Ion chromatographic separation of hydrogen ion and other common mono- and divalent cations

We introduced an approach to the ion chromatographic determination of common mono- and divalent cations including hydrogen ion and demonstrated the ability of a C30 column dynamically coated first with dodecylsulfate and then with 18-crown-6 ether to separate the cations by ion-exchange mechanism. Using an ethylenediamine solution containing a small concentration of 18-crown-6 ether and lithium dodecylsulfate at pH 6.2 as eluent, the cations were eluted in the order Li < Na+ < NH4+ < H+ < K+ < Mg2+ < Ca2+ with symmetrical peaks. The conductivity vs. concentration plots were linear about three orders of magnitude, from millimolar to micromolar; and the detection limits were all < 0.6 microM. Rainwater was analyzed directly using this ion chromatographic system with satisfactory results.     

{Pt

Prolonged evacuation of [{Pt(CO)(3)}(2)](2+) (1), the first homoleptic, dinuclear, cationic platinum(I) carbonyl complex, results in reversible disproportionation. Complex 1 was formed by dissolution of PtO(2) in concentrated H(2)SO(4) under an atmosphere of CO [Eq. (a)], and completely characterized by NMR ((13)C, (195)Pt), IR, and Raman spectroscopy.     

Cyano-bridged hexanuclear Fe4M2 (M = Ni, Co, Mn) clusters: spin-canted antiferromagnetic ordering of Fe4Ni2 cluster

Heterobimetallic hexanuclear cyano-bridged complexes, [{Fe(Tp)(CN)3}4{M(MeCN)(H2O)2}(2)].10H2O.2MeCN [M = Ni (1), Co (2), Mn (3); Tp = hydrotris(1-pyrazolyl)borate], have been synthesized in H2O-MeCN solution. Complexes 1-3 are isostructural and hexanuclear with [{Fe(Tp)(CN)3}4{M(MeCN)(H2O)2}2] units linked by hydrogen bonds to form a 2D-structure in the solid state. Complex 1 is a canted antiferromagnet that undergoes a field-induced spin-flop-like transition at approximately 1 T and 2 K. At 4.45 K 1 has a transition to paramagnetic state of noninteracting S = 4 magnetic clusters. However, 2 and 3 show antiferromagnetic intracluster coupling. Facile loss of solvent from 2 alters the local symmetry resulting in changing the intracluster interaction from antiferro- to ferromagnetic.     

DOPING LEVEL INCREASE OF POLY(3-METHYLTHIOPHENE)FILM DURING ELECTROCHEMICAL POLYMERIZATION PROCESS

The Raman spectra of poly(3-methylthiophene) (PMeT) films with different thicknesses, which have beenelectrochemically deposited on a flat stainless steel electrode surface by direct oxidation of 3-methylthiophene in borontrifluoride diethyl etherate (BFEE) at a constant applied potential of 1.38 V (versus SCE), have been investigated byexcitation with a 633-nm laser beam. The spectroscopic results demonstrated that the doping level of PMeT film wasincreasing during film growth. This finding was also confirmed by electrochemical examination. Moreover, the Raman bandsassigned to radical cations and dications in doped PMeT films were found approximately at 1420 and 1400 cm~(-1),respectively. Radical cations and dications coexist on the backbone of PMeT as conductive species and their concentrationsincrease with the increase of doping level. Successive cyclic voltammetry was proved to be an effective approach toimproving the doping level of as-grown thin compact PMeT film.     

Enhanced electrical conductivity in chemically modified carbon nanotube/methylvinyl silicone rubber nanocomposite

Chemically modified multiwalled carbon nanotubes/methlyvinyl silicone rubber (m-MWNT/VMQ) nanocomposites with relatively good dispersion of nanotubes were prepared by treating the surface of MWNT using γ-aminopropyltriethoxy silane (KH550). Significant enhanced electrical conductivity was discovered in the m-MWNT/VMQ nanocomposites. The results could be attributed a strong interaction between m-MWNT and VMQ which was from the chemically modification of the surface for MWNT. The electrical property was also discussed in order to understand the percolation and electrical transport mechanism. The m-MWNT/VMQ nanocomposites with high conductivity in this study are promising application as one of novel functional materials.     

The morphological effects upon enzymatic degradation of poly(butylene succinate-co-butylene terephthalate)s (PBST)

In this work, the enzymatic degradation of poly(butylene succinate-co-butylene terephthalate) (PBST) copolyesters was studied using the lipase from Pseudomonas (Lipase PS^®). The biodegradation behavior was found to strongly depend on the overall impacts of several important factors as the BT comonomer structure and molar content, thermal characteristics, morphology, the enzyme-substrate, and so forth. Further, the biodegraded residual film samples were allowed to be analyzed by means of gel permeation chromatography (GPC), proton nuclear magnetic resonance (¹H NMR), differential scanning calorimeter (DSC), small angle X-ray scattering (SAXS), and scanning electron microscope (SEM). On the experimental evidences, an exo-type mechanism of enzymatic chain hydrolysis preferentially occurring in the amorphous region was suggested for the PBST film samples.     

Ruthenium-based Conjugated Polymer and Metal-organic Framework Nanocomposites for Glucose Sensing

Many studies have focused on effective ways to exploit enzyme immobilization on an electrode surface to help improve the performance of enzymatic electrochemical biosensors. Herein, a novel glucose sensor was fabricated by immobilizing glucose oxidase (GOx) onruthenium-based conjugated polymer (CP) and metal-organic framework (MOF) nanocomposites. This has not only reduced the applied potential to 0.2 V (vs. Ag/AgCl), but also improved the effective surface area for enzyme immobilization.PPG@Ru@UiO-66-NH₂ was tailored by controlled chemical synthesis from a pre-synthesized water-soluble conjugated polymer (poly(N-phenylglycine)) and metal-organic framework (UiO-66-NH₂). The resulting nanocomposites were characterized using Fourier transform infrared spectroscopy, X-ray fluorescence, scanning electron microscopy, and cyclic voltammetry. The PPG@Ru@UiO-66-NH₂/GOx coated electrodedisplayed a linear measurementrange for glucose from 1 mM to 10 mM, with a sensitivity of 45.92 μA ⋅ mM⁻¹cm⁻¹ and limit of detection of5 μM( ). Furthermore, the practical application of the fabricatedglucosesensor was tested in simulative blood samples with satisfactoryaccuracy. This approach alsoopens a new door for applications regarding both enzymatic electrochemical biosensors and enzymatic biofuel cells (EBFCs).     

A convenient catalytic approach to synthesize straight boron nitride nanotubes using synergic nitrogen source

Straight boron nitride nanotubes (BNNTs) with pure hexagonal phase were conveniently prepared by heating the mixture of Mg(BO₂)₂ · H₂O, NH₄Cl, NaN₃ and Mg powder in an autoclave at 600 °C for 20–60 h. These BNNTs had diameters mainly ranging 30–300 nm and lengths up to 5 μm, and a majority of them had at least one closed end. Besides the traditional end tips, additional cone-like tips were frequently found to be attached on the BNNTs. The effects of temperature, reactants and the possible mechanism of the catalytic formation of the BNNTs are discussed.     

Photochemical attachment of organic monolayers onto H-terminated Si(111): radical chain propagation observed via STM studies

Photochemical reactions of terminal alkenes with hydrogen-terminated silicon surfaces are being used by many groups to produce covalently attached organic monolayers with a wide range of terminal functionalities. Despite the considerable activity in this area, the mechanism for these reactions has not been definitively established. Here we present STM and HREELS data on a sequence of partially reacted samples, showing the progress of the reaction. The attachment reaction is found to proceed via formation of irregularly shaped islands that appear to grow by a pseudorandom walk process. These data support a radical chain propagation mechanism previously suggested for this reaction. However, since the photons employed here (447 nm) lack sufficient energy for Si-H bond cleavage, an alternate mechanism for initiating the chain reaction appears to be required.