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Highly Sensitive Optical Detection of Humidity on Polymer/Metal Nanoparticle Hybrid Films

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journal contribution
posted on 13.03.2007, 00:00 by Norman A. Luechinger, Stefan Loher, Evagelos K. Athanassiou, Robert N. Grass, Wendelin J. Stark
Porous metal films for optical humidity sensing were prepared from copper nanoparticles protected by a 2−3 nm carbon coating, a silicon tenside, and a polymeric wetting agent. Exposure to water or solvent vapor revealed an exceptional sensitivity with optical shifts in the visible light range of up to 50 nm for a change of 1% in relative humidity. These properties could be attributed to a combination of surface plasmon resonance effects at low humidity and thin film interference at higher water or solvent concentration in the surrounding air. The simple concept and use of ultra-low-cost materials suggests application of such porous metal-film-based optical humidity sensors in large-scale applications for food handling, storage, and transport.