Dual-signal and dual-function probe Ni-MOF@Fe-CDs for sensitive and visual detection of uric acid

In recent years, the development of nanozyme technology has provided new solutions, but some problems such as insufficient catalytic activity and limited multitarget detection capabilities still need to be addressed. Herein, iron-carbon dots (Fe-CDs) were loaded onto the petals of typical nanoflowery Ni-MOFs, and Ni-MOF@Fe-CDs with excellent catalytic performance and fluorescence characteristics were successfully prepared. Electron paramagnetic resonance (EPR) indicates that •OH is the key intermediate formed during the highly efficient catalytic process of H₂O₂ by Ni-MOF@Fe-CDs. The steady-state kinetic results show the nanozymes exhibit excellent peroxidase-like activity with K_m of 1.18 mM and V_max of 9.82 × 10^-8 M•s^-1. The study also found that 2,3-diaminophenazine (DAP) could quench the fluorescence of Ni-MOF@Fe-CDs, and the quenching mechanism between them was further investigated in depth. The inner filter effect (IFE) is dominated in the quench process, which is supported by the IFE-induced inhibition efficiency accounting for 85.2% of the total inhibition efficiency. Combined with the nanozyme and o-phenylenediamine (OPD), a highly sensitive dual-mode (colorimetric-ratiometric fluorescence) platform has been successfully developed for the quantitative analysis of H₂O₂ and uric acid (UA), with a detection limit for UA as low as 0.072 μM. In the analysis of UA in actual urine samples, the recovery rate was in the range of 92.2-107.6% (RSD < 2.9%), verifying the accuracy and reliability of the method. Compared with single-mode sensors for UA detection, the dual output signals endowed to the sensing platform constructed in this work provide complementary sensing performance and realize mutual verification of the detection signals. This approach offers a new strategy for rapid and sensitive detection of UA, with significant potential for translational applications.