Anchoring Zn^II-Coordination Polymers on Electrospun Cellulose Carbon Fibers for RET-PET Controllable Detection of Vitamin B₁₂ and Furazolidone: Insights from Experiments and Theory

The present work demonstrates the fabrication of two Zn^II-based coordination polymers (CPs) functionalized on electrospun carbon nanofibers for selective vitamin B₁₂ and furazolidone screening. The synthesized materials have been characterized by Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Herein, the emissive nature of the nanofiber composites has been exploited toward the detection of vitamin B₁₂ with a detection limit of 0.65 ppm (K_sv = 2.0 × 10⁵ M^-1) (Zn CNF-1) and 0.62 ppm (K_sv = 2.1 × 10⁵ M^-1) (Zn CNF-2) within a short response time (∼5 s). Incorporating cellulose carbon nanofibers and judicious alteration of the polar dangling subunits in the ligand backbone affected the photophysical properties with electronic distributions that ultimately inflated the detection limit at parts per million level compared to single-component CPs. In addition, Zn CNF-2 served as an aqueous-phase sensor toward furazolidone with an extremely low detection limit of 0.11 ppm and K_sv of 1.0 × 10⁵ M^-1 (response time ∼ 5 s). The quenching phenomenon through mechanisms like photoinduced electron transfer (PET), resonance energy transfer (RET), weak noncovalent interactions, etc., was investigated with several experimental (UV-vis, fluorescence, XPS, cyclic voltammetry, time-correlated single photon counting) and theoretical analyses. Additionally, Zn CNFs were exploited for quantitative analysis of targeted analytes from real-world samples and food supplements with appreciable detection limits and recovery percentages. Moreover, host-guest interactions through “switch-on-off” may be utilized to fabricate INHIBIT logic circuitry in molecular logic gate applications. In summary, the developed electrospun nanofiber composites (Zn CNF-1 and Zn CNF-2) are thermochemically robust and recyclable and work efficiently in a very short response time with their real-field implementations.