Highly Sensitive Fiber-Optic SPR Urea Sensor Based on ZIF-8/Urease

A highly sensitive fiber-optic urea sensor was designed and experimentally demonstrated based on surface plasmon resonance (SPR) effect and metal-organic zeolite framework (MOF), [zeolite imidazole skeleton-8 (ZIF-8)]/urease modification. The SPR effect was excited by plating gold film on the thin core fiber (TCF) in multimode-thin core-multimode fiber (MMF) structure, which behaved high refractive index sensitivity. The ZIF-8/urease composite film was grown on the gold film by rapid aqueous phase synthesis method, in which the ZIF-8 could immobilize more urease and made urease and urea fully contact. Since the urease catalyzed urea hydrolysis would change the refractive index, the measurement of urea concentration was realized with high sensitivity and good selectivity. Experimental results showed that the urea measurement sensitivity of the proposed sensor could reach 6 nm/mM within the concentration range of 1–7 mM, which has great application potential in the field of human health monitoring.