UIO-66-(OH)₂-Modified Optical Fiber SPR Sensor for Boric Acid Concentration Detection

It is important to detect whether the concentration of boric acid in industrial wastewater meets the discharge limit. Conventional chemical detection methods are complex, time-consuming, and difficult to operate. This article modifies the metal organic frameworks (MOFs) material UIO-66-(OH)2 on the surface of the gold film of the optical fiber SPR sensor, achieving specific detection of low concentration boric acid. The metallic-like properties of this material enhance the SPR phenomenon, increasing the refractive index sensitivity of the sensor to 4706.67 nm/RIU, which is 87% higher than before modification. In addition, a large number of hydroxyl and phenolic hydroxyl groups on the surface of UIO-66-(OH)2 material form coordination bonds to specifically adsorb boric acid, achieving specific detection of boric acid concentration with a sensitivity of 2.807 nm/lg(pM/mL) and a detection limit of 124.06 pM/mL. The boric acid concentration detection SPR sensor proposed in this article provides a new method for detecting microsubstances by material-modified optical fiber SPR sensor.