Reaction-based Indicator displacement Assay (RIA) for the selective colorimetric and fluorometric detection of peroxynitrite

Using the self-assembly of aromatic boronic acids with Alizarin Red S (ARS), we developed a new chemosensor for the selective detection of peroxynitrite. Phenylboronic acid (PBA), benzoboroxole (BBA) and 2-(N,N-dimethylaminomethyl)phenylboronic acid (NBA) were employed to bind with ARS to form the complex probes. In particular, the ARS–NBA system with a high binding affinity can preferably react with peroxynitrite over hydrogen peroxide and other ROS/RNS due to the protection of the boron via the solvent-insertion B–N interaction. Our simple system produces a visible colorimetric change and on–off fluorescence response towards peroxynitrite. By coupling a chemical reaction that leads to an indicator displacement, we have developed a new sensing strategy, referred to herein as RIA (Reaction-based Indicator displacement Assay).     

Voltammetry of electroactive liquid redox systems: anion insertion and chemical reactions in microdroplets of para-tetrakis(6-methoxyhexyl) phenylenediamine, para- and meta-tetrahexylphenylenediamine

The effect of the structure of the organic precursor molecule on the electroinsertion of anions and on the formation of materials in the ionic liquid state is compared for three compounds, para-N, N, N′, N′-tetrahexylphenylenediamine (p-THPD), meta-N, N, N′, N′-tetrahexylphenylene diamine (m-THPD), and para-N, N, N′, N′-tetrakis(6-methoxyhexyl)phenylenediamine (p-TMHPD), by characterising their condensed phase voltammetric properties in aqueous media. The electrochemically driven anion insertion in p-THPD and p-TMHPD in the presence of ClO₄ ⁻, F⁻, Cl⁻, Br⁻, I⁻, and SO₄ ²⁻ is shown to be extremely sensitive to structure. The introduction of the methoxy end groups in p-TMHPD causes (1) a considerable shift to more negative electroinsertion potentials, (2) a less stable response which upon continuous cycling decreases, and (3) considerably lower anion selectivity. For the insertion of sulfate, only p-TMHPD yields an electrochemical response which is shown to be consistent with insertion of the dianion SO₄ ²⁻. The electrochemical oxidation of a deposit of m-THPD is accompanied by anion insertion and a chemical reaction step in an EC-type electrochemical process. The product of the chemical step is electrochemically active and results in a new reversible electroinsertion process. Starting materials and products of the microdroplet reactions are characterised by Maldi-TOF mass spectrometry and a reaction mechanism based on condensed phase polymerisation is proposed. Received: 15 November 1999 / Accepted: 2 December 1999     

Photoelectrochemically driven processes at the N,N,N′,N′-tetrahexylphenylenediamine microdroplet|electrode|aqueous electrolyte triple interface

Novel photoelectrochemical processes are observed upon irradiation of the liquid|liquid|solid triple interface at microdroplets of N,N,N′,N′-tetrahexyl-para-phenylenediamine (THPD) deposited onto a basal plane pyrolytic graphite electrode and immersed in aqueous electrolyte solution. In the presence of neutral THPD, cathodic photo responses, and in the presence of THPD⁺, anodic photo responses with anion-dependent characteristics, are observed. A maximum in the photocurrents observed at intermediate coverage of the electrode surface suggests that the triple interface THPD|electrode|aqueous electrolyte is the reaction zone. This is the first report of photoelectrochemical processes at this type of interface. Electronic Publication     

Cs[Si3O6(OH)] and Rb[Si2O4(OH)]: two novel phyl­losilicates

The crystal structures of two novel phyl­losilicates with compositions Cs[Si₃O₆(OH)] (caesium hydroxo­hexa­oxotetra­otri­silicate) and Rb[Si₂O₄(OH)] (rubidium hydroxo­hexa­oxotetrao­di­silicate) have been characterized by X‐ray diffraction. The topology of the caesium phyl­losilicate silica sheet consists of interconnected four‐ and six‐membered rings and thus differs from all of the previously reported phyl­losilicates. The topology of the rubidium phyl­losilicate silica sheet consists of six‐membered rings only, in boat conformations, resulting in a corrugated sheet similar to that observed in δ‐Na₂Si₂O₅. Both of the title compounds exhibit the characteristic sandwich structure of sheet silicates, with the Cs atom ninefold coordinated and the Rb atom eightfold coordinated to the framework O atoms.     

Complex Fluids Based on the Flexible One-Dimensional Mineral Polymers [K(MPS4)]∞ (M=Ni,Pd): Autofragmentation to Concave,Cyclic (PPh4)3[(NiPS4)3]

A remarkable autofragmentation/rearrangement sequence results in the unprecedented formation of inorganic concave cyclic anion [(NiPS₄)₃]³⁻ (structure shown on the right) upon dissolving the potassium salt of the charged mineral polymer ¹_∞[NiPS₄]⁻ in DMF; the initial complex fluid has a transient anisotropic texture that can be identified by optical microscopy under polarized light. In contrast, the complex fluid that results upon dissolving ¹_∞[PdPS₄]⁻ is stable up to 323 K as persistent, flexible, charged chains.     

PEARL: the high pressure neutron powder diffractometer at ISIS

The PEARL instrument at ISIS has been designed for, and dedicated to, in situ studies of materials at high pressure, using the Paris–Edinburgh press. In recent years, upgrades to the instrument have led to improvements in data quality and the range of achievable pressures and temperatures; currently 0.5–28?GPa and 80–1400?K. This paper describes the technical characteristics of the instrument, its current capabilities, and gives a brief overview of the science that has been performed, using representative examples.     

Functionalized Carbon Nanoparticles,Blacks and Soots as Electron‐Transfer Building Blocks and Conduits

Functionalized carbon nanoparticles (or blacks) have promise as novel active high‐surface‐area electrode materials, as conduits for electrons to enzymes or connections through lipid films, or as nano‐building blocks in electroanalysis. With previous applications of bare nanoblacks and composites mainly in electrochemical charge storage and as substrates in fuel cell devices, the full range of benefits of bare and functionalized carbon nanoparticles in assemblies and composite (bio)electrodes is still emerging. Carbon nanoparticles are readily surface‐modified, functionalized, embedded, or assembled into nanostructures, employed in bioelectrochemical systems, and incorporated into novel electrochemical sensing devices. This focus review summarizes aspects of a rapidly growing field and some of the recent developments in carbon nanoparticle functionalization with potential applications in (bio)electrochemical, photoelectrochemical, and electroanalytical processes.     

Synthesis of Di‐, Tri‐, and Tetrasubstituted Oxetanes by Rhodium‐Catalyzed O?H Insertion and C?C Bond‐Forming Cyclization

Oxetanes offer exciting potential as structural motifs and intermediates in drug discovery and materials science. Here an efficient strategy for the synthesis of oxetane rings incorporating pendant functional groups is described. A wide variety of oxetane 2,2‐dicarboxylates were accessed in high yields, including functionalized 3‐/4‐aryl‐ and alkyl‐substituted oxetanes and fused oxetane bicycles. Enantioenriched alcohols provided enantioenriched oxetanes with complete retention of configuration. The oxetane products were further derivatized, while the ring was maintained intact, thus highlighting their potential as building blocks for medicinal chemistry.     

Investigation of the Effects of Environmental Fatigue on the Mechanical Properties of GFRP Composite Constituents Using Nanoindentation

Background

Fatigue failure criteria for fibre reinforced polymer composites used in the design of marine structures are based on the micromechanical behaviour (e.g. stiffness properties) of their constituents. In the literature, there is a lack of information regarding the stiffness degradation of fibres, polymer matrix and fibre/matrix interface regions affected by environmental fatigue.

Objective

The aim of present study is to characterize the stiffness properties of composite constituents using the nanoindentation technique when fatigue failure of composites is due to the combined effect of sea water exposure and cyclic mechanical loads.

Methods

In the present study, the nanoindentation technique was used to characterize the stiffness properties of composite constituents where the effects of neighbouring phases, material pile up and viscoplasticity properties of the polymer matrix are corrected by finite element simulation.

Results

The use of finite element simulation in conjunction with nanoindentation test data, results in more accurate estimation of projected indented area which is required for measuring the properties of composite constituents. In addition, finite element simulation provides a greater understanding of the stress transfer between composite constituents during the nanoindentation process.

Conclusions

Results of nanoindentation testing on the composite microstructure of environmentally fatigue failed composite test coupons establish a strong link to the stiffness degradation of the fiber/matrix interface regions, verifying the degradation of composite constituents identified by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis.