State Carbon-13 Nuclear Magnetic Resonance Research Articles

Biodegradable polyurethanes foam and foam fullerenes nanocomposite strips by one-shot moulding: Physicochemical and mechanical properties

Biodegradable polyurethanes foam as well as foam strips have been formulated by the renowned one-shot process. Commercially available biodegradable trifunctional polyol, polycaprolactone triol (major, ~77 wt%) and isophorone diisocyanate were chosen to react in the presence of other essential components to formulate the PU foams from the paper cup as well as foam strips using mould at ambient temperature. The formulation of foams has been efficiently attempted by successive steps by alteration of the components such as chain extender, quantity of water and isocyanate index. In situ addition of fullerenes (0.1, 0.4 and 1.0 wt%) into the composition of PU foam strips formulation in mould found to afford the three samples of PU-fullerenes nanocomposite. In case of polyurethanes-fullerenes nanocomposite foam strips, nanomaterial of fullerenes was identified to disperse uniformly in the bulk of sample to incorporate the enhancement in physicochemical and mechanical properties value as compared to the control PU foam strip. The battery of analyses such as physicochemical, morphological and mechanical properties was studied for each foam samples, including control and PU-fullerenes nanocomposite strips. Solid state carbon-13 nuclear magnetic resonance spectral data for the foam revealing desired properties was collected to corroborate the chemical functional groups in the molecular structure network.

Chelating modified cellulose bearing pendant heterocyclic moiety for effective removal of heavy metals.

Cellulose bearing pendant Schiff base with heterocyclic chelating groups (CMC-Bz) was synthesized, which were fully characterized using various instrumental techniques such as solid state carbon-13 nuclear magnetic resonance (13C-NMR), Fourier transform infrared (FTIR), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX) spectra. The adsorption of toxic metals onto cellulosic material was tested in a batch mode operation. The adsorption functional factors such as pH, adsorbent dose, metal ion concentration, equilibrium time and temperature were experimentally optimized for the maximum removal of Cu(II) and Pb(II) ions. Adsorption isotherms were evaluated with Langmuir, Freundlich, Temkin and Redlich-Peterson isotherms. Kinetic parameters and equilibrium adsorption capacities were investigated for pseudo-first-order, pseudo-second-order and intra-particle diffusion models. Thermodynamic parameters and reusability were also evaluated.

Use of chemical modification to determine the binding of Cd(II), Zn(II) and Cr(III) ions by orange waste

This study focuses on the roles played by three major functional groups (amine, carboxyl and hydroxyl) in the orange waste biomass for sorption of three heavy metals (Cd 2+, Zn 2+ and Cr 3+). The biosorbent was chemically modified to block the mentioned functional groups in order to determine their contribution to the adsorption of metals. Fourier transform infrared (FTIR) and solid state carbon-13 nuclear magnetic resonance ( 13C NMR) spectroscopy were used to investigate the chemical modification. Additionally, batch biosorption tests were carried out with the different biosorbents in order to determine the possible reduction in metal uptake with the chemically modified biosorbent. Blocking of the COOH groups by chemical esterification resulted in an important reduction in metal binding. Nevertheless, no significant modification in metal removal was observed with acetylated and methylated orange waste.

Paramagnetic Effects on Solid State Carbon-13 Nuclear Magnetic Resonance Spectra of Soil Organic Matter

The effects of paramagnetic species on solid state 13C nuclear magnetic resonance (NMR) spectra were quantified in a series of doping experiments. The degree of signal loss caused by paramagnetic metals was shown to depend not only on the quantity, but also on the nature of the paramagnetic species, as well as the intimacy of contact with the organic substrate and the type of NMR experiment. Two mechanisms of signal loss were distinguished—signal loss via loss of magnetic field homogeneity, which affects all 13C nuclei in a sample, and signal loss via interaction between electronic and nuclear spins, the effects of which were localized to the close environment of the paramagnetic species. Loss of field homogeneity is important for manganese species, but not for copper species, and is equally important for both cross polarization and Bloch decay experiments. The interaction between electronic and nuclear spins is highly dependent on the spin-lattice relaxation rate constant of the free electron (T1e), as cations with very short T1e values (e.g., Pr3+) cause less signal loss than cations with longer T1e values (e.g., Cu2+, Mn2+). Cross polarization spectra are shown to be more susceptible than Bloch decay spectra to this mechanism of signal loss. Signal loss and increased relaxation rates brought about by paramagnetic species can be used to provide information on soil organic matter (SOM) heterogeneity in the submicron range. This is demonstrated for SOM doped with paramagnetic cations where selective signal loss and increased relaxation rates are used to determine the nature of cation exchange sites.

Studies of mercurated derivatives of acetylacetone and ethyl acetoacetate by solid state nuclear magnetic resonance and vibrational spectroscopies

Seven new mono- and/or dimercurated compounds involving acetylacetone (2,4-pentanedione) or ethyl acetoacetate (3-ethyl ketobutanoate) were synthesized in aqueous medium. In all cases, mercuration occurred at methylene carbon atoms. All compounds were carefully analyzed by solid state carbon-13 nuclear magnetic resonance. Assignments were confirmed by using selective sequences, which allowed a total editing of the spectra. It was shown that deshielding of 13C mercurated sites occurred when the rate of mercuration increased. It was also possible to measure direct 1J( 199 Hg 13 C) coupling constants. The main bands of the vibrational spectra (infrared and Raman) were assigned. It was proved that v(C = O) and δ(C(γ)-H) could be directly related to the mercuration rate of molecules.

Effects of synthetic estrogens, ( R, R)-(+)-, ( S, S)-(−)-, dl- and meso-hexestrol stereoisomers on microtubule assembly

We previously reported on the inhibition of microtubule polymerization and the formation of ribbon structures by synthetic estrogens [Sato et al., J Biochem 101: 1247–1252, 1987]. The present investigation aimed to analyse these effects in vitro on stereochemical point of view, using hexestrol isomers (( R, R)-(+)-hexestrol, ( S, S)-(−)-hexestrol and meso-hexestrol) and dl-hexestrol. Among hexestrols, dl-hexestrol showed the highest activity in ribbon formation from microtubule proteins at 100 μM. On the other hand, meso-hexestrol was distinguished from others by inhibition of microtubule assembly and formation of a large amount of aggregates from purified tubulin in the presence of MgCl 2 and DMSO. These results were discussed with physico-chemical properties of hexestrols, e.g. absolute configurations as well as circular dichroism spectra and solid state carbon-13 nuclear magnetic resonance spectra.

Solid state carbon-13 nuclear magnetic resonance study of Canadian coals

The solid state carbon-13 nuclear magnetic resonance characterization of a series of 20 Canadian coals ranging in rank from lignite to semi-anthracite is reported. The results are discussed in terms of chemical shift changes with increasing rank and possible correlations with reactivity as related to low rank coal upgrading and liquefaction behaviour. Proximate, ultimate and maceral analyses are correlated among themselves, as well as with NMR-derived parameters.

Chemical changes during natural oxidation of a high volatile bituminous coal

Core drilling of near surface seams near Wakefield NSW has provided high volatile bituminous coal samples that have been subject to varying degrees of natural in situ oxidation. Five levels of oxidation have been defined, mainly on visual evidence, ranging from unoxidised coal to highly oxidised material. Samples of each oxidation level have been investigated by chemical analysis, Fourier transform infrared spectroscopy (FTIR) and solid state carbon-13 nuclear magnetic resonance spectroscopy (NMR) with cross-polarization and magic angle spinning. The results show that mineral matter, moisture and oxygen content increase with oxidation, whereas carbon, hydrogen and specific energy decrease. Moisture determination is suggested as a quick, facile method for indicating the oxidation level for a coal sample from this seam. FTIR showed a marked loss of aliphatic C-H groups with increasing oxidation, and an increase in carbonyl and carboxylate groups. Aromatic C-H groups were much less affected by oxidation. Solid state carbon-13 NMR showed increasing carbon aromaticity with oxidation, but showed substantial carbonyl carbon only at the highest oxidation level. No evidence was found for an increase in aromatic substituents during oxidation; if anything, there is a small decrease in substituents.