Presence Of CuO Nanoparticles Research Articles

Thermostability, pH stability and dye degrading activity of a bacterial laccase are enhanced in the presence of Cu2O nanoparticles

The present study relates to a nanotechnology enabled method in which purified laccase from Escherichia coli AKL2 was supplemented with 100μM copper oxide nanoparticles (Cu2O) (NP-laccase). The activity, half life and stability of NP-laccase were enhanced by 4, 42 and 36-fold respectively at high temperature (80°C) and also over a wide range of pH (4–12) than laccase (in the presence of 0.18mM CuSO4). Thermodynamic analysis of the nanoparticle-induced enzyme stability revealed an enhanced entropy–enthalpy compensation at 80°C, which reflected the maintenance of its native structure. This was further supported by CD studies. The enhanced activity and thermostability of NP-laccase can be utilized for efficient decolorisation of dyes (both phenolic and azo).

Nanoscrystalline CuO: Synthesis and application as an efficient catalyst for the preparation of 1,2,3-triazole acyclic nucleosides via 1,3-dipolar cycloaddition

article i nfo Nanowire CuO particles with an average diameter range of 2.5-3.7 nm were examined as catalysts for the 1,3- dipolar cycloadditions of organic azides to terminal alkynes. The material was successfully synthesized at room temperature from metallic copper powder by a facile solution-phase method in the presence of nitric acid, sodium hydroxide (NaOH) and ethylene glycol (EG) as growth-directing agent. The crystallinity, purity, morphology, specific surface areas and structural features of the as-prepared nanowires were characterized by powder X-ray diffraction, Brunauer-Emmett-Teller (BET) method and high-Transmission Electron Microscopy. Under mild reaction conditions, the addition of organic azides to terminal alkynes gives 1,4-disubstituted 1,2,3- triazole as a single regioisomer in good yields with reusability of the catalyst. The present click reaction protocol of terminal alkynes, via 1,3-dipolar cycloaddition with various organic azides allows the regioselective synthesis of 1,2,3-triazole acyclic nucleosides in good yields. We have then initiated the one-pot tandem (3+2) cycload- dition where benzylchloride was reacted with propargyl derivatives and sodium azide in the presence of CuO nanoparticles as catalyst.

Nano-CuO/Epoxy Composites: Thermal Characterization and Thermo-Oxidative Degradation

It is found that 5% CuO nanoparticle/epoxy nancomposite showed the best thermal properties via calorimetry analysis due to homogeneous dispersion of nanofillers. The nanocomposite exhibited an increase in storage modulus, glass transition temperature, and cross-link density from the pure epoxy system. Thermo-oxidative degradation of the cured epoxy systems with 5% and without CuO nanoparticles was studied by thermogravimetry analysis to determine the reaction mechanism in air. The results indicated that the degradation mechanism of the pure epoxy system is influenced by the presence of CuO nanoparticles. For the nanocomposite, analysis of the results suggests that the reaction mechanism obeys the three-dimensional diffusion (D3) mechanism.

Nanocrystalline copper(II) oxide-catalyzed one-pot four- component synthesis of polyhydroquinoline derivativesunder solvent-free conditions

The efficient and environmentally friendly method for the one-pot synthesis of polyhydroquinolines has been developed in the presence of CuO nanoparticles. The multi-component reactions of aldehydes, dimedone, ethyl acetoacetate andammonium acetate were carried out under solvent-free conditions to afford some polyhydroquinoline derivatives. This method provides several advantages including high yields, low reaction times and little catalyst loading.

Changes in the Daphnia magna midgut upon ingestion of copper oxide nanoparticles: A transmission electron microscopy study

This work is a follow-up of our previous paper ( Heinlaan et al., 2008. Chemosphere 71, 1308–1316) where we showed about 50-fold higher acute toxicity of CuO nanoparticles (NPs) compared to bulk CuO to water flea Daphnia magna. In the current work transmission electron microscopy (TEM) was used to determine potential time-dependent changes in D. magna midgut epithelium ultrastructure upon exposure to CuO NPs compared to bulk CuO at their 48 h EC 50 levels: 4.0 and 175 mg CuO/L, respectively. Special attention was on potential internalization of CuO NPs by midgut epithelial cells. Ingestion of both CuO formulations by daphnids was evident already after 10 min of exposure. In the midgut lumen CuO NPs were dispersed whereas bulk CuO was clumped. By the 48th hour of exposure to CuO NPs (but not to equitoxic concentrations of bulk CuO) the following ultrastructural changes in midgut epithelium of daphnids were observed: protrusion of epithelial cells into the midgut lumen, presence of CuO NPs in circular structures analogous to membrane vesicles from holocrine secretion in the midgut lumen. Implicit internalization of CuO NPs via D. magna midgut epithelial cells was not evident however CuO NPs were no longer contained within the peritrophic membrane but located between the midgut epithelium microvilli. Interestingly, upon exposure to CuO NPs bacterial colonization of the midgut occurred. Ultrastructural changes in the midgut of D. magna upon exposure to CuO NPs but not to bulk CuO refer to its nanosize-related adverse effects. Time-dependent solubilisation of CuO NPs and bulk CuO in the test medium was quantified by recombinant Cu-sensor bacteria: by the 48th hour of exposure to bulk CuO, the concentration of solubilised copper ions was 0.05 ± 0.01 mg Cu/L that was comparable to the acute EC 50 value of Cu-ions to D. magna (48 h CuSO 4 EC 50 = 0.07 ± 0.01 mg Cu/L). However, in case of CuO NPs, the solubilised Cu-ions 0.01 ± 0.001 mg Cu/L, explained only part of the toxicity.

ChemInform Abstract: Copper‐Catalyzed Stereoselective Synthesis of Vinyl Selenides under Ligand‐Free Conditions.

AbstractA mild and efficient protocol allows the stereoselective synthesis of vinyl selenides in the presence of CuO nanoparticles as a recyclable catalyst.

Mercury oxidation by copper oxides in combustion flue gases

The two main gaseous mercury species in combustion flue gas are elemental mercury (Hg 0) and oxidized mercury (Hg 2+). In the coal combustion process using an installed wet FGD system, Hg 2+ is captured and Hg 0 emitted since Hg 2+ is soluble in water. Oxidation of Hg 0 upstream of the FGD would significantly reduce Hg emission. In the presence of CuO nanoparticles, oxidation of Hg 0 to Hg 2+ proceeded under low HCl concentration in a simulated combustion flue gas. This paper describes the effects of reaction temperature, catalyst particle size, area velocity on mercury oxidation with CuO particles and the performance demonstration of CuO mercury oxidation with actual combustion flue gases. In simulated combustion flue gases, the conversion of Hg 0 to Hg 2+ increased as the reaction temperature decreased, but the conversion decreased as the particle size increased. Mercury oxidation with CuO nanoparticles of 50 nm in diameter was not significantly affected by area velocity in the range of 47 to 235 m 3/(h m 2), but the mercury oxidation with CuO particles of 1.1 μm was decreased over 100 m 3/(h m 2). In an actual combustion flue gas, CuO nanoparticles showed mercury oxidation as in the case with the simulated coal combustion flue gas.

Reusable Copper-Catalyzed Cross-Coupling Reactions of Aryl Halides with Organotins in Inexpensive Ionic Liquids

A combination of Cu2O nanoparticles with P(o-tol)3 shows highly catalytic activity for the Stille cross-coupling reaction. A series of copper catalysts and ligands were evaluated, and Cu2O nanoparticles combined with P(o-tol)3 provided the best results. In the presence of Cu2O nanoparticles and P(o-tol)3, a variety of aryl halides including aryl chlorides underwent the Stille reaction with organotins smoothly in moderate to excellent yields using inexpensive TBAB (n-Bu4NBr) as the medium. It is noteworthy that the Cu2O/P(o-tol)3/TBAB system can be recovered and reused at least three times without any loss of catalytic activity among the reactions of aryl iodides and activated aryl bromides.