Thermal,mechanical and water barrier properties of graphene oxide/polyvinyl alcohol/polyol composite films

The novel polymer composite of polyvinyl alcohol (PVA), polyol(PO) and graphene oxide (GO) was used to prepare the PVA/PO and GO/PVA/PO with different weight percents of GO (0.5 and 1% denoted as (0.5 wt%)GO/PVA/PO and (1 wt%)GO/PVA/PO, respectively) through solution casting blend technique. The structure–properties of all used films were confirmed by scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and mechanical properties. The SEM results exhibited the uniform and homogeneous dispersion of GO in the PVA/PO blend matrix. The TEM and XRD analysis confirmed the structure and exfoliation of GO nanosheets, respectively. Thermal stability suggested that (0.5 wt%)GO/PVA/PO and (1 wt%) GO/PVA/PO films are more stable than PVA/PO. The tensile strength of (0.5 wt%)GO/PVA/PO and (1 wt%)GO/PVA/PO films reached 270.5% and 1349.6%, respectively, which are higher than that of the PVA/PO film. The decrease in the water absorption (WA) of GO/PVA/PO was found from 110.5 to 38.4%. The physico-mechanical properties of used films suggested that the prepared GO/PVA/PO blend composite films can be applied in food packaging areas.     

Visible-light-activated selective synthesis of sulfoxides via thiol-ene/oxidation reaction cascade

A convenient, highly selective and metal-free synthesis of sulfoxides from alkenes and thiols using NHPI as an inexpensive and reusable organophotoredox catalyst is reported. The protocol involves radical thiol-ene/oxidation reaction cascade and utilizes visible light and air (O₂) as inexpensive, readily available, non-toxic and eco-sustainable reagents to afford up to 96% yields of the product at room temperature.     

Nanohybrid Comprising Gold Nanoparticles – MoS2 Nanosheets for Electrochemical Sensing of Folic Acid in Serum Samples

Folic acid (FA) deficiency is associated with several clinical conditions such as megaloblastic anemia, neuropsychiatric, and pregnancy-related syndromes, this makes FA an important metabolite to be monitored. We have fabricated an electrochemical biosensor based on gold nanoparticles decorated molybdenum disulfide nanosheets (AuNPs−MoS₂NSs) nanocomposite as a transducer matrix for specific and rapid electrochemical detection of FA. Differential pulse voltammetry (DPV) studies displayed a rapid analytical response of the fabricated AuNPs−MoS₂NSs/GCE sensor probe towards FA in a wide concentration range of 0.001–100 μM with a very low detection limit of 0.72±0.03 nM. The selectivity of the fabricated sensor probe has been examined in the presence of interferents such as dopamine, uric acid, ascorbic acid, glucose, and urea. The clinical potential of the fabricated biosensor was established by monitoring FA in human serum samples. The developed AuNPs−MoS₂NSs/GCE sensor probe showed high reproducibility and stability, indicating its promise for FA detection in clinical settings.     

Practical Access to meta-Substituted Anilines by Amination of Quinone Imine Ketals Derived from Anisidines: Efficient Synthesis of Anti-Psychotic Drugs

Reversing the conventional site-selectivity of C−H activation provides efficient retrosynthetic disconnections to otherwise unreactive bonds. Described herein is the Brønsted acid-catalyzed reaction that selectively performs meta-amination of anisidines with aliphatic-, heterocyclic- and aromatic amines in a one-pot procedure. In addition to dramatically simplifying the synthesis of meta-substituted anilines, our approach has the advantage of the scalability and remarkable functional group tolerance, including late-stage functionalization of pharmaceutical compounds and natural products. The control experiments and detailed computational analysis provide insight into the reaction mechanism and the origin of meta-selectivity. The protocol extended to the synthesis of challenging tri-aminated arenes and successfully applied for the efficient synthesis of 5-HT6 receptor antagonists, the anti-psychotic drugs viz.. SB-214111, SB-258510, and specifically, anti-schizophrenic drug SB-271046.     

Some Diels–Alder adducts of 6-vinyl-1-oxa-4-thiaspiro[4.5]dec-6-ene

6-Vinyl-1-oxa-4-thia­spiro­[4.5]­dec-6-ene has been reacted with dienophiles, such as N-phenyl­male­imide (NPM), N-methyl­triazoline-2,5-dione (MTAD) and di­methyl­acetyl­ene di­carboxyl­ate (DMAD), to assess the 1,3-diastereofacial selection caused by the acetal function. In each case, a mixture of two diastereoisomers was produced. The crystal structures of the products of the addition of NPM and MTAD syn to the acetal oxy­gen, 2-phenyl-2,3,3a,4,5,5a,6,7,8,9,9a,9b-dodeca­hydro-1H-benz­[e]­iso­indole-6-spiro-2′-[1′,3′]­oxa­thiol­ane-1,3-dione, C₂₀H₂₁NO₃S, (IIa), and 2-methyl-5,7,8,9,10,10a-hexa­hydro-1H-1,2,4-triazolo­[1,2-a]­cinnoline-7-spiro-2′-[1′,3′]­oxa­thiol­ane-1,3-dione, C₁₃H₁₇N₃O₃S, (IIIa), respectively, and the product of the addition of DMAD syn to the acetal sulfur, di­methyl 1,2,3,4,4a,7-hexa­hydro­naphthalene-1-spiro-2′-[1′,3′]­oxa­thiol­ane-5,6-di­carboxyl­ate, C₁₆H₂₀O₅S, (IVb), have been determined. All three structures are composed of independent mol­ecules separated by normal van der Waals distances. The 1-oxa-4-thia heterocyclic ring has an envelope conformation in the three structures and the S—Csp³ bond distances differ significantly from each other, as observed in comparable structures; the remaining molecular dimensions are as expected.     

d/f-Polypnictides Derived by Non-Classical Ln2+ Compounds: Synthesis,Small Molecule Activation and Optical Properties

Reduction chemistry induced by divalent lanthanides has been primarily focused on samarium so far. In light of the rich physical properties of the lanthanides, this limitation to one element is a drawback. Since molecular divalent compounds of almost all lanthanides have been available for some time, we used one known and two new non-classical reducing agents of the early lanthanides to establish a sophisticated reduction chemistry. As a result, six new d/f-polyphosphides or d/f-polyarsenides, [K(18-crown-6)] [Cp′′₂Ln(E₅)FeCp*] (Ln=La, Ce, Nd; E=P, As) were obtained. Their reactivity was studied by activation of P₄, resulting in a selective expansion of the P₅ rings. The obtained compounds [K(18-crown-6)] [Cp′′₂Ln(P₇)FeCp*] (Ln=La, Nd) are the first examples of an activation of P₄ by a f-element-polypnictide complex. Additionally, the first systematic femtosecond (fs)-spectroscopy investigations of d/f-polypnictides are presented to showcase the advantages of having access to a broader series of lanthanide compounds.     

Thermally Activated Delayed Fluorescence and Phosphorescence Quenching in Iminophosphonamide Copper and Zinc Complexes

The synthesis of copper and zinc complexes of four variably substituted iminophosphonamide ligands is presented. While the copper complexes form ligand-bridged dimers, the zinc compounds are monomeric. Due to different steric demand of the ligand the arrangement of the ligands within the dimeric complexes varies. Similar to the structurally related iminophosphonamide complexes of alkali metals and calcium, the steady-state and time-resolved photoluminescence (PL) of four of the seven compounds studied here as solids in a temperature range of 5–295 K can be described within the scheme of thermally activated delayed fluorescence (TADF). Accordingly, they exhibit bright blue-green phosphorescence at low temperatures (<100 K), which turns into delayed fluorescence by increasing the temperature. However, unusually, the fluorescence is practically absent in two copper complexes which otherwise still conform to the TADF scheme. In these cases, the excited singlet states decay essentially non-radiatively and their thermal population from the corresponding low-lying triplet states efficiently quenches PL (phosphorescence). Three other copper and zinc complexes only exhibit prompt fluorescence, evidencing a wide variation of photophysical properties in this class of compounds. The excited states of the copper complex with especially pronounced phosphorescence quenching were also investigated by low-temperature time-resolved infrared spectroscopy and quantum chemical calculations.     

Investigation of sub‐micron size cenosphere fillers and filler loading on the mechanical and tribological peculiarity of polyester composites

This paper investigates the effect of sub‐micron size cenosphere filler and filler loading on mechanical and dry sliding wear property of polyester composites. Composites are fabricated by filling with 10 and 20 wt% of 800 and 200‐nm size of cenosphere filler particles. Neat polyester composite is also prepared for comparison analysis. Dry sliding wear test is conducted for these composites over a range of sliding distance with different sliding velocities and applied loads on a pin‐on‐disc wear test machine. Taguchi methodology and analysis of variance (ANOVA) is used to analyze the friction and wear characteristics of the composites. The artificial neural network (ANN) approach is implemented to the friction and wear data for corroboration. In this work, mechanical properties of composites such as hardness, tensile strength, tensile modulus, flexural strength, and compressive strength revealed that mechanical properties and wear resistance of the composites increase with a decrease in the particle size. The measured Young's moduli are comparable to standard theoretical prediction models. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand the dominant wear mechanisms. Finally, optimal factor settings are determined using a genetic algorithm (GA). Copyright © 2017 John Wiley & Sons, Ltd.