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International audienceHumic substances (HS) perform a fundamental role in aquatic environments, exhibiting different levels of reactivity in retaining metal ions and organic pollutants. Also, they control the primary production of these ecosystems and act in the carbon sequestering process. In order to improve our understanding vis-à-vis the structural and functional features of HS from aquatic systems, this study aimed to chemically and spectroscopically characterize humic acids (HA) isolated from bottom sediment samples of a stream in a Brazilian subtropical microbasin by elemental analysis, and infrared (FT-IR), ultraviolet and visible (UV-Vis) and solid-state 13C nuclear magnetic resonance (CP-MAS 13C NMR) spectroscopies, thermogravimetry (TG), and scanning electron microscopy (SEM). Although all samples originated from the same environment, the data showed that the HA have distinct chemical and spectroscopic properties, and that the location and characteristics of the sampling points from which the sediments were collected played an important role in the differences observed. Furthermore, vascular plant matter is probably the main contributor to these samples

Fourier transform infrared spectroscopy (FT-IR) analysis was conducted on europium-doped hydroxyapatite,Ca10-xEux(PO4)6(OH)2nanocrystalline powders (Eu:HAp) with0≤xEu≤0.2. Antimicrobial studies were also performed for the first time on Eu:HAp. The antimicrobial properties of Eu:HAp nanoparticles with0≤xEu≤0.2on Gram-negative (E. coli ATCC 25922,Pseudomonas aeruginosa 1397) and Gram-positive (Staphylococcus aureus 0364,Enterococcus faecalis ATCC 29212) bacteria systems and a species of fungus (Candida albicans ATCC 10231) were reported. Our study demonstrates that the antimicrobial activity of Eu:HAp nanoparticles is dependent on the europium concentration.