Determination of low-level99Tc in environmental samples by high resolution ICP-MS

An analytical method has been developed for the determination of low-level⁹⁹Tc in environmental samples by High Resolution ICP-MS. The method consists of leaching of⁹⁹Tc by HNO₃ and separation by three different solvent extractions with 30% TOA-xylene, MEK, and cyclohexanone. Finally, purification of⁹⁹Tc was made by using an anion exchange resin column to reduce dissolved solids content. The final solution was adjusted to 1M HNO₃ for introducing into the HR-ICP-MS. The accuracy and precision of the method was confirmed to be satisfactory by applying this technique to the determination of⁹⁹Tc in IAEA marine algae sample (AG-B-1). Measurements of⁹⁹Tc using 0.5–2.5 g of sediment samples from the Irish Sea, UK, were successfully performed by the present method.     

Highly monodisperse chemically reactive sub-micrometer particles: polymer colloidal photonic crystals

Chemically reactive particles with controllable sizes from 383 to 756 nm in very narrow size distributions (well below 5%) have been synthesized by the modified surfactant-free emulsion homopolymerization of inhibitor-free glycidyl methacrylate with the dropwise addition of ionic initiators during the initial reaction of 10 min. The effects of monomer concentration and the amount of initiator were systematically studied on the particle diameter. In addition, changes of the particle diameter and its size distribution during the whole synthesis process were also investigated. The mechanism for the formation of coalesced and highly monodisperse chemically reactive colloidal particles was discussed based on the colloidal stability governed by chemical reaction and physical interactions between the precursor or primary particles. Colloidal photonic crystals with different brilliant visible colors in a large scale were prepared by shearing assembly of such chemically reactive monodisperse particles with spin coating technique. The reflection wavelengths in the visible spectrum range are from the high-order including the second-order light diffraction of the as-prepared PGMA photonic crystals. Such monodisperse chemically reactive particles will be very useful in optical and sensing technologies, and in biochemical analysis.