We describe recent advances made in our laboratories in the general field oforganically and bio-organically doped sol-gel sensors. The developmentsdescribed are: (a) The first miniaturization of a sol-gel sensor down to themicrons scale, with potential applications to near-field optical microscopy,using a fluorescent pH-indicator. (b) The first successful sol-gelencapsulation of purified polyclonal antibodies, and in particular ananti-nitroaromatics immunoglobulin, with which selective sensing ofnitroaromatics, an important class of environmental pollutants, wasdemonstrated, (c) The leaching problem, occasionally encountered in dopingprocedures, is solved by two methodologies: First, TMOS polymerization athigh acidity and low water content was found to result in non-leachable yetreactive matrices, as demonstrated with O2 sensing by excitedstate pyrene and with H+ sensing by excited state pyranine; andsecond, doping with molecules capable of forming a covalent bond within theencapsulating cage results in the permanent anchoring of the dopant. Thus,Methyl-Red, a pH indicator, was derivatized with a silylating residue, and apolymerizing TMOS was doped with it forming a pH-shifted indicator. Withboth methodologies, leachability was practically zero.
