Transition metal ions-doped polyaniline/graphene oxide nanostructure as high performance electrode for supercapacitor applications

Journal of Solid State Electrochemistry - Polyaniline/graphene oxide (PANI/GO) co-doped with Zn2+ and Fe3+ was synthesized via a simple and low cost one-step chronoamperometry method on stainless...     

γ-aminobutyric acid and collagen peptides as recyclable bifunctional biocatalysts for the solvent-free one-pot synthesis of 2-aminobenzothiazolomethyl-2-naphthols

γ-aminobutyric acid (GABA) and Isinglass a collagen peptide have been utilized as highly efficient bifunctional biocatalysts for the efficient and convenient synthesis of 2-aminobenzothiazolomethyl-2-naphthols through a one-pot three-component Mannich reaction between diverse aldehydes, 2-naphthol and 2-aminobenzothiazole under solvent-free condition in high yields. Moreover, GABA could be recycled and reused at least four times without noticeable loss of its activity.     

Time-domain dielectric relaxation of poly(methyl methacrylate) and nitrile rubber

The time-domain dielectric response (after-effect) of poly(methyl methacrylate) (PMMA) and nitrile butadiene rubber (NBR) to a voltage step (100 V) was measured at varying temperatures. From the variation of the sample capacitanceC with time, we determined the ratioF _d/C, withF _d=(dC/dlnt)_max and C denoting the difference between the initial and the extrapolated equilibrium capacitance values. For PMMA around room temperature (RT) this ratio assumed values similar to those reported for mechanical stress relaxation. With NBR, such values were observed only at temperatures significantly below RT. A modified Kohlrausch-Williams-Watts (stretched exponential) function provided a good fit to the measuredC(t) data.     

Bromodimethylsulfonium bromide mediated Michael addition of amines to electron deficient alkenes

Bromodimethylsulfonium bromide has been found to be an efficient catalyst for the Michael addition of a wide variety of amines to electron deficient alkenes at room temperature. The protocol is very simple and chemoselective. Aliphatic and benzylic amines undergo conjugate addition within a very short period under solvent-free conditions and provide excellent yields of products.     

Regeneration of carbonyl compounds by cleavage of CN bonds under mild and completely heterogeneous conditions

Oximes, hydrazones, semicarbazones and azines are converted to the corresponding carbonyl compounds using a combination of Zr(HSO₄)₄ and wet SiO₂ in good to high yields under completely heterogeneous conditions.     

An earth-abundant bimetallic catalyst coated metallic nanowire grown electrode with platinum-like pH-universal hydrogen evolution activity at high current density

A self-supported and flexible current collector solely made of earth-abundant elements, NiCo layered double hydroxide (LDH) wrapped around Cu nanowires (Cu-Ws) grown on top of commercially available Cu mesh (Cu-m), outperforms the benchmark 40 wt% Pt/C in catalyzing the electrochemical hydrogen evolution reaction (HER). The Cu-m/Cu-W/NiCo-LDH cathode operates both in acidic and alkaline media exhibiting high turnover frequencies (TOF) at 30 mV (0.3 H₂ s⁻¹ in 1 M KOH and 0.32 H₂ s⁻¹ in 0.5 M H₂SO₄, respectively) and minimal overpotentials of 15 ± 6 mV in 1 M KOH and 27 ± 2 mV in 0.5 M H₂SO₄ at −10 mA cm⁻². Cu-m/Cu-W/NiCo-LDH outperforms the activity of 40 wt% Pt/C that needs overpotentials of 22 and 18 mV in 1 M KOH and 0.5 M H₂SO₄, respectively. With a tremendous advantage over Pt/C in triggering proton reduction with fast kinetics, similar mass activity and pH-universality, the current collector demonstrates outstanding operational durability even at above −1 A cm⁻². The high density of electronic states near the Fermi energy level of Cu-Ws is found to be a pivotal factor for efficient electron transfer to the NiCo-LDH catalyst. This class of self-supported electrodes is expected to trigger rapid progress in developing high performance energy conversion and storage devices.

A flexible self-supported electrode made of earth-abundant elements, NiCo layered double hydroxide wrapped around Cu nanowires grown on Cu mesh, outperforms the benchmark 40 wt% Pt/C in catalyzing electrochemical hydrogen evolution reaction.     

Modeling of biliverdin reduction process: regio-specificity and H-bonding

Octa ethyl biliverdin (OEBV) has been employed as a model for natural biliverdin and its geometry has been optimized by using semiempirical (AM1, PM3), DFT, and hybrid ONIOM methods. Geometries and energetics of formation of octa ethyl bilirubin (OEBR) formed by reduction from OEBV via three carbon sites β, γ, and δ have been obtained. It has been shown that γ-OEBR has two configurational isomers (named γ₁ and γ₂), which can convert to each other by internal 1,5-hydrogen shift. The results show that, within the accuracy level of semiempirical methods, all three isomers namely, β, γ₁, and δ-OEBR are of similar stability whereas, at higher level of theory, γ₁-OEBR is less stable than others. Moreover, γ₂-isomer with one more of its pyrrole rings being aromatic can achieve a higher symmetry, and is the most stable among others by at least 5–6 kcal mol⁻¹ based on various methods employed. It is interesting to note that the ridge-tile conformation, which has been confirmed for natural bilirubin was not observed for calculated geometries of γ₁- and γ₂-isomers. A conformational analysis show that an energy barrier of 25 kcal mol⁻¹ must be surmounted for γ₂ to obtain the ridge-tile geometry.

OEBV was synthesized and purified from octa ethyl porphyrin iron (III) chloride, and was reduced to OEBR by sodium borohydride (NaBH₄). Chemical reduction of OEBV with NaBH₄ was followed in CDCl₃ and CD₃OD solutions and the product was characterized by ¹H NMR and UV–Vis spectroscopy. The results show that γ₂-isomer as the major product, forms along with γ₁ via an equilibrium tautomerization reaction.     

Reaktion von primären Alkylhydroperoxiden mit Amidoschwefelsäurechlorid: Alkyl(amidosulfonyl)peroxide

The novel peroxides H₂NSO₂OOCH₂ R (1 a:R=CH₂CH₃;1 b:R=CH₂CH₂CH₃) are obtained by reaction of sulphamoyl chloride with the appropriate hydroperoxides in the presence of pyridine (temperature below –30 °C, solvent diethyl ether). The solvent-free liquids1 deflagrate at ca. 0 °C. Hydrolysis or ammonolysis of1 generates the hydroperoxide and sulphamic acid or sulphamide, respectively. Controlled thermolysis of1 affords sulphamic acid and carbonyl compounds, i.e. propanal andn-propyl propanoate from1 a, butanal, 2-methylpropanal andn-butyln-butyrate from1 b. These products suggest a nonradical cyclic decomposition path-way.

     

Use and Evaluation of Newly Synthesized Fluorescence Probes to Detect Generated OH• Radicals in Fibroblast Cells

Reactive oxygen species (ROS) are pro-oxidant molecules synthesized in body with various functions and are essential for life. Increasing in reactive oxygen species or decreasing in antioxidants level cause oxidative stress which is very harmful. OH? radical is one of ROS’s, with tendency to bind to lipids, DNA and proteins which cause irreversible damage in cells. The most devastating consequences related to excess OH? radicals occur via direct binding to nucleic acids and proteins. Quantification of this high reactive radical with short life time is difficult. Electron Spin Resonance, Fluorescence, and Luminescence Spectroscopy are commonly used to determine the level of ROS. Fluorescence Probes have higher specificity and sensitivity with their excellent sensors to detect ROS’s compare to the other methods. Also, there are different probes specifically designed for each radical. The purpose of this study was to identify the probe better suiting for detection of OH? radical levels. The two most recommended fluorescence probes, 2-[6-(4 V-Hydroxy) phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (HPF) and coumarin-3-carboxylic acid (3-CCA) to determine OH? radical levels were compared. Following the formation of OH? radical with Fenton reaction, HPF and 3-CCA probes were added to cells and spectrofluorometric measurements were performed in their respective wavelengths. The mean amplitude of fluorescence for HPF was 32.72?±?2.37 F.I (n?=?40) and for 3-CCA was 52.11?±?0.5 F.I (n?=?40). This difference was statistically significant. 3-CCA also demonstrated more stable measurements at different days compered to HPF.