Six new bromophenols, 3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)pyrocatechol (1), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-hydroxymethyldiphenylmethane (2), 2,2',3-tribromo-3',4,4',5-tetrahydroxy-6'-ethyloxymethyldiphenylmethane (3), (+/-)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde (4), (+/-)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propylaldehyde dimethyl acetal (5), and 3-bromo-4,5-dihydroxybenzoic acid methyl ester (6), together with eight known bromophenols, 3-bromo-4,5-dihydroxybenzaldehyde (7), 2,3-dibromo-4,5-dihydroxybenzyl alcohol (lanosol, 8), 2,3-dibromo-4,5-dihydroxybenzyl methyl ether (9), 2,3-dibromo-4,5-dihydroxybenzyl ethyl ether (10), 2,3-dibromo-4,5-dihydroxybenzylaldehyde (11), bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (12), 3-bromo-4-(2,3-dibromo-4,5-dihydroxybenzyl)-5-methoxymethylpyrocatechol (13), and 2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenyl methane (14), were isolated from the red alga Rhodomela confervoides. Their structures were elucidated by chemical and spectroscopic methods including IR, HRFABMS, and 1D and 2D NMR techniques.
OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. b s t r a c tTwo commercial variants of the cast heat resistant grade HP40Nb (Fe-25Cr-35Ni, Nb modified) were exposed to CO/CO 2 gases at 982 and 1080°C in order to simulate exposure to the carbon and oxygen potentials realised in steam reformers under normal and overheated conditions. Both alloys developed external chromium-rich oxide scales, intradendritic silica precipitates and interdendritic oxide protrusions where primary, interdendritic carbides were oxidised in situ. Surprisingly, the lower silicon content alloy developed a more continuous internal silica layer, thereby slowing external scaling. Intradendritic oxidation was fast in both alloys, and is attributed to interfacial oxygen diffusion. Both alloys underwent rapid internal carburisation, indicating that their oxide scales failed to prevent carbon access to the underlying alloys under these reaction conditions.
In this study, the low-cost processing residue of Radiata pine (Pinus radiata D. Don) was used as the lone carbon source for synthesis of CQDs (Carbon quantum dots) with a QY (The quantum yield of the CQDs) of 1.60%. The CQDs were obtained by the hydrothermal method, and +a PVA-based biofilm was prepared by the fluidized drying method. The effects of CQDs and CNF (cellulose nanofibers) content on the morphology, optical, mechanical, water-resistance, and wettability properties of the PVA/CQDs and PVA/CNF/CQDs films are discussed. The results revealed that, when the excitation wavelength was increased from 340 to 390 nm, the emission peak became slightly red-shifted, which was induced by the condensation between CQDs and PVA. The PVA composite films showed an increase in fluorescence intensity with the addition of the CNF and CQDs to polymers. The chemical structure of prepared films was determined by the FTIR spectroscopy, and no new chemical bonds were formed. In addition, the UV transmittance was inversely proportional to the change of CQDs content, which indicated that CQDs improved the UV barrier properties of the films. Furthermore, embedding CQDs Nano-materials and CNF into the PVA matrix improved the mechanical behavior of the Nano-composite. Tensile modulus and strength at break increased significantly with increasing the concentration of CQDs Nano-materials inside the Nano-composite, which was due to the increased in the density of crosslinking behavior. With the increase of CQDs content (>1 mL), the water absorption and surface contact angle of the prepared films decreased gradually, and the water-resistance and surface wettability of the films were improved. Therefore, PVA/CNF/CQDs bio-nanocomposite films could be used to prepare anti-counterfeiting, high-transparency, and ultraviolet-resistant composites, which have potential applications in ecological packaging materials. IntroductionPolyvinyl alcohol (PVA) is a kind of semi-crystalline polymer with a linear structure and strong hydrogen bonds intermolecular. It has been widely used in papermaking [1], textiles [2], coatings [3], adhesives [4], packaging [5], and biomedicine [6] because of its toughness [7], adhesiveness [8], biocompatibility [9], swelling behavior [10], lack of toxicity [11], and sufficient thermal stability; it is also odorless and tasteless. However, PVA is highly hydrophilic and water-soluble [12], and its light transmittance is not suitable for light-barrier packaging [13]. In order to expand the application of PVA, much attention has been paid to fabricating functional PVA composites. The existence of hydrogen-bonding groups in PVA structure and the ability to form hydrogen bonds makes PVA suitable for mixing with other materials to improve its functional properties [14,15]. In previous studies, the prepared silica in situ enhanced PVA/chitosan biodegradation films [16], PVA/tea polyphenol composite films [17], PVA reinforced with cellulose nanocrystals or cellulose nanofibers (CNF) [18], and CNF/PVA-borax hybrid foams [19] had...
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