CoOOH-induced synthesis of fluorescent polydopamine nanoparticles for the detection of ascorbic acid

Abstract

As an important biological small molecule, ascorbic acid (AA) plays a key role in many bioprocesses. Here, we developed a novel method to evaluate AA based on the redox reaction between CoOOH and AA. In our work, a nanosystem was constructed with fluorescent polydopamine (PDA) nanoparticles and CoOOH nanosheets, which were used as signal indicators and an oxidant respectively. This is the first time that fluorescent PDA nanoparticles were synthesized through oxidation by CoOOH nanosheets. In the absence of AA, dopamine was oxidized to quinone derivatives and further spontaneously polymerized into fluorescent PDA nanoparticles which had strong fluorescence signals. When there was AA in the reaction system, CoOOH nanosheets would be reduced to Co²⁺, which would prevent the synthesis of fluorescent PDA nanoparticles due to the absence of oxidant CoOOH, resulting in weak fluorescence. We hence used the fluorescence intensity of the PDA nanoparticles to detect AA concentration. The fluorescence of this sensing platform was linear with the concentration of AA in the range of 0–500 μM with a detection limit of 4.8 μM. In addition, the sensor was simple, fast, label-free, and low cost, and may be used to detect other small molecules based on the redox reaction.