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 Fe3+ ion
concentration, while the yellow fluorescence was essentially unaffected.
Interestingly, TBHQ can restore the fluorescence intensity of b-CPDs.
Meanwhile, the fluorescence mechanism of Fe3+ 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-Fe3+. Thus, the
d-CPDs probe was able to detect Fe3+ accurately in an “on–off”
manner and thus TBHQ in an “off–on” manner. At
an optimal Fe3+ 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.