The surfaces of materials play a central role in determining their properties and performance. In applications ranging from energy storage to medicine to computation, scientists need to understand the composition and structure of surfaces to explain their behavior and improve their characteristics. These surfaces include the interfaces found within batteries, the proteins on the surface of a cell, and the interfaces in new kinds of plastics. Understanding surfaces and interfaces is a challenge, however, because the composition and structure of surfaces can vary over tiny distances. These tiny distances can be just one-billionth of a meter, called a nanometer, and the structures may contain just one hundred atoms. To overcome this challenge, the instrument acquired through this Major Research Instrumentation grant is allowing far deeper insight into surfaces by combining a tool that measures composition, called infrared spectroscopy, with a tool that measures nano-sized structures. The resulting instrument, called a nano-infrared spectrometer, enables scientists to study many complex surfaces in detail. This new understanding is enabling important advances in numerous areas of science and technology. In addition, this instrument is providing graduate, undergraduate, and high school students - including those in underrepresented groups - with access to and training on the instrument. The instrument is housed in a shared instrument facility in the Chapel Hill Analytical Nanofabrication Laboratory (CHANL) at the University of North Carolina at Chapel Hill, where the instrument provides hands-on opportunities for training, education, and research.
Traditional infrared (IR) spectroscopy is a powerful tool that provides deep insight into the composition of materials, but its poor spatial resolution has limited its applications in nanoscience and nanotechnology. To overcome this challenge, the instrument acquired combines IR microscopy with an atomic force microscope (AFM) to measure IR spectra with a spatial resolution of approximately 10 nm. This new tool allows the composition of heterogeneous surfaces to be studied, such as the distribution of proteins on the surface of cells or the interfaces in organic photovoltaics. A distinctive feature of this nano-IR system is the use of multiple quantum cascade lasers as a light source. Collectively, these lasers operate from 800 1/cm to 3600 1/cm, which is an unusually broad range. This range facilitates measurements of many common functional groups, from C-F at 800 1/cm to O-H and N-H at 3600 1/cm. This new capability is allowing complex surfaces to be measured, such as the electrode/electrolyte interface in batteries, where the composition varies on the 10-nm length scale. The ability to discern spatial variations in the chemical functionality of battery electrodes will allow fundamental insight into, for example, mechanisms of degradation. The uses of the nano-IR spectrometer extend beyond measuring functional groups. For example, the instrument is enabling studies on plasmonic nanostructures, where the AFM tip is used to map the spatial distribution of the plasmonic component. These diverse capabilities allow nano-IR to have applications that extend from nanophotonics to electrochemistry to cellular biology.
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.