Nanoporous Fluorescent Microresonators for Non-wired Sensing of Volatile Organic Compounds down to the ppb Level

Luminescent resonators have been exploited as promising non-wired sensors for volatile organic compounds (VOCs). Nonetheless, their sensitivity is insufficient to detect dilute VOCs down to ppb concentration ranges due to the little physisorption quantity on the surface. Here, we report a nanoporous fluorescent resonator that exhibits an enhanced optical response to VOC molecules by accumulative physisorption in the pores and, thus, detects VOCs with concentration down to ppb ranges. A polymer with intrinsic microporosity is allowed to assemble into spherical microparticles (MSPIM-1) that exhibit whispering gallery-mode resonance. The resonance peak undergoes a spectral shift upon exposure to a model gaseous compound (pyridine) with an excellent sensitivity (0.40 nm ppm(-1)) and limit-of-detection (470 ppb) without losing its linearity down to 800 ppb. Adsorption of pyridine in the pores and the underlying molecular mechanism can be quantitatively evaluated based on the change in the refractive index. MSPIM-1 preferentially detects aromatic hydrocarbons and pyridine while is less responsive to highly polar or non-polar chemicals.