Bimetallic Ln-MOF nanofibrous membrane as colorimetric fluorescent test strip for 1, 4-dioxane-glycol mixture ratio sensing

Abstract

A bimetallic Ln-MOF nanofibrous membrane (NFM) was successfully fabricated by in situ growth of Eu/Tb-MOF crystals onto electrospun polycaprolactam (PA6) nanofibers. For better combining with PA6 nanofibers, the Eu/Tb-MOFs were made into nanocrystals. Characterization with PXRD, FT-IR, EDS and XPS confirmed that the crystal structure of the Eu/Tb-MOFs maintained well on PA6 NFM. The as-prepared Eu/Tb-MOF@PA6 NFM can be used as a colorimetric fluorescent test strip for instant detection of the volume ratio of 1, 4-dioxane in 1, 4-dioxane-glycol mixture. With the increase of 1, 4-dioxane, the test strip presented color changes from green to red, which can be easily distinguished by the naked eye. In view of this, the conversion rate of the condensation reaction of glycol to 1, 4-dioxane will be preliminarily estimated without the help of equipment. More importantly, the test strip exhibited better convenience and reversibility compared with powdered Ln-MOFs because no separation process was needed for test strip before and after recovering. Benefiting from sufficient amide groups in PA6 for anchoring Eu/Tb-MOF particles, the test strip showed satisfactory stability in cycling experiments. This work will provide a new insight into the development of fluorescent test strip based on electrospun MOF NFM for quantitatively monitoring the reaction process.