RESUMO
The impact of Eu3+ doping at the Sr2+ and Sn4+ sites in SrSnO3 on its structural and electronic properties was studied and correlated with the photocatalytic efficiency. The compounds were synthesized using a modified Pechini method. Refinement of the synchrotron X-ray diffraction (S-XRD) data showed that the samples had an orthorhombic Pbnm symmetry. The incorporation of Eu into the lattice led to increased short- and long-range disorder, inducing additional distortion in the SnO6. XANES measurements revealed that mixed Eu valences (Eu3+ and Eu2+) were present in Eu-doped samples, and DFT calculations confirmed the presence of these ions at Sr2+/Sr4+ sites in the SrSnO3, resulting in changes in the electronic behavior. The catalytic performance toward Remazol yellow dye photodegradation and the catalysts' surface properties were also evaluated. The catalytic efficiency followed the order of Sr(Sn0.99Eu0.01)SnO3 > (Sr0.99Eu0.01)SnO3 > SrSnO3. The order was clearly related to selected-site doping that changed the degree of the inter- and intraoctahedral distortion and the introduction of different Eu midgap states, which apparently favor charge separation upon photoexcitation during photocatalysis. The results shown here are of great importance to the functionalization of SrSnO3 and other perovskite materials by lanthanoid ions, especially Eu3+, for effective applications as photocatalysts.
RESUMO
Analysis of the metaproteome of microbial communities is important to provide an insight of community physiology and pathogenicity. This study evaluated the metaproteome of endodontic infections associated with acute apical abscesses and asymptomatic apical periodontitis lesions. Proteins persisting or expressed after root canal treatment were also evaluated. Finally, human proteins associated with these infections were identified. Samples were taken from root canals of teeth with asymptomatic apical periodontitis before and after chemomechanical treatment using either NaOCl or chlorhexidine as the irrigant. Samples from abscesses were taken by aspiration of the purulent exudate. Clinical samples were processed for analysis of the exoproteome by using two complementary mass spectrometry platforms: nanoflow liquid chromatography coupled with linear ion trap quadrupole Velos Orbitrap and liquid chromatography-quadrupole time-of-flight. A total of 308 proteins of microbial origin were identified. The number of proteins in abscesses was higher than in asymptomatic cases. In canals irrigated with chlorhexidine, the number of identified proteins decreased substantially, while in the NaOCl group the number of proteins increased. The large majority of microbial proteins found in endodontic samples were related to metabolic and housekeeping processes, including protein synthesis, energy metabolism and DNA processes. Moreover, several other proteins related to pathogenicity and resistance/survival were found, including proteins involved with adhesion, biofilm formation and antibiotic resistance, stress proteins, exotoxins, invasins, proteases and endopeptidases (mostly in abscesses), and an archaeal protein linked to methane production. The majority of human proteins detected were related to cellular processes and metabolism, as well as immune defense. Interrogation of the metaproteome of endodontic microbial communities provides information on the physiology and pathogenicity of the community at the time of sampling. There is a growing need for expanded and more curated protein databases that permit more accurate identifications of proteins in metaproteomic studies.