There is a growing interest on nanoparticle safety for topical use. The benefits of nanoparticles have been shown in several scientific fields, but little is known about their potential to penetrate the skin. This study aims at evaluating in vitro skin penetration of silver nanoparticles. Experiments were performed using the Franz diffusion cell method with intact and damaged human skin. Physiological solution was used as receiving phase and 70 microg/cm2 of silver nanoparticles coated with polyvinylpirrolidone dispersed in synthetic sweat were applied as donor phase to the outer surface of the skin for 24h. The receptor fluid measurements were performed by electro thermal atomic absorption spectroscopy (ETAAS). Human skin penetration was also determined by using transmission electron microscope (TEM) to verify the location of silver nanoparticles in exposed membranes. Median silver concentrations of 0.46 ng cm(-2) (range
Hydrogen production by photocatalytic reforming of aqueous solutions of ethanol and glycerol was studied with the use of impregnated and embedded CuO(x)/TiO(2) photocatalysts. Embedded CuO(x)@TiO(2) was prepared by a water-in-oil microemulsion method, which consists in the formation of Cu nanoparticles in the microemulsion followed by controlled hydrolysis and condensation of tetraisopropyl orthotitanate with the aim of covering the protected metal particles with a surrounding layer of porous titanium oxyhydroxide. Mild calcination leads to the complete removal of the organic residues, the crystallization of TiO(2), and an unavoidable oxidation of copper. Two reference samples were prepared by classical wet impregnation of preformed TiO(2) with different ratios of anatase, rutile, and brookite polymorphs. The two supports were prepared by sol-gel (TiO(2)-SG) and microemulsion (TiO(2)-ME) methods. Superior performances have been observed for the embedded system, which shows higher hydrogen production rates with respect to the impregnated systems using either ethanol or glycerol as sacrificial molecules. Deep structural characterization of the materials has been performed by coupling high resolution transmission electron microscopy (HRTEM), high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), X-ray absorption fine structure (XAFS), and electron paramagnetic resonance (EPR) techniques. Correlation between copper oxidation state and its dispersion and reactivity has been attempted. Finally, the stability of the CuO(x)/TiO(2) catalysts was also studied with respect to carbonaceous deposits and copper leaching.
Valorization of chemicals: The Cu photodeposited on pure anatase or multi‐phase TiO2 leads to the formation of nanostructured visible‐light driven photocatalysts (see figure), which are active in the valorization of ethanol or glycerol.
There are limited data on carbon-based nanoparticles and very few data on other metal nanoparticles increasingly used in industry. The article reviews the literature on the percutaneous absorption of nanoparticles and their effect on skin.
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