In this article the structural and electronic properties of CeO 2 and Ce 1-x Zr x O 2 nanoparticles are investigated using time-resolved X-ray diffraction, X-ray absorption near-edge spectroscopy (XANES), and density functional calculations. CeO 2 and Ce 1-x Zr x O 2 (x e 0.5) particles in sizes between 4 and 7 nm were synthesized using a novel microemulsion method. The atoms in these nanoparticles adopted a cubic or pseudocubic crystal structure. The lattice constant decreased with increasing Zr content, varying from 5.4019 Å in CeO 2 to 5.3066 Å in Ce 0.5 Zr 0.5 O 2 . Within the cubic structure, the Zr atoms exhibited structural perturbations that led to different types of Zr-O distances and nonequivalent O atoms in the Ce 1-x Zr x O 2 compounds. Upon the addition of Zr to CeO 2 , the Zr positive charge in Ce 1-x Zr x O 2 is smaller than in pure ZrO 2 whereas the Ce positive charge is larger than in pure CeO 2 . Combination of these geometrical and electronic effects produced Zr L III -edge and O K-edge XANES spectra with a distinctive line-shape not seen in pure ZrO 2 or CeO 2 . The doping with Zr increases the thermal stability of the ceria nanoparticles and their chemical reactivity toward hydrogen. At temperatures between 300 and 900 °C, the Ce 1-x Zr x O 2 nanoparticles reacted with H 2 and water evolved into gas phase. XANES showed the generation of Ce 3+ cations (without reduction of Zr 4+ ) but an absence of diffraction lines different from fluorite-type ones was noted. There was an expansion in the unit cell of the reduced particles probably as a consequence of a partial Ce 4+ f Ce 3+ transformation and the sorption of hydrogen into the bulk of the material. The Ce 1-x Zr x O 2 nanoparticles interact with H 2 and reduce at lower temperatures than bulk Ce 1-x Zr x O 2 systems. This important difference could originate in an enhancement in chemical reactivity characteristic of nanostructured materials.

Hydrochromic materials have been actively investigated in the context of humidity sensing and measuring water contents in organic solvents. Here we report a sensor system that undergoes a brilliant blue-to-red colour transition as well as ‘Turn-On’ fluorescence upon exposure to water. Introduction of a hygroscopic element into a supramolecularly assembled polydiacetylene results in a hydrochromic conjugated polymer that is rapidly responsive (<20 μs), spin-coatable and inkjet-compatible. Importantly, the hydrochromic sensor is found to be suitable for mapping human sweat pores. The exceedingly small quantities (sub-nanolitre) of water secreted from sweat pores are sufficient to promote an instantaneous colorimetric transition of the polymer. As a result, the sensor can be used to construct a precise map of active sweat pores on fingertips. The sensor technology, developed in this study, has the potential of serving as new method for fingerprint analysis and for the clinical diagnosis of malfunctioning sweat pores.

No abstract

For Abstract see ChemInform Abstract in Full Text.

Scope Anthocyanins, the natural pigments in plant foods, have been associated with cancer prevention. However, the content of anthocyanins in staple foods is typically low and the mechanisms by which they exert anti-cancer activity is not yet fully defined. Methods and results We selected an anthocyanin-enriched purple-fleshed sweet potato clone, P40, and investigated its potential anti-cancer effect in both in vitro cell culture and in vivo animal model. In addition to a high level of total phenolics and antioxidant capacity, P40 possesses a high content of anthocyanins at 7.5 mg/g dry matter. Treatment of human colonic SW480 cancer cells with P40 anthocyanin extracts at 0–40 μM of peonidin-3-glucoside equivalent resulted in a dose-dependent decrease in cell number due to cytostatic arrest of cell cycle at G1 phase but not cytotoxicity. Furthermore, dietary P40 at 10–30% significantly suppressed azoxymethane-induced formation of aberrant crypt foci in the colons of CF-1 mice in conjunction with, at least in part, a lesser proliferative PCNA and a greater apoptotic caspase-3 expression in the colon mucosal epithelial cells. Conclusion These observations, coupled with both in vitro and in vivo studies reported here, suggest anthocyanin-enriched sweet potato P40 may protect against colorectal cancer by inducing cell cycle arrest, anti-proliferative and apoptotic mechanisms.