Synthesis and adsorption properties of colloid-imprinted mesoporous carbons using poly(vinylidene chloride-co-vinyl chloride) as a carbon precursor

A facile synthesis of micro- and mesoporous carbons has been proposed using colloidal silica nanoparticles with diameter of ∼24 nm and poly(vinylidene chloride-co-vinyl chloride) (Saran) as a carbon precursor. The resulting carbons possessed large specific surface area, ∼800 m²/g, and approximately the same volume of micro- and mesopores, each about 50% of the total pore volume. While the size of micropores was around 1 nm, the large and uniform spherical mesopores (about 24 nm) resemble the diameters of silica colloids used. Nitrogen adsorption measurements proved that these mesopores were interconnected and accessible. The well-developed microporosity was created mainly by decomposition of Saran copolymer during carbonization.     

Spectral triangulation molecular contrast optical coherence tomography with indocyanine green as the contrast agent

We report a new molecular contrast optical coherence tomography (MCOCT) implementation that profiles the contrast agent distribution in a sample by measuring the agent's spectral differential absorption. The method, spectra triangulation MCOCT, can effectively suppress contributions from spectrally dependent scatterings from the sample without a priori knowledge of the scattering properties. We demonstrate molecular imaging with this new MCOCT modality by mapping the distribution of indocyanine green, a FDA-approved infrared red dye, within a stage 54 Xenopus laevis.     

Schisandra rubriflora Fruit and Leaves as Promising New Materials of High Biological Potential: Lignan Profiling and Effect-Directed Analysis

The effect-directed detection (EDD) of Schisandra rubriflora fruit and leaves extracts was performed to assess their pharmacological properties. The EDD comprised TLC—direct bioautography against Bacillus subtilis, a DPPH assay, as well as α-glucosidase, lipase, tyrosinase, and acetylcholinesterase (AChE) inhibition assays. The leaf extracts showed stronger antioxidant activity than the fruit extract as well as inhibition of tyrosinase and lipase. The fruit extract was found to be extremely active against B. subtilis and to inhibit α-glucosidase and AChE slightly more than the leaf extracts. UHPLC–MS/MS analysis was carried out for the bioactive fractions and pointed to the possible anti-dementia properties of the dibenzocyclooctadiene lignans found in the upper TLC fractions. Gomisin N (518 mg/100 g DW), schisanhenol (454 mg/100 g DW), gomisin G (197 mg/100 g DW), schisandrin A (167 mg/100 g DW), and gomisin O (150 mg/100 g DW) were the quantitatively dominant compounds in the fruit extract. In total, twenty-one lignans were found in the bioactive fractions.     

Endogenous contrast blood flow imaging in embryonic hearts using hemoglobin contrast subtraction angiography

The genetic basis of congenital heart disease is yet to be defined, and the interactions between the malformed heart and biomechanical cardiac performance remain poorly understood. Functional optical imaging enables detailed biomechanical phenotyping of cardiac dysfunction in small animal models, which in turn enables specific gene-phenotype relationship. We have developed a new microangiography technique based on flow imaging using endogenous hemoglobin contrast enabling in vivo assessment and biomechanical phenotyping of Xenopus tropicalis embryonic heart. We demonstrated that hemoglobin contrast angiography can be used to quantify physiological response to treatment with well-established cardioactive drugs.     

Development of a novel direct bioautography-thin-layer chromatography test: optimization of growth conditions for gram-negative bacteria, Escherichia coli

With the aim of developing a TLC-direct bioautography assay using Escherichia coli as test bacteria, various parameters influencing the viability of microorganisms on TLC plates were examined and checked for flumequine standards. The optimal times for preincubation and incubation of bacterial broth were 20 h at 37 degrees C and 2 h at 37 degrees C, respectively. The optimal viscosity of the broth was obtained for 0.05% agarose solution in Mueller-Hinton broth. Various incubation times of the seeded TLC plates were also tested (5 h proved to be optimal). After incubation, the plates were sprayed with 0.2% aqueous [3-(4,5-dimethyldiazol-2-yl)-2,5 diphenyltetrazolium bromide] (MTT) solution and incubated for 0.5 h at 37 degrees C. The precision of the method was evaluated by the repeatability (intraday assay) and intermediate precision (interday assay). The regression coefficients were 0.9977 and 0.9968, respectively, for intraday and interday curves. The calibration curves show good linearity in the range of 0.005-0.50 microg (0.5-50.0 microg/mL). The established LOD of flumequine equaled 0.5 microg/mL, i.e., 5 ng flumequine in the spot. The developed direct bioautography test significantly enhances the sensitivity of the TLC method.     

Adsorption characterization of surfactant-templated ordered mesoporous silicas synthesized with and without hydrothermal treatment

This work reports a systematic study of ordered mesoporous silicas (OMSs) synthesized with and without hydrothermal treatment at 373 K for a series of surfactants of different alkyl chain length (from C10 to C18). For these samples nitrogen adsorption and small angle X-ray scattering (SAXS) data were measured to characterize their adsorption and surface properties. Namely, nitrogen adsorption isotherms were used to evaluate their specific surface area, pore volume and pore size distribution, whereas SAXS data provided information about their structural ordering. It is shown that while the room temperature synthesis afforded OMS samples with cubic MCM-48 structure, an additional 5-day hydrothermal treatment of these samples at 373 K caused their transformation to MCM-41 (two-dimensional hexagonal structure) and improved their pore uniformity, which was manifested by reducing the width of pore size distribution.     

Quantitation of the enantiomers of rimantadine and its hydroxylated metabolites in human plasma by gas chromatography/mass spectrometry.

A gas chromatographic/mass spectrometric procedure has been developed for the quantitation in human plasma of the enantiomers of rimantadine and its three hydroxylated metabolites. The assay utilized derivatization of all analytes with the optically active reagent S-alpha-methyl-alpha-methoxy(pentafluorophenyl)acetic acid, selective ion monitoring, methane negative ion chemical ionization mass spectrometry and stable isotope dilution techniques. This method has been used to measure plasma concentrations of the enantiomers of rimantadine, m-hydroxyrimantadine and p-hydroxyrimantadine (equatorial and axial epimers) in the ranges 2.5-250, 2.5-50, 1.25-62.5 and 1.25-62.5 ng/mL, respectively, in six subjects given a single 200 mg dose of racemic rimantadine. Although there are no significant differences in the concentration-time profiles of R- and S-rimantadine, large stereospecific differences in the disposition of their metabolites are observed.     

Equilibrium isotherms and isosteric heat for CO<Subscript>2</Subscript> adsorption on nanoporous carbons from polymers

Four nanoporous carbons obtained from different polymers: polypyrrole, polyvinylidene fluoride, sulfonated styrene–divinylbenzene resin, and phenol–formaldehyde resin, were investigated as potential adsorbents for carbon dioxide. CO₂ adsorption isotherms measured at eight temperatures between 0 and 60 °C were used to study adsorption properties of these polymer-derived carbons, especially CO₂ uptakes at ambient pressure and different temperatures, working capacity, and isosteric heat of adsorption. The specific surface areas and the volumes of micropores and ultramicropores estimated for these materials by using the density functional theory-based software for pore size analysis ranged from 840 to 1990 m² g^?1, from 0.22 to 1.47 cm³ g^?1, and from 0.18 to 0.64 cm³ g^?1, respectively. The observed differences in the nanoporosity of these carbons had a pronounced effect on the CO₂ adsorption properties. The highest CO₂ uptakes, 6.92 mmol g^?1 (0 °C, 1 atm) and 1.89 mmol g^?1 (60 °C, 1 atm), were obtained for the polypyrrole-derived activated carbon prepared through a single carbonization-KOH activation step. The working capacity for this adsorbent was estimated to be 3.70 mmol g^?1. Depending on the adsorbent, the CO₂ isosteric heats of adsorption varied from 32.9 to 16.3 kJ mol^?1 in 0–2.5 mmol g^?1 range. Overall, the carbons studied showed well-developed microporosity and exceptional CO₂ adsorption, which make them viable candidates for CO₂ capture, and for other adsorption and environmental-related applications.     

Benzene Adsorption Isotherms on MCM-41 and their Use for Pore Size Analysis

This work is focused on the elaboration of methodology for adsorption characterization of porous silicas by using benzene adsorption isotherms measured on good quality MCM-41 materials. Three MCM-41 samples were synthesized by using tetraethyl orthosilicate (TEOS) as silica source and surfactants, octyltrimethylammonium (C8), decyltrimethylammonium (C10) and cetyltrimethylammonium (C16) bromides as templates. A characteristic feature of this synthesis was relatively long hydrothermal treatment (5 days) at 373 K, which gave well ordered samples as evidenced by powder XRD analysis. Benzene adsorption isotherms measured on these MCM-41 samples were used to evaluate such standard quantities as the BET specific surface area, total pore volume, external surface area and the volume of ordered mesopores, and to obtain the statistical film thickness (t-curve) as well as the Kelvin-type relation, which describes the dependence between pore width and condensation pressure for benzene on silica at 298 K. The latter relations were incorporated into the Barrett-Joyner-Halenda algorithm to extend its applicability to calculate the pore size distributions from benzene adsorption data.     

Critical discussion of simple adsorption methods used to evaluate the micropore size distribution

The well-known simple adsorption methods used to evaluate the micropore size distribution from low pressure adsorption isotherms were examined by employing model isotherms for slit-like graphite micropores obtained from nonlocal density functional theory. It was shown that in the range of pore sizes from about 0.4 to 0.9 nm, the Horvath Kawazoe (HK) method satisfactorily reproduces the shape of the micropore size distribution, but the pore sizes are underestimated. In the case of micropores wider than 0.9 nm, the method fails as the formation of the monolayer on the pore walls produces a peak corresponding to 0.6 nm micropores on the HK pore size distribution. Therefore, the HK method indicates the presence of microporosity even for nonporous samples. The Dubinin-Astakhov adsorption isotherms were also examined and it was shown that their application to represent local adsorption isotherms for homogeneous pores is questionable. However, the adsorption potential distributions seem to be promising for micropore analysis.Nomenclature A Adsorption potential kJ/mol - C ₁ Constant in Eq. 3 and 4 kJ * nm/mol - C ₂ Constant in Eq. 3 and 4 nm³ - C ₃ Constant in Eq. 3 and 4 nm⁹ - C ₄ Constant in Eq. 3 and 4 - d Adsorbate molecule diameter nm - d _A Adsorbent atom diameter nm - G Change in the Gibbs free energy kJ/mol - J Pore size distribution cm³/(g*nm) - R The universal gas constant = 8.31431 J/(mol * K) - T Absolute temperature K - V Amount adsorbed expressed in cm³ of liquid adsorbate per 1 g of the adsorbent = 0.0015468 * amount adsorbed expressed in cm³ STP/g cm³/g - x Pore width nm - X Differential adsorption potential distribution cm³ * mol/(g*kJ) - Constant defined as nm - p Pressure Pa - p ₀ Saturated pressure = 760 torr = 101325 Pa Pa - P _c Condensation pressure Pa - Degree of pore filling - S _BET BET specific surface area m²/g - S _ex External surface area obtained fromt-plot method m²/g - V _mi Micropore volume obtained fromt-plot method cm³/g - V ₁ Total pore volume cm³/g - E Characteristic energy in the Dubinin-Astakhov equation kJ/mol - n Exponent in the Dubinin-Astakhov equation