Designer electrode interfaces simultaneously comprising three different metal nanoparticle (Au, Ag, Pd)/carbon microsphere/carbon nanotube composites: progress towards combinatorial electrochemistry

In this report gold, silver and palladium metal nanoparticles are sep. supported on glassy carbon microspheres (GCM) using bulk electroless deposition techniques to produce three different materials labeled as GCM-Au, GCM-Ag and GCM-Pd resp. These three materials are then combined together into a composite film on a glassy carbon (GC) electrode surface using multiwalled carbon nanotubes (MWCNTs). The MWCNTs serve to not only mech. support this composite film as a binder but they also help to wire up each modified GCM to the underlying substrate. The intelligently designed structure of this electrode interface allows this single modified electrode to simultaneously behave as if it were a macrodisc electrode constructed of gold, silver or palladium, while using only a fraction of the equiv. amt. of these precious metals. Also this unique structure allows the possibility of combinatorial electrochem. to be realized using a relatively facile electrode construction which avoids the problems of alloy formation, co-deposition and the formation of bimetallic species. For instance a mixt. of several different analytes, which can each only be detected on a different specific substrate, can simultaneously be detd. using one electrode in a single voltammetric expt. Alternatively a substrate could undergo electrocatalytic reactions on one substrate, while the products, and hence the progress of this reaction, can be studied at a different substrate simultaneously at the same electrode surface. Proof-of-concept examples are presented herein and the designer electrode interface is shown to produce anal. responses to model target analytes such as hydrazine, bromide and thallium(I) ions that are comparable, if not better, than those obtained at metal macrodisc electrodes and even at other state-of-the-art nanoparticle modified electrodes.