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      Volume 131, Issue 5

      May 2019

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    • Gold nanoparticles decorated silicate sol-gel matrix embedded reduced graphene oxide and manganese ferrite nanocompositematerials- modified electrode for glucose sensor application

      T RAVINDRAN MADHURA G GNANA KUMAR RAMASAMY RAMARAJ

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      Gold nanoparticles decorated on silicate sol-gel matrix embedded manganese ferrite (MnFe2O4)-reduced graphene oxide (rGO) nanocomposites were synthesized through a facile chemical method. The prepared sampleswere characterized by using powder X-ray diffraction (XRD),UV–vis absorption spectroscopy (UV-VIS), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) analyses. The Au nanostructures on rGO-MnFe2O4improved the electrocatalytic activity of the rGO-MnFe2O4@Au composite-materials-modified electrodes towards glucose oxidation. Cyclic voltammetry and amperometric methods were used to evaluate the electrocatalytic activity of the rGO-MnFe2O4@Au modified electrodes towards glucose oxidation in 0.1 MNaOH at a less-positive potential (0.2 V) in the absence of any enzyme or redox mediator. The nanocompositemodified electrode (GCE/EDAS/rGO-MnFe2O4@Au) was successfully used for the amperometric sensing ofglucose and the experimental detection limit of 10 μM glucose was observed. The common interfering agents did not interfere with the detection of glucose. The present sensor showed good stability, reproducibility, and selectivity. The nanocomposite-modified electrode was successfully used for the determination of glucose in the urine sample.

    • Specific detection of hypochlorite: a cyanine based turn-on fluorescent sensor

      SOHAM SAMANTA SENJUTI HALDER UTSAB MANNA GOPAL DAS

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      Judiciously designed cyanine based fluorogenic probe (L) can exhibit interesting solvent polarity induced isomerization. The probe displayed a highly selective TURN-ON fluorescence response towards hypochlorite among various reactive oxygen species (ROS) and analytes in a mixed aqueous medium. Thesensing process was attributed to the formation of a probe-OCl adduct which results in restricting the donor acceptor extended conjugation. The detection limit was found to be as low as 3 μM. The proposed sensing mechanism is supported by mass spectrometric analysis and HPLC study

    • Deformation of E4 (E = P, As, Sb) tetrahedron structures via doping two atoms with elements from group 13: a study of the pseudo-Jahn–Teller effect

      ALI REZA ILKHANI

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      White phosphorus and yellow arsenic are the most famous inorganic four-membered tetrahedral molecules in nature. Due to the recent application of the tetrahedron-based system as a carrier in drug delivery, the manipulation of the E4 (E = P, As, Sb) tetrahedron structure by replacing two of the E atoms by elements from group 13 (D = Al, Ga, In) has been computationally explored. The symmetry-breaking phenomenon induced by the pseudo-Jahn–Teller effect was reported in the E2D2 tetrahedral structure. State averaging of thefour low-lying electronic states along the a2 deformation normal coordinate for the series in CASSCF(4,4)/cc–pVTZ–(PP) was carried out to formulate the (1A1 + 2A1 + 1A2) ⊗ a2 PJTE problem and their corresponding coupling constants estimated by fitting the obtained state energies. Moreover, the deformed C2v tetrahedral configuration of ED2 can be restored by i ) the protonation of the D atoms or ii) trapping a noble gas dication in the center cavity cage of the systems. Furthermore, the calculated thermodynamic properties of the E2D2 show that the protonation reaction acts as a spontaneous process fulfilling the ∆G‹0 conditions and the considered series obeys the Bronsted–Lowry base behaviors.

    • An imine-based colorimetric chemodosimeter for the detection of hypochlorite (ClO- ) in aqueous media: its application in test strips and real water samples

      DONGJU YUN JU BYEONG CHAE CHEAL KIM

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      A highly selective colorimetric chemodosimeter ASAD, (E)-2-((4-(diethylamino)-2-hydroxybenzylidene) amino)-5-methoxybenzenesulfonic acid, was readily synthesized and characterized. The probe ASAD could selectively recognize hypochlorite (ClO-) through an oxidative cleavage of C=N bond with acolor change from yellow to colorless and detected it down to a low concentration of 0.95 μM. Importantly, ASAD could be employed as a practical and efficient optical sensor for ClO− in test strips and water samples. Moreover, the detection process of ASAD to hypochlorite was demonstrated by UV-vis spectroscopy, NMR titration and theoretical calculations.

    • Olefin metathesis of fatty acids and vegetable oils

      VYSHNAVI YELCHURI K SRIKANTH R B N PRASAD M S L KARUNA

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      The article reviews various olefin metathesis reactions namely self-metathesis (SM), crossmetathesis (CM), acyclic diene metathesis (ADMET) polymerization, ring closing metathesis (RCM) and ring opening metathesis (ROM) reactions for the synthesis of a variety of platform chemicals with potential industrialapplications from vegetable oils and fatty acids. Different fatty acids employed for various metathesis reactions were oleic, linoleic, linolenic, eicosenoic, erucic, petroselinic, sterculic, undecenoic and ricinoleic acids, while vegetable oils used were Helianthus (sunflower), Brassica napus (rapeseed), Glycine max(soybean), Hevea brasiliensis (rubber), Butea monosperma(palash), Nicotiana tabacum (tobacco) and Sterculia foetida (jangli badam). Even though Grubbs’ catalysts were employed formost of the reactions, other catalysts such as rhenium,molybdenum and tungsten based have also been used for selective reactions of vegetable oils and fatty acids.The article reviews some of the mechanistic pathways involved in the generation of unusual intermediates from fatty acids and triglycerides.

    • Synergistic and antagonistic co-antioxidant effects of flavonoids with trolox or ascorbic acid in a binary mixture

      LEVON A TAVADYAN SEYRAN H MINASYAN

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      By using the ORAC method, the values of the antiperoxyradical capacity of binary mixtures of bioflavonoids (quercetin, rutin, morin and naringin) with trolox or ascorbic acid, and individual antioxidants in the aqueous medium were determined. Through these values and the data of square wave voltammetry (SWV) method, the non-additive effects in the binary mixtures were revealed. Synergy in the binary mixtures was observed in the presence of flavonoids (rutin and naringin) having O-glucosyl group in the molecular structure. Flavonoids without a glucosyl group in the molecular structure (quercetin and morin), having relatively small values of the oxidation potential and low bond dissociation enthalpy (BDE) of the most reactive OH group in the mixtures with trolox or ascorbic acid, have shown antagonistic effects. In this work, ‘skeletal’ kinetic models are considered, explaining the non-additive effect of co-antioxidants under study, conditioned by the possibility of antioxidant regeneration with high (synergy) or low (antagonism) antiradical capacity

    • Beryllium ion sensing through the ion pair formation between the electrochemically reduced ferrocenyl naphthoquinone radicals and Be2+ ions

      SECIL KIRLANGIC ATASEN YUSUF ALCAY OZGUR YAVUZ BARIS YUCEL ISMAIL YILMAZ

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      We explored the mechanistic aspects of ion pair formation between electrochemically reduced radicals (Fc–cnq–1a•−/Fc–cnq–1b•−) and dianions (Fc–cnq–1a2−/Fc–cnq–1b2−) of ferrocenyl naphthoquinones (Fc–cnq–1a and Fc–cnq–1b) and several metal ions by cyclic voltammetry (CV), squarewave voltammetry (SWV) and spectroelectrochemistry, for the first time. The experiments demonstrated that Fc–cnq–1a2−/Fc–cnq–1b2− were moderately affected with Na+, K+ and Cs+ by slightly shifting to the anodic side, but were strongly influenced with Li+ ion. Fc–cnq–1a•−/Fc–cnq–1b•− were not affected by alkali metal ions, indicating no ion pair formation between the radicals and these ions. Fc–cnq–1a2-/Fc–cnq–1b2- was not evolved in the presence of Be2+, Mg2+ and Ca2+, but Fc–cnq–1a•−/Fc–cnq–1b•− appeared with theircathodic waves, and participated with intermediates, [(Fc–cnq–1b)2•−–Be2+ and [(Fc–cnq–1a).-–Cl]. The most pronounced effect on the ion-pair formation of the Fc–cnq–1a•−/Fc–cnq–1b•− was observed in Be2+,indicating that Fc–cnq–1a or Fc–cnq–1b can selectively sense ultra-trace amount of Be2+ (LOD=3.6 ppb)among the other metal ions with SWV titration, for the first time, based on the strong ion pair formation reaction between the radicals and Be2+.

    • Synthesis of micro-mesoporous molecular sieve ZSM-5/SBA-15: tuning aluminium content for tert-butylation of phenol

      LING XU QIANG ZHANG MIAO ZHANG LILI MAO JING HU ZONGRUI LIU YAN XIE

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      Micro-mesoporous ZSM-5/SBA-15 molecular sievewas derived from mesoporous molecular sieves SBA-15 by hydrothermal crystallization approach. The silica-alumina ratio significantly affects the structure and catalytic performance of ZSM-5/SBA-15. When the nSi/nAl is less than 25, the two-dimensional hexagonal pore structure of SBA-15 keeps intact with relatively low crystallinity of the pore wall. However, when the nSi/nAl is larger than 50, the SBA-15 pores are severely damaged. When nSi/nAl is 25, the catalyst ZSM-5/SBA-15 retainsrelatively good pore structure and shows excellent catalytic performance with 96.2% phenol conversion and 53.5% selectivity to 2,4-ditert-butyl phenol in the tert-butylation of phenol.

    • Are water-xylitol mixtures heterogeneous? An investigation employing composition and temperature dependent dielectric relaxation and time-resolved fluorescence measurements

      EJAJ TARIF KALLOL MUKHERJEE ANJAN BARMAN RANJIT BISWAS

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      Aqueous xylitol solutions at six different concentrations were studied employing dielectric relaxation (DR) and time-resolved fluorescence (TRF) measurements in the temperature range 295–323 K. The focus was to explore the solution heterogeneity aspect via monitoring the viscosity coupling of the average relaxation rates at various temperatures. TRF measurements were done using both hydrophobic and hydrophilic probes to explore the preferences, if any, for solute locations in these binary mixtures. Energy-selective population excitations and the corresponding fluorescence emissions did not suggest any significant spatial heterogeneity in solution structure within the lifetimes of these probes. DRmeasurements and TRF experiments indicated mild deviations from the hydrodynamic viscosity dependence of themeasured relaxation rates. All these suggestmild spatiotemporal heterogeneity for these water-xylitol mixtures in the temperature range considered. In addition, DRtimescales appear to originate from reorientational and H-bond relaxation dynamics, excluding the possibilityof full molecular rotations

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