Graphene Nanocomposites Based Electrochemical Sensing Platform for Simultaneous Detection of Multi-drugs

Three reduced graphene oxide nanocomposites were employed to achieve the simultaneous electrochemical determination of multi-drugs including acetaminophen (ACTM), carbendazim (CB) and ciprofloxacin (CFX). All nanocomposite modified electrodes showed improved current responses for three drugs. Notably cauliflower-like platinum nanoparticles decorated reduced graphene oxide modified electrode (or Pt−RGO/GCE) exhibited the best performance in terms of electrochemical stability. Using Pt−RGO/GCE, the linear detect ranges of 30–120 μM, 25–115 μM and 10–25 μM, and detection limit values of 3.49, 2.96, and 1.53 μM were achieved for ACTM, CB and CFX respectively. The electrode was further used for the successful determination of above drugs in tap and river water using differential pulse voltammetry. From the obtained results, we believe that Pt-RGO/GCE is highly promising for the fabrication of robust electrochemical sensors for simultaneously determining ACTM, CB and CFX or similar types of drugs in the future.     

Effects of post-deposition annealing on chemical composition of SiNx film in SiO2/SiNx/SiO2/Si stacked structure

To systematically evaluate the quality of SiN_x films in multi-stacked structures, we investigated the effects of post-deposition annealing (PDA) on the film properties of SiN_x within the SiO₂/SiN_x/SiO₂/Si stacked structure by performing X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), Fourier transform infrared (FT-IR) spectroscopy, and scanning transmission electron microscope–electron energy loss spectroscopy (STEM-EELS) analyses. The XPS results showed that PDA induces the oxidation of the SiN_x layer. In particular, new finding is that Si-rich SiN_x in the SiN_x layer is preferentially oxidized by PDA even in multi-stacked structure. The XRR results showed that the SiN_x layer becomes thinner, whereas the interface layer between the SiN_x layer and Si becomes thicker. It is concluded by STEM-EELS and XPS that this interface layer is SiON layer. The density of N–H and Si–H bonding within the stacked structure strongly depends on the PDA temperature. Our study helps elucidate the properties of SiN_x films in stacked structures from various perspectives.     

Mass spectrometric monitoring of oxidation of aliphatic C6–C8 hydrocarbons and ethanol in low pressure oxygen and air plasmas

Experimental and theoretical studies on the oxidation of saturated hydrocarbons (n‐hexane, cyclohexane, n‐heptane, n‐octane and isooctane) and ethanol in 28 Torr O₂ or air plasma generated by a hollow cathode discharge ion source were made. Ions corresponding to [M + 15]⁺ and [M + 13]⁺ in addition to [M ? H]⁺ and [M ? 3H]⁺ were detected as major ions where M is the sample molecule. The ions [M + 15]⁺ and [M + 13]⁺ were assigned as oxidation products, [M ? H + O]⁺ and [M ? 3H + O]⁺, respectively. By the tandem mass spectrometry analysis of [M ? H + O]⁺ and [M ? 3H + O]⁺, H₂O, olefins (and/or cycloalkanes) and oxygen‐containing compounds were eliminated from these ions. Ozone as one of the terminal products in the O₂ plasma was postulated as the oxidizing reagent. As an example, the reactions of C₆H₁₄^+? with O₂ and of C₆H₁₃⁺ (CH₃CH₂CH⁺CH₂CH₂CH₃) with ozone were examined by density functional theory calculations. Nucleophilic interaction of ozone with C₆H₁₃⁺ leads to the formation of protonated ketone, CH₃CH₂C(=OH⁺)CH₂CH₂CH₃. In air plasma, [M ? H + O]⁺ became predominant over carbocations, [M ? H]⁺ and [M ? 3H]⁺. For ethanol, the protonated acetic acid CH₃C(OH)₂⁺ (m/z 61.03) was formed as the oxidation product. The peaks at m/z 75.04 and 75.08 are assigned as protonated ethyl formate and protonated diethyl ether, respectively, and that at m/z 89.06 as protonated ethyl acetate. Copyright © 2016 John Wiley & Sons, Ltd.     

Highly active polymeric organocatalyst: Chiral ionic polymers prepared from 10,11‐didehydrogenated cinchonidinium salt

Since few examples of 10,11‐didehydrogenated (3‐ethynyl) cinchona alkaloids have been utilized as organocatalysts in asymmetric reaction, we synthesized 10,11‐didehydrogenated cinchonidine. The 3‐vinyl group of cinchonidine was transformed into a 3‐ethynyl functionality. Based on the resulting 10,11‐didehydrogenated cinchonidine, the corresponding quaternary ammonium salt and its dimers were prepared. The ion‐exchange reaction between the quaternary ammonium salt and sodium sulfonate produced the quaternary ammonium sulfonate as a stable ionic compound. Chiral ionic polymers were then synthesized by the ion‐exchange polymerization of the 10,11‐didehydrogenated cinchonidinium salt dimer and a disulfonate. The chiral ionic polymers were found to be capable of efficiently catalyzing the asymmetric alkylation of N‐(diphenylmethylene)glycine tert‐butyl ester. The enantioselectivities obtained with the polymeric catalysts were higher than those obtained with the corresponding monomeric catalyst. Dimers of 10,11‐didehydrogenated cinchonidinium salts were prepared. Treatment of the dimer with disodium disulfonate gave the chiral ionic polymers, which showed high catalytic activity in asymmetric benzylation of N‐(diphenylmethylen)glycine tert‐butyl ester. The polymeric catalysts were reused several times without the loss of catalytic activity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 621–627     

First Cellulose Langmuir‐Blodgett Films towards Photocurrent Generation Systems

Langmuir‐Blodgett films of a cellulose derivative containing porphyrins, porphyrin‐cellulose, were fabricated in order to construct a cellulose‐based molecular photocurrent generation system. On visible light illumination of the LB monolayer film deposited on an ITO electrode, anodic photocurrents were observed with a quantum yield of 1.6% at an applied potential of 0 V versus SCE, and 3.8–4.6% at 0.2–0.3 V versus SCE. These values indicate that the self‐quenching of the photoexcited porphyrins in the cellulose LB film was suppressed, while porphyrin moieties in the LB film had a densely packed structure. This is because the porphyrins are located at a distance of approximately 1.0 nm along the cellulose backbone.

     

Static light scattering from poly(ethylene oxide) in methanol

Static light scattering measurements were performed on dilute solutions of monodisperse poly(ethylene oxide) (PEO) in methanol at 25°C. PEOs of five different molecular weights ranging from nominal M_w = 8.6 × 10⁴ to 9.13 × 10⁵ were used. Linear Zimm plots were obtained for all the PEO samples: no downturn was observed at small angles, indicating that no large aggregates of PEO molecules exist in the solution. From the plots, values of the weight-average molecular weight, M_w, the radius gyration, R_G, and the second virial coefficient, A₂, were successfully determined for respective PEOs. Observed relationship between R_G and M_w indicates that methanol is certainly a good solvent for the polymer. © 1996 John Wiley & Sons, Inc.     

Temperature-induced reversal of proton tautomerism: role of hydrogen bonding and aggregation in 7-hydroxyquinolines

UV-vis absorption spectra of 7-hydroxyquinolines in saturated hydrocarbon solvents were measured at various temperatures between 293 and 77 K. The tautomeric equilibrium was found to reverse when the temperature was lowered. At 293 K, the enol form was exclusively present. As the temperature was lowered, the enol form decreased substantially, and the keto form became predominant. A close examination of the spectral changes suggests that the reversal of the tautomeric equilibrium at lower temperatures proceeds in two steps: aggregation of the enol forms by intermolecular hydrogen bonding and further aggregation of the hydrogen-bonded aggregates.     

Inhibitory effects of 3,3',4,5'-tetrahydroxystilbene and 3,3',4,5'-tetrahydroxybibenzyl, the constituents of Cassia garrettiana on antigen-induced histamine release in vitro.

3,3',4,5'-Tetrahydroxystilbene (I) and 3,3',4,5'-tetrahydroxybibenzyl (II), isolated from the heartwood of Cassia garrettiana Craib (Leguminosae), showed inhibitory effects on antigen-induced histamine release from rat peritoneal mast cells in vitro. The inhibitory effect of I (IC50 = 30.2 microM) was much stronger than that of II (greater than 100 microM). Compound II, as well as I (IC50 = 7.3 microM) reported previously, also inhibited the histamine release from human peripheral basophils induced by anti-immunoglobulin E (IgE) in vitro, and its IC50-value was 68.0 microM. These results suggest that the trans-olefin structure in the molecule may be necessary for I to have an inhibitory effect on histamine release. Considering that disodium cromoglycate did not show any significant inhibitory effect on anti-IgE-induced histamine release from human basophils, the strong inhibitory effects of I in both tests are of considerable interest.