied carbons is almost the same, whereas the chemical composition and the acid-base properties of surface layers differ drastically from amphoteric (initial de-ashed carbon D43/1, Carbo-Tech, Essen, Germany) and acidic (carbon modified with concentrated HNO3 and fuming H2SO4) to strongly basic (carbon modified with gaseous NH3). Benzene adsorption isotherms measured from aqueous solution at three temperatures (298, 313, and 323 K) and at the neutral pH level are reported.

Parameterization of the corrected Dubinin-Serpinsky adsorption isotherm equation.

A recently proposed new modification of the Dubinin-Serpinsky adsorption isotherm equation, the CDS formula, is analyzed. We develop the equation describing the isosteric enthalpy of adsorption, and we give the meaning of the empirical parameters occurring in the CDS model. Finally the application of the CDS equation and related enthalpy formula describing experimental water adsorption and enthalpy data measured on two microporous carbons is shown.

Heterogeneous Do-Do model of water adsorption on carbons.

The model of water adsorption on carbons proposed five years ago by Do and Do is analyzed and improved. Following the experimental evidence that for activated carbons surface active groups differ in the value of the energy of interaction with water molecules, we propose to extend the original model to take this fundamental feature into account. For the original DD model, as well as proposed new heterogeneous one (HDDM), we develop also the corresponding isosteric enthalpy of adsorption formulas.

Estimating the pore size distribution of activated carbons from adsorption data of different adsorbates by various methods.

Experimental adsorption isotherms of four adsorbates (N2, Ar, C6H6, and CCl4) as well as adsorption enthalpy (C6H6 and CCl4) measured on two strictly microporous carbons are used to evaluate the porosity of adsorbents (i.e., pore size distributions (PSDs) and average pore diameter ( Lav )).

Developing the solution analogue of the Toth adsorption isotherm equation.

The well-known Toth adsorption isotherm equation developed formerly for adsorption of vapors is converted into its solution analogue. It is shown that this equation can be successfully applied to the description of adsorption data of organics on activated carbons.