Synergistic enhancement of fluorescein-K₃[Fe(CN)₆] CL by MoO_3-x NPs for sensitive and noninvasive detection of uric acid in saliva

MoO_3-x NPs was rapidly synthesized at room temperature by an easy stirring method. It was interesting to find that MoO_3-x NPs induce OH⁻ to generate active free radicals (ROS), which is a highly promising property in chemiluminescence (CL). Benefiting from the abundant oxygen vacancy, MoO_3-x NPs adsorbs H₂O₂ and turn it into ·OH. The oxidase activity of fluorescein under visible light had already been reported, which catalyzes dissolved oxygen to become O₂⁻· and continue to convert to H₂O₂. By creating the synergy effect with fluorescein, MoO_3-x NPs strengthen the CL intensity of K₃[Fe(CN)₆]-fluorescein system significantly. Utilizing the quench effect of uric acid for the CL intensity, we developed a rapid, simple, and highly sensitive CL platform for uric acid detection. The linear range was 5–80 µM and the detection limit (LOD) for uric acid was 3.11 µM (S/N = 3). This work expanded the application of MoO_3-x NPs in the CL field and developed a simple and highly sensitive CL sensing system to detect UA in human saliva.