Application of sol-gel technology for the fabrication of optical sensors for hazardous metal ions and chemical warfare agents

Sol-gels have unique advantages over many materials in terms of sensor design and construction. The practical design of optical sensors utilizing transition metal ion dopants (or using organic dopants for the detection of transition metals) in the sol-gel matrix is the subject of the dissertation work presented. Three sensors were constructed using the sol-gel matrix. One sol-gel matrix for the encapsulation of metal nanoparticles is presented.; A thiolated silane is the basis for the detection of nickel (II) and cobalt (II) ions. The sensor described changes from clear and colorless to blood red in the presence of cobalt (II) ions and from clear and colorless to brown in the presence of nickel (II) ions. The detection limits of the sensors are 2.8 x 10-4 mM (280 nM) for Co 2+ and 7.7 x 10-5 mM (77 nM) for Ni 2+.; The stabilization of noble metal nanoparticles in a sol-gel matrix was achieved using bis[3-(triethoxysilyl)propyl]-tetrasulfide in a tetramethyl orthosilicate matrix. This matrix has the ability to stabilize gold nanoparticles and has limited success stabilizing silver nanoparticles. This stabilization is of importance for rational material design using the unique properties of nanoparticles.; A charge-transfer-based sol-gel optical detector was constructed for a chemical warfare agent analogue of HD. The ligand-to-metal charge transfer was shown between Cu2+ and 2-chlororethyl methyl sulfide. The color changes from sky blue to canary yellow when the charge transfer complex was present. The detection limits for the HD sensor were determined to be 0.03 muL per 1.5 mL sensor volume (200 muM).; A sensor utilizing a nickel (II) center was produced for a nerve agent analogue of VX. The observed color change is from a faint green to a brown color. The detection limit of the VX sensor is 3.4 x 10-3 mM. From the VX sensor, a double sensor for HD and VX was also constructed using a dual-sensing center of Cu2+ and Ni2+. The Cu2+ detects the HD analogue with a limit of 0.06 muL per 1.5 mL sensor volume (400 muM) and the Ni2+ detects the VX analogue with a DL of 3.0 x 10-3 mM.