Discovery of nitric oxide in marine ecological system and the chemical characteristics of nitric oxide

Nitric oxide was discovered in both the lab and the alga culture pond of Daya Bay (1―300 m3) before the growth of alga reached the maximum. The results included: (1) NO was detected before the growth of alga reached the maximum in the case of red tide alga and food alga, and the concentration of NO decreased rapidly after the growth maximum; (2) the curve between NO con-centration and time indicated that the concentration of NO in the daytime was more than that at night, and the maximal concentration of NO appeared in the midday (1―3 pm); (3) the growth of alga reached the maximum in the alga culture pond of Daya Bay in about 8―10 d, and NO was discovered in 5―7 d; (4) the measured NO concentration was 10-9 mol/L, 10-9―10-8 mol/L, and 10-8 mol/L for Haeterosigma akashiwo, mixed alga in Daya Bay and Chaetoceros Curvisetus individually; (5) the relation of illumination with NO production was discussed.     

Influence of cerium oxide on properties of glass–ceramic sealants for solid oxide fuel cells

The influence of the cerium oxide concentration on the properties of glasses and glass ceramics of the SiO₂–Al₂O₃–CaO–Na₂O–MgO–K₂O–B₂O₃–CeO₂ system as potential adhesive and sealing materials for solid oxide fuel cells was studied. According to the data of differential scanning calorimetry, variation of the CeO₂ concentration does not appreciably influence the glass transition and crystallization temperatures of glasses. As the cerium oxide concentration is increased, the linear thermal expansion coefficient increases for the glasses but decreases for the partially crystalline samples. The gluing temperature of the glass sealants prepared allows their use for joining YSZ solid electrolytes with interconnectors of Crofer22APU type in solid oxide fuel cells..     

Enthalpy of mixing in the propylene oxide–dimethylformamide and propylene oxide–ethylene glycol systems

Heat of mixing of propylene oxide with N,N-dimethylformamide and ethylene glycol has been determined by means of microcalorimetry. Theoretically suggested choice of the aprotic solvent as a selective separating agent for the propylene oxide–methanol binary mixture has been experimentally justified.     

Phase equilibrium in aqueous two-phase systems containing ethylene oxide–propylene oxide block copolymers and dextran

Phase equilibrium of aqueous two-phase systems containing the polysaccharide dextran and ethylene oxide (EO)/propylene oxide (PO) triblock copolymers was investigated in this work. Phase diagrams at 25.0 °C were experimentally obtained for systems formed by either dextran 19 (average molar mass of 8200 g mol⁻¹) or dextran 400 (average molar mass of 236 kg mol⁻¹) and one of the following block copolymers F38, F68, F108, P105 and P103, which present different structures in terms of EO/PO ratios and molar masses. It was possible to assess the influence of the polymer features on the phase equilibrium: the main factors affecting phase equilibrium being the size of dextran molecule and the structure (mainly the EO/PO ratio) of the copolymer. The Flory–Huggins equation was used to correlate the experimental data with good qualitative agreement, allowing the inference that changes in the copolymer hydrophobicity are the main responsible for the observed phase diagrams.     

A novel oxygen-dependent deoximation by nitric oxide

A variety of aldoximes and ketoximes were oxidized to corresponding aldehydes and ketones by nitric oxide in the presence of oxygen.A presumed mechanism was suggested.     

Sulfated binary and trinary oxide solid superacids

A series of sulfated binary and trinary oxide solid superacids were prepared, and their catalytic activities for n-butane isomerization at low temperature were measured. The incorporation of different metal oxides into ZrO2 may produce a positive or negative effect on the acid strength and catalytic activity of the solid superacids. Sulfated oxides of Cr-Zr, Fe-Cr-Zr and Fe-V-Zr are 2 - 3 times more active than the reported sulfated Fe-Mn-Zr oxide. The enhancement in the superacidity and catalytic activity of these new solid superacids has been discussed on account of the results of various characteriation techniques.     

Argentic oxide mediated N-dearylation of β-lactams

A method is described for the N-dearylation of N-(4-methoxy- or 4-ethoxyphenyl)-2-azetidinones with argentic oxide. The yields are good-to-excellent and the reaction is simple, efficient, and fast.     

Selective assembly of cyclodextrins on poly(ethylene oxide)–poly(propylene oxide) block copolymers

This paper presents a computational study on the formation of a molecular necklace formed by specific threading of cyclodextrins (CDs) on block copolymers. Structural as well as energetic principles for the selective complexation of - and -cyclodextrin with poly(ethylene oxide)–poly(propylene oxide) block copolymers (PEO–PPO) are elucidated considering a diblock copolymer of equimolecular composition (PEO)4–(PPO)4 as guest. A non-statistical distribution of CDs, i.e. -CDs primarily located on the PEO chain and -CDs on PPO blocks of the polymer, is based on a variety of structural features and energetic preferences considering both potential as well as solvation energies. This selectivity becomes already obvious considering 1:1 complexes between PEO and PPO monomers and the two CDs, but is increasingly evident when calculating higher order ensembles. Besides the host–guest interaction, docking between CDs themselves is an important, also non-statistical, prerequisite for the self-assembly of highly ordered tubes. The formation of intermolecular hydrogen bonds between adjacent CDs in a tubular aggregate gives an important contribution to the overall stability of the molecular necklace. The net effect, based on the preferential interaction between host and guest as well as between the host molecules themselves, results in the formation of a stable, highly ordered macromolecular, multicomponent aggregate.     

Sol–gel derived nano zinc oxide for the reduction of zinc oxide level in natural rubber compounds

Zinc oxide (ZnO) nanoparticles are synthesized by polymeric sol–gel method and characterized by X-ray diffraction, field-emission scanning electron microscopy. The cure characteristics, mechanical properties and thermal behaviour of natural rubber (NR) systems containing nano ZnO are investigated and compared to those of NR with micro-sized (conventional) ZnO. The NR vulcanizate with 0.5 phr (parts per hundred parts of rubber) sol–gel derived nano ZnO shows improvement in the curing and mechanical properties in comparison to the NR vulcanizate with 5 phr conventional ZnO. Thermogravimetric analysis reveals that nano ZnO impose better thermal stability than conventional ZnO in the NR vulcanizates. Thus, nano ZnO not only acts as a curing activator but also nano filler to improve the resulting properties of the NR vulcanizates. More essentially nano ZnO leads to the reduction of ZnO level in the NR compounds. Therefore, sol–gel derived nano ZnO diminishes the pollution of aquatic environment due to higher amount of conventional ZnO in rubber compounds.     

Poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene)oxide triblock copolymers at the water/air interface and in foam films

The behavior of commercial poly(ethylene oxide)(PEO)–poly(propylene oxide)(PPO)–PEO triblock copolymers at the water/air interface and in microscopic foam films is studied. In aqueous solution these amphiphilic nonionic substances exhibit a surfactant-like aggregation and adsorption behavior. Even below the critical micelle concentration (cmc) the surface concentration is so high that the PEO chains are squeezed and protrude into the solution in order to accommodate to the situation at the interface. As evidenced by measurements of the ellipticity of light reflected from the free surface of the solution a PEO brush is created at the fluid interface. The microscopic foam film is used as a tool for investigating the normal interaction between two PEO brushes facing each other. Stable foam films are obtained at concentrations below the cmc and steric repulsion predominates (in 0.1 M NaCl). A brush-to-brush contact is established only at higher capillary pressures and the disjoining pressure isotherm follows de Gennes' scaling prediction. At lower pressure a softer steric repulsion occurs. It is governed by the bulk copolymer concentration and hence is fundamentally different from the brush-to-brush repellency. On the whole PEO–PPO–PEO copolymers behave as nonionic surfactants, but the large size of their molecules exemplifies the excluded-volume features. Received: 13 July 1999/Accepted: 27 July 1999     

Transformations of sclareol oxide by bromination. Synthesis of driman-8α, l l-diol from sclareol oxide

Depending on reaction conditions, the reaction of sclareol oxide with N-bromosuccinimide affords either 12-bromo- or 12,16-dibromosclareol oxide, whereas the reaction of sclareol oxide with bromine in methanol gives l2-monobromide or (13S)-1 1,12-dibromo-8,13-epoxy-13-methoxy-14,15-bisnorlabdane. Dehydrobromination of the latter with potassium hydroxide in toluene in the presence of polyethylene glycol gives (13S)-12-bromo-8, 13-epoxy-l3-methoxy-14,15-bisnorlabd-11-ene, ozonolysis of which followed by reduction of the ozonide with LiAlH₄ affords drimane-8, 11 I-diol.Translated fromIzvestiya Akademi Nauk. Seriya Khimicheskaya, No. 11, pp.2780–2784, November,1996     

Iridium oxide fabrication and application: A review

Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis(e.g.,chlorine evolution reaction,detoxification,and oxygen evolution reaction).Such versatility is attributed to the distinct features of iridium oxides,such as their activity,biocompatibility,conductivity,and durability.The features and properties of iridium oxides are strongly dependent on the fabrication method.In this review,methodologies relating to the synthesis and fabrication of solid-state iridium oxides have been thoroughly collected and discussed.Structuring and crystallization techniques for iridium oxides are also noted.At the end of the review,the effects of utilizing a certain fabrication method on the characteristics of the iridium oxide product are recapitulated,together with the recommended application of the product in various fields.     

Is benzene oxide homoaromatic? A microcalorimetric study

Rate constants and heats of reaction for the aromatization of benzene oxide (1) and the acid-catalyzed aromatization of benzene hydrate (2) in highly aqueous solution giving phenol and benzene, respectively, have been measured by heat-flow microcalorimetry. The measured heat of reaction of benzene oxide, DeltaH = -57.0 kcal mol(-1), is much larger than that of benzene hydrate, DeltaH = -38.7 kcal mol(-1), despite an unusually low reactivity of benzene oxide, rate ratio 0.08. The measured enthalpies agree with those calculated using the B3LYP hybrid functional corrected with solvation energies derived from semiempirical AM1/SM2 calculations. Comparison with the measured enthalpies of the corresponding reactions of the structurally related 1,3-cyclohexadiene oxide (3) and 2-cyclohexenol (4) of DeltaH = -24.9 kcal mol(-1) (includes a small calculated correction of -1.2 kcal mol(-1)) and DeltaH approximately 0 kcal mol(-1), respectively, gives a smaller aromatization energy for the benzene oxide than for the benzene hydrate reaction (DeltaDeltaDeltaH = 6.6 kcal mol(-1)). This suggests that benzene oxide is unusually stabilized by a significant amount of homoaromatization as has been proposed previously (J. Am. Chem. Soc. 1993, 115, 5458). This unusual stability accounts for more than half of the approximately 10(7) times lower than expected reactivity of benzene oxide toward acid-catalyzed isomerization. The rest is suggested to originate from an unusually high energy of the carbocation-forming transition state.     

Recent advances in graphene oxide catalyzed organic transformations

Graphene oxide(GO), as a metal-free and readily available carbocatalyst, has been extensively applied in catalytic organic transformations. This minireview aims to give an overview of the progress on the application of native GO as a catalyst for various organic transformations in the past decade(mainly from 2011 to 2020).     

Recent advances in graphene oxide catalyzed organic transformations

Graphene oxide(GO), as a metal-free and readily available carbocatalyst, has been extensively applied in catalytic organic transformations. This minireview aims to give an overview of the progress on the application of native GO as a catalyst for various organic transformations in the past decade(mainly from 2011 to 2020).     

Polyethylene oxide—polysiloxane branched copolymers and networks

The hydrosilylation of vinyl methyl and divinyl ethers of oligoethylene glycols with polyhydridosiloxanes in the presence of chloroplatinic acid is accompanied by side processes, namely, polymerization of vinyl ethers and homodehydrocondensation of polyhydridosiloxanes. The electrical conductivity of ∼1M solutions of lithium triflate or bis(trifluoromethylsulfonyl) imide in the resulting hydrosilylation products is ∼10⁻⁵ S cm⁻¹.     

Effect of bovine serum albumin on the micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers in aqueous solutions by fluorescence spectroscopy

Effect of bovine serum albumin (BSA) on the temperature-dependent association behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers was investigated using pyrene fluorescence spectroscopy. The critical micellization temperature (CMT) of pluronics in aqueous solution was increased by the addition of BSA. A closed association model was used to obtain the standard free energies (△G0), enthalpies (△H 0), and entropies (△S 0) of micellization. The standard enthalpy and entropy of micellization for pluronic polymers in water were decreased with an increase of the BSA content. The more PPO component in the pluronic polymer, the higher the changed values of micellization enthalpy and entropy. The hydrophobic part of the pluronics, PPO, was responsible for the interaction between pluronics and BSA. Hydrophobic interaction between PPO and BSA was correlated to the alternation of the PPO-PPO interaction by the addition of BSA, which would shift the CMT toward higher temperature and alter the thermodynamic parameters of micellization for pluronics in aqueous solutions.     

Facile synthesis of mesoporous magnesium oxide–graphene oxide composite for efficient and highly selective adsorption of hazardous anionic dyes

Mesoporous magnesium oxide–graphene oxide composite (MGC) has been synthesized using a facile post-immobilization method by mixing pre-synthesized magnesium oxide (MgO) with graphene oxide (GO). MgO used for fabrication of the composite has been synthesized using an environment-friendly method involving gelatin as a template. XRD, Raman and EDX analyses have confirmed the presence of MgO and GO in the composite. FTIR and SEM analyses of synthesized MGC have further elucidated the surface functionalities and morphology, respectively. Using N₂ adsorption–desorption isotherm, BET surface area of MGC has been calculated to be 55.9 m² g^?1 and BJH analysis confirmed the mesoporous nature of MGC. The application of synthesized MGC as a selective adsorbent for various toxic anionic dyes has been explored. Batch adsorption studies have been carried out to investigate the influence of different adsorption parameters on the adsorption of two anionic dyes: indigo carmine (IC) and orange G (OG). The maximum adsorption capacities exhibited by MGC for IC and OG are 252.4 and 24.5 mg g^?1, respectively. Plausible mechanism of dye adsorption has been explained in detail using FTIR analysis. In a mixture of cationic and anionic dyes, MGC selectively adsorbs anionic dyes with high separation factors, while in binary mixtures of anionic dyes, both dyes are adsorbed efficiently. Thus, MGC has been shown to be a potential adsorbent for the selective removal of anionic dyes from wastewater.