Cobalt-Adsorbed Polypyrrole Film on Carbon Nanoparticles Shows Promise as Non-Noble-Metal Catalyst
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ficity can only be attributed to the presence of gold nanoparticles, according to the researchers, since there was no specificity when only the medium in which the gold particles were suspended was used. Furthermore, the researchers said, the nanoparticles enabled PCR amplification at lower annealing temperatures than current techniques allow without compromising specificity. The single-stranded DNA binding protein SSB selectively binds to single-stranded DNA, but not to double-stranded DNA. The researchers said that the optimizing effect of gold nanoparticles is greater than that of SSB that is commercially available. Gold nanoparticles bind more strongly to single-stranded DNA than double-stranded DNA because double-stranded DNA has a higher surface charge density, and anionic DNA strands do not bind to the negatively charged surfaces of citrate-stabilized nanoparticles. The researchers also said that adenine, thymine, guanine, and cytosine—the bases of which DNA is composed—contain nitrogen atoms that display high affinities to gold. These bases are more exposed in single-stranded DNA than double-stranded DNA, which means that there is a higher interaction between the gold nanoparticles and the DNA bases, the researchers said. They furthermore reported that the rigidity of the double-stranded DNA prevents the DNA from wrapping around the nanoparticles, but the more bendable single-stranded DNA readily wraps around them. The researchers said that this technique may find application in many other PCRs that require high specificity or high yields. MARÍA PÍA ROSSI
Cobalt-Adsorbed Polypyrrole Film on Carbon Nanoparticles Shows Promise as Non-Noble-Metal Catalyst Billions of dollars per year are currently being invested in fuel cell research and development worldwide. Currently, several materials-related issues, such as an alternative to Pt catalysts, must be addressed before fuel cell technology is able to supplant natural resources like oil as primary energy sources. M. Yuasa, A. Yamaguchi, H. Itsuki, K. Tanaka, M. Yamamoto, and K. Oyaizu of the Tokyo University of Science in Japan have investigated carbon nanoparticles with cobalt polypyrrole coatings as non-noble-metal catalysts for fuel cell electrodes. According to their study, reported in the August 23 issue of Chemistry of Materials (p. 4278; DOI: 10.1021/cm050958z), the cobalt atoms are coordinated by four nitrogens and the structure is maintained even after heat treatment at 700°C. The researchers have found an increase in catalytic activity after the high-temperature heat treatments. M. Yuasa and co-workers used fluid-bed electrolysis to deposit polypyrrole (PPy) coatings on high-surface-area carbon black particles (BET surface area, ~800 m2/g). Carbon black (CB) is a common support used for platinum-based catalysts. The PPy-coated CB particles were then suspended in a solution of cobalt acetate in CH3OH, which was then refluxed to allow formation of cobalt ions at the respective sites. Current–voltage measurements, extended x-ray absorption fine structure
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