Supermolecular structure variety of PMP membranes

Thermogravimetry was applied in order to study the variety of the phase structure of poly(4-methyl-1-pentene) (PMP) membranes. The results gave indirect information about the morphology of the polymeric systems. DTG curves, recorded for the membranes including residual amount of solvent, exhibited three processes. The processes were interpreted as a removal of the solvent molecules occluded in different local structures: ‘real’ amorphous; ‘semi-ordered’ amorphous, crystalline. The location of the molecules in those structures was correlated with chain behaviours studied using dynamic mechanical analysis. The relaxation processes (α_g, α_c) were analysed with a special attention to the amount of occluded solvent molecules.     

Effect of salt modification and acid activation on ethylene adsorption properties of sepiolite

The adsorption of ethylene (C₂H₄) on sepiolite from Eski?ehir, Turkey and on its salt modified forms (NaS, KS, CaS and MgS) and treated with 1, 3 and 5 M HCl solutions (SH, S3H and S5H) was investigated. The sepiolite samples were characterized using X-ray diffraction, X-ray fluorescence, thermogravimety, differential thermal analysis and N₂ adsorption methods. The C₂H₄ adsorption isotherms of all clay samples were obtained at 20 °C up to 37 kPa. The uptake of C₂H₄ decreased as HS > CaS > NaS > S > MgS > KS > H3S > H5S for sepiolite samples. Capacity of sepiolites for C₂H₄ ranged from 0.478 to 0.622 mmol/g. It was found that the adsorbed amount of C₂H₄ on sepiolite samples decreased with increasing acid concentrations.     

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)₄X₂, where M = Cu, X = Cl, NO₃ and CH₃COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)₄Cl₂ complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.     

Sulfonium Ion Derivatization,Isobaric Stable Isotope Labeling and Data Dependent CID- and ETD-MS/MS for Enhanced Phosphopeptide Quantitation,Identification and Phosphorylation Site Characterization

An amine specific peptide derivatization strategy involving the use of novel isobaric stable isotope encoded ‘fixed charge’ sulfonium ion reagents, coupled with an analysis strategy employing capillary HPLC, ESI-MS, and automated data dependent ion trap CID-MS/MS, -MS³, and/or ETD-MS/MS, has been developed for the improved quantitative analysis of protein phosphorylation, and for identification and characterization of their site(s) of modification. Derivatization of 50 synthetic phosphopeptides with S,S′-dimethylthiobutanoylhydroxysuccinimide ester iodide (DMBNHS), followed by analysis using capillary HPLC-ESI-MS, yielded an average 2.5-fold increase in ionization efficiencies and a significant increase in the presence and/or abundance of higher charge state precursor ions compared to the non-derivatized phosphopeptides. Notably, 44% of the phosphopeptides (22 of 50) in their underivatized states yielded precursor ions whose maximum charge states corresponded to +2, while only 8% (4 of 50) remained at this maximum charge state following DMBNHS derivatization. Quantitative analysis was achieved by measuring the abundances of the diagnostic product ions corresponding to the neutral losses of ‘light’ (S(CH₃)₂) and ‘heavy’ (S(CD₃)₂) dimethylsulfide exclusively formed upon CID-MS/MS of isobaric stable isotope labeled forms of the DMBNHS derivatized phosphopeptides. Under these conditions, the phosphate group stayed intact. Access for a greater number of peptides to provide enhanced phosphopeptide sequence identification and phosphorylation site characterization was achieved via automated data-dependent CID-MS³ or ETD-MS/MS analysis due to the formation of the higher charge state precursor ions. Importantly, improved sequence coverage was observed using ETD-MS/MS following introduction of the sulfonium ion fixed charge, but with no detrimental effects on ETD fragmentation efficiency.     

Synthesis,Characterization and Structure of [Fe(2,2′-bipy)<Subscript>3</Subscript>]<Subscript>2</Subscript>[α-Mo<Subscript>8</Subscript>O<Subscript>26</Subscript>]: An α-Octamolybdate-Supported Compound Formed During the Diffuse Process

The α-octamolybdate-supported compound: [Fe(2,2′-bipy)₃]₂[α-Mo₈O₂₆] has been unexpectedly synthesized during a diffuse process and characterized by the IR spectroscopy, UV–Vis diffuse reflectance spectroscopy and the single crystal X-ray diffraction. The title compound exhibits an interesting 3D honeycomb ‘host’ supramolecular network with 1D channels, in which only α-octamolybdate anions ‘guests’ reside. The title compound shows the anisotropic property and probably will be applied as a novel semiconductor in the future.     

A new form of MgTa2O6 obtained by the molten salt method

Using molten salt route (with NaCl/KCl as the salt) we have been able to synthesize a new form of magnesium tantalate at 850°C. Powder X-ray diffraction data could be inde_xed on an orthorhombic unit cell with lattice parameters, ‘a’ = 15.36(1) ?, ‘b’ = 13.38(1) ? and ‘c’ = 12.10(1) ?. High resolution transmission electron microscopy and electron diffraction studies confirm the results obtained by X-ray studies. Energy dispersive X-ray spectroscopy helps ascertain the composition of MgTa₂O₆. The title compound shows a dielectric constant of ∼24 with a low dielectric loss of 0.006 at 100 kHz at room temperature. Dielectric constant is nearly unchanged with rise in temperature while the loss shows a very marginal increase (0.007 at 300°C). Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Modulated-temperature thermomechanical analysis

By employing a ‘modulated-temperature’ heating programme composed of a series of heat-isotherm stages, it is possible to separate the change in dimensions of an oriented material during heating into two contributions: a thermally ‘reversing’ component which is due to linear thermal expansion and a ‘non-reversing’ part arising from relaxation to the disordered state on heating aboveT _g. Some preliminary results for biaxially drawn poly(ethylene terephthalate) film are presented. These experiments were carried out at the Thermal Methods & Conservation Science Laboratory, Department of Chemistry, Birkbeck College, University of London.     

Fractionation of nano- and microparticles in a rotating conoidal coiled column

A method for the continuous-flow fractionation of particles in a transverse centrifugal field in a rotating conoidal coiled (RCC) column has been developed. A model of a planetary centrifuge with a conoidal drum of a special construction has been tested. The effects of the rotation and revolution speed of the conoidal RCC, as well as the direction and pumping rate of the mobile phase on the behavior of particles smaller than 1 μm have been studied. The conditions have been selected and optimized for the retention and elution of spherical particles of the ‘150 nm’, ‘400 nm’, and ‘900 nm’ standard samples of silica gel (Polyscience Inc.). The possibility of using RCC for the analysis and production of monodisperse standard particle samples has been demonstrated. In particular, the ‘900 nm’ particles have been separated from admixtures of small (100–200 nm) particles and nonspherical 1–2 μm particles present in the sample. The separated fractions have been characterized by electron microscopy.     

TiO<Subscript>2</Subscript>-assisted photodegradation of pharmaceuticals — a review

Pharmaceutical compounds have been detected in the environment and potentially arise from the discharge of excreted and improperly disposed medication from sewage treatment facilities. In order to minimize environmental exposure of pharmaceutical residues, a potential technique to remove pharmaceuticals from water is the use of an advanced oxidation process (AOP) involving titanium dioxide (TiO₂) photocatalysis. To evaluate the extent UV/TiO₂ processes have been studied for pharmaceutical degradation, a literature search using the keywords ‘titanium dioxide’, ‘photocatalysis’, ‘advanced oxidation processes’, ‘pharmaceuticals’ and ‘degradation’ were used in the ISI Web of Knowledge TM, Scopus TM and ScienceDirect TM databases up to and including articles published on 23 November 2011. The degradation rates of pharmaceuticals under UV/TiO₂ treatment were dependent on type and amount of TiO₂ loading, pharmaceutical concentration, the presence of electron acceptors and pH. Complete mineralization under particular experimental conditions were reported for some pharmaceuticals; however, some experiments reported evolution of toxic intermediates during the photocatalytic process. It is concluded that the UV/TiO₂ system is potentially a feasible wastewater treatment process, but careful consideration of the treatment time, the loading and the type of TiO₂ (doped vs. undoped) used for a particular pharmaceutical is necessary for a successful application (198 words).      

Characterization of the Structure and Catalytic Activity of Pt/Sepiolite Catalysts

Four catalysts containing 1% w/w Pt deposited on various sepiolite supports were prepared. Two natural sepiolites and another two obtained by acid treatment of one of them were used. Both the sepiolites used as metal supports and the catalysts were characterized for structure and surface properties, using (1)H and (29)Si MAS NMR spectroscopy, and (29)Si CP/MAS NMR spectroscopy, in addition to hydrogen, pyridine, and CO(2) chemisorption measurements. The activity of the catalysts in the hydrogenation of benzene to cyclohexane and the dehydrogenation of cyclohexane to benzene was examined and the catalyst supported on the natural sepiolite called Pangel was found to be the most active of all. Copyright 2000 Academic Press.     

Photoinduced Electron Transfer Supramolecular Fluorescent Switch of Mono-6-p-nitrobenzoyl-β-cyclodextrin with Porphyrin Derivative

A novel supramolecular fluorescence switch system consisted of a perfect host/electron-acceptor mono-6-p-nitrobenzoyl-β-cyclodextrin (p-NBCD) and an ideal guest/electron-donor (adamantane-C₄-porphyrin) was reported. The ‘ON’ and ‘OFF’ states of fluorescence switch were droved by solvent polarity.     

Synthesis and characterization of Ni<Subscript>0.6</Subscript>Zn<Subscript>0.4</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nano-particles obtained by auto catalytic thermal decomposition of carboxylato-hydrazinate complex

Ni_0.6Zn_0.4Fe₂O₄ nano-particles have been synthesized by self-propagating auto-combustion of nickel zinc ferrous fumarato-hydrazinate complex. The precursor complex has been characterized by chemical analysis, IR, AAS, thermal analysis and isothermal mass loss studies. The precursor on ignition undergoes self-propagating auto combustion to give Ni_0.6Zn_0.4Fe₂O₄. The X-ray diffraction studies confirmed the single phase formation of nano-size ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. TEM observation showed the average particle size to be 20 nm. Infrared and magnetization studies were also carried out on the ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. The lower value of saturation magnetization and higher Curie temperature of ‘as synthesized’ ferrite also hint at the nano size nature.     

Thermal Behavior of VARIOUS sulfone-based diimid-diacids Solvated with Polar Organic Solvents

Thermal analysis techniques were performed to reveal ‘crystalline solvate’ behavior between organic compounds and polar solvents. Diimide-dicarboxylic acid (DIDA) was formed by reacting 3,3'-diaminodiphenylsulfone (3,3'-DPS) or 4,4'-diaminodiphenylsulfone (4,4'-DPS) with trimellitic anhydride (TMA) in some polar solvents (PSv). The products could crystallize upon cooling in a polar solvent media to form a solvate containing a finite quantity of solvents, leading to what can be termed as ‘crystalline solvates’ (CS). This study has demonstrated that sampling techniques in TG and DSC must be kept to be as similar as possible, which is a critical point in practices of thermal analysis techniques. DSC analysis revealed that there are two endothermic peaks in the CS, with the lower one being the de-solvate temperature of CS (T _d) at which the solvated solvent molecules were removed, and the higher peak being the melting point of the de-solvated DIDA (T _m). T _d was found to vary with the types of polar solvents and structures of DIDA. The TG result indicated that most of the sulfone-based DIDA-CS contained 2 moles of solvent per mole of solvate. X-ray analysis revealed that different crystalline structures were found for DIDA-CS solvated with different solvent molecules, but all de-solvated DIDA possessed the same crystal unit. This revised version was published online in July 2006 with corrections to the Cover Date.     

The architecture of Platonic polyhedral links

A new methodology for understanding the construction of polyhedral links has been developed on the basis of the Platonic solids by using our method of the ‘n-branched curves and m-twisted double-lines covering’. There are five classes of platonic polyhedral links we can construct: the tetrahedral links; the hexahedral links; the octahedral links; the dodecahedral links; the icosahedral links. The tetrahedral links, hexahedral links, and dodecahedral links are, respectively, assembled by using the method of the ‘3-branched curves and m-twisted double-lines covering’, whereas the octahedral links and dodecahedral links are, respectively, made by using the method of the ‘4-branched curves’ and ‘5-branched curves’, as well as ‘m-twisted double-lines covering’. Moreover, the analysis relating topological properties and link invariants is of considerable importance. Link invariants are powerful tools to classify and measure the complexity of polyhedral catenanes. This study provides further insight into the molecular design, as well as theoretical characterization, of the DNA polyhedral catenanes.     

Ultrahydrophobic aluminium surfaces: properties and EIS measurements of different oxidic and thin-film coated states

Firstly, the contribution summarises important results of the work dedicated to the formation of ultrahydrophobic aluminium surfaces. This treatment comprises sulphuric acid anodisation under intensified temperature and current density conditions (‘SAAi’) as well as subsequent chemical modification (‘C’). The usual sulphuric acid anodisation (‘SAAu’) was included for comparison. These various states were examined by electrochemical impedance spectrometry (EIS) to derive typical EIS-related features, especially for the ultrahydrophobic states compared to the anodised surfaces. Based on well-defined spectra types, modelling yielded results, preferentially with regard to the nano-porosity of the oxidic layers. EIS measurements allowed the conclusion that the original nano-porosity underwent specific changes due to the chemical modification variants employed. The chances of EIS predicting the stability of the ultrahydrophobically modified systems are critically assessed on the background of standardised weathering tests.     

Calorimetry of Portland cement with metakaolins, quartz and gypsum additions

In this work two aluminic pozzolans (metakaolins) and a non-pozzolan were added to two Portland cements with very different mineral composition, to determine the effect on the rate of heat release and the mechanisms involved. The main analytical techniques deployed were: conduction calorimetry, pozzolanicity and XRD. The results showed that the two metakaolins induced stimulation of the hydration reactions due to the generation of pozzolanic activity at very early stage, because of their reactive alumina, Al₂O₃^r− contents, mainly. Such stimulation was found to be more specific than generic for more intense C₃A hydration than C₃S, at least at very early on into the reaction, and more so when 7.0% SO₃ was added, and for this reason, such stimulation is described as ‘indirect’ to differentiate it from the ‘direct’ variety. As a result of both stimulations, the heat of hydration released is easy to assimilate to a Synergistic Calorific Effect.     

A theoretical study of the reactivity of carbon monoxide with cyclobutadiene

GRINDOL molecular orbital calculations have been performed for the cyclobutadiene-carbonmonoxide (CB-CO) complex. Starting from the rectangular structure of CB with the CO molecule along the C₂-axis perpendicular to the ring, geometry optimization leads to a stable C_4u-structure with the square geometry of CB moiety as the distance (CB-CO) decreases. A hill top in the potential energy curve corresponds to transition of CB from rectangular to square geometry. Bader’s population analysis carried out for different optimized geometries clearly reveals that the stability of the CB-CO complex arises due to ππ* back donation from CB to the CO molecule. The cause of the ‘hill top’ in the potential energy curve is also explained in the light of Bader’s population analysis. Results of trapping of products arising from photochemical reactions with CB is also discussed.     

Underpotential surface reduction of mesoporous CeO<Subscript>2</Subscript> nanoparticle films

The formation of variable-thickness CeO₂ nanoparticle mesoporous films from a colloidal nanoparticle solution (approximately 1–3-nm-diameter CeO₂) is demonstrated using a layer-by-layer deposition process with small organic binder molecules such as cyclohexanehexacarboxylate and phytate. Film growth is characterised by scanning and transmission electron microscopies, X-ray scattering and quartz crystal microbalance techniques. The surface electrochemistry of CeO₂ films before and after calcination at 500 °C in air is investigated. A well-defined Ce(IV/III) redox process confined to the oxide surface is observed. Beyond a threshold potential, a new phosphate phase, presumably CePO₄, is formed during electrochemical reduction of CeO₂ in aqueous phosphate buffer solution. The voltammetric signal is sensitive to (1) thermal pre-treatment, (2) film thickness, (3) phosphate concentration and (4) pH. The reversible ‘underpotential reduction’ of CeO₂ is demonstrated at potentials positive of the threshold. A transition occurs from the reversible ‘underpotential region’ in which no phosphate phase is formed to the irreversible ‘overpotential region’ in which the formation of the cerium(III) phosphate phase is observed. The experimental results are rationalised based on surface reactivity and nucleation effects.     

Thermal investigation of ‘molten starch’

Detailed thermal analysis studies have shown that a ‘molten starch’ phase is obtained during controlled heating of starch. Before the ‘molten’ stage, depolymerisation of starch produces lower molecular weight compounds like dextrins, oligo, di- and monosaccharides, as well as other types of compounds. These compounds should have ideal properties for plasticizing starches because of the similarities of the molecules, helping lower phase changes in collaboration with molecular weight decrease. Interestingly, it was found previously that these materials only act as adhesives in a narrow temperature range around 523 K (250 °C) (Shuttleworth et al. J Mater Chem 19(45):8589–8593, 2009). Materials were investigated using thermal and mechanical analyses of single lap joints.