Metal-organic frameworks/graphene oxide synergistic enhanced optical fiber SPR sensor for ultra-trace lead ions detection

The detection of lead ions (Pb²⁺) is critical due to its harmful effects to human health, even in trace amounts. In this paper, a novel optical fiber surface plasmon resonance (SPR) sensor for ultra-trace detection of Pb²⁺ is proposed. The sensing probe consists of a metal-organic frameworks (MOF)/graphene oxide (GO) composite sensitized layer modified on the gold (Au)-based optical fiber. In the presence of Pb²⁺, DNAzyme specifically recognizes Pb²⁺ and cleaves the substrate strand, resulting in the detachment of gold nanoparticles (AuNPs) conjugated to the substrate from the sensing region, which reduces the surface refractive index (RI) and thus causes a spectral blue shift. The optical fiber SPR sensor exhibits exceptional sensing performance, featuring a RI sensitivity of 4248.64 nm/RIU, achieving detection of Pb²⁺ with a limit of detection of 3.419 pM. The synergistic effect of MOF and GO enlarges the specific surface area of the bound biochemical molecules and improves the electron transport rate, offering the possibility of high-performance sensing. Furthermore, the sensor we proposed exhibits excellent specificity and stability, possessing significant research potential, as well as providing a foundation for experimental exploration into high performance optical fiber sensing devices.