Cottrell College Science Awards - 2013
Jodi L. O'Donnell
Cholesteric Liquid Crystalline Porphyrins and their Efficacy as VOC Sensors
We need fast, accurate sensors to tell us precisely what chemicals are present in our environment.
Jodi L. O’Donnell and Lucas J. Tucker are taking a novel approach to designing and making what are called chromophoric liquid crystalline chemical sensors. As the term “chromophoric” implies, these sensors change color in the presence of certain chemicals.
Specifically, O’Donnell, Tucker and their students will be trying to create useful sensors that reveal the presence of various types of volatile organic compounds (VOCs). According to the EPA, VOCs are emitted by a wide variety of products -- paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, and many others. VOCs have low boiling points, which means their molecules readily evaporate from liquid or solid, and enter the surrounding air.
The researchers will be trying to create VOC sensors by using a class of compounds called porphyrins, which are commonly found in the body – for example, heme, the active site of hemoglobin, a protein in red blood cells that carries oxygen, is a porphyrin.
O’Donnell and Tucker will be working with what are called cholesteric liquid crystalline porphyrins. As early as the 1880s, researchers noticed that cholesteric substances changed colors as they cooled or were exposed to external stimuli. The color changes occur because temperature affects the crystal-like nature of the molecules, which in turn bend light rays in certain ways in a process called polarization.
The researchers will design various forms of the sensitive cholesteric liquid crystalline porphyrins. Then thin films of these materials will be exposed to different VOCs and much like how hemoglobin changes color in the presence of oxygen, the sensors will produce specific color changes for specific VOCs. These color changing effects will be enhanced by the crystal-like nature induced by the presence of the cholesteric component.