Ultrasonic preparation of mesoporous silica using pyridinium ionic liquid

Mesoporous silica matrices have been prepared via classic acid catalyzed and sono-catalyzed sol-gel routes. Tetramethoxysilan (TMOS) and methyl-trimethoxysilane (MTMS) were used as silica precursors, and N-butyl-3-methylpyridinium tetrafluoroborate ([bmPy][BF₄]) was employed as co-solvent and pore template. The ionic liquid (IL) to silica mole ratio was varied between 0.007 and 0.07. Nitrogen adsorption-desorption and small-angle neutron scattering measurements were used to characterize the obtained materials. The ionic liquid played the role of catalyst that affected the formation of the primary xerogel particles, and changed the porosity of the materials. Ultrasound treatment resulted in microstructure change on the level of the colloid particle aggregates. In comparison with IL containing xerogels, the IL containing sonogels show increased pore diameter, bigger pore volumes and diminished surface areas.     

Alert-QSAR. Implications for Electrophilic Theory of Chemical Carcinogenesis

Given the modeling and predictive abilities of quantitative structure activity relationships (QSARs) for genotoxic carcinogens or mutagens that directly affect DNA, the present research investigates structural alert (SA) intermediate-predicted correlations A(SA) of electrophilic molecular structures with observed carcinogenic potencies in rats (observed activity, A = Log[1/TD(50)], i.e., [Formula: see text]). The present method includes calculation of the recently developed residual correlation of the structural alert models, i.e., [Formula: see text]. We propose a specific electrophilic ligand-receptor mechanism that combines electronegativity with chemical hardness-associated frontier principles, equality of ligand-reagent electronegativities and ligand maximum chemical hardness for highly diverse toxic molecules against specific receptors in rats. The observed carcinogenic activity is influenced by the induced SA-mutagenic intermediate effect, alongside Hansch indices such as hydrophobicity (LogP), polarizability (POL) and total energy (Etot), which account for molecular membrane diffusion, ionic deformation, and stericity, respectively. A possible QSAR mechanistic interpretation of mutagenicity as the first step in genotoxic carcinogenesis development is discussed using the structural alert chemoinformation and in full accordance with the Organization for Economic Co-operation and Development QSAR guidance principles.     

Atomic force microscopy characterization of synthetic pyrimidinic oligodeoxynucleotides adsorbed onto an HOPG electrode under applied potential

In order to better understand the adsorption mechanism of nucleic acids at electrode surface, MAC Mode atomic force microscopy (MAC Mode AFM) was used to investigate the adsorption of a 10-base synthetic oligodeoxynucleotide (ODN) with the sequence 5′-CTTTTTCTTT-3′ containing only pyrimidinic bases, onto a highly oriented pyrolytic graphite (HOPG) electrode. Free adsorption and adsorption at applied potentials of +0.30 and +0.65 V versus AgQRE, were carried out. AFM images in air demonstrated that the molecules adsorb spontaneously on the electrode surface. The ODNs have the tendency to self-assemble from solution onto the solid support in a tight and well-spread two-dimensional lattice covering the entire surface, showing the existence of different molecular conformations and exposing parts of the HOPG surface. The degree of surface coverage and the adsorption pattern were directly dependent on ODN concentration and immobilization procedure. During free adsorption, the hydrophobic interactions of the ODNs with the HOPG represent the main adsorption mechanism. When a positive potential is applied to the HOPG, electrostatic interactions between the positively charged electrode surface and the negatively charged sugar-phosphate backbones of ODNs are predominant.     

Economic implications of pre- and post-combustion calcium looping configurations applied to gasification power plants

Gasification is a promising conversion technology to deliver high energy efficiency simultaneously with low energy and cost penalties for carbon capture. This paper is devoted to in-depth economic evaluations of pre- and post-combustion Calcium Looping (CaL) configurations for Integrated Gasification Combined Cycle (IGCC) power plants. The poly-generation capability, e.g. hydrogen and power co-generation, is also discussed. The post-combustion CaL option is a gasification power plant in which the flue gases from the gas turbine are treated for CO₂ capture in a carbonation–calcination cycle. In pre-combustion CaL option, the Sorbent Enhanced Water Gas Shift (SEWGS) feature is used to produce hydrogen which is used for power generation. As benchmark case, a conventional gasification power plant without carbon capture was considered. Net power output of evaluated cases is in the range of 550–600 MW with more than 95% carbon capture rate. The pre-combustion capture configuration was evaluated also in hydrogen and power co-generation scenario. The evaluations are concentrated for estimation of capital costs, specific investment cost, operational & maintenance (O&M) costs, CO₂ removal and avoidance costs, electricity costs, sensitivity analysis of technical and economic assumptions on key economic indicators etc.     

Physicochemical Characterization and Drug Release Properties of Methyl-Substituted Silica Xerogels Made Using Sol–Gel Process

In this work, a multi-analytical approach involving nitrogen porosimetry, small angle neutron and X-ray scattering, Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, X-ray diffraction, thermal analysis and electron microscopy was applied to organically modified silica-based xerogels obtained through the sol–gel process. Starting from a tetraethoxysilane (TEOS) precursor, methyltriethoxysilane (MTES) was added to the reaction mixture at two different pH values (2.0 and 4.5) producing hybrid xerogels with different TEOS/MTES molar ratios. Significant differences in the structure were revealed in terms of the chemical composition of the silica network, hydrophilic/hydrophobic profile, particle dimension, pore shape/size and surface characteristics. The combined use of structural characterization methods allowed us to reveal a relation between the cavity dimensions, the synthesis pH value and the grade of methyl substitution. The effect of the structural properties on the controlled Captopril release efficiency has also been tested. This knowledge facilitates tailoring the pore network for specific usage in biological/medical applications. Knowledge on structural aspects, as reported in this work, represents a key starting point for the production of high-performance silica-based hybrid materials showing enhanced efficacy compared to bare silica prepared using only TEOS.     

Novel semi-interpenetrating network hydrogels based on monosaccharide oligomers with itaconic moiety: synthesis and properties

Hydrogel-based drug delivery systems encounter great scientific attention nowadays. Semi-interpenetrating network systems with hydrogel features have been studied as potential drug carriers due to their water intake capacity, biocompatibility and biodegradability. One of the most important features of drug delivery systems is biocompatibility and as such materials derived from natural resources seem to be more appropriate to act as excipients. In this respect, two new semi-interpenetrating networks (semi-IPNs) with hydrogel features based on chitosan, two novel oligomers derived from monosaccharides and 2-hydroxyethylmethacrylate (HEMA) have been synthesized and characterized using FTIR, thermogravimetry, SEM/EDX and swelling behavior. The new sugar-derived oligomers (GI and MI) with double bonds available for further polymerization were obtained by polycondensation of 1,3-propanediol with dicarboxylic acids derived from glucose/mannose skeleton with itaconic anhydride moieties. GI and MI oligomers were characterized by FTIR, NMR spectroscopy and ESI–MS spectrometry, which showed molecular weights of about 7000 Da and linear polymerization chain structure. The new semi-IPNs show good thermal behavior and these hydrogels display a swelling tendency by loading significantly more water in an acid environment than in a neutral solution. Moreover, these superabsorbent hydrogels are able to load significant amount of hydrosoluble active principle (herein the antibiotic levofloxacin) and their releasing profile is marked by an important “burst effect”.     

Techno-economic and environmental evaluations of large scale gasification-based CCS project in Romania

Gasification is a promising technology in terms of reducing carbon capture energy and cost penalties as well as for multi-fuel multi-product operation capability. The paper evaluates two carbon capture options in terms of main techno-economic indicators. The first option involves pre-combustion capture, the syngas being catalytically shifted to convert carbon species into CO₂ and H₂. Gas–liquid absorption is used for separate H₂S and CO₂ capture, then clean gas is used for power generation. The second capture option is based on post-combustion capture using chemical absorption. The most promising gasifiers were evaluated in a CCS design.     

Techno-economic and environmental performances of glycerol reforming for hydrogen and power production with low carbon dioxide emissions

This paper is evaluating from the conceptual design, thermal integration, techno-economic and environmental performances points of view the hydrogen and power generation using glycerol (as a biodiesel by-product) reforming processes at industrial scale with and without carbon capture. The evaluated hydrogen plant concepts produced 100,000 Nm³/h hydrogen (equivalent to 300 MW_th) with negligible net power output for export. The power plant concepts generated about 500 MW net power output. Hydrogen and power co-generation was also assessed. The CO₂ capture concepts used alkanolamine-based gas–liquid absorption. The CO₂ capture rate of the carbon capture unit is at least 90%, the carbon capture rate of the overall reforming process being at least 70%. Similar designs without carbon capture have been developed to quantify the energy and cost penalties for carbon capture. The various glycerol reforming cases were modelled and simulated to produce the mass & energy balances for quantification of key plant performance indicators (e.g. fuel consumption, energy efficiency, ancillary energy consumption, specific CO₂ emissions, capital and operational costs, production costs, cash flow analysis etc.). The evaluations show that glycerol reforming is promising concept for high energy efficiency processes with low CO₂ emissions.     

Polydimethylsiloxanes Cross-Linked by 4,4′-(1,3-Phenylenedioxy)-Dianiline within in situ Generated Silica Network

Polydimethylsiloxanes side-functionalized in different degrees with chloromethyl groups were reacted with 4,4′-(1,3-phenylenedioxy)-dianiline when the secondary amino groups formation and cross-linking occur. The reactions were carried out in a silica sol-gel system and thus two networks are simultaneously formed: siloxane-organic network and the silica one. Different techniques were used to characterize the formed systems: FTIR to verify the structure, DMA for analysis of the thermomechanical behavior, SEM and AFM for the evaluation of the morphology and surface topography. The elemental distribution within the samples was determined by EDX. The water vapours sorption capacity was measured in the dynamic regime.