| This thesis describes a new method for artificial olfaction: “ Smell-Seeing.” Employing an array of metalloporphyrins and chemoselective dyes, the method enables detection of a wide range of odorants based on their unique color change patterns. This approach overcomes many practical limitations of existing electronic noses, including water vapor susceptibility and low sensitivity for toxic, metal-binding vapors.; Responses of a two-dimensional array of metalloporphyrins supported on reverse phase silica provided vivid, unique color change patterns for a range of ligating vapors (e.g., alcohols, amines, ethers, phosphines, thiols). Flatbed scanners were used for digital imaging, and color change patterns were obtained via image subtraction using standard software. Weakly-coordinating vapors such as arenes and halocarbons were also differentiable due to solvatochromic shifts occurring within the dye library. Diffuse reflectance spectroscopy showed that solid state spectral shifts were similar to those seen for solution ligation.; Reproducible responses were obtained at concentrations as low as 460 ppb, with a 35 ppb detection limit for decylamine vapor. The metalloporphyrin array demonstrated interpretable and reversible responses even to mixtures of strong ligands, such as pyridines and phosphites. Colorimetric responses exhibited monotonic changes upon exposure to increasing concentrations of a given analyte, enabling quantitation. The metalloporphyrin array showed no susceptibility to water vapor; analyte detection was possible even in the presence of a large water background. Principal component analysis showed low redundancy in the sensor responses, while hierarchical cluster analysis revealed logical groupings of analytes containing similar chemical functionalities. Use of solvatochromic and pH-sensitive dyes enabled differentiation of organic acids. Discrimination of ligands and acids was possible even at 0.6 ppm using the expanded dye array. Quantitative differentiation of a family of amines was shown for concentrations ranging from 0.6 ppm to saturated vapor. Shape-selective zinc siloxylporphyrins aided in the discrimination of such isofunctional analytes.; To reduce response times, the “Smell-Seeing” array was miniaturized. Deposition of plasticized metalloporphyrin/polymer films on Teflon posts gave microarrays with faster response times (approximately 20fold) than reverse phase silica arrays at low analyte concentration. A prototype digital “Smell Camera” was developed to provide a portable version of the “Smell-Seeing” approach. |
