Ana Luísa Costa

Insights into the Photophysics and Supramolecular Organization of Congo Red in Solution and the Solid State

Steady-state and time-resolved absorption and fluorescence measurements are reported for Congo Red (CR) in aqueous and dimethylsulfoxide (DMSO) solutions. The very low fluorescence quantum yield (≈10-4 ) for CR in dilute solutions together with the absence of a triplet state indicates that internal conversion is the dominant deactivation route with more than 99.99 % of the quanta loss (attributed to the energy gap law for radiationless transitions). Although no direct evidence for trans-cis photoisomerization was obtained from absorption or fluorescence data, the global analysis of fs-transient absorption data indicates the presence of a photoproduct with a lifetime of ≈170 ps that is suggested to be associated with such a process. Spectral data for more concentrated CR solutions indicate the presence of oblique or twisted J-type aggregates. These results are compared with spectra for CR in the solid state (sodium salt) and intercalated in a layered double hydroxide via a one-step co-precipitation route. Powder XRD and electronic spectral data for the nanohybrid indicate that the CR guest molecules are intercalated as a monolayer consisting of slipped cofacial J-type aggregates.

Luminescent Properties of [UO2(TFA)2(DMSO)3], a Promising Material for Sensing and Monitoring the Uranyl Ion

An uranyl complex [UO2(TFA)2(DMSO)3] (TFA=deprotonated trifluoroacetic acid; DMSO=dimethyl sulfoxide) has been successfully synthesized by reacting UO2(CH3COO)2·H2O with one equivalent of (CF3CO)2O and DMSO. The complex has been characterized by single-crystal X-ray diffraction, X-ray powder diffraction, elemental analysis, FT-IR spectroscopy, thermal analysis and absorption and emission spectroscopies. The spectroscopic properties of the material make it suitable for its application in the sensing and monitoring of uranyl in the PUREX process.

Type 1 diabetes in children is not a predisposing factor for oral yeast colonization.

Abstract Type 1 diabetes mellitus (T1D) is considered a risk factor associated with oral yeast infections. The aim of this study was to evaluate the yeast oral carriage (in saliva and mucosal surface) of children with T1D and potential relation with host factors, particularly the subset of CD4+ T cells. Yeasts were quantified and identified in stimulated saliva and in cheek mucosal swabs of 133 diabetic T1D and 72 healthy control subjects. Salivary lymphocytes were quantified using flow cytometry. The presence of yeasts in the oral cavity (60% of total patients) was not affected by diabetes, metabolic control, duration of the disease, salivary flow rate or saliva buffer capacity, by age, sex, place of residence, number of daily meals, consumption of sweets or frequency of tooth brushing. Candida albicans was the most prevalent yeast species, but a higher number of yeast species was isolated in nondiabetics. T1D children with HbA1c ≤ 7.5 (metabolically controlled) presented higher number of CD4+ T salivary subsets when compared with the other groups of children (non‐diabetic and nonmetabolically controlled) and also presented the highest number of individuals without oral yeast colonization. In conclusion, T1D does not predisposes for increased oral yeast colonization and a higher number of salivary CD4+T cells seems to result in the absence of oral colonization by yeasts.