Monday 8 September 2008

Tiny Gold Clusters As Top-Notch Catalysts Identified By NIST And Partners

�For most of us, gold is only valuable if we possess it in large-sized pieces. However, the "larger is wagerer" rule isn't the eccentric for those interested in exploiting gold's exceptional ability to catalyse a wide variety of chemical reactions, including the oxidation of poisonous carbon monoxide (CO) into harmless carbon dioxide at room temperatures. That process, if industrialized, could potentially amend the strength of catalytic converters that clean automobile exhaust and breathing devices that protect miners and firefighters. For this purpose, nanoclusters - gold atoms bound together in crystals smaller than a strand of DNA - ar the size most treasured.



Using a pair of scanning transmission electron microscopy (STEM) instruments for which spherical aberration (a system fault yielding bleary images) is corrected, researchers at the National Institute of Standards and Technology (NIST), Lehigh University (Bethlehem, Pa.) and Cardiff University (Cardiff, Wales, United Kingdom) for the first fourth dimension achieved state of the art resolution of the active gold nanocrystals absorbed onto iron oxide surfaces. In fact, the resolution was sensitive enough to fifty-fifty visualize individual gold atoms.



The work is reported in Science.



Surface science studies accept suggested that there is a critical size reach at which gold nanocrystals supported by iron oxide become highly active as catalysts for CO oxidisation. However, the theory is based on research victimisation idealized catalyst models made of gold absorbed on titanium oxide. The NIST/Lehigh/Cardiff aberration-corrected STEM imaging proficiency allows the researchers to study the real iron oxide catalyst systems as synthesized, identify all of the gold structures deliver in each sample, and then qualify which bunch up sizes are most active in CO conversion.



The enquiry team observed that size matters a lot - samples ranged from those with little or no catalytic bodily process (less than 1 percent CO conversion) to others with nigh 100 per centum efficiency. Their results revealed that the most active gold nanoclusters for CO conversion ar bilayers or so 0.50.8 nanometer in diameter (40 times smaller than the common cold virus) and containing about 10 gold atoms. This finding is consistent with the previous surface science studies done on the gold-titanium oxide models.





A.A. Herzing, C.J. Kiely, A.F. Carley, P. Landon and G.J. Hutchings. Identification of active gold nanoclusters on iron oxide supports for CO oxidization. Science, Vol. 321, Issue 5894, Sept. 5, 2008.



Source: Michael E. Newman

htNational Institute of Standards and Technology (NIST)




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