Facile Approach for the Fabrication of Vapor Sensitive Spin Transition Composite Nanofibers

In this work polymer nanofibers were functionalized by incorporation of the spin transition (ST) compound [Fe(H₂btm)₂(H₂O)₂]Cl₂ (FeH2btm) (H2btm=di(1H-tetrazol-5-yl)methane). FeH2btm is an interesting compound due to its ability to reversibly and sensitively switch between high spin (HS) and low spin (LS) state when exposed to common volatile compounds (VOC) like ammonia and methanol. By using polyvinylidene fluoride (PVDF) as the main compound, inhibiting interactions between the complex and polymer were minimized. By using UV-Vis spectroscopy, the visible and reversible switching between HS and LS state when exposed to an ammonia or hydrochloric acid atmosphere was confirmed. Powder X-Ray diffraction (PXRD), scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy (EDX) show a homogenous distribution of FeH2btm with no major crystalline accumulations and a mean fiber diameter of 106±20 nm. The composite fiber has a similarly high thermal stability as the pure FeH2btm, as shown by thermogravimetric analysis (TGA). Mössbauer spectroscopy indicates an incomplete spin transition after exposition to ammonia. This could be due to low permeability of the VOC into the composite fiber.