This Small Grant for Exploratory Research (SGER) project addresses the need to engineer active surfaces for the detection of nitroaromatic, nitramine, and nitrate ester compounds, which are the primary constituents of explosive devices. Hybrid, nanostructured surfaces will be constructed from transparent conductive composites (TCCs) decorated with conjugated conductive oligomer wires. Selective binding of the target to the oligomer alters the electron charge mobility in the TCC, which in turn affects the redox state of the TCC. The binding event, therefore, can be effectively read out through measuring the conductivity of the TCC or through color changes to the TCC.
The work will consist of developing thin-film TCC sensors and testing the sensors with respect to the three representative nitro-derivatives. TCCs combine gold nanoparticles in a conducting polymer matrix to create a hybrid material that is conductive, flexible, and electrochromic. For instance, the TCC can switch from opaque to dark green depending on its redox state. Conjugated oligomers that are functionalized with thiol groups at one end and nitro-derivative receptors at the other provide the basis for selectivity and sensing. The thiol group anchors the oligomer to the metal sites on the TCC surface and the receptor starts the charge transfer mechanism when targeted with the appropriate molecule. Key issues that will be evaluated include TCC formulation, processing of the TCC into thin films (solution based or solid state), and functionalization of the TCC with the appropriate oligomer wire.
Intellectual merit: Currently, the most common type of transparent sensor is based on indium tin oxide (ITO) films. ITO suffers from significant drawbacks including a high processing cost, the limited supply of indium and its low mechanical robustness. This research serves to establish a new type of high-impact transparent sensor based on TCCs without the disadvantage of ITO. However, structure/property relationships are relatively unknown for TCCs. The research will, for the first time, identify and establish those relationships to lead to predictable control over TCC properties. Specifically, this research will explore compositional effects and will assess film processing strategies in controlling performance. The latter is important in that there are tradeoffs between scalability of the process and control over the nanostructure. Such research will have impact beyond just TCC films, for it will lend invaluable insight into the processing of nanostructured materials where order and spatial distributions dominate properties.
Broader Impacts: There are many potential applications of TCC films beyond sensors including nonlinear optical components, colloidal stabilizers, catalytic agents, and surface coatings that will greatly improve security and quality of life. The project will lead to outreach programs that include local high school teachers and students to enhance and diversify curriculums in chemistry, physicochemistry, and foundations of engineering. It will also provide a mechanism for including a diverse research group. The PI is committed to include female and underrepresented graduate students in her research. Currently, her group has four female students, two with Hispanic backgrounds.
