Chemical Identification of Single Ultrafine Particles Using Surface-Enhanced Infrared Absorption

Abstract

Due to their large impact on health and environmental safety, fine and ultrafine particles are of special importance. While infrared (IR) spectroscopy can yield important material-specific information, direct investigation of small samples or single nano-objects is impossible, due to the great mismatch between particle size and IR wavelengths. Fortunately, surface-enhanced infrared absorption spectroscopy allows detection of $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ ultrafine dust particles a few tens of nanometers in diameter. The extraordinary near-field enhancement of the IR vibrational signal is achieved using plasmonically resonant Au ``bowtie'' apertures, in which the ultrafine specks are easily trapped.