New effective catalysts based on mesoporous nanofibrous carbon for selective oxidation of hydrogen sulfide

The systems based on granular mesoporous nanofibrous carbonaceous (NFC) materials synthesized by decomposition of hydrocarbons over nickel- containing catalysts are promising catalysts for selective oxidation of hydrogen sulfide. Sample series of nanofibrous carbon with three main types of their fiber structures and different contents of metal catalysts inherited from the catalysts for their synthesis were studied in this reaction. The correlation between NFC structure and its activity and selectivity in hydrogen sulfide oxidation was determined. The metal inherited from the initial catalysts for the synthesis of NFC influences the activity and selectivity of the resulting carbon catalysts. A particular influence is observed in the case of the catalyst withdrawn from the synthesis reactor at the stage of stationary operation of the metal catalyst (low specific carbon yields per unit weight of the catalyst). The presence of the metal phase results in an increase in the carbon catalyst activity and in a decrease in the selectivity to sulfur. NFC samples with the highest activity and selectivity are nanotubes and those with graphite planes perpendicular to the axis of the fibers. Carbon nanotubes have high selectivity, while samples obtained on copper–nickel catalysts also possess high activity. The promising NFC catalysts provide high conversion and selectivity (almost independent of the molar oxygen/hydrogen sulfide ratio) when a large excess of oxygen is contained in the reaction mixture.

Laser-induced site-selective silver seeding on polyimide for electroless copper plating

Ag particles were generated on Ag+-doped polyimide film by laser direct writing, followed by selective copper deposition using the metallic silver particles as seeds. Laser irradiation caused in situ reduction and agglomeration of silver on the polyimide film. The copper lines were less uniform and compact with higher scanning velocity and the width of the deposited copper line could reach 25 mu m. Equations of the relationship between scanning velocity and connectivity of the deposited copper patterns have been derived. The process was characterised by AFM, XPS, SEM, and semiconductor characterisation system.

Selective chemical measurement based upon chemiluminescence detection

This thesis describes the utilisation of chemiluminescence (chemically generated light) for clinical diagnosis and process monitoring. Innovative instrumentation was developed for the direct monitoring of toxin levels in patients undergoing haemodialysis. This unique approach enables the efficacy of individual treatments to be continuously assessed thus enhancing patient outcomes.

Investigations of Tris(2,2'-bipyridyl)ruthenium(II) as a chirally selective chemiluminescence reagent

Enantiomers of Tris(2,2'-bipyridyl)ruthenium(II) were selectively resolved and utilised in chiral kinetic studies. Instrumentation was designed and built for the collection of kinetic data from their chemiluminescence reactions. After testing the kinetic profiles of various enantiomerically pure analyte reagent combinations, results proved to be inconclusive and further testing is still required.

The assessment of тт-тт selective stationary phases for two-dimensional HPLC analysis of foods : application to the analysis of coffee

Differences between alkyl, dipole–dipole, hydrogen bonding, and π-π selective surfaces represented by non-resonance and resonance π-stationary phases have been assessed for the separation of ‘Ristretto’ café espresso by employing 2DHPLC techniques with C18 phase selectivity detection. Geometric approach to factor analysis (GAFA) was used to measure the detected peaks (N), spreading angle (β), correlation, practical peak capacity (n_p) and percentage usage of the separations space, as an assessment of selectivity differences between regional quadrants of the two-dimensional separation plane. Although all tested systems were correlated to some degree to the C18 dimension, regional measurement of separation divergence revealed that performance of specific systems was better for certain sample components. The results illustrate that because of the complexity of the ‘real’ sample obtaining a truly orthogonal two-dimensional system for complex samples of natural origin may be practically impossible.

Exploring the use of the tripeptide Gly–Gly–His as a selective recognition element for the fabrication of electrochemical copper sensors

The modification of electrodes with the tripeptide Gly–Gly–His for the detection of copper in water samples is described in detail. The tripeptide modified electrode was prepared by first self-assembling 3-mercaptopropionic acid (MPA) onto the gold electrode followed by covalent attachment of the tripeptide to the self-assembled monolayer using carbodiimide coupling. The electrodes were characterized using electrochemistry, a newly developed mass-spectrometry method and quantum mechanical calculations. The mass spectrometry confirmed the modification to proceed as expected with peptide bonds formed between the carboxylic acids of the MPA and the terminal amine of the peptide. Electrochemical measurements indicated that approximately half the MPA molecules in a SAM are modified with the peptide. The peptide modified electrodes exhibited high sensitivity to copper which is attributed to the stable 4N coordinate complex the peptide formed around the metal ion to give copper the preferred tetragonal coordination. The formation of a 4 coordinate complex was predicted using quantum mechanical calculation and confirmed using mass spectrometry. The adsorption of the copper to the peptide modified electrode was consistent with a Langmuir isotherm with a binding constant of (8.1 ± 0.4) 1010 M−1 at 25 °C.

Predictors of antidepressant response : a selective review

Modern antidepressant drugs have response rates in the 65% range. Considerable effort has been made to predict which patients would be more likely to respond to antidepressant treatment. Some progress has been made, more in finding psychological predictors than biological predictors of antidepressant response. In spite of slow progress, these findings have made a valuable contribution towards the understanding of antidepressant response. In future it may be possible for psychiatrists to use a more broad-based approach, tailoring therapies to the clinical profile of individuals.

Highly selective and sensitive DNA assay based on electrocatalytic oxidation of ferrocene bearing zinc(II)-cyclen complexes with diethylamine

A highly selective and sensitive electrochemical biosensor has been developed that detects DNA hybridization by employing the electrocatalytic activity of ferrocene (Fc) bearing cyclen complexes (cyclen = 1,4,7,10-tetraazacyclododecane, Fc[Zn(cyclen)H2O]2(ClO4)4 (R1), Fc(cyclen)2 (R2), Fc[Zn(cyclen)H2O](ClO4)2 (R3), and Fc(cyclen) (R4)). A sandwich-type approach, which involves hybridization of a target probe hybridized with the preimmobilized thiolated capture probe attached to a gold electrode, is employed to fabricate a DNA duplex layer. Electrochemical signals are generated by voltammetric interrogation of a Fc bearing Zn−cyclen complexes that selectively and quantitatively binds to the duplex layers through strong chelation between the cyclen complexes and particular nucleobases within the DNA sequence. Chelate formation between R1 or R3 and thymine bases leads to the perturbation of base-pair (A−T) stacking in the duplex structure, which greatly diminishes the yield of DNA-mediated charge transport and displays a marked selectivity to the presence of the target DNA sequence. Coupling the redox chemistry of the surface-bound Fc bearing Zn−cyclen complex and dimethylamine provides an electrocatalytic pathway that increases sensitivity of the assay and allows the 100 fM target DNA sequence to be detected. Excellent selectivity against even single-base sequence mismatches is achieved, and the DNA sensor is stable and reusable.

Synthesis, x-ray structure of ferrocene bearing Bis(Zn-cyclen) complexes and the selective electrochemical sensing of TpT

The new ligand, [Fc(cyclen)₂] (5) (Fc=ferrocene, cyclen=1,4,7,10-tetraazacyclododecane), and corresponding Zn^II complex receptor, [Fc{Zn(cyclen)(CH₃OH)}₂](ClO₄)₄ (1), consisting of a ferrocene moiety bearing one Zn^II-cyclen complex on each cyclopentadienyl ring, have been designed and prepared through a multi-step synthesis. Significant shifts in the ¹H NMR signals of the ferrocenyl group, cf. ferrocene and a previously reported [Fc{Zn(cyclen)}]²⁺ derivative, indicated that the two Zn^II-cyclen units in 1 significantly affect the electronic properties of the cyclopentadienyl rings. The X-ray crystal structure shows that the two positively charged Zn^II-cyclen complexes are arranged in a trans like configuration, with respect to the ferrocene bridging unit, presumably to minimise electrostatic repulsion. Both 5 and 1 can be oxidized in 1:4 CH₂Cl₂/CH₃CN and Tris-HCl aqueous buffer solution under conditions of cyclic voltammetry to give a well defined ferrocene-centred (Fc⁰/+) process. Importantly, 1 is a highly selective electrochemical sensor of thymidilyl(3′-5′)thymidine (TpT) relative to other nucleobases and nucleotides in Tris-HCl buffer solution (pH 7.4). The electrochemical selectivity, detected as a shift in reversible potential of the Fc⁰/+ component, is postulated to result from a change in the configuration of bis(Zn^II-cyclen) units from a trans to a cis state. This is caused by the strong 1:1 binding of the two deprotonated thymine groups in TpT to different Zn^II centres of receptor 1. UV-visible spectrophotometric titrations confirmed the 1:1 stoichiometry for the 1:TpT adduct and allowed the determination of the apparent formation constant of 0.89±0.10×10⁶ M⁻¹ at pH 7.4.

Differential mobilization of blubber fatty acids in lactating Weddell seals : evidence for selective use

A major source of energy during lactation in mammals is provided through the mobilization of blubber fatty acids (FAs). We investigated the extent to which FAs were mobilized to support both maternal metabolic requirements and milk production in the Weddell seal and how this was reflected in the FA composition of the pup’s blubber at the end of lactation (EL). FA composition of postpartum female blubber was similar in the 2 yr of study (2002 and 2003) but differed markedly by EL. Pup blubber FAs (at EL) were also different between years and did not match that of the mother’s milk or blubber. Milk FA composition changed during lactation, which may have been a reflection of an increase in pup energy demands at different stages of development. In addition, there was evidence of feeding by some females during lactation, with higher levels of some FAs in the milk than in the blubber. Our results indicate that differential mobilization of FAs occurred in lactating Weddell seals and that this was related to total body lipid stores at postpartum. Furthermore, growing pups did not store FAs unmodified, providing evidence that selective use does occur and also that using FA composition to elucidate dietary sources may be problematic in growing individuals.