Vapor Sensing Using Conjugated Molecule-Linked Au Nanoparticles in a Silica Matrix

Cross-linked assemblies of nanoparticles are of great value as chemiresistor-type sensors. Herein, we report a simple method to fabricate a chemiresistor-type sensor that minimizes the swelling transduction mechanism while optimizing the change in dielectric response. Sensors prepared with this methodology showed enhanced chemoselectivity for phosphonates which are useful surrogates for chemical weapons. Chemoselective sensors were fabricated using an aqueous solution of gold nanoparticles that were then cross-linked in the presence of the silica precursor, tetraethyl orthosilicate with the alpha-, omega-dithiolate (which is derived from the in situ deprotection of 1,4-di(Phenylethynyl-4', 4 ''-diacetylthio)-benzene (1) with wet triethylamine). The cross-linked nanoparticles and silica matrix were drop coated onto interdigitated electrodes having 8 mu m spacing. Samples were exposed to a series of analytes including dimethyl methylphosphonate (DMMP), octane, and toluene. A limit of detection was obtained for each analyte. Sensors assembled in this fashion were more sensitive to dimethyl methylphosphonate than to octane by a factor of 1000. Copyright (C) 2009 Shawn M. Dirk et al.