The organization of organic-capped gold nanoparticles in PS-b-PMMA monolayers is investigated. The preferred location of the particles within the block copolymer template is found to depend on both nanoparticle size and the length of the aliphatic capping agent. In the case of relatively short ligands, the particles behave as hard spheres and their incorporation in the polymer matrix can be qualitatively rationalized by entropic considerations. Three distinct arrangements are observed. Particles that are small, relative to the radius of gyration of the host polymer, evenly disperse within the PS domains, whereas the largest particles are considered form ordered, island-like aggregates. Particles of intermediate size exhibit the most striking arrangement, being relegated to the PS-PMMA interface to form organized ring structures. The tendency of these particles to assemble at the interface is sufficiently strong to force a modification of the polymer morphology to accommodate the particles at higher loadings. As the number of particles is increased, the circular PS-b-PMMA surface micelles elongate to form nanostrands.

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A new cloud point extraction procedure has been developed for the quantification of plutonium(IV) in environmental samples. The separation procedure can be either coupled to inductively coupled plasma mass spectrometry (ICPMS) or α spectrometry for plutonium quantification. The method uses a combination of selective ligand (P,P'-di(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP])) and micelle shielding by bromine formation to enable quantitative extraction of Pu in highly acidic solutions. Cross-optimization of all parameters (nonionic and ionic surfactant, chelating agent, bromate, bromide, and pH) led to optimal of the extraction conditions. Figures of merit of the method for the detection using α spectrometry and ICPMS are reported (limit of detection, limit of quantification, minimal detectable activity, and recovery). Quantitative extractions (>95%) were obtained for a wide variety of aqueous and digested samples (synthetic urine, wastewater, drinking water, seawater, and soil samples). The method features the first successful coupling between α spectrometry and cloud point extraction and is the first demonstration of CPE suitability with metaborate fusion as a sample preparation approach, techniques used extensively in nuclear industries.

This article describes the development of a procedure for the bulk separation and determination of rare earth elements in soils by combining alkaline fusion, cloud point extraction, and inorganic mass spectrometry.