Colorimetry/Smartphone Dual-Mode Sensing Platform Based on Nanorod-Shaped Ni–Fe MOFs for Ascorbic Acid Detection

The rational design of nanozymes with excellent enzyme-like catalytic activity and high stability has been a promising objective for biochemistry. Total antioxidant capacity (TAC) is a vital indicator of oxidative stress in humans. Herein, a smartphone-based visual sensing platform utilizing nanorod-shaped Ni–Fe-based metal–organic frameworks (Ni–Fe-MOFs) as peroxidase-mimic nanozymes was developed for the fast, portable, low-cost, and on-site determination of ascorbic acid (AA). The nanorod-shaped Ni–Fe-MOFs are beneficial for single electron transfer, which suggests that the nanorod-shaped Ni–Fe-MOFs can be utilized as a good nanozyme for the detection of AA. The detection mechanism proves that the most active oxygen is ·OH and O2·– species for the peroxidase-mimic catalytic capability. The nanorod-shaped Ni–Fe-MOFs display a high affinity for 3,3′,5,5′-tetramethylbenzidine (TMB) and can be employed for the determination of AA, with a low detection limit of 0.094 μM. The proposed strategy implies that the detection of AA in human serum samples is feasible, thus generating data with fine precision. This work not only offers insight for designing highly efficient peroxidase-mimic nanozymes but also broadens their utilization for the detection of AA.