Application of a Modified CuO Nanoparticles Carbon Paste Electrode for Simultaneous Determination of Isoperenaline,Acetaminophen and N‐acetyl‐L‐cysteine

A 1‐[2‐hydroxynaphthylazo]‐6‐nitro‐2‐naphthol‐4‐sulfonate/ CuO nanoparticles modified carbon paste electrode (HNNSCCPE) was constructed and the electro‐oxidation of isoprenaline at the surface of the modified electrode was studied using cyclic voltammetry (CV), chronoamperometry (CHA), and square wave voltammetry (SWV). Under the optimized conditions, the square wave voltammetric peak current of isoprenaline increased linearly with isoprenaline concentrations in the range of 1.0×10^?7 to 7.0×10^?4 M and detection limit of 5.0×10^?8 M was obtained for isoprenaline. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of isoprenaline, acetaminophen and N‐acetyl‐L‐cysteine which makes it suitable for the detection of isoprenaline in the presence of acetaminophen and N‐acetyl‐L‐cysteine in real samples.     

Insights into Electrochemical CO2 Reduction on SnS2: Main Product Switch from Hydrogen to Formate by Pulsed Potential Electrolysis

Tin disulfide (SnS₂) is a promising candidate for electrosynthesis of CO₂-to-formate while the low activity and selectivity remain a great challenge. Herein, we report the potentiostatic and pulsed potential CO₂RR performance of SnS₂ nanosheets (NSs) with tunable S-vacancy and exposure of Sn-atoms or S-atoms prepared controllably by calcination of SnS₂ at different temperatures under the H₂/Ar atmosphere. The catalytic activity of S-vacancy SnS₂ (V_s-SnS₂) is improved 1.8 times, but it exhibits an exclusive hydrogen evolution with about 100 % FE under all potentials investigated in the static conditions. The theoretical calculations reveal that the adsorption of *H on the V_s-SnS₂ surface is energetically more favorable than the carbonaceous intermediates, resulting in active site coverage that hinders the carbon intermediates from being adsorbed. Fortunately, the main product can be switched from hydrogen to formate by applying pulsed potential electrolysis benefiting from in situ formed partially oxidized SnS_2−x with the oxide phase selective to formate and the S-vacancy to hydrogen. This work highlights not only the V_s-SnS₂ NSs lead to exclusively H₂ formation, but also provides insights into the systematic design of highly selective CO₂ reduction catalysts reconstructed by pulsed potential electrolysis.     

Electron affinity and redox potential of tetrafluoro-p-benzoquinone: A theoretical study

The electron affinity of tetrafluoro-p-benzoquinone (2.69 eV) and the mono- (2.10 eV), 2,3-di- (2.29 eV), 2,5-di- (2.28 eV), 2,6-di- (2.31 eV) and tri- (2.48 eV) fluoro derivatives of p-benzoquinone have been calculated via standard ab initio molecular orbital theory at the G3(MP2)-RAD level of theory. Comparison of calculated electron affinities with the available experimental values shows excellent agreement between theory and experiment. The reduction potential of tetrafluoro-p-benzoquinone in acetonitrile vs. SCE (−0.03 V) has been calculated at the same level of theory and employing a continuum model of solvation (CPCM), and is also in excellent agreement with the experimental value (−0.04 V vs. SCE).     

Chlorinated polyethylene nanocomposites using PCL/clay nanohybrid masterbatches

Exfoliated nanocomposites were prepared by dispersion of poly(ε-caprolactone) (PCL) grafted montmorillonite nanohybrids used as masterbatches in chlorinated polyethylene (CPE). The PCL-grafted clay nanohybrids with high inorganic content were synthesized by in situ intercalative polymerization of ε-caprolactone between silicate layers organo-modified by alkylammonium cations bearing two hydroxyl functions. The polymerization was initiated by tin alcoholate species derived from the exchange reaction of tin(II) bis(2-ethylhexanoate) with the hydroxyl groups borne by the ammonium cations that organomodified the clay. These highly filled PCL nanocomposites (25 wt% in inorganics) were dispersed as masterbatches in commercial chlorinated polyethylene by melt blending. CPE-based nanocomposites containing 3-5 wt% of inorganics have been prepared. The formation of exfoliated nanocomposites was assessed both by wide-angle X-ray diffraction and transmission electron microscopy. The thermal and thermo-mechanical properties were studied as a function of the filler content, by differential scanning calorimetry and dynamic mechanical analysis, respectively. The mechanical properties were also assessed by tensile tests. The Young’s modulus of CPE is increased by a decade when a PCL-grafted clay masterbatch is exfoliated to reach 5 wt% of clay in the resulting nanocomposite. The influence of PCL-grafting on the properties of these nanocomposites was investigated by comparison with materials obtained with ungrafted-PCL.     

Ab Initio Theoretical Studies on the Kinetics of Hydrogen Abstraction Type Reactions of Hydroxyl Radicals with CH<Subscript>3</Subscript>CCl<Subscript>2</Subscript>F and CH<Subscript>3</Subscript>CClF<Subscript>2</Subscript>

The hydrogen abstraction reactions from CH₃Cl₂F (R-141b) and CH₃CClF₂ (R-142b) by OH radicals are studied theoretically by semi-classical transition state theory. The stationary points for the reactions are located by using KMLYP density functional method along with 6-311++G(2d,2p) basis set and MP2 method along with 6-311+G(d,p) basis set. Single-point energy calculations are performed by the CBS-Q and G4 combination methods on the geometries optimized at the KMLYP/6-311++G(2d,2p) level of theory. Vibrational anharmonicity coefficients, x _ij , which are needed for semi-classical transition state theory calculations, are computed at the KMLYP/6-311++G(2d,2p) and MP2/6-311+G(d,p) levels of theory. The computed barrier heights are slightly sensitive to the quantum-chemical method. Thermal rate coefficients are computed over the temperature range from 200 to 2000 K and they are shown to be in accordance with available experimental data. On the basis of the computed rate coefficients, the tropospheric lifetime of the CH₃CCl₂F and CH₃CClF₂ are estimated to be about 6.5 and 12.0 years, respectively.     

A review of recent methods for the determination of ranges of feasible solutions resulting from soft modelling analyses of multivariate data

Soft modelling or multivariate curve resolution (MCR) are well-known methodologies for the analysis of multivariate data in many different application fields. Results obtained by soft modelling methods are very likely impaired by rotational and scaling ambiguities, i.e. a full range of feasible solutions can describe the data equally well while fulfilling the constraints of the system. These issues are severely limiting the applicability of these methods and therefore, they can be considered as the most challenging ones. The purpose of the current review is to describe and critically compare the available methods that attempt at determining the range of ambiguity for the case of 3-component systems. Theoretical and practical aspects are discussed, based on a collection of simulated examples containing noise-free and noisy data sets as well as an experimental example.     

Tyrosine sensing on phthalic anhydride functionalized chitosan and carbon nanotube film coated glassy carbon electrode

Phthaloylchitosan (PHCS) has been synthesized by a simple and low-cost method using chitosan and phthalic anhydride as organic precursors by microwave irradiation. Techniques of nuclear magnetic resonance (NMR), FT-IR spectroscopy and transmission electron microscope (TEM) were used to characterize the structure and properties of the Phthaloylchitosan. Moreover, glassy carbon electrode modified with Phthaloylchitosan and carbon nanotube (PHCS–CNT/GCE) was prepared by casting of the PHCS–CNT solution on GCE. The electrochemical behavior of PHCS–CNT/GCE was investigated and compared with the electrochemical behavior of Phthaloylchitosan modified GC (PHCS/GC), carbon nanotube modified GC (CNT/GC) and unmodified GC using cyclic voltammetry (CV). The Phthaloylchitosan film is electrochemically inactive; similar background charging currents are observed at bare GC. Electrochemical parameters, including apparent diffusion coefficient for the Fe(CN)₆^3-/4- redox probe at PHCS–CNT/GCE is comparable to values reported for GCE, CNT/GCE and PHCS/GCE. The PHCS–CNT/GCE sensor responded linearly to tyrosine (Tyr) in the concentration of 1.0 × 10^–6 to 8.0 × 10^–4 M with detection limit of 3.0 × 10^–7 M at 3σ using amperometry. In addition, the PHCS–CNT/GCE displayed good reproducibility, high sensitivity and good selectivity towards the determination of Tyr, making it suitable for the determination of Tyr in clinical and medicine.     

Assembly of Terpenoid Cores by a Simple,Tunable Strategy

Oxygenated, polycyclic terpenoid natural products have important biological activities. Although total synthesis of such terpenes is widely studied, synthetic strategies that allow for controlled placement of oxygen atoms and other functionality remains a challenge. Herein, we present a simple, scalable, and tunable synthetic strategy to assemble terpenoid‐like polycycloalkanes from cycloalkanones, malononitrile, and allylic electrophiles, abundantly available reagent classes.