Tertiary butylhydroquinone (TBHQ), one of the most common antioxidants in many foods, has attracted widespread attention due to its potential risk to human health. In this work, an "on-off-on" ratiometric fluorescent probe was prepared using dual-emission carbonized polymer dots (d-CPDs), which can be used to detect TBHQ in edible oils. The ratiometric fluorescent sensing system consisted of blue fluorescent CPDs (b-CPDs) as the response signal and yellow fluorescent CPDs (y-CPDs) as the internal reference material. The blue fluorescence of b-CPDs was gradually quenched with increasing Fe ion concentration, while the yellow fluorescence was essentially unaffected. Interestingly, TBHQ can restore the fluorescence intensity of b-CPDs. Meanwhile, the fluorescence mechanism of Fe on b-CPDs was investigated by density functional theory, both after the addition of TBHQ, and CPDs were released and their fluorescence was restored due to the competitive reaction of TBHQ-Fe. Thus, the d-CPDs probe was able to detect Fe accurately in an "on-off" manner and thus TBHQ in an "off-on" manner. At an optimal Fe concentration, the ratiometric sensing system provided fine linearities for determining TBHQ in the range from 0.2 to 2 μM and an ingenious detection limit of 0.052 μM. The CPDs ratiometric fluorescent probe designed in this work may have a broader application in the rapid, susceptive, and low-cost determination of TBHQ in various foods.
