Identifying and measuring the amount of naturally occurring or emitted gases and metal species in a highly sensitive way is critical for ensuring the welfare of the public; the safety of first responders, military personnel, and employees in high-risk workplace settings; and the capability to assess the impact of gases and metals that are key to a sustainable global environment. This project develops an unexplored chemical sensing method that is based on the position of light beams being shifted when minute levels of a gas or metal ion are encountered. A team of chemists, physicists, and engineers is taking advantage of the properties of light waves when they bounce off the surface of nanometer-sized metal layers coated with thin films of environmentally friendly ionic liquids. The project aims to offer unprecedented, low-cost monitoring of atmospheric gases and metal ions in the environment, under a wide variety of conditions and locations. Mass production of miniaturized sensors that use the new method has the potential for widespread use of the sensors by people from many walks of life. The multidisciplinary collaborative nature of this research impacts the education of graduate and undergraduate students who are trained using a teamwork approach. To encourage educational opportunities for high school students from underrepresented groups, student interns from the East Cleveland School District are trained through a jointly organized workshop. The workshop has lecture and laboratory components and focuses on how the cross-disciplinary research between engineering and science can address current and pressing needs in society.

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professors B. Gurkan, Hinczweski, Strangi, and U. Gurkan at Case Western Reserve University are addressing development of a new "universal" method for the detection of gases and metal ions. The three specific aims of the study are: (1) engineering a photonic nanostructure to dramatically enhance the Goos-Hanchen (GH) displacement of an incident laser beam, allowing for ultrasensitive detection of local permittivity changes; (2) understanding of the refractive index changes of the ionic liquid layer above the nanostructure, in the presence of solutes such as carbon dioxide and metal salts; and (3) evaluating sensitivity and responsiveness of the multiplex interface. The sensing mechanism is based on GH displacement, where a laser beam internally reflected at a prism surface is displaced along the surface. The size of the GH shift depends on the structure and refractive indices of the materials on top of the prism, including the ionic liquid layer. The photonic nanostructure amplifies the magnitude of the GH shift so that it becomes easily detectable. The photonic nanostructure consisting of alternating dielectric or metal layers with different hierarchical arrangements and architectures are computationally designed and created by nanofabrication. To suppress interferences, multiplexing is employed by the use of different ionic liquids on the top layer with tailorable permittivity changes upon exposure to target analytes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

National Science Foundation (NSF)
Division of Chemistry (CHE)
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Robin McCarley
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Case Western Reserve University
United States
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