Determination of low-level plutonium in seawater by sector field inductively coupled plasma mass spectrometry: method validation.

Sources of plutonium isotopes to the marine environment are well defined, both spatially and temporally which makes plutonium (Pu) a potential tracer for oceanic processes. This paper presents the optimisation and validation of an analytical procedure for ultra-trace determination of Pu isotopes (239Pu and 240Pu) in seawater based on the external calibration and sector field inductively coupled plasma mass spectrometry (SF ICP-MS) determination. Additionally, method for Pu isotope ratio (240Pu/239Pu) in marine samples is also discussed. A combination of two-step anion exchange (AG1-X8) and one-step extraction chromatography (TEVA) was very efficient resulting in uranium (U) decontamination factor of 5 × 106-1 × 108. A full validation approach in line with ISO 17025 standard and Eurachem guidelines was followed. With this in mind, blanks, recovery (87 ± 8 %, k = 2), within-laboratory repeatability (5.6 %), limits of detection (0.12 and 0.08 fg mL-1 for 239Pu and 240Pu, respectively) and expanded uncertainty (13 %, k = 2) were systematically assessed. The procedure was applied for the determination of 239Pu and Pu in seawater sample coming from Mediterranean Sea. Obtained results were in good agreement with results obtained with alpha spectrometry, applied on the same seawater sample. Pu/239Pu atom ratio in seawater sample from the Mediterranean Sea was also determined. The precision and accuracy of 240Pu/239Pu isotopic ratio analysis were carefully examined using NBS-947 isotopic standard. 240Pu/239Pu ratio was found to be 0.187 ± 0.006 and is in agreement with accepted ratios for the global fallout of Pu.

Enhanced efficiency of dye-sensitized solar cells doped with green phosphors LaPO4:Ce, Tb or (Mg, Zn)Al11O19:Eu.

We have successfully introduced green phosphors LaPO4:Ce, Tb (G4) or (Mg, Zn)Al11O19:Eu (G2) into TiO2 photoelectrode of dye-sensitized solar cells. The conversion efficiency of the G4-doped device was enhanced by 30% compared with the pristine TiO2 photoelectrode. The green phosphor doped at 5-wt.% ratio contributed to the reduction of resistances of the surface and interface of the photoelectrode and to the great enhancement of the absorption spectrum in UV-visible and near-infrared regions. The internal resistances and absorbance of the photoelectrode directly affect the power conversion efficiency. Green phosphor plays an important role towards the realization of high-efficiency dye-sensitized solar cells.

Enhanced efficiency of dye-sensitized solar cells with novel synthesized TiO2.

An anatase TiO2 and three kinds of novel TiO2 nanoparticles were prepared by a hydrothermal method for dye-sensitized solar cells (DSSCs), which were obtained by mixing NaOH (10 M), KOH (14 M) and LiOH (10 M) solution with an anatase TiO2 powder, respectively. The TiO2 working electrodes of DSSCs were prepared and the photoelectric properties of the cells were characterized. The influence of different poly(ethylene glycol) contents in TiO2 films with and without HNO3 treatment on the electron transfer in DSSCs were investigated. It is found that the DSSC with HNO3 (0.002 mol/l)-treated film containing 16.7 wt% PEG shows the higher power conversion efficiency of 6.0%, which was mainly depended on the degrees of TiO2 pore size and uniformity of TiO2 films.

Application of microencapsulated isoflavone into milk.

This study was designed to develop a microencapsulated, water-soluble isoflavone for application into milk and to examine the hypocholesterolemic effect of such a milk product in a rat diet. The coating material was medium-chain triglyceride (MCT) and the core material was water-soluble isoflavone. The microencapsulation efficiency was 70.2% when the ratio (w/w) of coating material to core material was 15:1. The isoflavone release from the microcapsules was 8% after 3-day storage at 40 degrees C. In in vitro study, 4.0-9.3% of water-soluble isoflavone in simulated gastric fluid was released in the pH range of 2 to 5 after 60 min incubation; however, in simulated intestinal fluid at pH 8, 87.6% of isoflavone was released from the capsules after 40 min incubation time. In sensory analysis, the scores of bitterness, astringency, and off-taste in the encapsulated isoflavone-added milk were slightly, but not significantly, different from those in uncapsulated, isoflavone-added milk. In blood analysis, total cholesterol was significantly decreased in the isoflavone-added group compared with that in the control after 6-week feeding. Therefore, this study confirmed the acceptability of MCT as a coating material in the microencapsulation of water-soluble isoflavone for application into milk, although a slight adverse effect was found in terms of sensory attributes. In addition, blood total cholesterol was lowered in rats which had been fed a cholesterol-reduced and microencapsulated, isoflavone-added milk for 6 weeks.