Gold, oxidative fluorination

Gold can be etched effectively with C2CI2F4 76) or with CCIF3 (77), while CF4/O2 etching causes staining. The observed staining is believed to be gold oxides, whose formation is enhanced by the presence of atomic fluorine (77). 

The successful oxidation of BrFs to [BrFe]" led to investigations on the oxidative fluorination of metals and metal fluorides. The first example was the successful oxidation of elemental gold to gold(V) (42), the treatment of Au powder in anhydrous HF giving a pale yellow solid, [KrF] [AuFe] , which is sparingly soluble in HF to give a pale yellow solution ... 

The LED top electrode (usually deposited directly onto porous silicon), also the optical window for EL output, is also a source of stabiUty concerns. Most devices use either ultrathin gold (a few nanometer thick in order to have a reasonable transparency to visible light) or indium tin oxide (ITO) electrodes. ITO shows better stabiUty than gold (Simons et al. 1997), in particular due to better air permeabiUty and better mechanical stabUity (ITO electrodes can be much thicker than gold ones). Fluorinated tin oxide electrodes exhibited much better stability (three orders of magnitude in... 

Bromine has a lower electron affinity and electrode potential than chlorine but is still a very reactive element. It combines violently with alkali metals and reacts spontaneously with phosphorus, arsenic and antimony. When heated it reacts with many other elements, including gold, but it does not attack platinum, and silver forms a protective film of silver bromide. Because of the strong oxidising properties, bromine, like fluorine and chlorine, tends to form compounds with the electropositive element in a high oxidation state. 

Other solutions to dealing with interferences in the detection of H O have included the use of a copperfll) diethyldithiocarbamate precolumn to oxidize the sample before it reaches the immobilized enzyme, as well as the use of a palladium/gold sputtered electrode which catalyzes the oxidation of hydrogen peroxide In addition, peroxidase has been used to catalyze the reaction between hydrogen peroxide and iodide ferrocyanide and organo-fluorine compounds Am-... 

The (compositionally) simplest mineral class comprises the native elements, that is, those elements, either metals or nonmetals that occur naturally in the native state, uncombined with others. Native gold, silver, and copper, for example, are metals that naturally occur in a ductile and malleable condition, while carbon - in the form of either graphite or diamond -and sulfur are examples of nonmetallic native elements. Next in compositional complexity are the binary minerals composed of two elements a metal or nonmetallic element combined with oxygen in the oxides, with a halogen - either fluorine, chlorine bromine, or iodine - in the halides, or sulfur, in the sulfides. The oxide minerals, for example, are solids that occur either in a somewhat hard, dense, and compact form in mineral ores and in rocks, or as relatively soft, unconsolidated sediments that melt at moderate to... 

The third group of solvents consists of those that are highly polar and autoioniz-ing. They are usually highly reactive and are difficult to keep pure because they react with traces of moisture and other contaminants. Some even react slowly with silica containers or dissolve electrodes of gold and platinum. An example of one of the more reactive of these solvents is bromine trifluoride. Nonfluoride salts, such as oxides, carbonates, nitrates, iodates, and other halides, are fluorinated ... 

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