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[en] Full text: The strontium stannate SrSnO3, is a ceramic material that has a structure compatible with a distorted perovskite and has been well studied due to its varied application, including as photocatalyst. However, it presents high band gap value, making it impractical for application photocatalysis in the visible region . Thus, it is interesting to search for alternatives that allow using catalysts in the visible region. Recently, literature presented heterogeneous coupling of oxides with carbon nitride (C3N4), which produces a composite with catalytic activity in the visible region and a reduced rate of recombination of photogenerated pairs . Thus, SrSnO3/g-C3N4 was prepared in two steps: first, SrSnO3 was synthesized by solid-state reaction, following the synthesis of the composite, using urea to form g-C3N4. It was verified the formation of the composite by XRD, FTIR, UV-Vis and Elementary Analysis (C, H and N). The photocatalytic activity was investigated by the degradation of Rhodamine-B (RhB, 5 mg L-1) irradiated under sunlight, obtaining 97.3% degradation, while pure SrSnO3 and g-C3N4 led to 5.6 % and 44.6% to RhB degradation, respectively. Thus, it was demonstrated the excellent photocatalytic activity of the composite. Complementary studies were also performed to evaluate the formation of hydroxyl radicals using UV and solar radiation. With UV radiation SrSnO3 has shown to be more efficient than SrSnO3/g-C3N4, however, when using solar radiation the heterostructure has shown to be about 5 times more efficient than pure catalyst. In addition, the toxicity of the degradation by-products was evaluated using the FET test. The results showed that either the initial RhB solution and the treated solution were not toxic to zebrafish embryos, thus no toxic intermediate seemed to be formed in the process. Summarizing, it was possible to observe that SrSEu3+ g-C3N4 increased visible light photocatalytic activity when compared to pure materials, being a promising photocatalyst to be used with sunlight.  Zhang, W. F.; Tang, J.; Ye, J. Photoluminescence and Photocatalytic Properties of SrSnO3 perovskite. Chem. Phys. Lett. 2006, 418 (1–3), 174–178.  Ong, W. J.; Tan, L. L.; Ng, Y. H.; Yong, S. T.; Chai, S. P. Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer to Achieving Sustainability? Chem. Rev. 2016, 116 (12), 7159–7329. (author)
[en] Pequi (Caryocar brasiliense Camb.), a typical fruit of Brazilian Cerrado, is well known in regional cookery and used in folk medicine to treat various illnesses. Mass spectrometry and chromatographic methods have identified the organic composition of pequi fruit pulp; however, NMR spectroscopy is used for the first time to characterize the nutritional components of organic and aqueous-ethanolic extracts. This spectroscopic technique determined the triacylglycerols in the pequi organic fraction, which is constituted mainly by oleate and palmitate esters, and detected the carbohydrate mixtures as the major components of aqueous and ethanolic fractions, respectively. In this study, presence of phenolic compounds was only evidenced in the ethanolic fraction. (author)
[en] Highlights: • Humic acid-HA, NaHCO3, MgSO4, KCl and CaCl2 change the stability and oxidation state of silver nanoparticle-AgNPs surface. • Ag3+ is formed on AgNPs surface mainly in presence of NaHCO3, MgSO4 and HA. • Toxicological endpoints in zebrafish embryos exposed to Ag3+ were not significant for acute exposure. • HA coated on AgNPs surface reduces the concentration of Ag ions released and the toxicity in zebrafish embryos. • HA acts as a natural attenuator/remediator of polluted water with AgNPs. - Abstract: The use of silver nanoparticles (AgNPs) result in an inevitable contact with aquatic environments. Here we study the behavior of AgNPs and the developmental toxicity in zebrafish embryos exposed to these nanoparticles (0–10 mg/L) with and without the presence of HA (20 mg/L), using zebrafish facility water (ZFW) and zebrafish growing media (ZGM). The presence of cations and HA gave rise to a decrease in Ag ion release and ζ-potential, an increase in the hydrodynamic diameter and oxidation of the AgNP surface. The results show that the presence of HA and cations in the media, as well as the silver speciation, i.e., the unusual presence of Ag3+, decreases the toxicity of AgNPs (LC50AgNPs: 1.19 mg/L; LC50AgNPs+HA: 3.56 mg/L), as well as silver bioavailability and toxicity in zebrafish embryos. Developmental alterations and the LC50 (1.19 mg/L) of AgNPs in ZFW were more relevant (p ≤ 0.05) than for AgNPs in ZGM (LC50 > 10 mg/L). It was demonstrated that the bioaccumulation and toxicity of AgNPs depends on several factors including AgNPs concentration, nanoparticle aggregation, dissolved silver ions, speciation of silver ions, the amount of salt in the environment, the presence of humic substances and others, and different combinations of all of these factors.