Infrared absorption spectroscopy is a powerful analytical tool that enables the identification of molecular species. The sensitivity of this technique, that is strongly limited by the small absorption cross-section of molecular vibration, can be greatly improved by resonant interaction with nano-antennas, via the surface enhanced infrared absorption (SEIRA) mechanism. Yet, most of the examples of SEIRA concerns solid-state molecular layers adsorbed on the nano-antennas, while the detection of gas traces still remains elusive, due to the spatial extent of the near-field that is used to resonantly amplify the molecular vibrations.Here we demonstrate a hybrid system composed of a plasmonic nano-antenna array coupled with nanosized zeolite coating for detection of volatile organic compounds in the near field of the resonators. The concerted action of the coating and the nano-antennas enabled us to detect record traces of benzene (25 ppb) within 10 minutes. This approach may ultimately allow the fabrication of a compact system for rapid detection of pharmaceutical and bio-compounds with high sensitivity and high selectivity.

The health and environmental effects of particulate matter (PM) in the air depend on several parameters. Besides particle size, shape, and concentration, the chemical nature of the PM is also of great importance. State-of-the-art PM sensors only detect the particle size and concentration. Small, low-cost sensors only identify PM according to PM2.5 and PM10 standards. Larger detectors measure the complete particle size distribution. However, the chemical composition of PM is not often assessed. The current paper presents the initial stages of the development of an infrared-based detector for the inline assessment of the chemistry of PM in the air. By combining a mini cyclone that is able to concentrate the particles at least a thousand fold and a hollow waveguide that aligns the flow of particles with infrared light, the feasibility of the concept was shown in this study. A clear differentiation between amorphous and crystalline silica was demonstrated at outdoor PM levels of lower than 1 mg per cubic meter.

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