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    Effect of the concentration and the type of dispersant on the synthesis of copper oxide nanoparticles and their potential antimicrobial applications
    (American Chemical Society, 2021-07-27)
    High Resolution Image Download MS PowerPoint Slide The bactericidal properties of copper oxide nanoparticles have growing interest due to potential application in the medical area. The present research investigates the influence of sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) on the production of copper oxide nanoparticles prepared from copper sulfate (CuSO 4 ) and sodium borohydride (NaBH 4 ) solutions. Different analytical techniques were used to determine the crystal nature, mean size diameter, and surface morphology of the copper oxide nanoparticles. The X-ray diffraction (XRD) patterns showed formation of nanoparticles of cuprite (Cu 2 O) and tenorite (CuO) when PVP and SDS were added at the beginning of the reaction. In fact, when the Cu/PVP ratio was 1.62, Cu 2 O nanoparticles were obtained. In addition, nanoparticles of CuO were synthesized when the Cu/PVP ratios were 0.54 and 0.81. On the other hand, a mixture of copper oxides (CuO and Cu 2 O) and cuprite (Cu 2 O) was obtained when PVP (Cu/PVP = 0.81 and 1.62) and SDS (Cu/SDS = 0.90) were added 30 min after the beginning of the reaction. Transmission electron microscopy (TEM) images show agglomerated nanoparticles with a size distribution ranging from 2 to 60 nm, while individual particles have sizes between 4.1 ± 1.9 and 41.6 ± 12.8 nm. The Kirby–Bauer method for the determination of antibacterial activity shows that small CuO (4.1 ± 1.9 nm) and Cu 2 O (8.5 ± 5.3 nm) nanoparticles inhibit the growth of Escherichia coli, Staphylococcus aureus MRSA, S. aureus and Pseudomonas aeruginosa bacteria. The antibacterial test of cotton fabric impregnated with nanoparticles shows positive results. The determination of the optimal ratio of copper oxide nanoparticles per cm 2 of fabric that are able to exhibit a good antibacterial activity is ongoing.
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    Effects of preparation method on catalytic behavior of Ni-Me (Me = Co, Nb)/?-Al2O3 for oxidative dehydrogenation of ethane
    (Sociedade Brasileira de Quimica, 2025-01-01)
    Catalysts based on Ni-Me (Me = Co, Nb) supported on γ-Al2O3 were prepared by the coprecipitation-chemical deposition method via reflux, and hydrothermal method for oxidative dehydrogenation of ethane. For coprecipitation method, ammonia and urea were used as precipitating agents. In both methods, the Ni content was 30 wt.%, whereas that of Me (Co, Ni) was 5 wt.%. The activity and selectivity towards ethylene appeared to depend strongly on the composition of the catalysts and, interestingly, on the preparation conditions. In the present article, it is shown that mixed hydrothermal samples using urea showed the best performance. Specifically, the hydrothermally prepared NiNb/γ-Al2O3 sample was the one that showed the highest values. The of Nb to Ni framework allowed to enrich with nucleophilic oxygen sites displayed via X-ray photoelectronic spectra (XPS) which lead to the formation of low reducible and selective sites.
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