A method based on a microemulsion route is presented to obtain magnetic nanoparticles of different sizes, offering several advantages with respect to other similar methods. It consists basically of the development of a microemulsion route above room temperature. Magnetic iron oxide particles with sizes ranging from 2 to 8 nm are obtained. The as-obtained product presents defined X-ray diffraction patterns, without the complications of working in an inert atmosphere or with extra amounts of Fe 2+ , thereby eliminating the need for further steps in order to achieve good crystallization of the material.

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J. M. CACHAZA, J. CASADO, A. CASTRO, and M. A. GPEZ QUINTELA. Can. J. Chem. 54, 3401 (1976).The kinetics of oxidation of nitrite to nitrate by hypochlorite ions in aqueous basic solution (pH 2. 11) have been studied using a dynamic spectrophotometric technique. The rate law is NO2-+ ClOH Z C1N02 + OHavec deux rhctions subskquentes paralleles du ClNO2: l'une, sa dkomposition unimolkulaire et l'autre une nouvelle attaque de I'espke N02-sur le CINOz.

Thermal annealing was used for the bottom-up fabrication of morphologically controlled gold-block-copolymer (Au-BC) nanocomposites. Three different blends formed by polystyrene (PS) homopolymer and PS-coated gold nanoparticles (PSSH@Au) were used as modifiers of asymmetric polystyrene-b-polymethylmethacrylate (PS-b-PMMA): PS26/PS26SH@Au, PS75/PS75SH@Au and PS167/PS167SH@Au (where the subscripts refer to the number of styrene monomeric units).The results indicated that all three blends used as modifiers (PSn/PSnSH@Au) were successfully located in the PS phase during thermally induced BC self-assembly for a composition range from 5 to 43 wt% without macro-phase separation. The PSnSH@Au moiety experienced molecular desorption, nanocrystal core coalescence and partial molecular re-encapsulation processes during thermal annealing, leading to sphere-like gold NPs with a larger average size (without exceeding an interdomain distance). Ligand chain length regulated the degree of coalescence and re-encapsulation, defining ultimate core size. Furthermore, proper combination of chain length and composition enabled tuning of NP partitioning and arrangement on different length scales through thermally activated cooperative assembly processes. These results have not only significant impact for establishing thermal processing as a useful tool for the precise control of NP size and distribution, but also much broader implications for many nanoparticle-based technologies.