Enhancing the efficiency of magnetically driven carbon nitride-based nanocomposites with magnetic nanoflowers for the removal of methylene blue dye at neutral pH.

The present study focuses on the elaboration of magnetic nanocomposites by the in situ incorporation of magnetite (Fe3O4) nanoparticles (NPs) with spherical and nanoflower-like morphologies in graphitic carbon nitride (g-C3N4) sheets using two different synthetic routes. Nanomaterials are characterized by TEM, SEM, XRD, FTIR, BET, zetametry, vibrating sample magnetometry, and UV-vis absorption spectroscopy. The decoration of the carbon nitride matrix with the magnetic NPs enhanced optical and textural properties. The influence of the morphology of the magnetic NPs on the adsorptive and photocatalytic properties of the nanocomposites under different pH conditions (4.5, 6.9, and 10.6) was assessed from batch tests to remove methylene blue (MB) from aqueous solutions. In extreme pH conditions, the nanocomposites exhibited lower or equivalent MB removal capacity compared to the pure g-C3N4. However, at neutral medium, the nanocomposite with incorporated Fe3O4 nanoflowers showed a significantly higher removal efficiency (80.7%) due to the combination of a high adsorption capacity and a good photocatalytic activity in this pH region. The proposed nanocomposite is a promising alternative to remove cationic dyes from water by magnetic assistance, since no pH adjustment of the polluted effluent is required, reducing costs and environmental impact in the dyeing industry.

Evaluation of the antimicrobial activity of silver nanoparticles obtained by microwave-assisted green synthesis using Handroanthus impetiginosus (Mart. ex DC.) Mattos underbark extract.

We describe here a green method for the preparation of silver nanoparticles (AgNPs), by a microwave-assisted synthesis route using Handroanthus impetiginosus underbark extract, with antibacterial activity. After optimizing the synthesis parameters with a Box-Benhken designed experiment, samples were characterized by powder XRD, TEM, UV-Vis spectroscopy, FTIR and zetametry. Using the overall optimized conditions of synthesis - time of reaction 15 min at 200 °C and plant extract/AgNO3 volume ratio equal to 10% - highly crystalline ∼13.4 nm-sized spherical AgNPs in a well-dispersed colloidal state were obtained. It was also proved that the plant extract compounds act as reductant and capping agents during synthesis to functionalize AgNPs, resulting in a negatively charged surface with high values of zeta potential in a wide range of pH, from acidic to alkaline media. Biological activity tests against Staphylococcus aureus and Escherichia coli and cell viability experiments showed that synthesized AgNPs were not toxic to HaCaT mammalian cells and presented a high efficiency against Gram-positive bacteria (S. aureus). This was associated with the synergistic combination of AgNP silver cores with the capping layer containing natural compounds with antimicrobial properties and considered an alternative to the AgNPs commonly obtained from conventional routes that present antibacterial effectiveness preferentially against Gram-negative strains.

Análise morfométrica do epitélio de revestimento do filamento branquial do guaru (Poecilia vivipara) exposto a frações do extrato da folha e casca do caule de Pequi (Caryocar brasiliensis) / Morphometric analysis of the lining epithelium of the gill filament off Guaru (Poecilia vivipara) exposed to fraction of leaf and bark extracts of Pequi (Caryocar brasiliensis)

O Cerrado brasileiro tem sido um dos domínios ecológicos mais explorado cientificamente nos dias atuais e na última década. Estudos recentes têm proposto o uso de extrato da folha e casca do caule de C. brasiliensis (pequi) como agente moluscicida, no intuito de combater o hospedeiro intermediário (Biomphalaria glabrata) do parasito causador da esquistossomose: Schistosoma mansoni. Como este molusco sempre está próximo a mananciais de água, questiona-se o impacto deste produto sobre a fauna aquática. Neste sentido, utilizamos a brânquia do peixe eurialino Poecilia vivipara (guaru), já bastante utilizado como bioindicador de poluição aquática, para testar a toxicidade de frações de extratos da folha e casca de caule de pequi. Um conjunto de 30 guarus adultos arranjados em 5 grupos experimentais foram expostos a frações aquosa, acetato de etila e etérea da folha e frações aquosa e acetato de etila da casca de caule de pequi, durante 24 horas. Mensurou-se a área e o perímetro dos filamentos branquiais nas regiões: basal, intermediária e apical. As análises estatísticas demonstraram que a área dos grupos experimentais não difere do controle. Porém, o perímetro das regiões basal e intermediária se diferenciaram significativamente do controle o que, todavia, não promoveu o comprometimento das atividades fisiológicas da brânquia. Assim, sugere-se que nas concentrações de 20 ppm, os extratos testados possam ser utilizados como moluscicidas em mananciais aquáticos, excetuando-se a fração aquosa da folha por ser letal nesta concentração