Resolving Nanocomposite Interfaces Via Simultaneous Submicrometer Optical-Photothermal Infrared-Raman Microspectroscopy

Nanocomposite materials are assuming increasingly important roles across contemporary materials science. Analytical characterizations and visualizations of nanoscale interphases/interfaces are critical to development of novel multiphase nanostructures and nanoscale systems. While conventional vibrational spectroscopies are indispensable physicochemical characterization tools, standard techniques such as Fourier-transform and quantum cascade laser infrared (IR) microspectroscopies are intrinsically limited in spatial resolution by the wavelength-dependent diffraction limit of IR light (approximate to 5-12 mu m). Optical-photothermal infrared (O-PTIR) with simultaneous hyperspectral Raman microspectroscopy (O-PTIR+R) is a novel all-optical technique that circumvents such diffraction limits, yielding position-specific IR spectra with sub-micrometer wavelength-independent resolution across the mid-IR. This work implements single-frequency O-PTIR with concomitant hyperspectral Raman microspectroscopy to resolve interfacial regions in a poly(octadecyl acrylate)-grafted-multiwall carbon nanotube (PODA-g-MWCNT) nanocomposite for wearable temperature sensors and highlights how the O-PTIR+R technique can be used for analytical characterization and visualization of other nanocomposite systems below resolution limitations of conventional IR spectroscopies.