Photoacoustic spectroscopy of surface adsorbed molecules using a nanostructured coupled resonator array

• Published in: Nanotechnology 2014-01, Vol.25 (3), p.035501-035501
• Main Authors: Lee, Dongkyu, Kim, Seonghwan, Van Neste, C W, Lee, Moonchan, Jeon, Sangmin, Thundat, Thomas
• Format: Article
• Language: English
• Subjects: anodic aluminum oxide; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; explosives; Fullerenes and related materials; Infrared and raman spectra and scattering; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; photoacoustic spectroscopy; Physics; resonator; sensing; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Visible and ultraviolet spectra
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/25/3/035501

A rapid method of obtaining photoacoustic spectroscopic signals for trace amounts of surface adsorbed molecules using a nanostructured coupled resonator array is described. Explosive molecules adsorbed on a nanoporous anodic aluminum oxide cantilever, which has hexagonally ordered nanowells with diameters and well-to-well distances of 35 nm and 100 nm, respectively, are excited using pulsed infrared (IR) light with a frequency matching the common mode resonance frequency of the coupled resonator. The common mode resonance amplitudes of the coupled resonator as a function of illuminating IR wavelength present a photoacoustic IR absorption spectrum representing the chemical signatures of the adsorbed explosive molecules. In addition, the mass of the adsorbed molecules as an orthogonal signal for quantitative analysis is determined by measuring the variation of the localized, individual mode resonance frequency of a cantilever on the array. The limit of detection of the ternary mixture of explosive molecules (1:1:1 of trinitrotoluene (TNT), cyclotrimethylene trinitramine (RDX) and pentaerythritol tetranitrate (PETN)) is estimated to be ∼100 ng cm−2. These multi-modal signals enable us to perform quantitative and rapid chemical sensing and analysis in ambient conditions.