The Effect of Flower-Like Magnesium Hydroxide Nanostructure on the Thermal Stability of Cellulose Acetate and Acrylonitrile–Butadiene–Styrene

Flower-like magnesium hydroxide (Mg(OH)₂) nanostructures were synthesized via a simple hydrothermal reaction at relatively low temperature. The Mg(OH)₂ nanostructures were then added to acrylonitrile–butadiene–styrene (ABS) and cellulose acetate (CA) polymers. The effect of Mg(OH)₂ nanostructures on the thermal stability of the polymeric matrixes has been investigated. The thermal decomposition of the nanocomposites shifts towards higher temperature in the presence of the Mg(OH)₂. The enhancement of thermal stability of nanocomposites is due to endothermically decomposition of magnesium hydroxide that releases of water and dilutes combustible gases. Nanostructures and nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), UL-94 test and limiting oxygen index (LOI) analysis.     

Hybrid-DFT Study and NBO Analysis of the Stereoelectronic Interaction Effects (Associated with the Anomeric Effects) on the Conformational Properties of 2,3,5,6-Tetrahalo-1,4-dioxanes and Their Analogs Containing S and Se Atoms

NBO analysis and hybrid density functional theory–based method (B3LYP/6-311+G**) was used to study the anomeric effects (AE), dipole–dipole interactions, and steric repulsion effects on the conformational properties of 2,3,5,6-tetrahalo-1,4-dioxane [halo = F (1), Cl (2), Br (3)], 2,3,5,6-tetrahalo-1,4-dithiane [halo = F (4), Cl (5), Br (6)], and 2,3,5,6-etrahalo-1,4-diselenane [halo = F (7), Cl (8), Br (9)]. B3LYP/6-311+G** results revealed a strong axial preference in compounds 1–3. Gibbs free energy difference (G _eq–G _ax) values (e.g., ΔG _eq-ax) between the axial and equatorial conformations of compound 1 to compound 3 are 8.19, 3.86, and 3.13 kcal mol^?1, respectively, as calculated by the B3LYP/6-311+G** level of theory. On the other hand, the NBO analysis of donor–acceptor (bond–antibond) interactions revealed that the AE for compounds 1–3 are ?12.26, ?16.46, and ?18.11 kcal mol^?1, respectively. Contrary to the increase of the AE values from compound 1 to compound 3, the increase of the steric repulsions (e.g., 1,3-syn-axial repulsions) could fairly explain the decrease of the axial conformation stability in compounds 1–3 compared to their equatorial conformations. Further, the correlations between the AE, structural parameters, and conformational behavior of compounds 4–9 have been investigated.     

Development of a needle trap device packed with titanium‐based metal‐organic framework sorbent for extraction of phenolic derivatives in air

We developed a novel method of needle trap device packed with titanium‐based metal‐organic framework for the extraction of phenolic derivatives in air followed by gas chromatography‐flame ionization detector analysis. The synthetized adsorbent was packed inside a 22‐gauge spinal needle. This method was first tested at laboratory scale, and then was used for field sampling of phenolic derivatives in air. A glass chamber placed on a heater at 60°C was used to provide different concentrations of phenolic derivatives. The desorption conditions and breakthrough volume were optimized using response surface methodology. The limit of detection and limit of quantitation of the proposed method were estimated to be in the range of 0.001–0.12 and 0.003–0.62 ng/mL, respectively, indicating a high sensitivity for the suggested sampler. Storing the packed needle trap device in a refrigerator at 4?C for 60 days did not dramatically affect the storage stability. Our findings indicated that there was a high correlation coefficient (R² = 0.99) between the measurement results of this method and the NIOSH recommended method (XAD‐7 sorbent tube). Therefore, it can be concluded that the needle trap device packed with titanium‐based metal‐organic framework can be used as a efficient method for extraction of phenolic derivatives in air.     

Preparation and evaluation of a new neurotensin analog labeled with 99mTc for targeted imaging of neurotensin receptor positive tumors

Neurotensin receptors are overexpressed in several human tumors and can be targets for tumors diagnosis and therapy. In this study, a new neurotensin analogue was labeled with ^99mTc via HYNIC and tricine/EDDA as coligands and investigated further. [HYNIC⁰, Gly⁷, Lys⁹, d-Tyr¹¹]-Neurotensin (7–13) was synthesized using a standard Fmoc strategy. Labeling with ^99mTc was performed at 100 °C for 10 min and radiochemical analysis involved ITLC and HPLC methods. The stability of radiopeptide was checked in the presence of humane serum at 37 °C up to 24 h. The receptor bound internalization and externalization rates were studied in neurotensin receptor expressing HT-29 cells. Biodistribution of radiopeptide was studied in nude mice bearing HT-29 tumor. Labeling yield of 98.6 ± 0.54 % (n = 3) was obtained corresponding to a specific activity of 81 MBq/nmol. Peptide conjugate showed good stability in the presence of human serum. The radioligand showed specific internalization into HT-29 cells (12.43 ± 0.52 % at 4 h). In biodistribution studies, a receptor-specific uptake was observed in neurotensin receptor positive organs so that after 1 h the uptakes in mouse intestine and tumor were 0.87 ± 0.16 and 0.63 ± 0.12 % ID/g respectively.     

Efficient thioacetalisation of carbonyl compounds

The thioacetalisation of a variety of heterocyclic, aromatic, and aliphatic carbonyl compounds (1 mmol) with ethane-1,2-dithiol (1 mmol) using silica sulphuric acid (SSA) is presented as an efficient heterogeneous catalyst under mild and solvent-free conditions at 60°C. The thioacetals were formed within a short reaction time (1–34 min) and isolated with 90–98 % yield following an extractive procedure and chromatography on silica gel. The competitive protection reaction between aldehyde and ketone with ethane-1,2-dithiol afforded the protected derivatives of benzaldehyde and acetophenone with 92 % and 8 % yields, respectively, indicating some selectivity.     

Silica-Supported Ferric Chloride (FeCl3-SiO2): An Efficient and Recyclable Heterogeneous Catalyst for the Preparation of Arylaminotetrazoles

An efficient method for preparation of 5-arylamino-1H-tetrazole and 1-aryl-5-amino-1H-tetrazole derivatives is reported using FeCl₃-SiO₂ as an effective heterogeneous catalyst. Generally, when the substituent in arylcyanamide is a strongly electron-withdrawing group, the position of the equilibrium would shift toward 5-arylamino-1H-tetrazole, whereas with an electron-releasing substituent, the position of the equilibrium would shift toward 1-aryl-5-amino-1H-tetrazole.     

Interaction of vitamins A,B1, C,B3 and D with zigzag and armchair boron nitride nanotubes: A DFT study

In this work, based on the density functional theory, the interaction of vitamins A, B1, C, B3 and D with (5, 5) armchair and (9, 0) zigzag single-walled boron nitride nanotubes (BNNTs) are studied. It is found that binding of vitamins A, B1, C, B3 and D with (9, 0) and (5, 5) BNNTs is thermodynamically favorable. Calculated solvation energies show that the solubility of functionalized (9, 0) BNNTs is higher than that of functionalized (5, 5) BNNT, and both dissolutions in water are spontaneous. The results showed that BNNTs can act as a suitable drug delivery vehicle for vitamins A, B1, C, B3 and D within biological systems. This study may provide a new insight into the development of the functionalized boron nitride nanotubes as drug delivery systems for virtual applications.     

DFT studies of functionalized zigzag and armchair boron nitride nanotubes as nanovectors for drug delivery of collagen amino acids

The interaction of collagen amino acids with (5, 5) armchair and (9, 0) zigzag single-walled boron nitride nanotubes (BNNTs) are studied using density functional theory. Our results show that the BNNTs can act as a suitable drug delivery vehicle of collagen amino acids within biological systems. DFT-LDA/DNP calculations revealed that the binding and solvation energies were negative for (5, 5)/(9, 0) BNNTs–collagen amino acid complexes implying the thermodynamic favorability and spontaneous interactions of collagen amino acids with BNNTs sidewall. These results were extremely relevant in order to identify the potential applications of functionalized BNNTs as drug delivery systems.     

Thermal analysis study on the simultaneous grain refinement and modification of 380.3 aluminum alloy

In this research, effect of integrated Al–10Sr–1Ti–2B master alloy has been studied on the microstructure and solidification characteristics of 380.3 aluminum alloy. Thermal Analysis has been used as a technique to study the cooling curves and first derivative curves during solidification of the alloy. Effect of integrated grain refiner and modifier on solidification parameters such as α-Al dendrite growth temperature (T _G,α), α-Al dendrite recalescence undercooling (?T _R,α), aluminum–silicon eutectic growth temperature (T _G,E), and eutectic recalescence undercooling (?T _R,E) has been determined. By increasing master alloy content, T _G,α and ?T _R,E have been increased, but, ?T _R,E has been decreased, and T _G,E increases first and then decreases. Aluminum–silicon eutectic depression temperature ( $ \Updelta T_{\text{G,E}}^{{{\text{Al}} - {\text{Si}}}} $ ) can be used as a parameter to control the modification of eutectic silicon. The results of this research indicate that the optimum level of Al–10Sr–1Ti–2B master alloy for the simultaneous grain refinement and modification of 380.3 alloy is about 0.5 mass%.     

Trichloroisocyanuric Acid (TCCA) and N-Chlorosuccinimide (NCS) as Efficient Reagents for the Direct Oxidative Conversion of Thiols and Disulfides to Sulfonyl Chlorides

Abstract

Trichloroisocyanuric acid (TCCA) and N-chlorosuccinimide (NCS) were found to be mild and efficient reagents for the direct oxidative conversion of sulfur compounds to the corresponding arenesulfonyl chlorides in good-to-excellent yields through the oxidative chlorination. The overall process is simple and practical, and it provides convenient access to a variety of aryl or heteroarylsulfonyl chlorides. The mild reaction conditions and the broad substrate scope render this method attractive and complementary to existing syntheses of aryl or heteroarylsulfonyl chlorides.