Electrostatic Attachment of Probe Species

In 2004, Leventis et al. [12] presented a study in which they demonstrated that probe-doped silica aerogels could be prepared by post-doping cationic mthenium probes and cationic probe-electron donor dyads into silica sol-gel monoliths. Ruthenium complexes have well-described properties and have been studied extensively by others (as noted in [4, 13]). 

The probe ruthenium(ll) frA-(l, 10-phenanthroline) and the electron donors 4-benzoyl-A-methylpyridinium and A-benzyl-A -methyl viologen were employed by Leventis et al. [12]. A base-catalyzed TMOS precursor recipe was used to prepare silica sol-gel monoliths. The wet gels were then soaked in methanol baths containing one of the dyads, or the mthenium complex, each of which is a cationic species that was taken up by the sol-gels to such an extent that no color was observed in the remaining bath solution. The doped gels 

The postdoping method is very simple and might be readily applicable to other cationic probe species. However, the dyad synthesis (described in detail in [12]) is complex. 

---