Recent advances in layered double hydroxides applied to photoprotection / Recentes avanços dos hidróxidos duplos lamelares aplicados à fotoproteção

ABSTRACT Layered double hydroxides have received more attention from researchers due to their range of applications, ease of synthesis and low cost of production. With broader knowledge about solar radiation effects on the body, the use of sunscreens has become even more important. The ability of some nanostructures, such as layered double hydroxides, to act as matrices has made it possible to obtain improvements in photoprotective formulations, with solutions to problems caused by radiation and sunscreens. This review article brings together the most recent advances of these clays, the layered double hydroxides, applied to photoprotection.

RESUMO Os hidróxidos duplos lamelares vêm ganhando maior atenção de pesquisadores, em decorrência da gama de aplicações, da facilidade de síntese e do baixo custo de produção. Com o crescente conhecimento sobre diversos efeitos da radiação solar sobre o organismo, a utilização de fotoprotetores tem se tornado indispensável. A capacidade de nanoestruturas, como os hidróxidos duplos lamelares, atuarem como matrizes possibilitou melhorias nas formulações fotoprotetoras, tendo em vista os problemas provocados pela radiação, bem como por alguns filtros solares. Este artigo de revisão reúne os avanços mais recentes destas argilas, os hidróxidos duplos lamelares, aplicados à fotoproteção.

Analysis of Methylmercury Concentration in the Blood of Koreans by Using Cold Vapor Atomic Fluorescence Spectrophotometry

BACKGROUND: Methylmercury is an organic form of mercury that is highly toxic to humans. Here, we present and establish a novel method to detect methylmercury concentrations in the blood of Koreans. METHODS: Methylmercury concentration was analyzed with an automated methylmercury analytic system (MERX, Brooks Rand Co., USA) using cold vapor atomic fluorescence spectrophotometry (CVAFS). A variety of biological materials were digested in methanolic potassium hydroxide solution. The analysis method was validated by examination of certified reference material (955c, National Institute of Standard and Technology, USA). We randomly selected 30 Korean adults (age 20 yr or older) to analyze total blood mercury and methylmercury concentrations. RESULTS: The detection limit and methylmercury recovery rate using this method were 0.1 pg/L and, 99.19% (range: 89.33-104.89%), respectively. The mean blood concentration of methylmercury was 4.54+/-2.15 microg/L (N=30). The mean proportion of methylmercury to the total mercury concentration was 78.27% (range: 41.37-98.80%). CONCLUSIONS: This study is the first report to analyze blood methylmercury concentration using CVAFS in Korea. We expect that this method will contribute to the evaluation of mercury exposure and the assessment of the toxicological impact of mercury in future studies.

Intercalation compounds involving inorganic

Two-dimensional inorganic networks can shown intracrystalline reactivity, i.e., simple ions, large species as Keggin ions, organic species, coordination compounds or organometallics can be incorporated in the interlayer region. The host-guest interaction usually causes changes in their chemical, catalytic, electronic and optical properties. The isolation of materials with interesting properties and making use of soft chemistry routes have given rise the possibility of industrial and technological applications of these compounds. We have been using several synthetic approaches to intercalate porphyrins and phthalocyanines into inorganic materials: smectite clays, layered double hydroxides and layered niobates. The isolated materials have been characterized by elemental and thermal analysis, X-ray diffraction, surface area measurements, scanning electronic microscopy, electronic and resonance Raman spectroscopies and EPR. The degree of layer stacking and the charge density of the matrices as well their acid-base nature were considered in our studies on the interaction between the macrocycles and inorganic hosts.

Chelation behaviour of some lanthanide [III], scandium [III], yttrium [III], thorium [IV] and uranium [VI] complexes with some hydroxy nitrosocoumarins

The stability constants of the lanthanide ions [La, Ce, Pr, Nd, Sm, Gd, Dy, Er and Yb]; Sc, Y, Th and UO22+ ions with some hydroxy nitrosocoumarins were determined in 40% ethanol-water mixture at 25 degree and 0.1 ionic strength. It was found that the stability constants of the complexes increased with increasing ionic radii, from Y to Sm. The so called Gadolinium break was observed with heavier lanthanides. Sc and Th complexes possessed the highest stability constants. The potentiometric measurements and conductimetric titrations showed that 1: 1 and 1: 2 [M: L] complexes were invariably formed