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Chemical and Engineering News
May 23,
Volume 83, Number 21
p. 38
Alternative to thiol monolayer
A variety of secondary amines condense with carbon disulfide (CS2) onto gold surfaces at room temperature, forming dithiocarbamate (DTC) monolayers that are considerably more robust than alkanethiol monolayers, according to a new study (J. Am. Chem. Soc. 2005, 127, 7328). Alexander Wei of Purdue University and coworkers produce the film simply by immersing a gold substrate into a solution containing an equimolar ratio of the amine and CS2. Depending on the amine used, the gold surface can thus be made more hydrophilic or hydrophobic. The researchers report that the dithiocarbamates, which are stable in acidic and basic aqueous environments, adsorb strongly and resist being displaced by competing alkanethiols. For example, when a monolayer of dibutyl DTC (shown) was exposed for 24 hours to a solution of 2-mercaptoethanol, which is known to completely displace alkanethiol monolayers, the DTC monolayer remained essentially intact. Wei believes that these ligands show particular promise for functionalizing surfaces exposed to relatively harsh environmental conditions.