Alina Adams

Bifunctional nanoparticle–SILP catalysts (NPs@SILP) for the selective deoxygenation of biomass substrates

Ruthenium nanoparticles were immobilized onto an acidic supported ionic liquid phase (RuNPs@SILP) in the development of bifunctional catalysts for the selective deoxygenation of biomass substrates. RuNPs@SILPs possessed high catalytic activities, selectivities and recyclabilities in the hydrogenolytic deoxygenation and ring opening of C8- and C9-substrates derived from furfural or 5-hydroxymethylfurfural and acetone. Tailoring the acidity of the SILP through the ionic liquid loading provided a molecular parameter by which the catalytic activity and selectivity of the RuNPs@SILPs were controlled to provide a flexible catalyst system toward the formation of different classes of value-added products: cyclic ethers, primary alcohols or aliphatic ethers.

Characterization of non-extractable 14C- and 13C-sulfadiazine residues in soil including simultaneous amendment of pig manure

Recently, we reported on soil fate of SDZ residues amended with pig manure treated with 14C-labeled sulfadiazine (14C-SDZ). The first objective of the present study was to determine whether this strategy can be substituted by application of 14C-SDZ to soil. The second objective was to characterize non-extractable SDZ residues by fractionation, size exclusion chromatography (SEC) and solid state 13C-NMR. The fate of 14C-SDZ was examined for 28 d, using two soils with and without amendment of pig manure. Mineralization of 14C-SDZ was low; extractable residues decreased to 7–30%. Compared to the previous study, results were similar. 14C-SDZ derived bound radioactivity was found in HCl-washings, fulvic, humic acids and humin. According to SEC, one bound 14C portion (70%) co-eluted with fulvic acids (above 910 g mol−1); the other consisted of adsorbed/entrapped 14C-SDZ. The 13C-SDZ study was performed for 30 d; humic acids were examined by 13C-NMR. A signal (100–150 ppm) was referred to 13C-SDZ. SEC and 13C-NMR demonstrated rapid integration of SDZ into humics.

Estimation of Self-Diffusion Coefficients of Small Penetrants in Semicrystalline Polymers Using Single-Sided NMR

A simple and fast way to measure proton self-diffusion coefficients of small penetrant molecules in semicrystalline polymers is introduced. The approach takes advantage of the strong static gradient of a mobile single-sided NMR sensor and it is demonstrated on PE samples with varying degrees of crystallinity fully saturated in either toluene or n-hexane. The self-diffusion coefficients were measured using the gradient stimulated echo sequence appended with a CPMG. It is also shown for the first time, with demonstration on PE plates several millimeter thick with different aging histories, that one-dimensional profiles of self-diffusion coefficients as a function of depth can be easily obtained.

Incorporation mechanisms of a branched nonylphenol isomer in soil-derived organo-clay complexes during a 180-day experiment.

The incorporation process of a defined (13)C- and (14)C-labeled nonylphenol isomer (4-(3,5-dimethylhept-3-yl)phenol) into soil-derived organo-clay complexes was investigated. Isolated organo-clay complexes were separated into humic subfractions. Noninvasive ((13)C-CP/MAS NMR) and invasive methods (sequential chemical degradation, pyrolysis) were applied to obtain detailed information about the mode of incorporation, chemical structure, and change of the incorporation character of nonextractable residues in course of incubation. (13)C-CP/MAS NMR measurements of humic acids revealed an increasing incorporation of phenolic compounds during the experimental time which was referred to residues of the introduced (13)C-labeled NP isomer. Detailed investigations by means of sequential chemical degradation indicated a predominant incorporation of nonextractable NP isomer residues via reversible ester (amide) bonds. In course of time, the amount of releasable compounds decreased, pointing to altering processes which affected the mode of incorporation. BBr3-treatment, RuO4 oxidation, and thermochemolysis released only low portions of nonextractable radioactivity giving evidence of strongly incorporated residues. With the comprehensive application of complementary methods (e.g., humic matter fractionation, (13)C-CP/MAS NMR, sequential chemical degradation) it was possible to provide a comparatively detailed insight into the incorporation behavior of the applied NP isomer.

Nondestructive Quantification of Local Plasticizer Concentration in PVC by 1H NMR Relaxometry

The properties of plasticized poly(vinyl chloride) (PVC) , one of the most important polymers today, are strongly dictated by the concentration of plasticizer. Yet, it has been impossible to quantify this concentration at different positions inside a PVC product without its destruction because of a lack of suitable analytical methods. Thus, this paper introduces a simple, fast, and efficient way to determine truly nondestructively the concentration of plasticizer in PVC by single-sided nuclear magnetic resonance (NMR). With the help of correlation curves between the concentration of plasticizer inside nonaged PVC samples and the corresponding volume-averaged NMR parameters, single-sided NMR allows the quantification of the local concentration of plasticizer in aged PVC plates at different depths by spatially resolved relaxation measurements. The presented approach represents a fundamental step toward in situ characterization of plasticized PVC.

Borazine-based inorganic–organic hybrid cyclomatrix microspheres by silicon/boron exchange precipitation polycondensation

The synthesis of borazine-based hybrid cyclomatrix polymers has been studied under various conditions. Crosslinked polymers obtained via a novel silicon/boron exchange precipitation polycondensation approach form hybrid cyclomatrix microspheres with a mean diameter of about 900 nm.

Metal-free reduction of the greenhouse gas sulfur hexafluoride, formation of SF5 containing ion pairs and the application in fluorinations

A protocol for the fast and selective two-electron reduction of the potent greenhouse gas sulfur hexafluoride (SF6) by organic electron donors at ambient temperature has been developed. The reaction yields solid ion pairs consisting of donor dications and SF5-anions which can be effectively used in fluorination reactions.

1H-NMR measurements of proton mobility in nano-crystalline YSZ

We report nuclear magnetic resonance (NMR) results on water saturated, dense, nano-crystalline YSZ samples (9.5 mol% yttria doped zirconia) which exhibit proton conductivity at temperatures as low as room temperature. (1)H-NMR spectra recorded under static and magic angle spinning conditions show two distinct signals. Their temperature-dependent behavior and their linewidths suggest that one can be attributed to (free) water adsorbed on the surface of the sample and the other one to mobile protons within the sample. This interpretation is supported by comparison with measurements on a single-crystalline sample. For the nano-crystalline samples motional narrowing is observed for the signal originating from protons in the sample interior. For these protons, the analysis of temperature and field dependent spin-lattice relaxation time T1 points towards diffusion in a confined two-dimensional geometry. We attribute this quasi two-dimensional motion to protons that are mobile along internal interfaces or nanopores of nano-crystalline YSZ.

A size-adjustable radiofrequency coil for investigating plants in a Halbach magnet

A radio-frequency coil with adjustable distance has been developed and tested for in-situ examination of growing plants. The Helmholtz-based coil design reduces laborious tuning and matching efforts encountered with solenoids wound around a growing stem or branch. Relaxation experiments were performed on tomato plants and winter wheat under controlled light irradiation. Changes in signal amplitude and in relaxation times T2 were recorded over day and night cycles. Peaks in distributions of relaxation times were attributed to different tissue components of two different plants.

Impact of Ionic Liquids on the Structure and Dynamics of Collagen

The changes in the structure and dynamics of collagen treated with two different classes of ionic liquids, bis-choline sulfate (CS) and 1-butyl-3-methyl imidazolium dimethyl phosphate (IDP), have been studied at the molecular and fibrillar levels. At the molecular level, circular dichroic studies revealed an increase in molar ellipticity values for CS when compared with native collagen, indicating cross-linking, albeit pronounced conformational changes for IDP were witnessed indicating denaturation. The impedance was analyzed to correlate the conformational changes with the hydration dynamics of protein. Changes in the dielectric properties of collagen observed upon treatment with CS and IDP reported molecular reorientation in the surrounding water milieu, suggesting compactness or destabilization of the collagen. This was further confirmed by proton transverse NMR relaxation time measurements, which demonstrated that the water mobility changes in the presence of the ILs. At the fibrillar level, differential scanning calorimetry thermograms for rat tail tendon collagen fibers treated with CS show a 5 °C increase in denaturation temperature, suggesting imparted stability. On the contrary, a significant temperature decrease was noticed for IDP, indicating the destabilization of collagen fibers. The obtained results clearly indicate that the changes in the secondary structure of protein are due to the changes in the hydration dynamics of collagen upon interaction with ILs. Thus, this study on the interaction of collagen with ionic liquids unfolds the propensity of ILs to stabilize or destabilize collagen depending on the changes invoked at the molecular level in terms of structure and dynamics of protein, which also got manifested at the fibrillar level.