FULL PUBLICATION
“O-PTIR enables optical photothermal detection of SEIRA to have increased sensitively relative to conventional SEIRA”
Reporting in Review of Scientific Instruments, researchers at NASA’s Jet Propulsion Laboratory have demonstrated unprecedented molecular detection capabilities by integrating optical photothermal infrared (O-PTIR) spectroscopy with Raman spectroscopy for concurrent surface-enhanced vibrational analysis.
The fundamental challenge addressed was achieving single-molecule sensitivity while obtaining complementary spectroscopic information from both infrared and Raman techniques simultaneously—a capability that has significant implications for trace surface analysis and planetary sample characterization.
The scientific data strongly supports the exceptional performance of the O-PTIR-based system. Using plasmonic substrates of silver nanospheres and gold-coated AFM tips, the researchers successfully detected individual molecules of Buckminsterfullerene (C60) and 1,2-bis(4-pyridyl) ethylene at concentrations as low as 27.3 ng/cm².
The concurrent acquisition of both SEIRA (Surface Enhanced Infrared Absorption) and SERS (Surface Enhanced Raman Spectroscopy) spectra from identical sample locations provided definitive molecular identification through complementary vibrational fingerprints.
The dual enhancement mechanism achieved through O-PTIR proved particularly powerful, with conventional SEIRA enhancement of ~10⁴ being amplified by the plasmonically enhanced 532 nm probe laser (enhancement ~10⁵), resulting in overall multiplicative enhancement approaching 10⁹.
This extraordinary sensitivity enabled detection of single molecules using a statistical dilution approach with binary mixtures, where observation of only one component spectrum from equimolar mixtures provided strong evidence for single-molecule detection.
The O-PTIR technique demonstrates transformative analytical capabilities for ultrasensitive molecular detection applications. Its ability to simultaneously provide infrared and Raman spectroscopic information at single-molecule sensitivity levels, combined with sub-micron spatial resolution, positions O-PTIR as an exceptionally powerful tool for trace analysis, contamination identification, and advanced materials characterization where traditional techniques lack sufficient sensitivity.
Mark S. Anderson
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
DOI: 10.1063/5.0136908
