Graphite Oxides: Effects of Permanganate and Chlorate Oxidants on the Oxygen Composition

Research on graphene materials has refocused on graphite oxides (GOs) in recent years. The fabrication of GO is commonly accomplished by using concentrated sulfuric acid in conjunction with: a) fuming nitric acid and KClO₃ oxidant (Staudenmaier); b) concentrated nitric acid and KClO₃ oxidant (Hofmann); c) sodium nitrate for in situ production of nitric acid in the presence of KMnO₄ (Hummers); or d) concentrated phosphoric acid with KMnO₄ (Tour). These methods have been used interchangeably in the graphene community, since the properties of GOs produced by these different methods were assumed as almost similar. In light of the wide applicability of GOs in nanotechnology applications, in which presence of certain oxygen functional groups are specifically important, the qualities and functionalities of the GOs produced by using these four different methods, side‐by‐side, was investigated. The structural characterizations of the GOs would be probed by using high resolution X‐ray photoelectron spectroscopy, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and Raman spectroscopy. Further electrochemical applicability would be evaluated by using electrochemical impedance spectroscopy and cyclic voltammetry techniques. Our analyses highlighted that the oxidation methods based on permanganate oxidant (Hummers and Tour methods) gave GOs with lower heterogeneous electron‐transfer rates and a higher amount of carbonyl and carboxyl functionalities compared with when using chlorate oxidant (Staudenmaier and Hofmann methods). These observations indicated large disparities between the GOs obtained from different oxidation methods. Such insights would provide fundamental knowledge for fine tuning GO for future applications.     

Monoammoniate of calcium amidoborane: synthesis, structure, and hydrogen-storage properties

The monoammoniate of calcium amidoborane, Ca(NH(2)BH(3))(2)·NH(3), was synthesized by ball milling an equimolar mixture of CaNH and AB. Its crystal structure has been determined and was found to contain a dihydrogen-bonded network. Thermal decomposition under an open-system begins with the evolution of about 1 equivalent/formula unit (equiv.) of NH(3) at temperatures <100 °C followed by the decomposition of Ca(NH(2)BH(3))(2) to release hydrogen. In a closed-system thermal decomposition process, hydrogen is liberated in two stages, at about 70 and 180 °C, with the first stage corresponding to an exothermic process. It has been found that the presence of the coordinated NH(3) has induced the dehydrogenation to occur at low temperature. At the end of the dehydrogenation, about 6 equiv. (～ 10.2 wt %) of hydrogen can be released, giving rise to the formation of CaB(2)N(3)H.     

Effect of solvents on the photophysical properties of substituted imidazonaphthyridine derivatives

The absorption and fluorescence characteristics of three substituted imidazonaphthyridine derivatives are studied in a series of organic solvents. The variation of Stokes shift with the polarity parameter of the solvent is studied and the excited state dipole moment of these derivatives is higher than the ground state dipole moment. The fluorescence lifetime profile shows single exponential decay in all the solvents. The fluorescence quantum yield, radiative and non-radiative rate constants are also calculated and these parameters show much variation in the change in substitution of these derivatives.     

Teleportation and dense coding with genuine multipartite entanglement

We present an explicit protocol E0 for faithfully teleporting an arbitrary two-qubit state via a genuine four-qubit entangled state. By construction, our four-partite state is not reducible to a pair of Bell states. Its properties are compared and contrasted with those of the four-party Greenberger-Horne-Zeilinger and W states. We also give a dense coding scheme D0 involving our state as a shared resource of entanglement. Both D0 and E0 indicate that our four-qubit state is a likely candidate for the genuine four-partite analogue to a Bell state.     

Discovery of indium complexes as water-tolerant Lewis acids

The work on development of organic reactions that are tolerant to air and moisture, especially that of carbon-carbon bond forming reactions, had only started in the early 1990s. Our laboratory had approached this subject when it was still in its infancy and had developed methodologies for that end. In this article, our decade of work on indium complexes as Lewis acids is summarised.     

Screening of nitrogen mustards and their degradation products in water and decontamination solution by liquid chromatography-mass spectrometry

Analysing nitrogen mustards and their degradation products in decontamination emulsions posed a significant challenge due to the different phases present in such matrices. Extensive sample preparation may be required to isolate target analytes. Furthermore, numerous reaction products are formed in the decontamination emulsion. A fast and effective qualitative screening procedure was developed for these compounds, using liquid chromatography-mass spectrometry (LC-MS). This eliminated the need for additional sample handling and derivatisation that are required for gas chromatographic-mass spectrometric (GC-MS) analysis. A liquid chromatograph with mixed mode column and isocratic elution gave good chromatography. The feasibility of applying this technique for detecting these compounds in spiked water and decontamination emulsion was demonstrated. Detailed characterisation of the degradation products in these two matrices was carried out. The results demonstrated that N-methyldiethanolamine (MDEA), N-ethyldiethanolamine (EDEA) and triethanolamine (TEA) are not the major degradation products of their respective nitrogen mustards. Degradation profiles of nitrogen mustards in water were also established. In verification analysis, it is important not only to develop methods for the identification of the actual chemical agents; the methods must also encompass degradation products of the chemical agents as well so as to exclude false negatives. This study demonstrated the increasingly pivotal role that LC-MS play in verification analysis.     

Detection of Bacterial Neutral Ceramidase in Diabetic Foot Ulcers with an Optimized Substrate and Chemoenzymatic Probes

Ceramidases (CDases) are important in controlling skin barrier integrity by regulating ceramide composition and affording downstream signal molecules. While the functions of epidermal CDases are known, roles of neutral CDases secreted by skin-residing microbes are undefined. Here, we developed a one-step fluorogenic substrate, S-B , for specific detection of bacterial CDase activity and inhibitor screening. We identified a non-hydrolyzable substrate mimic, C6 , as the best hit. Based on C6 , we designed a photoaffinity probe, JX-1 , which efficiently detects bacterial CDases. Using JX-1 , we identified endogenous low-abundance PaCDase in a P. aeruginosa monoculture and in a mixed skin bacteria culture. Harnessing both S-B and JX-1 , we found that CDase activity positively correlates with the relative abundance of P. aeruginosa and is negatively associated with wound area reduction in clinical diabetic foot ulcer patient samples. Overall, our study demonstrates that bacterial CDases are important regulators of skin ceramides and potentially play a role in wound healing.     

Controlled flux behaviour of membrane processes

Controlling ultrafiltration (UF) and microfiltration (MF) membrane fluxes at or around a region where fouling is minimal can provide an interesting and economic operating regime. Selectivity may be enhanced and cleaning may be easier. For a given flux it is sometimes possible to filter a product suspension at the same trans-membrane pressure (TMP) as for pure water (PWP), but this can require a lot of energy input to maintain cross-flow or high shear in other ways if high fluxes are required. The critical flux is the flux above which one starts to observe fouling. By operating at lower cross-flow velocities and just above the critical flux, and thus, with lower TMPs, periodic cleaning can be effected by temporarily stopping permeation. A change in feed rate demands a change in flux which is obtained by temporarily increasing energy inputs. Controlled flux improves macromolecular fractionation. As flux increases the rejection of high molecular weight materials decreases whilst that of lower molecular weight materials decreases. This paper discusses the causes of fouling and the use controlled flux operation to mitigate its effects.