Resumo em Inglês:

Abstract CeO2 with a hollow sphere morphology and a surface sensitized with gold (Au) and palladium (Pd) nanoparticles (NPs) was investigated as a photocatalyst for solar-driven hydrogen (H2) production. Structural characterization by X-ray diffraction (XRD) and morphological analysis by scanning electron microscopy (SEM) confirmed the successful synthesis of the materials and revealed that no significant structural alterations occurred in the CeO2 support following the surface modification procedures. Raman spectroscopy revealed a shift in the characteristic vibrational band of CeO2 upon sensitization with metallic NPs, which was attributed to the generation of oxygen vacancies within the oxide lattice. The surface modification of the hollow CeO2 spheres with metal NPs, exhibiting an average particle size of 6.38 ± 0.08 nm, contributed to an enhanced absorption of visible light and a concomitant increase in photocatalytic H2 evolution. The modified photocatalysts demonstrated improved performance due to both the tailored morphology of the support, achieving an activity of 19.9 μmol∙g-1∙h-1, and its sensitization with metallic NPs, which further elevated the H2 production rate to 45.4 μmol∙g-1∙h-1. These findings underscore the potential of combining morphological control with strategic chemical modification as an effective approach for the design of high-performance photocatalysts for solar H2 generation.

Resumo em Inglês:

Abstract This study aimed to explore the effects of diets with different concentrations of lemon (Citrus limon) extract (CLE) on the growth, survival, hematological, and plasmatic variables of the Amazon tambaqui (Colossoma macropomum) infected by Aeromonas hydrophila. Six diets (in triplicate) with graded concentrations of CLE (0.0, 0.2, 0.4, 0.8, 1.6, and 3.2 g kg-1) were supplied to the fish for 60 days. Afterward, the fish were infected with A. hydrophila for 10 days. Flavonoids and polysaccharides were the main constituents of CLE. Quadratic models indicated optimal feed conversion ratio and growth performance at 1.62 and 1.90 g CLE kg-1 of diet (P < 0.05). The plasma aspartate aminotransferase activity was higher in the control group than in the other groups (P < 0.05). As the CLE inclusion level increased, hematological parameters increased proportionally (P < 0.05). After the bacterial challenge, no mortality or skin lesions were observed in tambaquis fed diets containing more than 0.8 g CLE kg-1 (P < 0.05). Therefore, adding 1.9 g CLE kg-1 to Amazon tambaqui juveniles’ diet is indicated, as it improves growth performance, feed conversion ratio, and overall health, and enhances resistance to diseases caused by A. hydrophila.