Nanoscale LnMOF-functionalized nonwoven fibers protected by a polydimethylsiloxane coating layer as a highly sensitive ratiometric oxygen sensor

Abstract

Combining the advantages of lanthanide luminescent and porous matrixes, lanthanide metal–organic frameworks (LnMOFs) show great potential in O₂ sensing. In this work, dual-emissive nanoscale LnMOFs, SUMOF-6-Eu, have been chosen as a ratiometric sensor that contains Eu³⁺-based luminescence as an O₂-sensitive probe and ligand (H₂pbydc)-based luminescence as an O₂-insensitive reference probe. In order to improve O₂ sensitivity, an in situ crystal-growth method was developed to fabricate nanoscale SUMOF-6-Eu soft films on flexible nonwoven polypropylene (PP) surfaces. After polydimethylsiloxane (PDMS)-coating treatment, the films show high chemical stabilities in moisture, long luminescence lifetimes (1.074 ms) and absolute quantum yields (62%). The coated nanoscale SUMOF-6-Eu films give rise to a high luminescence quenching efficiency of 89.9% at 1 atm O₂ (R₀/R₁₀₀ = 7.66) with perfectly linear Stern–Volmer plots (K_SV = 6.73, R² = 0.99765), good reversibility, short response/recovery times (10/60 s) and low detection limits (0.45%). This is the first example of soft LnMOF films protected by a water-resistant PDMS layer for ratiometric O₂ sensing.