Parts-per-Million Detection of Volatile Organic Compounds via Surface Plasmon Polaritons and Nanometer-Thick Metal–Organic Framework Films
Max L. Tietze, Martin Obst, Giel Arnauts, Nathalie Wauteraerts, Sabina Rodríguez‐Hermida, Rob Ameloot
Abstract
Because of their guest adsorption properties, metal–organic frameworks (MOFs) are promising materials to realize chemical sensors. However, achieving high sensitivities requires the reproducible deposition of well-defined MOF films and their integration with a suitable sensor design. In this work, we report the sensitive detection of volatile organic compounds (VOCs) by transducing the adsorption in zeolitic imidazolate framework 8 (ZIF-8) thin films, prepared by chemical vapor deposition (MOF-CVD), into surface plasmon polariton (SPP) shifts measured via total internal reflection ellipsometry (TIRE). It is shown that defect formation during MOF-CVD alters the VOC uptake. However, SPP resonances tunable over the entire Vis–NIR range and as sharp as 14 nm are obtained for optimized synthesis conditions. Record-breaking shifts stronger than 150 nm upon methanol uptake and a limit of detection below 1 ppm are observed. By modeling the TIRE spectra, changes in the ZIF-8 refractive index from 1 × 10–4 (single-digit ppm VOC concentration) up to 0.06 are resolved with a resolution better than 1 × 10–5.